Tomas
Tropical Storm Tomas is slowly barreling toward western Haiti whilst gradually intensifying. As of the latest NHC intermediate (8:00 PM EDT) advisory, here is the latest information on Tomas:
Wind: 60 mph, with higher gusts
Movement: NNE at 8 mph
Pressure: 993 mb
Location: 16.9°N 75.9°W
Category: Tropical storm
Analysis of shortwave and infrared satellite loops indicate that Tomas is gradually becoming better organized as it approaches western Haiti. Deep convection has increased substantially in both areal coverage and intensity, and now completely covers the circulation center. Additionally, a large, loosely-defined convective band containing heavy precipitation stretches southward to northward for several hundred miles from Panama to Haiti, and then into Tomas' center.
Upper-level outflow is good to the northeast, fair to the east, and poor elsewhere, especially to the south and southwest. The poor outflow in these areas is being caused by 20 kt of southwesterly vertical wind shear associated with an unseasonably strong deep-layer trough and associated cold front currently moving across the Gulf of Mexico and western Atlantic. The latest run of the SHIPS model, however, depicts considerably shear of Tomas, only 13 kt. This is a rather sharp contrast to the aforementioned CIMSS observation. Given high-cloud motions observed on satellite imagery, I am inclined to go with the SHIPS model's assessment of the vertical shear.
The SHIPS model, along with the GFS, the latter of which has its observations based upon output from the SHIPS, forecast an upper-wind environment that is at least marginally conducive to continued gradual intensification of the tropical cyclone before it reaches the coast of eastern Cuba or western Haiti in about 18-24 hours.
Vertical shear is forecast to increase substantially by 30-36 hours, however, as Tomas loses its upper-level support and the upper flow becomes zonal. At that point, there are two scenarios, as depicted in the global model fields:
1. Tomas continues generally northward to north-northeastward under the influence of the aforementioned deep-layer trough, and quickly becomes extratropical as it enters an environment of strong baroclinicity.
2. Tomas instead moves generally eastward, remaining more distant to the trough. While this would prevent the cyclone from becoming extratropical, vertical shear would still be prohibitive enough to allow for the storm to weaken and ultimately dissipate.
The NHC is splitting the difference between the two scenarios, as a sort of compromise. Either way, Tomas will ultimately meet its demise over the western or central Atlantic Ocean over the next several days. Indeed, given the strong vertical shear profiles forecast by both the SHIPS and the GFS, Tomas may not survive throughout the entire forecast period (five days). Rapid weakening is certainly a distinct possibility once Tomas loses its upper-level support and moves into the aforementioned belt of westerly to southwesterly vertical shear.
I anticipate that Tomas will become a minimal hurricane with 75 mph winds over the next 24 hours, provided the center remains offshore. Any deviation to the right of the current NHC forecast track will bring the center of southwestern Haiti.
It is unlikely that Tomas will become anything stronger than an 80 mph hurricane due to an only marginally favorable upper-level wind environment andinteraction with the mountainous terrain of eastern Cuba and western Haiti.
The intensity of Tomas is wholly irrelevant however, as either way, the storm is likely to produce very heavy rains across eastern Cuba and western Haiti through at least Saturday. Like Jeff Masters, I suspect that the heaviest rains associated with Tomas will be found along the southwest and northwest Haitian peninsulas, since the cyclone appears to have moved farther west than what the NHC was predicting this time yesterday. I forecast that anywhere from 5 - 8 inches will fall over these peninsulas, with locally higher amounts. Lesser, but still heavy amounts, in excess of 3 - 6 inches, with locally higher amounts, are possible farther east across the country, both along coastal and inland areas. This includes the capital city of Port-au-Prince, where residents are still living in tents subsequent to the January 12 earthquake, and are also battling a cholera epidemic. Finally, Jamaica can anticipate 1 - 3 inches of rain, with locally higher amounts, particularly along the eastern end of the island, which has the greatest exposure to Tomas' heavy precipitation.
