Invest 90L
I have officially ceased monitoring 90L. It will still come close to the Carolinas within the next day or so, but will gradually weaken as it does so. Ultimately, it will be picked up by a large and powerful upper-level trough swinging southward from the north Atlantic. The system will also eventually be absorbed into this trough, losing its identity over the next several days. Impacts will be minor, though Bermuda may receive some tropical storm force winds, rough seas, and brief periods of heavy rainfall over the next couple of days as the system meanders in the general area.
Caribbean disturbance
The models have been less aggressive in recent runs over the possibility of a tropical disturbance in the western Caribbean. Vertical shear will still be quite low, however. Any culprit for a potential system in this area will come from Invest 90E, currently in the Eastern Pacific located over the Gulf of Tehauntepec. All of the models, save the CMC, unanimously bring this system to tropical storm status in about 48-72 hours, bringing the system across southeastern Mexico. In about four to five days, a weakness is forecast to develop in the Caribbean ridge, forcing the remnants of the system eastward into the western Caribbean. This is a very similar situation to Alma/Arthur in May of 2008.
Until I see some model consistency with this, however, I will not buy into it, though it's certainly possible, and definitely worth keeping an eye on. Vertical shear will be more than sufficient for organization of any system in this area, so it will need to be watched.
On one final note, the models have also recently been forecasting a gradual relaxation of the vertical shear across the Gulf of Mexico over the next week or so, as well as the eastern Atlantic Ocean. While I wouldn't expect any development in either of the aforementioned areas at the moment, it's certainly an indicator that La Nina is finally beginning to dominate. I suspect that we could see two to three storms in June, depending on the timing of the next upward MJO pulse.
Tuesday, May 25, 2010
Monday, May 24, 2010
Tropical weather analysis - May 24, 2010
Invest 90L
Invest 90L continues to look highly disorganized today, and has changed very little, if any, in overall organization since this time yesterday. Visible satellite animations depict the broad surface circulation is located near 28N 70W. This circulation is plainly seen, as it is completely removed from any thunderstorm activity, which is located well to the north and east of the center. While this is certainly characteristic of a subtropical cyclone, analysis of the Cyclone Phase Diagrams from FSU indicate that this system has not yet developed a low-level warm core. Unless this occurs, this system cannot become a subtropical cyclone. Also, to continue the trend of the last several days, there appear to be several small swirls embedded within the large cyclonic envelope, a further testament to the storm's presently disorganized state. Though it is not certain, as it is quite hard to tell with all the cirrus overhead, I suspect that another vorticity center is located near 30N 71W, though this circulation is also weakening. An earlier ASCAT pass indicated that the overall circulation associated with this system is very broad, covering a large area from the Greater Antilles westward and northward, including the Bahamas and all the way up to New England.
Said pass also indicates that this system's circulation is not entirely closed, and also that a large swath of 25-30 kt sustained winds exist east of the broad center(s). Due to the typical low-bias of ASCAT measurements, it is safe to assume that there is a large portion of gale force winds well to the east of the center, owing to the large pressure gradient between the subtropical ridge and 90L. It is likely that these winds exist along the northern end of the circulation as well, though unfortunately, the recent ASCAT pass missed this area, and there are insufficient surface observations north of the center to really confirm this suspicion. Animation of water vapor imagery indicates that a large amount of continental dry air continues to advance eastward into the broad center, owing to an upper-level low centered near 33N 81W, across central South Carolina. Analysis of winds from 100-500 mb, courtesy of University of Wisconsin CIMSS, depicts this low rather well, and it appears to have deepened somewhat over the last several hours. However, the models unanimously foresee this low has reached its peak and will gradually weaken and move southwest from this point on.
However, I suspect that this low will still be close enough to continue ingesting dry air into 90L for the next day or so. The models all agree on a track east of the Carolinas by around 48 hours, as 90L moves under the influence of the subtropical ridge to the east. Where they diverge is thereafter, as they all handle the timing and strength of the large north Atlantic trough differently. The CMC depicts the system will get picked up by the trough at around 54 hours; the GFS foresees the same, though it loses the identity of this system much quicker than the other models, at just 72 hours; the NOGAPS doesnot foresee 90L ever getting caught up into the aforementioned trough, and instead leave it to meander across the mid-latitudes of the Atlantic Ocean for several days in the wake of the trough. While this solution is possible, the current longwave pattern still favors anomalous troughing across the northeastern United States and Atlantic Canada, and so 90L will eventually be picked up by a trough, even if not the one that the CMC and GFS are predicting. Finally, the ECMWF offers an interesting but unrealistic scenario: 90L never gets picked up by the trough, and instead maintains a completely separate entity throughout the next week and beyond, eventually becoming a powerful extratropical low across the north Atlantic.
I'm going with the GFS scenario, having the system interact with the trough by 54 hours, and completely lose its identity by 72 hours within the trough. Rough seas are still likely from Georgia to New England over the next several days, even if the system doesn't develop, which I don't suspect that it ever will, despite the forecast of gradually decreasing vertical shear. Why? The environment is simply too dry, and the upper low that was previously atop the system has since detached. The NHC only gives this system a 20% chance of developing over the next 48 hours, and I am inclined to agree with them.
Synopsis in layman's terms
Development of 90L into a subtropical cyclone is looking increasingly less likely. However, regardless of development, gale force winds are a certainty north and east of the center. This will produce rough ocean conditions from Georgia northward to New England over the next several days.
Caribbean disturbance
The models have suddenly jumped on the development bandwagon again for the western Caribbean, this time by 120 to 144 hours (5-6 days). The instigator for this system is the remnants of the current Eastern Pacific disturbance centered across the Gulf of Tehauntepec, west of Central America. This situation appears to be very similar to the Alma/Arthur situation in May 2008, and is worth keeping an eye on. However, while still forecast to lessen across the western Caribbean over the next four to six days, vertical shear will still only be at marginally favorable levels for tropical cyclogenesis, and so the CMC and GFS, the only models that foresee development in this area, may be overdoing it. They forecast that the system will move ENE across eastern Cuba by around five days from now. If the system forms further south, it will have a much greater chance of becoming a tropical depression. All in all, I'm still not impressed with this area, though it does bear watching, but I'd rather see some model consistency first.
Synopsis in layman's terms
A tropical disturbance could form in the western Caribbean over the next several days, though development into a tropical depression or storm is not anticipated. Locally heavy rainfall will be possible across portions of the Greater Antilles, however.
Invest 90L continues to look highly disorganized today, and has changed very little, if any, in overall organization since this time yesterday. Visible satellite animations depict the broad surface circulation is located near 28N 70W. This circulation is plainly seen, as it is completely removed from any thunderstorm activity, which is located well to the north and east of the center. While this is certainly characteristic of a subtropical cyclone, analysis of the Cyclone Phase Diagrams from FSU indicate that this system has not yet developed a low-level warm core. Unless this occurs, this system cannot become a subtropical cyclone. Also, to continue the trend of the last several days, there appear to be several small swirls embedded within the large cyclonic envelope, a further testament to the storm's presently disorganized state. Though it is not certain, as it is quite hard to tell with all the cirrus overhead, I suspect that another vorticity center is located near 30N 71W, though this circulation is also weakening. An earlier ASCAT pass indicated that the overall circulation associated with this system is very broad, covering a large area from the Greater Antilles westward and northward, including the Bahamas and all the way up to New England.
Said pass also indicates that this system's circulation is not entirely closed, and also that a large swath of 25-30 kt sustained winds exist east of the broad center(s). Due to the typical low-bias of ASCAT measurements, it is safe to assume that there is a large portion of gale force winds well to the east of the center, owing to the large pressure gradient between the subtropical ridge and 90L. It is likely that these winds exist along the northern end of the circulation as well, though unfortunately, the recent ASCAT pass missed this area, and there are insufficient surface observations north of the center to really confirm this suspicion. Animation of water vapor imagery indicates that a large amount of continental dry air continues to advance eastward into the broad center, owing to an upper-level low centered near 33N 81W, across central South Carolina. Analysis of winds from 100-500 mb, courtesy of University of Wisconsin CIMSS, depicts this low rather well, and it appears to have deepened somewhat over the last several hours. However, the models unanimously foresee this low has reached its peak and will gradually weaken and move southwest from this point on.