Rainfall in excess of 2 - 4 inches with locally higher amounts is also possible across the Dominican Republic, especially the western portion of the country.
As far as track is concerned, based upon various steering analysis as well as computer model forecasts, I pretty much concur with the NHC's current forecast track, taking the cyclone center across extreme eastern Cuba in about 18 hours, followed by a generally NNE motion with an eventual turn to the NE, then E. However, it is possible that Tomas could come a little more westward and impact more of Cuba and less of Haiti, based upon current CIMSS steering analyses.
However, my own forecast track is a bit west of the NHC's at days three through five, based on various steering data I've analyzed, as it appears that ridging could be a bit stronger than anticipated during that time.
It no longer appears likely that Tomas will stall in the vicinity of Hispaniola. The trough appears to be strong enough to deflect it out to sea, which is great news.
Elsewhere
Elsewhere in the tropics, several of the global models are calling for another tropical depression to form in the eastern or central Caribbean in about 5 - 7 days. The eventual track of this system is uncertain, but right now, there are two possibilities that I see:
1. This system runs into Central America.
2. This system becomes another system that threatens Hispaniola and the Greater Antilles.
It is impossible to choose which scenario is more likely at this juncture. The catalyst for this system could be a perturbation in an unusually active ITCZ, currently near 13N 60W.
We will have to watch this situation closely, as upper-level winds are forecast to begin improving across the central Caribbean during this time.
Thursday, November 4, 2010
Sunday, October 24, 2010
Tropical weather analysis - October 24, 2010
Richard
Hurricane Richard put on a burst of intensification this morning, which brought it to the 10th hurricane of this very active season. The last time 10 or more hurricanes occurred in a season was in 2005, and before that, 1998. Even more remarkable is the 17 named storms we've had. Historical records indicate that the last time this occurred was in 1995, when 19 named storms developed.
As of the latest (4:00 PM CDT) NHC advisory on Richard, here is the latest information:
Wind: 90 mph, with higher gusts
Movement: WNW at 13 mph
Pressure: 981 mb
Location: 17.2°N 88.0°W
Category: 1 (Saffir-Simpson Hurricane Wind Scale)
Visible satellite animations depict a small but well-organized hurricane, with recent images indicating a more symmetrical eye and eyewall. In addition, spiral banding has increased and become more organized as well, particularly to the north.
Doppler radar out of Belize also shows that Richard is a well-organized hurricane.
I suspect that Richard will make landfall between Rockville and Belmopan in about 3-5 hours as an intensifying Category 1 hurricane. It is not out of the question, however, for Richard to attain Category 2 status prior to landfall, and residents of Belize should be vigilant for that possibility.
If this forecast track verifies, Rockville will be on the worst side of the hurricane, and may be close enough to catch Richard's eastern eyewall. Sustained Category 1 force winds (74-95 mph) are possible in this area, with higher gusts.
Sustained tropical storm force winds are already impacting a portion of mainland Belize, and sustained hurricane force winds are not far off, and should begin impacting central Belize in about 2 and a half to 3 hours.
Given that Richard is intensifying, sustained tropical storm force winds will be possible all the way to the western end of the Yucatan Peninsula through Monday night or Tuesday morning. Sustained hurricane force winds may penetrate as far inland as western Belize.
In addition to the wind, Richard is expected to produce a storm surge in excess of 3 to 5 feet near and to the north of where the center makes landfall. This surge will be accompanied by large, destructive waves.
The National Hurricane Center forecasts that 3-6 inches of rain will fall across the Bay Islands, Belize, and the southern Yucatan Peninsula, with lesser amounts (1-2 inches) possible across northern Honduras. They predict that localized amounts could be in excess of 10 inches across the Bay Islands, Belize, and the Yucatan Peninsula.
This pretty much falls in line with my own forecast, and interests in the aforementioned areas should be on alert for the possibility of dangerous, life-threatening flash floods and mudslides, especially in mountainous areas.