However, I suspect that this low will still be close enough to continue ingesting dry air into 90L for the next day or so. The models all agree on a track east of the Carolinas by around 48 hours, as 90L moves under the influence of the subtropical ridge to the east. Where they diverge is thereafter, as they all handle the timing and strength of the large north Atlantic trough differently. The CMC depicts the system will get picked up by the trough at around 54 hours; the GFS foresees the same, though it loses the identity of this system much quicker than the other models, at just 72 hours; the NOGAPS doesnot foresee 90L ever getting caught up into the aforementioned trough, and instead leave it to meander across the mid-latitudes of the Atlantic Ocean for several days in the wake of the trough. While this solution is possible, the current longwave pattern still favors anomalous troughing across the northeastern United States and Atlantic Canada, and so 90L will eventually be picked up by a trough, even if not the one that the CMC and GFS are predicting. Finally, the ECMWF offers an interesting but unrealistic scenario: 90L never gets picked up by the trough, and instead maintains a completely separate entity throughout the next week and beyond, eventually becoming a powerful extratropical low across the north Atlantic.
I'm going with the GFS scenario, having the system interact with the trough by 54 hours, and completely lose its identity by 72 hours within the trough. Rough seas are still likely from Georgia to New England over the next several days, even if the system doesn't develop, which I don't suspect that it ever will, despite the forecast of gradually decreasing vertical shear. Why? The environment is simply too dry, and the upper low that was previously atop the system has since detached. The NHC only gives this system a 20% chance of developing over the next 48 hours, and I am inclined to agree with them.
Synopsis in layman's terms
Development of 90L into a subtropical cyclone is looking increasingly less likely. However, regardless of development, gale force winds are a certainty north and east of the center. This will produce rough ocean conditions from Georgia northward to New England over the next several days.
Caribbean disturbance
The models have suddenly jumped on the development bandwagon again for the western Caribbean, this time by 120 to 144 hours (5-6 days). The instigator for this system is the remnants of the current Eastern Pacific disturbance centered across the Gulf of Tehauntepec, west of Central America. This situation appears to be very similar to the Alma/Arthur situation in May 2008, and is worth keeping an eye on. However, while still forecast to lessen across the western Caribbean over the next four to six days, vertical shear will still only be at marginally favorable levels for tropical cyclogenesis, and so the CMC and GFS, the only models that foresee development in this area, may be overdoing it. They forecast that the system will move ENE across eastern Cuba by around five days from now. If the system forms further south, it will have a much greater chance of becoming a tropical depression. All in all, I'm still not impressed with this area, though it does bear watching, but I'd rather see some model consistency first.
Synopsis in layman's terms
A tropical disturbance could form in the western Caribbean over the next several days, though development into a tropical depression or storm is not anticipated. Locally heavy rainfall will be possible across portions of the Greater Antilles, however.
Sunday, May 23, 2010
Tropical weather analysis - May 23, 2010
Invest 90L
Invest 90L continues to look unimpressive today, with a completely exposed surface circulation exposed to the south of the deep convection, as revealed per the latest animated visible satellite imagery. This particular circulation appears to be rapidly dissipating as it moves southward away from the deep convection. This swirl is clearly visible at 25N 70W. It appears that 90L is poised to undergo another center relocation, common of weak, sheared systems such as this one. It appears that a new center might be forming some 50-75 miles to the northeast, at around 26N 68W. Vertical shear has lessened considerably over the system today, with CIMSS analysis now depicting only 10-20 kt of southwesterly shear over the disturbance, due to the upper-level low, which yesterday evening was at 300 mb, moving atop the surface center of 90L. This is the first sign of a transition to a subtropical cyclone. Animation of water vapor imagery also confirms this. It also confirms a large amount of dry air is slowly approaching the system from the west. This will continue to hamper any rapid development, despite sufficiently warm SSTs and adequate vertical shear.
Interestingly, the loosely-organized bands of convection well to the east of the surface center appear to be more impressive and dominant right now, as both low-level convergence and upper-level divergence have increased along said band, while slightly decreasing near the center. I suspect this is because the new center, the one at 26N, has yet to fully form itself, and is thus not dominant. That should change soon as the new center strengthens.
90L has finally picked up speed today as steering currents have restrengthened slightly. Visible satellite imagery reveals a clear N component of motion, along the western extent of the subtropical ridge. Due to the influence of a shortwave trough to the west, stretching from Georgia to just offshore New Jersey, along with the aforementioned ridge, this system will continue moving in a general N fashion, at times possibly just E of N. All of the models appear to have poorly initialized the system, save the GFS, and even that particular model is a tad too far to the E. Hence, I remain to the left of model guidance for the first 6-12 hours, at which point I am in complete agreement with it, save the CMC, which erroneously keeps the ridge weaker for longer, and doesn't begin the system's forecast NW turn until around 48 hours. All of the other models, including the GFS, which has performed particularly well with this system so far, turn the system NW much sooner, by around 24 hours. Hence, I have discounted the CMC's ridiculous solution, and am in complete agreement with the bulk of the model guidance in calling for a N movement for the first 12-18 hours, after which point a gradual NW motion should commence as the subtropical ridge restrengthens somewhat.
By around 72 hours, the system will have made its point of closest approach to the East Coast of the United States, and the majority of the guidance agrees that the system will come within about 125 miles of the South Carolina/North Carolina border during that time. The CMC, being an outlier, is much further to the east, along the eastern North Carolina coast. This is considered highly unrealistic for now. By 78 hours, the system will begin to stall just offshore, due to interaction with a large and powerful extratropical cyclone that will be dropping southward from Atlantic Canada during this time. The GFS and NOGAPS forecast that the system will be well on its way into the circulation of said extratropical cyclone by 84 hours, though interestingly, the NOGAPS and ECMWF foresee that the system will ultimately be able to break free of the influence of the extratropical cyclone and meander southwestward across the western Atlantic for a couple of days. I will keep an eye on this potential situation very carefully. 90L should not make landfall.
Synopsis in layman's terms
A large and complex low pressure area, currently centered several hundred miles east of the Bahamas, near 26N 68W, has the potential to develop into a subtropical cyclone over the next 24 hours. Regardless of development, gale force winds will develop in association with the system, particularly the northern and eastern sides, producing dangerous sea conditions from Georgia to Virginia, over the next several days. The system could come dangerously close to either of the Carolina coasts by around 72 hours, before stalling and moving away from the area.
Caribbean disturbance
None of the models are predicting the possibility of a tropical disturbance in the Caribbean at this point. It's just as I suspected; 90L will steal most of the energy from the area, as will a possible low pressure area in the Gulf of Tehuantepec that could form in about 4-5 days. Though a tropical disturbance is not expected, seasonal heavy rainfall can be expected across the area. Certainly, nothing destructive appears likely at this time, fortunately. However, one very important thing that the models have been consistent on over the last several days is a gradual and significant relaxation of the vertical wind shear across the Caribbean. It starts with the southwest Caribbean, then gradually lifts northward out of the western Caribbean by around 5-6 days. Models have been very consistent on the timing of this event also, which could be a sign that atmospheric conditions are finally starting to become more favorable.
Synopsis in layman's terms
No tropical development is likely across any portion of the Caribbean over the next week. The only likely threat is seasonal heavy rainfall.
Invest 90L continues to look unimpressive today, with a completely exposed surface circulation exposed to the south of the deep convection, as revealed per the latest animated visible satellite imagery. This particular circulation appears to be rapidly dissipating as it moves southward away from the deep convection. This swirl is clearly visible at 25N 70W. It appears that 90L is poised to undergo another center relocation, common of weak, sheared systems such as this one. It appears that a new center might be forming some 50-75 miles to the northeast, at around 26N 68W. Vertical shear has lessened considerably over the system today, with CIMSS analysis now depicting only 10-20 kt of southwesterly shear over the disturbance, due to the upper-level low, which yesterday evening was at 300 mb, moving atop the surface center of 90L. This is the first sign of a transition to a subtropical cyclone. Animation of water vapor imagery also confirms this. It also confirms a large amount of dry air is slowly approaching the system from the west. This will continue to hamper any rapid development, despite sufficiently warm SSTs and adequate vertical shear.
Interestingly, the loosely-organized bands of convection well to the east of the surface center appear to be more impressive and dominant right now, as both low-level convergence and upper-level divergence have increased along said band, while slightly decreasing near the center. I suspect this is because the new center, the one at 26N, has yet to fully form itself, and is thus not dominant. That should change soon as the new center strengthens.
90L has finally picked up speed today as steering currents have restrengthened slightly. Visible satellite imagery reveals a clear N component of motion, along the western extent of the subtropical ridge. Due to the influence of a shortwave trough to the west, stretching from Georgia to just offshore New Jersey, along with the aforementioned ridge, this system will continue moving in a general N fashion, at times possibly just E of N. All of the models appear to have poorly initialized the system, save the GFS, and even that particular model is a tad too far to the E. Hence, I remain to the left of model guidance for the first 6-12 hours, at which point I am in complete agreement with it, save the CMC, which erroneously keeps the ridge weaker for longer, and doesn't begin the system's forecast NW turn until around 48 hours. All of the other models, including the GFS, which has performed particularly well with this system so far, turn the system NW much sooner, by around 24 hours. Hence, I have discounted the CMC's ridiculous solution, and am in complete agreement with the bulk of the model guidance in calling for a N movement for the first 12-18 hours, after which point a gradual NW motion should commence as the subtropical ridge restrengthens somewhat.
By around 72 hours, the system will have made its point of closest approach to the East Coast of the United States, and the majority of the guidance agrees that the system will come within about 125 miles of the South Carolina/North Carolina border during that time. The CMC, being an outlier, is much further to the east, along the eastern North Carolina coast. This is considered highly unrealistic for now. By 78 hours, the system will begin to stall just offshore, due to interaction with a large and powerful extratropical cyclone that will be dropping southward from Atlantic Canada during this time. The GFS and NOGAPS forecast that the system will be well on its way into the circulation of said extratropical cyclone by 84 hours, though interestingly, the NOGAPS and ECMWF foresee that the system will ultimately be able to break free of the influence of the extratropical cyclone and meander southwestward across the western Atlantic for a couple of days. I will keep an eye on this potential situation very carefully. 90L should not make landfall.
Synopsis in layman's terms
A large and complex low pressure area, currently centered several hundred miles east of the Bahamas, near 26N 68W, has the potential to develop into a subtropical cyclone over the next 24 hours. Regardless of development, gale force winds will develop in association with the system, particularly the northern and eastern sides, producing dangerous sea conditions from Georgia to Virginia, over the next several days. The system could come dangerously close to either of the Carolina coasts by around 72 hours, before stalling and moving away from the area.
Caribbean disturbance
None of the models are predicting the possibility of a tropical disturbance in the Caribbean at this point. It's just as I suspected; 90L will steal most of the energy from the area, as will a possible low pressure area in the Gulf of Tehuantepec that could form in about 4-5 days. Though a tropical disturbance is not expected, seasonal heavy rainfall can be expected across the area. Certainly, nothing destructive appears likely at this time, fortunately. However, one very important thing that the models have been consistent on over the last several days is a gradual and significant relaxation of the vertical wind shear across the Caribbean. It starts with the southwest Caribbean, then gradually lifts northward out of the western Caribbean by around 5-6 days. Models have been very consistent on the timing of this event also, which could be a sign that atmospheric conditions are finally starting to become more favorable.
Synopsis in layman's terms
No tropical development is likely across any portion of the Caribbean over the next week. The only likely threat is seasonal heavy rainfall.
Saturday, May 22, 2010
Tropical weather analysis - May 22, 2010
Invest 90L
Invest 90L continues to look highly disorganized, and it appears that if there was indeed a closed surface center this time yesterday, it has since dissipated, and the system is now an open trough. However, this is largely negligible because the system is a non-tropical entity, and hasn't even made the transition to a subtropical cyclone. The last of the visible satellite imagery, along with shortwave infrared satellite imagery, and buoy data indicate a complete lack of westerly winds along the south side of the circulation, as well as some northeasterly winds along the western flank of the circulation, indicating that the system has indeed lost the closed surface circulation it once had. The broad and ill-defined center is elongated SW to NE, owing to strong westerly shear in excess of 30 kt. Based on the aforementioned meteorological tools, I have done my best to take a shot at guessing the poorly-defined circulation center, and I have fixed a center at 26N 67W. 90L had a slight center relocation today.
Analysis of water vapor imagery, along with certain CIMSS products, indicates that a weak but elongated upper-level low has pinched off from the shortwave trough to the NW of the system, near 27N 66W. Steering currents within the vicinity of the upper low are weak to nonexistent, and so this low will move very little over the next 24 hours. Even if it attempts to collocate itself about the surface center (a sign of subtropical transition), strong upper-level shear will quickly decouple the two circulations. All of the computer models predict the current shortwave to the NW of the system to completely dissipate within 24 hours. During this time, the models agree that upper-level shear should subside enough to the point where the aforementioned upper low can align itself above the surface center. This is when any potential transition into a subtropical cyclone will start to transpire. Additionally, with the upper low collocated above the surface center, vertical shear will remain considerably lessened beyond 24 hours, because shear is weak along the axis of any system. This will allow 90L to continue deepening as it moves slowly N along the western edge of the subtropical ridge, since shear stays favorable.
This N motion should continue until around 72 hours, at which point a turn to the NW is expected. The transition to a subtropical cyclone should be complete probably by around 36-42 hours. By day four, the system will be making its point of closest approach to the East Coast of the United States, at which point all models foresee it being just east of the North Carolina coast. However, one very interesting trend in the models that started with the GFS this time yesterday, is the absorption of 90L/Alex into a large extratropical low forecast to drop southward from the North Atlantic Ocean on the afternoon of May 26. While I would prefer to see a little bit more consistency, since the models may not foresee any additional center reformations until the system becomes better organized (and thus in turn, the ultimate position of the system relative to the east coast could be a couple degrees off), other models aside from the GFS have been following suit in this possible absorption, and this cannot be completely ignored at this point. We will see how things evolve in the model fields over the next day or so. Said assimilation could occur either before or after landfall. It's too early to tell at this point which scenario is correct.
I do eventually foresee 90L/Alex getting close to the North Carolina coast by the afternoon of the 26th, and it is anybody's guess as to what might happen at that point. It could continue inland before becoming extratropical, owing to the aforementioned Atlantic extratropical low, or it could skip landfall entirely and become absorbed a day or so earlier. Or, it could simply meander slowly off the coast until the low absorbs it.
Synopsis in layman's terms
Invest 90L has the potential to become a subtropical cyclone prior to reaching the North Carolina coast on Wednesday, May 26. I put the odds of this happening at about 40%. Regardless of development, gale force winds will develop in association with the system, particularly on the north side, owing to the large pressure gradient between the low and the subtropical ridge. These winds will produce rip currents and high surf all across the eastern seaboard, from Georgia all the way up to perhaps Virginia, over the next several days. There is large uncertainty in what 90L/Alex will do after nearing the coast on day four. Interests all along the Carolinas and Virginia should carefully monitor the progress of this system over the next several days.
Caribbean low pressure area
In about a week from now, all of the models, save the GFS, foresee an area of disturbed weather across the western Caribbean. The overall trend for this has been further west. I still do not really buy into this scenario, as I would like to see some consistency in the time frame, something we've not had thus far with this potential system. However, models have been consistent in gradually lifting out the vertical shear across the southwest, central, and even a portion of the western Caribbean by around five days. This will allow any potential area of disturbed weather that forms there to take advantage of the favorable upper-level conditions, and potentially spin up. Any system forming here would likely move eastward, owing to the weakened subtropical ridge, imparted by the aforementioned North Atlantic extratropical low, the same one forecast to absorb 90L/Alex. While Haiti may not be a direct target, it still needs to be on guard for possible flash flooding and mudslides associated with anything that might form in this area.
Synopsis in layman's terms
Models continue to predict the possibility of an area of disturbed weather across the Caribbean in about a week. The trend has been further west with regards to location, and it now appears that any system that develops will do so in the western or west-central Caribbean. Anything forming here would head eastward, putting portions of the Greater Antilles at risk for heavy rainfall and mudslides.