As is always the case with landfalling tropical systems, Richard could produce isolated tornadoes, especially in the right-front quadrant.
After landfall, Richard will steadily weaken, and given its small size, it may not survive the trek across Belize and the Yucatan Peninsula.
However, given current organizational trends observed on satellite imagery, along with the fact that these areas aren't terribly mountainous, I expect that Richard will be able to survive the crossing intact (albeit in a severely weakened state, obviously), and will emerge into the southeastern Bay of Campeche in about 36 hours as a severely weakened, vertically tilted tropical depression.
It's worth noting that the 12z GFDL forecasts that Richard will move much slower across Belize, Guatemala, and Mexico. As a result, Richard doesn't enter the Bay of Campeche until much later -- at day three or four. That would coincide with the GFS' forecast of somewhat lower (but still prohibitive) westerly to west-southwesterly vertical wind shear across that portion of the Gulf of Mexico.
Consequently, that model foresees Richard reintensifying to a hurricane before making a second and final landfall near Veracruz, Mexico. However, both the GFDL and the HWRF aren't at all notorious for recognizing obvious shearing conditions, so it's quite likely that this model is failing to appreciate just how fragile Richard will be after crossing the Yucatan, and just how prohibitive zonal shear is to tropical cyclogenesis and intensification.
My own forecast track agrees quite well with the NHC's current one, albeit slightly farther east, as previously noted, for the first 6-12 hours.
The HWRF is an eastern outlier, and forecasts that Richard will accelerate toward the NE toward the Big Bend area of Florida after entering the Gulf of Mexico north of the Yucatan Peninsula. However, the rest of the models are not in agreement with this, and 12z steering forecasts from PSU's e-wall indicate that the low-level flow will be southeasterly, and since Richard is expected to be a very weak tropical cyclone after emerging into the Bay of Campeche, he should move generally NW at that point. Richard would have to maintain some vertical integrity in order for it to follow the track of the HWRF, and this will not be the case.
Sorry JFV, looks like you'll have to wait until next year to get your much fantasized hurricane hit.
Watches and warnings
Invest 90L
A tropical wave in the eastern Atlantic located a few hundred miles west-northwest of the westernmost Cape Verde Islands, dubbed "Invest 90L" by the National Hurricane Center, continues to produce disorganized showers and thunderstorms.
Vertical shear is prohibitively strong, but the GFS predicts that shear will fall in about three to four days as the system moves generally NW, which may allow for some slow development during that time. Indeed, several of the global models eventually foresee this becoming at least a tropical depression. It is not out of the question we could see Tropical Storm Shary from this.
90L is no threat to land areas, nor will it ever be.
Elsewhere
Elsewhere in the tropics, several of the global models, most notably the GFS and ECMWF, are forecasting the development of a tropical cyclone in the eastern Caribbean Sea in about 7-10 days. The latter turns this system into a powerful, westward-moving hurricane, which is a little unnerving. The GFS forecasts that vertical shear will start to lessen in this part of the Caribbean by day seven as well, so this certainly bears watching.
Hurricane Richard put on a burst of intensification this morning, which brought it to the 10th hurricane of this very active season. The last time 10 or more hurricanes occurred in a season was in 2005, and before that, 1998. Even more remarkable is the 17 named storms we've had. Historical records indicate that the last time this occurred was in 1995, when 19 named storms developed.
As of the latest (4:00 PM CDT) NHC advisory on Richard, here is the latest information:
Wind: 90 mph, with higher gusts
Movement: WNW at 13 mph
Pressure: 981 mb
Location: 17.2°N 88.0°W
Category: 1 (Saffir-Simpson Hurricane Wind Scale)
Visible satellite animations depict a small but well-organized hurricane, with recent images indicating a more symmetrical eye and eyewall. In addition, spiral banding has increased and become more organized as well, particularly to the north.
Doppler radar out of Belize also shows that Richard is a well-organized hurricane.