Invest 90L continues to look highly disorganized, and it appears that if there was indeed a closed surface center this time yesterday, it has since dissipated, and the system is now an open trough. However, this is largely negligible because the system is a non-tropical entity, and hasn't even made the transition to a subtropical cyclone. The last of the visible satellite imagery, along with shortwave infrared satellite imagery, and buoy data indicate a complete lack of westerly winds along the south side of the circulation, as well as some northeasterly winds along the western flank of the circulation, indicating that the system has indeed lost the closed surface circulation it once had. The broad and ill-defined center is elongated SW to NE, owing to strong westerly shear in excess of 30 kt. Based on the aforementioned meteorological tools, I have done my best to take a shot at guessing the poorly-defined circulation center, and I have fixed a center at 26N 67W. 90L had a slight center relocation today.
Analysis of water vapor imagery, along with certain CIMSS products, indicates that a weak but elongated upper-level low has pinched off from the shortwave trough to the NW of the system, near 27N 66W. Steering currents within the vicinity of the upper low are weak to nonexistent, and so this low will move very little over the next 24 hours. Even if it attempts to collocate itself about the surface center (a sign of subtropical transition), strong upper-level shear will quickly decouple the two circulations. All of the computer models predict the current shortwave to the NW of the system to completely dissipate within 24 hours. During this time, the models agree that upper-level shear should subside enough to the point where the aforementioned upper low can align itself above the surface center. This is when any potential transition into a subtropical cyclone will start to transpire. Additionally, with the upper low collocated above the surface center, vertical shear will remain considerably lessened beyond 24 hours, because shear is weak along the axis of any system. This will allow 90L to continue deepening as it moves slowly N along the western edge of the subtropical ridge, since shear stays favorable.
This N motion should continue until around 72 hours, at which point a turn to the NW is expected. The transition to a subtropical cyclone should be complete probably by around 36-42 hours. By day four, the system will be making its point of closest approach to the East Coast of the United States, at which point all models foresee it being just east of the North Carolina coast. However, one very interesting trend in the models that started with the GFS this time yesterday, is the absorption of 90L/Alex into a large extratropical low forecast to drop southward from the North Atlantic Ocean on the afternoon of May 26. While I would prefer to see a little bit more consistency, since the models may not foresee any additional center reformations until the system becomes better organized (and thus in turn, the ultimate position of the system relative to the east coast could be a couple degrees off), other models aside from the GFS have been following suit in this possible absorption, and this cannot be completely ignored at this point. We will see how things evolve in the model fields over the next day or so. Said assimilation could occur either before or after landfall. It's too early to tell at this point which scenario is correct.
I do eventually foresee 90L/Alex getting close to the North Carolina coast by the afternoon of the 26th, and it is anybody's guess as to what might happen at that point. It could continue inland before becoming extratropical, owing to the aforementioned Atlantic extratropical low, or it could skip landfall entirely and become absorbed a day or so earlier. Or, it could simply meander slowly off the coast until the low absorbs it.
Synopsis in layman's terms
Invest 90L has the potential to become a subtropical cyclone prior to reaching the North Carolina coast on Wednesday, May 26. I put the odds of this happening at about 40%. Regardless of development, gale force winds will develop in association with the system, particularly on the north side, owing to the large pressure gradient between the low and the subtropical ridge. These winds will produce rip currents and high surf all across the eastern seaboard, from Georgia all the way up to perhaps Virginia, over the next several days. There is large uncertainty in what 90L/Alex will do after nearing the coast on day four. Interests all along the Carolinas and Virginia should carefully monitor the progress of this system over the next several days.
Caribbean low pressure area
In about a week from now, all of the models, save the GFS, foresee an area of disturbed weather across the western Caribbean. The overall trend for this has been further west. I still do not really buy into this scenario, as I would like to see some consistency in the time frame, something we've not had thus far with this potential system. However, models have been consistent in gradually lifting out the vertical shear across the southwest, central, and even a portion of the western Caribbean by around five days. This will allow any potential area of disturbed weather that forms there to take advantage of the favorable upper-level conditions, and potentially spin up. Any system forming here would likely move eastward, owing to the weakened subtropical ridge, imparted by the aforementioned North Atlantic extratropical low, the same one forecast to absorb 90L/Alex. While Haiti may not be a direct target, it still needs to be on guard for possible flash flooding and mudslides associated with anything that might form in this area.
Synopsis in layman's terms
Models continue to predict the possibility of an area of disturbed weather across the Caribbean in about a week. The trend has been further west with regards to location, and it now appears that any system that develops will do so in the western or west-central Caribbean. Anything forming here would head eastward, putting portions of the Greater Antilles at risk for heavy rainfall and mudslides.
Friday, May 21, 2010
This storm is the first in a series of three hurricanes that made landfall along the southeast Louisiana coast during the destructive 1860 Atlantic hurricane season. The hurricane caused a total of $260,000 (1860 USD) in damage, and killed over 47 people across its destructive trek.
Storm History
A tropical storm was first detected about 100 miles west of Tampa, Florida in the early morning hours of August 8, already packing estimated sustained winds of 45 kt (50 mph). This system likely formed a couple days earlier, to the east of the eastern Florida coastline, likely within the vicinity of the northern Bahamas. The recently formed tropical cyclone moved steadily westward across the northern Gulf of Mexico, under the influence of a concentrated area of easterly flow along the south side of the subtropical ridge, which extended westward to about the Mississippi coast. By the late afternoon hours of August 9, the cyclone attained hurricane status while located a couple hundred miles south of Pensacola, Florida, still moving westward. In the early morning hours of August 11, the system is estimated to have become a major hurricane while centered about 120 miles south of the Mouth of the Mississippi River. The hurricane was still moving westward at this time, but was quickly slowing down, as steering currents collapsed due to the weakening of the subtropical ridge.
Consequently, the hurricane took a northwesterly turn shortly thereafter, still moving painfully slow. Late that afternoon, the hurricane began to speed up, while also gradually turning northward and northeastward, owing to a further collapse of the ridge. The hurricane reached an estimated peak intensity of 110 kt (130 mph) before making its landfall just to the west of the western tip of Plaquemines Parish late on the evening of August 11. After landfall, the hurricane accelerated northeastward as steering currents restrengthened with the approach of a shortwave trough. Because of the swift forward speed of the tropical cyclone, it was able to retain Category 3 status as it moved across southern Mississippi. It weakened to a Category 1 hurricane by the time it had entered western Alabama late in the afternoon of August 12. The cyclone then began to take on a more easterly component of motion, riding the north side of the subtropical ridge. The cyclone weakened to a tropical storm late that same evening, and continued eastward through southern Alabama and Georgia, eventually emerging into the western Atlantic just offshore the southwestern coast of South Carolina near noon on August 14.
Shortly after the early morning hours of August 15, the cyclone once again turned northeastward ahead of the aforementioned trough, and ceased being tracked while located at 33.3N 72.0W. During this time, the cyclone still had 50 kt (60 mph) sustained winds near its center, though these were likely confined to the eastern or northeastern quadrant of the weakening circulation. This system likely later became an extratropical gale center as it moved across the higher latitudes of the north Atlantic.
Track
Figure 1. Track of the hurricane.
Impact
Louisiana
A 12 foot storm surge submerged portions of the Mississippi River Delta. Most of the buildings in Proctorville were destroyed, along with its lighthouse. Additionally, the lighthouse at Bayou St. John was also destroyed, along with the lighthouse keeper's dwelling; the Cat Island tower was also destroyed by the powerful hurricane. Cat Island itself was inundated by surge, which drowned all 300 cows on the island. The hurricane also destroyed a sizable portion of the sugar cane crop, as well as the corn and rice crops. In the small community of Pilottown, located in Plaquemines Parish, the hurricane uprooted trees; a 10 foot storm surge also inundated the parish. The Mississippi River rose a total of three feet during the hurricane.
Mississippi
Louisiana was not the only state impacted by the ferocious hurricane. Storm surges were observed east of the cyclone's center, all along the Mississippi coast.
Florida
Though no major effects occurred, there was some impact to the western Florida Panhandle. On August 11, Pensacola received 3.03 inches of rain, as well as gale force winds.
Storm History
A tropical storm was first detected about 100 miles west of Tampa, Florida in the early morning hours of August 8, already packing estimated sustained winds of 45 kt (50 mph). This system likely formed a couple days earlier, to the east of the eastern Florida coastline, likely within the vicinity of the northern Bahamas. The recently formed tropical cyclone moved steadily westward across the northern Gulf of Mexico, under the influence of a concentrated area of easterly flow along the south side of the subtropical ridge, which extended westward to about the Mississippi coast. By the late afternoon hours of August 9, the cyclone attained hurricane status while located a couple hundred miles south of Pensacola, Florida, still moving westward. In the early morning hours of August 11, the system is estimated to have become a major hurricane while centered about 120 miles south of the Mouth of the Mississippi River. The hurricane was still moving westward at this time, but was quickly slowing down, as steering currents collapsed due to the weakening of the subtropical ridge.
Consequently, the hurricane took a northwesterly turn shortly thereafter, still moving painfully slow. Late that afternoon, the hurricane began to speed up, while also gradually turning northward and northeastward, owing to a further collapse of the ridge. The hurricane reached an estimated peak intensity of 110 kt (130 mph) before making its landfall just to the west of the western tip of Plaquemines Parish late on the evening of August 11. After landfall, the hurricane accelerated northeastward as steering currents restrengthened with the approach of a shortwave trough. Because of the swift forward speed of the tropical cyclone, it was able to retain Category 3 status as it moved across southern Mississippi. It weakened to a Category 1 hurricane by the time it had entered western Alabama late in the afternoon of August 12. The cyclone then began to take on a more easterly component of motion, riding the north side of the subtropical ridge. The cyclone weakened to a tropical storm late that same evening, and continued eastward through southern Alabama and Georgia, eventually emerging into the western Atlantic just offshore the southwestern coast of South Carolina near noon on August 14.
Shortly after the early morning hours of August 15, the cyclone once again turned northeastward ahead of the aforementioned trough, and ceased being tracked while located at 33.3N 72.0W. During this time, the cyclone still had 50 kt (60 mph) sustained winds near its center, though these were likely confined to the eastern or northeastern quadrant of the weakening circulation. This system likely later became an extratropical gale center as it moved across the higher latitudes of the north Atlantic.
Track
Figure 1. Track of the hurricane.
Impact
Louisiana
A 12 foot storm surge submerged portions of the Mississippi River Delta. Most of the buildings in Proctorville were destroyed, along with its lighthouse. Additionally, the lighthouse at Bayou St. John was also destroyed, along with the lighthouse keeper's dwelling; the Cat Island tower was also destroyed by the powerful hurricane. Cat Island itself was inundated by surge, which drowned all 300 cows on the island. The hurricane also destroyed a sizable portion of the sugar cane crop, as well as the corn and rice crops. In the small community of Pilottown, located in Plaquemines Parish, the hurricane uprooted trees; a 10 foot storm surge also inundated the parish. The Mississippi River rose a total of three feet during the hurricane.
Mississippi
Louisiana was not the only state impacted by the ferocious hurricane. Storm surges were observed east of the cyclone's center, all along the Mississippi coast.
Florida
Though no major effects occurred, there was some impact to the western Florida Panhandle. On August 11, Pensacola received 3.03 inches of rain, as well as gale force winds.
Tuesday, May 18, 2010
Louisiana hurricane history - Part 2: 1856 Last Island hurricane (Aug 9 - Aug 12)
The "Last Island" hurricane of August 1856 was a particularly strong and destructive Category 4 hurricane, having attained 130 kt (150 mph) winds prior to its landfall in southeastern Louisiana at that intensity. This hurricane was unusual in that it became so strong during only the second week of August. The exact amount of deaths brought on by the hurricane are unknown, but is estimated anywhere between 200-400. The hurricane was so destructive that it caused the once resort known as Last Island to split into several small barrier islands, now known as Isle Dernieres.
Storm History
The origins of this hurricane is quite unclear, but it could have formed in one of two ways: a) from a complex interaction of several meteorological features over across the western Atlantic and adjacent Bahama Islands, a la Hurricane Katrina in 2005, or b) from a tropical wave that emerged from the west coast of Africa, formed into a Cape Verde hurricane in the far eastern Atlantic Ocean, and moved WNW across the Greater Antilles, a la Hurricane 5 during the exact same year. Regardless of the origin, it is clear that this hurricane's circulation had fully recovered from possible passage over the island(s) of the Greater Antilles, as evidenced by its rapid intensification from the morning of August 9, when it was first detected, (during which time it was located less than 150 miles WNW of the Dry Tortugas) up until its landfall late on the evening of August 10.
Initially, the hurricane moved steadily west-northwest. Eventually, however, the subtropical ridge collapsed somewhat, allowing for a northwesterly component of motion as the hurricane neared the coast. This northwestern turn occurred near noon on the 10th. During this time, the hurricane attained Category 4 status while centered less than 100 miles south of the Mouth of the Mississippi River. Also from this point onward, the forward speed of the hurricane gradually slowed as the ridge continued to steadily weaken with the approach of a shortwave trough to the west. Approximately twelve hours after attaining Category 4, the hurricane attained its estimated peak intensity of 150 mph and 934 mb (though, again, NOAA now suspects that the hurricane could have flirted with Category 5 status, meaning that it had winds of 155 mph, and I am inclined to agree with this -- quite strongly I might add, particularly due to the fact that the hurricane was still intensifying up until landfall, which implies that the friction from land interaction may have tightened up the circulation and deepened the convection within the eyewall both during and shortly after landfall) just as it made landfall between Cocodrie and Morgan City.
During the last two and a half days of its existence, namely when it was located at 27.7N 89.1W, the hurricane took a very similar path as 1992's Hurricane Andrew, owing to a very similar -- nearly identical, synoptic steering pattern, embedded between a trough to the west and a ridge to the east. After landfall, the devastating hurricane slowed to a crawl as it moved very slowly northwest, then northward across central Louisiana for nearly two days. The hurricane passed about 50 miles to the west of the capital city of Baton Rouge as a hurricane around noontime on the 11th. Finally, steering currents began to restrengthen in the early morning hours of August 12 as the aforementioned trough drew ever closer to the tropical cyclone, which was nearing southwestern Mississippi at this time. Shortly thereafter, the system officially ceased being tracked, though it is still estimated to have contained sustained winds of 45 kt (50 mph) during this time, and so it is likely that the system persisted for at least another twelve hours, and probably dissipated somewhere over eastern Mississippi.
Track
Figure 1. Track of the hurricane.
Impact
New Orleans received a staggering 13.14 inches of rain from the storm. Further west, the town of Abbeville, located in Vermilion Parish, was completely destroyed by the monstrous hurricane. Additionally, severe flooding was experienced throughout Plaquemines Parish.
On August 9, inhabitants on the island noticed a frightening roaring sound emanating from the Gulf of Mexico, which would soon turn very violent. During this time, cattle that were present on the island paced nervously back and forth for several hours, clearly sensing danger. Later that day, the skies darkened as torrential rainfall began to fall, with the slow-moving hurricane impacting the general area for two consecutive days. All 100 of the structures on Last Island was destroyed by the ferocious hurricane.
On August 10, tourists on the island noted the ferocity of the waves as the hurricane was approaching. Later on, a survivor, Rev. Robert McAllister, would write a rather frightening but simultaneously sobering excerpt on the destructive hurricane: "Each breaker extended to the right and left as far as the eye, straining its vision, could reach... We did not know then as we did afterwards that the voice of those many waters was solemnly saying to us, 'Escape for thy life."
One other interesting thing about this storm is the story of the tourists on the island attending a party at the hotel, while the hurricane drew ever closer, the winds outside steadily increasing. When the storm made landfall on the 10th, the conditions outside rapidly worsening, the aforementioned tourists anxiously awaited the arrival of the island's service steamer, labeled Star, but it failed to arrive in time. At around 4 AM on the morning of August 10, the hurricane's massive storm surge inundated the entire island, obliterating all of the structures present therein, including the multiple-story resort hotel. Star was grounded by the ferocious cyclone, although fortunately, a few people managed to survive by climbing aboard the now wrecked vessel.