I suspect that Richard will make landfall between Rockville and Belmopan in about 3-5 hours as an intensifying Category 1 hurricane. It is not out of the question, however, for Richard to attain Category 2 status prior to landfall, and residents of Belize should be vigilant for that possibility.
If this forecast track verifies, Rockville will be on the worst side of the hurricane, and may be close enough to catch Richard's eastern eyewall. Sustained Category 1 force winds (74-95 mph) are possible in this area, with higher gusts.
Sustained tropical storm force winds are already impacting a portion of mainland Belize, and sustained hurricane force winds are not far off, and should begin impacting central Belize in about 2 and a half to 3 hours.
Given that Richard is intensifying, sustained tropical storm force winds will be possible all the way to the western end of the Yucatan Peninsula through Monday night or Tuesday morning. Sustained hurricane force winds may penetrate as far inland as western Belize.
In addition to the wind, Richard is expected to produce a storm surge in excess of 3 to 5 feet near and to the north of where the center makes landfall. This surge will be accompanied by large, destructive waves.
The National Hurricane Center forecasts that 3-6 inches of rain will fall across the Bay Islands, Belize, and the southern Yucatan Peninsula, with lesser amounts (1-2 inches) possible across northern Honduras. They predict that localized amounts could be in excess of 10 inches across the Bay Islands, Belize, and the Yucatan Peninsula.
This pretty much falls in line with my own forecast, and interests in the aforementioned areas should be on alert for the possibility of dangerous, life-threatening flash floods and mudslides, especially in mountainous areas.
As is always the case with landfalling tropical systems, Richard could produce isolated tornadoes, especially in the right-front quadrant.
After landfall, Richard will steadily weaken, and given its small size, it may not survive the trek across Belize and the Yucatan Peninsula.
However, given current organizational trends observed on satellite imagery, along with the fact that these areas aren't terribly mountainous, I expect that Richard will be able to survive the crossing intact (albeit in a severely weakened state, obviously), and will emerge into the southeastern Bay of Campeche in about 36 hours as a severely weakened, vertically tilted tropical depression.
It's worth noting that the 12z GFDL forecasts that Richard will move much slower across Belize, Guatemala, and Mexico. As a result, Richard doesn't enter the Bay of Campeche until much later -- at day three or four. That would coincide with the GFS' forecast of somewhat lower (but still prohibitive) westerly to west-southwesterly vertical wind shear across that portion of the Gulf of Mexico.
Consequently, that model foresees Richard reintensifying to a hurricane before making a second and final landfall near Veracruz, Mexico. However, both the GFDL and the HWRF aren't at all notorious for recognizing obvious shearing conditions, so it's quite likely that this model is failing to appreciate just how fragile Richard will be after crossing the Yucatan, and just how prohibitive zonal shear is to tropical cyclogenesis and intensification.
My own forecast track agrees quite well with the NHC's current one, albeit slightly farther east, as previously noted, for the first 6-12 hours.
The HWRF is an eastern outlier, and forecasts that Richard will accelerate toward the NE toward the Big Bend area of Florida after entering the Gulf of Mexico north of the Yucatan Peninsula. However, the rest of the models are not in agreement with this, and 12z steering forecasts from PSU's e-wall indicate that the low-level flow will be southeasterly, and since Richard is expected to be a very weak tropical cyclone after emerging into the Bay of Campeche, he should move generally NW at that point. Richard would have to maintain some vertical integrity in order for it to follow the track of the HWRF, and this will not be the case.
Sorry JFV, looks like you'll have to wait until next year to get your much fantasized hurricane hit.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* BELIZE
A HURRICANE WATCH IS IN EFFECT FOR...
* EAST COAST OF YUCATAN MEXICO FROM PUNTA GRUESA TO CHETUMAL
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* EAST COAST OF YUCATAN MEXICO FROM PUNTA GRUESA TO CHETUMAL
Invest 90L
A tropical wave in the eastern Atlantic located a few hundred miles west-northwest of the westernmost Cape Verde Islands, dubbed "Invest 90L" by the National Hurricane Center, continues to produce disorganized showers and thunderstorms.