After the event, Last Island was split into several small barrier islands, and these islands reportedly remained submerged for several days after the hurricane's passage, only to reappear as sandbars later. Subsequent to the powerful storm, the remains of the aforementioned vessel, Star, were the only evidence that an island had ever existed there. There were a total of 400 tourists on the island, but less than half survived the frightening storm.
Storm History
The origins of this hurricane is quite unclear, but it could have formed in one of two ways: a) from a complex interaction of several meteorological features over across the western Atlantic and adjacent Bahama Islands, a la Hurricane Katrina in 2005, or b) from a tropical wave that emerged from the west coast of Africa, formed into a Cape Verde hurricane in the far eastern Atlantic Ocean, and moved WNW across the Greater Antilles, a la Hurricane 5 during the exact same year. Regardless of the origin, it is clear that this hurricane's circulation had fully recovered from possible passage over the island(s) of the Greater Antilles, as evidenced by its rapid intensification from the morning of August 9, when it was first detected, (during which time it was located less than 150 miles WNW of the Dry Tortugas) up until its landfall late on the evening of August 10.
Initially, the hurricane moved steadily west-northwest. Eventually, however, the subtropical ridge collapsed somewhat, allowing for a northwesterly component of motion as the hurricane neared the coast. This northwestern turn occurred near noon on the 10th. During this time, the hurricane attained Category 4 status while centered less than 100 miles south of the Mouth of the Mississippi River. Also from this point onward, the forward speed of the hurricane gradually slowed as the ridge continued to steadily weaken with the approach of a shortwave trough to the west. Approximately twelve hours after attaining Category 4, the hurricane attained its estimated peak intensity of 150 mph and 934 mb (though, again, NOAA now suspects that the hurricane could have flirted with Category 5 status, meaning that it had winds of 155 mph, and I am inclined to agree with this -- quite strongly I might add, particularly due to the fact that the hurricane was still intensifying up until landfall, which implies that the friction from land interaction may have tightened up the circulation and deepened the convection within the eyewall both during and shortly after landfall) just as it made landfall between Cocodrie and Morgan City.
During the last two and a half days of its existence, namely when it was located at 27.7N 89.1W, the hurricane took a very similar path as 1992's Hurricane Andrew, owing to a very similar -- nearly identical, synoptic steering pattern, embedded between a trough to the west and a ridge to the east. After landfall, the devastating hurricane slowed to a crawl as it moved very slowly northwest, then northward across central Louisiana for nearly two days. The hurricane passed about 50 miles to the west of the capital city of Baton Rouge as a hurricane around noontime on the 11th. Finally, steering currents began to restrengthen in the early morning hours of August 12 as the aforementioned trough drew ever closer to the tropical cyclone, which was nearing southwestern Mississippi at this time. Shortly thereafter, the system officially ceased being tracked, though it is still estimated to have contained sustained winds of 45 kt (50 mph) during this time, and so it is likely that the system persisted for at least another twelve hours, and probably dissipated somewhere over eastern Mississippi.
Track
Figure 1. Track of the hurricane.Impact
New Orleans received a staggering 13.14 inches of rain from the storm. Further west, the town of Abbeville, located in Vermilion Parish, was completely destroyed by the monstrous hurricane. Additionally, severe flooding was experienced throughout Plaquemines Parish.
On August 9, inhabitants on the island noticed a frightening roaring sound emanating from the Gulf of Mexico, which would soon turn very violent. During this time, cattle that were present on the island paced nervously back and forth for several hours, clearly sensing danger. Later that day, the skies darkened as torrential rainfall began to fall, with the slow-moving hurricane impacting the general area for two consecutive days. All 100 of the structures on Last Island was destroyed by the ferocious hurricane.
On August 10, tourists on the island noted the ferocity of the waves as the hurricane was approaching. Later on, a survivor, Rev. Robert McAllister, would write a rather frightening but simultaneously sobering excerpt on the destructive hurricane: "Each breaker extended to the right and left as far as the eye, straining its vision, could reach... We did not know then as we did afterwards that the voice of those many waters was solemnly saying to us, 'Escape for thy life."
One other interesting thing about this storm is the story of the tourists on the island attending a party at the hotel, while the hurricane drew ever closer, the winds outside steadily increasing. When the storm made landfall on the 10th, the conditions outside rapidly worsening, the aforementioned tourists anxiously awaited the arrival of the island's service steamer, labeled Star, but it failed to arrive in time. At around 4 AM on the morning of August 10, the hurricane's massive storm surge inundated the entire island, obliterating all of the structures present therein, including the multiple-story resort hotel. Star was grounded by the ferocious cyclone, although fortunately, a few people managed to survive by climbing aboard the now wrecked vessel.
After the event, Last Island was split into several small barrier islands, and these islands reportedly remained submerged for several days after the hurricane's passage, only to reappear as sandbars later. Subsequent to the powerful storm, the remains of the aforementioned vessel, Star, were the only evidence that an island had ever existed there. There were a total of 400 tourists on the island, but less than half survived the frightening storm.
Sunday, May 16, 2010
Louisiana hurricane history - Part 1: 1855 hurricane (Sep 15 - Sep 17)
Storm History
A particularly strong and damaging hurricane, this particular storm was first detected as a rapidly intensifying Category 1 hurricane about 250-300 miles south of the Mouth of the Mississippi River on September 15, 1855. It is likely that this hurricane originated, given the track, as a tropical wave that moved off the coast of Africa during the first of the month. At the time, the storm had estimated 1 minute sustained surface winds of 70 kt (80 mph), and was moving very slowly to the north, owing to a weak and flattened ridge to the east, which imparted a solid southerly steering regime over the hurricane, which caused it to move northward. Later that afternoon, the system took a brief jog to the northwest. This jog was probably not due to a brief, local restrengthening of the aforementioned ridge.
Rather, it was more likely due to internal structural changes within the eyewall, common of hurricanes at Category 2 intensity and above (96+ mph, Saffir-Simpson Hurricane Scale). Though the science is presently not well understood, it is speculated that sudden convective changes within the eyewall can cause a hurricane to make unexpected jogs, sometimes lasting up to several hours. Needless to say, such jogs (or, more commonly referred to as "wobbles") can be crucial with regards to a particular location feeling or escaping the brunt of a hurricane.
Late that evening, the hurricane had intensified into a major hurricane (111+ mph), having achieved Category 3 intensity less than 200 miles from the Mouth of the Mississippi River. At this time, the hurricane's maximum sustained winds (1-minute) are estimated to be at 105 kt (120 mph). Also during this time, the hurricane accelerated northward slightly as the southerly winds around the ridge strengthened, the hurricane having completed its earlier northwesterly jog. Just a little over six hours later, the hurricane made landfall in central Plaquemines Parish, Louisiana, having continued rapidly intensifying up until landfall. Though the maximum sustained winds within the hurricane are estimated to be at 110 kt (130 mph) during the time of landfall, I find it more likely that it was a low-end Category 4, and more likely had winds of 115 kt (135 mph).
I base this on the following: the hurricane, on the fifth "best track" extrapolated position (as seen on the track below), when it was located approximately 28.8N 89.5W in the early morning hours of September 16, had still not fully moved ashore (though the northern eyewall may have been experienced from Buras to Venice during this time). This, along with with the northern eyewall interacting with land, may have generated enough friction to tighten up the circulation a bit as well as enhance the convection in the eyewall, which in turned strengthened the surface winds. I am in agreement with most of the intensity noted on the track below, though I suspect that the cyclone maintained hurricane status a bit further inland across southeastern Mississippi than is estimated. I suspect that the system finally met its demise across the mountains of eastern Tennessee, undoubtedly triggering heavy rainfall and severe weather there.
Track
Figure 1. Track of the hurricane.
Impact
Louisiana
The wharf and bathhouses were destroyed, while four feet of water is estimated to have inundated Proctor's Landing. Water rises were noted across Lake Borgne as early as the afternoon of September 15, while the hurricane was still over 200 miles offshore. Several homes were destroyed in the vicinity of Lake Borgne, as the winds increased from a "smart breeze" by sunset to a "perfect hurricane" by midnight.
Mississippi
On Cat Island, the lighthouse keeper's dwelling was decimated, with the lighthouse itself being decayed into a state of "severe peril". Both the Atchafalaya and Ship Shoal lighthouses were grounded, having been torn from their moorings. Both lighthouses would later be repaired and fully operational again in 1856.
The ship Venice was pushed onto the banks of the Mississippi River by the hurricane's strong winds. As a result, said ship experienced leaking. Lastly, the steamer J.S. Chenoweth sank to the bottom of the Mississippi.
Florida
Impacts were felt as far east as Apalachicola Bay offshore northwestern Florida. Interestingly, the hurricane appears to be rather small, evidenced by a pressure reading of merely 29.93" (1013 mb) at New Orleans at 7 AM on September 16 as the eye passed around 20-25 miles east of that city. However, given the undoubtedly large pressure gradient (evidenced by the ridge to the east) apparent across the northern and northeastern Gulf of Mexico during this time, it is not so unfathomable that impacts were felt as far east as Apalachicola Bay. Remember, strong winds experienced far away from the center of a hurricane are not always a direct result of the hurricane itself; in some cases, a large and powerful pressure gradient (the difference between low and high pressure) is the catalyst for strong winds.
I suspect that such was the case here as well, and why New Orleans received very little in the way of any significant impacts from the hurricane, despite having its eye pass less than 30 miles to the east, and why Apalachicola Bay received some impact, despite being much further away from the eye. I suspect that rain impacts were minimal to nonexistent there, and the primary impact came from wave action/storm surge, along with perhaps some 25-30 kt (30 to 35 mph) gusts.
A particularly strong and damaging hurricane, this particular storm was first detected as a rapidly intensifying Category 1 hurricane about 250-300 miles south of the Mouth of the Mississippi River on September 15, 1855. It is likely that this hurricane originated, given the track, as a tropical wave that moved off the coast of Africa during the first of the month. At the time, the storm had estimated 1 minute sustained surface winds of 70 kt (80 mph), and was moving very slowly to the north, owing to a weak and flattened ridge to the east, which imparted a solid southerly steering regime over the hurricane, which caused it to move northward. Later that afternoon, the system took a brief jog to the northwest. This jog was probably not due to a brief, local restrengthening of the aforementioned ridge.
Rather, it was more likely due to internal structural changes within the eyewall, common of hurricanes at Category 2 intensity and above (96+ mph, Saffir-Simpson Hurricane Scale). Though the science is presently not well understood, it is speculated that sudden convective changes within the eyewall can cause a hurricane to make unexpected jogs, sometimes lasting up to several hours. Needless to say, such jogs (or, more commonly referred to as "wobbles") can be crucial with regards to a particular location feeling or escaping the brunt of a hurricane.
Late that evening, the hurricane had intensified into a major hurricane (111+ mph), having achieved Category 3 intensity less than 200 miles from the Mouth of the Mississippi River. At this time, the hurricane's maximum sustained winds (1-minute) are estimated to be at 105 kt (120 mph). Also during this time, the hurricane accelerated northward slightly as the southerly winds around the ridge strengthened, the hurricane having completed its earlier northwesterly jog. Just a little over six hours later, the hurricane made landfall in central Plaquemines Parish, Louisiana, having continued rapidly intensifying up until landfall. Though the maximum sustained winds within the hurricane are estimated to be at 110 kt (130 mph) during the time of landfall, I find it more likely that it was a low-end Category 4, and more likely had winds of 115 kt (135 mph).
I base this on the following: the hurricane, on the fifth "best track" extrapolated position (as seen on the track below), when it was located approximately 28.8N 89.5W in the early morning hours of September 16, had still not fully moved ashore (though the northern eyewall may have been experienced from Buras to Venice during this time). This, along with with the northern eyewall interacting with land, may have generated enough friction to tighten up the circulation a bit as well as enhance the convection in the eyewall, which in turned strengthened the surface winds. I am in agreement with most of the intensity noted on the track below, though I suspect that the cyclone maintained hurricane status a bit further inland across southeastern Mississippi than is estimated. I suspect that the system finally met its demise across the mountains of eastern Tennessee, undoubtedly triggering heavy rainfall and severe weather there.
Track
Figure 1. Track of the hurricane.Impact
Louisiana
The wharf and bathhouses were destroyed, while four feet of water is estimated to have inundated Proctor's Landing. Water rises were noted across Lake Borgne as early as the afternoon of September 15, while the hurricane was still over 200 miles offshore. Several homes were destroyed in the vicinity of Lake Borgne, as the winds increased from a "smart breeze" by sunset to a "perfect hurricane" by midnight.
Mississippi
On Cat Island, the lighthouse keeper's dwelling was decimated, with the lighthouse itself being decayed into a state of "severe peril". Both the Atchafalaya and Ship Shoal lighthouses were grounded, having been torn from their moorings. Both lighthouses would later be repaired and fully operational again in 1856.
The ship Venice was pushed onto the banks of the Mississippi River by the hurricane's strong winds. As a result, said ship experienced leaking. Lastly, the steamer J.S. Chenoweth sank to the bottom of the Mississippi.
Florida
Impacts were felt as far east as Apalachicola Bay offshore northwestern Florida. Interestingly, the hurricane appears to be rather small, evidenced by a pressure reading of merely 29.93" (1013 mb) at New Orleans at 7 AM on September 16 as the eye passed around 20-25 miles east of that city. However, given the undoubtedly large pressure gradient (evidenced by the ridge to the east) apparent across the northern and northeastern Gulf of Mexico during this time, it is not so unfathomable that impacts were felt as far east as Apalachicola Bay. Remember, strong winds experienced far away from the center of a hurricane are not always a direct result of the hurricane itself; in some cases, a large and powerful pressure gradient (the difference between low and high pressure) is the catalyst for strong winds.
I suspect that such was the case here as well, and why New Orleans received very little in the way of any significant impacts from the hurricane, despite having its eye pass less than 30 miles to the east, and why Apalachicola Bay received some impact, despite being much further away from the eye. I suspect that rain impacts were minimal to nonexistent there, and the primary impact came from wave action/storm surge, along with perhaps some 25-30 kt (30 to 35 mph) gusts.
Monday, May 3, 2010
My spiritual journey
My spiritual journey has been, at least to me, a rather interesting, and also frightening journey. In its simplest form, I am an ex-Christian who is presently a weak atheist (or "agnostic atheist", if you prefer). Onto the actual story.
I was raised in a strongly Christian (specifically Protestant) household. Naturally (because children, generally, when indoctrinated into a particular mindset or belief, don't often question it), I believed in the Christian God throughout my childhood. At around age nine, I first accepted Jesus Christ as my Lord and Savior. Upon said acceptance, I felt an immense degree of joy. Perhaps expectantly, given that I was a young child at the time (though, not to sound offensive, this would likely suffice for most adults, as well), this, to me, was definitive proof of the existence of the Christian God.
Despite this fact, however, I really didn't take Christianity all that seriously after the first couple years or so. Fast forward to the summer of 2004, and I once again asked Christ into my heart. This time, I truly lived the life of a Christian. In fact, no sooner had I started spreading the gospel (despite all of my theological inexperience, which, in hindsight, was actually more detrimental than beneficial) of Jesus Christ, and the good news of salvation, all over the internet. Indeed, for several months there, I never put down my Bible, and I never stopped praying. I had, to say the least, a passion for the Christian God.
In fact, believe it or not (and not to toot my horn because, if the Christian God does actually exist, then it was his doing, not mine), I won approximately eight people to Jesus Christ, and I still retain contact with some of these people today (though most are unaware of my recent apostasy). At this point, I had experienced enough that I naively thought that I had objective evidence for the existence of this particular god (this also reaffirmed what I perceived to be "proof" of the Christian God) -- namely, the conversions of nonbelievers/non-practicing Christians to Jesus Christ. In case that sounds offensive to the layman, I'm not saying that there can't (or isn't) be evidence for the existence of the Christian God. Rather, what I'm saying is that there is no objective (meaning completely obvious to each person, regardless of whether or not they believe in said god) evidence for such a deity. Subjectively, it's obviously a different story, since subjectivity implies that said evidence is only sufficient for a single individual, rather than humanity as a whole.
After this is where the interesting bit begins. From this point onward, I gradually stopped reading my Bible as well as engaging in daily prayer. Needless to say, for anyone even slightly theologically inclined (even outside Christianity), the aforementioned acts are critically important for spiritual growth. Without that, your faith quickly becomes weak, and susceptible to collapse. At this point, you're probably thinking "What happened? How did he so rapidly lose passion for God, when he was winning souls? What caused him to stop reading/praying?". And you know something? You would be completely justified in your curiosity. Hence, it is therefore my obligation to enlighten you. After all, there had to be a catalyst for my sudden and unexpected change. Cause and effect, right?
To make a long story short, several months after turning 13, I began to notice the immense degree of dogmatism and intolerance that most Protestants in my area seemed to so strongly hold (at least from my perspective). Of course, as to not make a generalization here (as that would just be wrong, both ethically and intellectually), I want to note that I am not attempting to speak for all Protestants, and especially not all Christians. Anyhow, I gradually became fed up with this dogmatism (as well as the fact that practically all the Christians I had ever conversed with or had known, family included, provided any real satisfactory answers to tough theological questions pertaining to the religion) and, while I still believed in the Christian God for a few years after that, I gradually lost interest in Christianity.
Though I did not label myself as such during this time, I realize that, in hindsight, I became an agnostic during the fall of 2007. This is where my deconversion truly began. While I didn't completely dismiss Christianity at this point, I was largely apathetic, as well as somewhat hostile. Finally, during the summer of 2008 (August), I officially declared myself an atheist. I was a strong atheist at this time (without initially having been aware of that designation), and asserted certainty that, not only did the Christian God exist, no other gods existed, as well. Obviously, this was quite an intellectually dishonest opinion to hold, since certainty is not something that can be inferred theologically, because the supernatural is by definition untestable by science. Even if it wasn't, there are other, more complex issues that would prevent any actual proof (or disproof) to be found. This includes things such as sensory perception, and the fact that, even if science could explain a purported supernatural phenomenon(s) (in this case god(s), it doesn't necessarily mean that a divine mechanism isn't behind the phenomenon being scientifically explained.
I met some rather nice Christians on a Facebook group (which I still visit today) just a couple months later, and they completely changed my view on Christianity by displaying love, compassion, and tolerance, something I felt that most Christians in my area sorely lacked. They softened my heart and opened my mind enough to effectively eradicate my arrogance (I considered myself intellectually superior to any and all theists, not just Christians, after I declared myself an atheist, even to the point of derogatorily calling people "stupid") and intolerance for people of opposing religious viewpoints.
One Christian in particular, stood out, and we later became friends. From anonymity, as well as for the sake of respecting my friend's privacy, I will not mention his name here. Let's just say that he quickly became very eager in reconverting me to Christianity, promising me that he would answer my questions and bring me "good arguments"; again, something I felt (and still do) most Christians in my area lacked. This particular group, along with prolonged theological debate on the GameFAQs Religion board, gradually changed my personality. I became a weak atheist during this time (which, again, simply means that, while I am an atheist, I am also agnostic). In November 2009, I gave Christianity another try by asking Christ into my heart once again. I quickly realized that I still didn't believe.
...Aaaaaaaaaaaaaaand, I think that's about it. Until next time, amigos.
Oh, sorry for my ramblings. Terrible, I know. :/
I was raised in a strongly Christian (specifically Protestant) household. Naturally (because children, generally, when indoctrinated into a particular mindset or belief, don't often question it), I believed in the Christian God throughout my childhood. At around age nine, I first accepted Jesus Christ as my Lord and Savior. Upon said acceptance, I felt an immense degree of joy. Perhaps expectantly, given that I was a young child at the time (though, not to sound offensive, this would likely suffice for most adults, as well), this, to me, was definitive proof of the existence of the Christian God.
Despite this fact, however, I really didn't take Christianity all that seriously after the first couple years or so. Fast forward to the summer of 2004, and I once again asked Christ into my heart. This time, I truly lived the life of a Christian. In fact, no sooner had I started spreading the gospel (despite all of my theological inexperience, which, in hindsight, was actually more detrimental than beneficial) of Jesus Christ, and the good news of salvation, all over the internet. Indeed, for several months there, I never put down my Bible, and I never stopped praying. I had, to say the least, a passion for the Christian God.
In fact, believe it or not (and not to toot my horn because, if the Christian God does actually exist, then it was his doing, not mine), I won approximately eight people to Jesus Christ, and I still retain contact with some of these people today (though most are unaware of my recent apostasy). At this point, I had experienced enough that I naively thought that I had objective evidence for the existence of this particular god (this also reaffirmed what I perceived to be "proof" of the Christian God) -- namely, the conversions of nonbelievers/non-practicing Christians to Jesus Christ. In case that sounds offensive to the layman, I'm not saying that there can't (or isn't) be evidence for the existence of the Christian God. Rather, what I'm saying is that there is no objective (meaning completely obvious to each person, regardless of whether or not they believe in said god) evidence for such a deity. Subjectively, it's obviously a different story, since subjectivity implies that said evidence is only sufficient for a single individual, rather than humanity as a whole.
After this is where the interesting bit begins. From this point onward, I gradually stopped reading my Bible as well as engaging in daily prayer. Needless to say, for anyone even slightly theologically inclined (even outside Christianity), the aforementioned acts are critically important for spiritual growth. Without that, your faith quickly becomes weak, and susceptible to collapse. At this point, you're probably thinking "What happened? How did he so rapidly lose passion for God, when he was winning souls? What caused him to stop reading/praying?". And you know something? You would be completely justified in your curiosity. Hence, it is therefore my obligation to enlighten you. After all, there had to be a catalyst for my sudden and unexpected change. Cause and effect, right?
To make a long story short, several months after turning 13, I began to notice the immense degree of dogmatism and intolerance that most Protestants in my area seemed to so strongly hold (at least from my perspective). Of course, as to not make a generalization here (as that would just be wrong, both ethically and intellectually), I want to note that I am not attempting to speak for all Protestants, and especially not all Christians. Anyhow, I gradually became fed up with this dogmatism (as well as the fact that practically all the Christians I had ever conversed with or had known, family included, provided any real satisfactory answers to tough theological questions pertaining to the religion) and, while I still believed in the Christian God for a few years after that, I gradually lost interest in Christianity.
Though I did not label myself as such during this time, I realize that, in hindsight, I became an agnostic during the fall of 2007. This is where my deconversion truly began. While I didn't completely dismiss Christianity at this point, I was largely apathetic, as well as somewhat hostile. Finally, during the summer of 2008 (August), I officially declared myself an atheist. I was a strong atheist at this time (without initially having been aware of that designation), and asserted certainty that, not only did the Christian God exist, no other gods existed, as well. Obviously, this was quite an intellectually dishonest opinion to hold, since certainty is not something that can be inferred theologically, because the supernatural is by definition untestable by science. Even if it wasn't, there are other, more complex issues that would prevent any actual proof (or disproof) to be found. This includes things such as sensory perception, and the fact that, even if science could explain a purported supernatural phenomenon(s) (in this case god(s), it doesn't necessarily mean that a divine mechanism isn't behind the phenomenon being scientifically explained.
I met some rather nice Christians on a Facebook group (which I still visit today) just a couple months later, and they completely changed my view on Christianity by displaying love, compassion, and tolerance, something I felt that most Christians in my area sorely lacked. They softened my heart and opened my mind enough to effectively eradicate my arrogance (I considered myself intellectually superior to any and all theists, not just Christians, after I declared myself an atheist, even to the point of derogatorily calling people "stupid") and intolerance for people of opposing religious viewpoints.
One Christian in particular, stood out, and we later became friends. From anonymity, as well as for the sake of respecting my friend's privacy, I will not mention his name here. Let's just say that he quickly became very eager in reconverting me to Christianity, promising me that he would answer my questions and bring me "good arguments"; again, something I felt (and still do) most Christians in my area lacked. This particular group, along with prolonged theological debate on the GameFAQs Religion board, gradually changed my personality. I became a weak atheist during this time (which, again, simply means that, while I am an atheist, I am also agnostic). In November 2009, I gave Christianity another try by asking Christ into my heart once again. I quickly realized that I still didn't believe.
...Aaaaaaaaaaaaaaand, I think that's about it. Until next time, amigos.
Oh, sorry for my ramblings. Terrible, I know. :/
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