Vertical shear is prohibitively strong, but the GFS predicts that shear will fall in about three to four days as the system moves generally NW, which may allow for some slow development during that time. Indeed, several of the global models eventually foresee this becoming at least a tropical depression. It is not out of the question we could see Tropical Storm Shary from this.
90L is no threat to land areas, nor will it ever be.
Elsewhere
Elsewhere in the tropics, several of the global models, most notably the GFS and ECMWF, are forecasting the development of a tropical cyclone in the eastern Caribbean Sea in about 7-10 days. The latter turns this system into a powerful, westward-moving hurricane, which is a little unnerving. The GFS forecasts that vertical shear will start to lessen in this part of the Caribbean by day seven as well, so this certainly bears watching.
Friday, October 22, 2010
Tropical weather analysis - October 22, 2010
Richard
Tropical Storm Richard is slowly intensifying. As of the most recent NHC advisory, here is the latest information on Richard:
Wind: 45 mph, with higher gusts
Movement: W at 5 mph
Pressure: 1005 mb
Location: 16.2°N 81.7°W
Category: Tropical storm
Visible satellite animations suggest that the center is located underneath the mass of deep convection, but the imagery also suggests some vertical shearing over the system. However, there are some indications that this shear is lessening. Additionally, Richard's cyclonic circulation appears to be wrapping some stratocumulus clouds into the western semicircle. Indeed, the latest run of the SHIPS model places 700-500 mb relative humidity values at only 59%, suggesting a very dry mid-level airmass. Finally, Richard's overall circulation envelope appears to be a bit elongated, as evidenced by low-cloud motions observed on satellite imagery. These factors should prevent any rapid intensification of Richard for now.
The dry air and shear notwithstanding, Richard certainly has the potential to become a formidable hurricane over the next several days, as upper-level winds are forecast to be quite favorable for intensification. There are also some indications on water vapor imagery that the very dry airmass is gradually moistening, and high cloud motions derived from satellite imagery imply a lessening of the aforementioned vertical shear.
I expect continued slow intensification of Richard over the next 18 hours, with a more steady rate of strengthening thereafter. However, the potential certainly exists for Richard to rapidly intensify beyond that time, given the very high oceanic heat content located across the western Caribbean Sea, and the light vertical shear profiles forecast.
I expect that by 24 hours, Richard will have become a hurricane.
Richard is currently located in a col region between a developing anticyclone across the Gulf of Mexico and a very potent longwave trough over the western and central Atlantic. This synoptic scale setup indicates that Richard will move only slowly in the short-term. Some erratic motion cannot be ruled out, as well.
Models are split into two camps: the first set, comprised of the CMC, NOGAPS, and UKMET forecast a much weaker Richard. As a result, a shortwave trough and associated cold front that is forecast by the models to branch off from the base of a longwave trough over the high plains/upper midwest in about three days has little appreciable effect on the cyclone. Should this scenario verify, Richard would move into Central America in about two to three days, and eventually into northeast Mexico or south Texas. In fact, the CMC and NOGAPS even lose Richard's circulation over the rugged terrain of Central America.
The latter set of models, comprised of the GFS, HWRF, GFDL, and ECMWF, forecast a deeper, more vertically respectable Richard to respond more significantly to the trough. As a result, these models have Richard turning NW to NNW in about four days toward a developing weakness in the ridge due to a southward movement of said trough toward the Gulf Coast states. In this scenario, Richard would expected to be in the eastern Bay of Campeche in the Gulf of Mexico at that time.
Given current trends, which suggests slow organization (but Richard is still undoubtedly struggling), as well as the forecast of an improving upper wind and thermodynamic environment, which appears to be happening as we speak, I will side with the latter camp.
This track tends to agree pretty well with the NHC's current one, although I am a bit farther to the east of their forecast track at days four and five.
Richard does not pose a significant threat to the United States, as vertical shear profiles are forecast to be quite unfavorable across the Gulf of Mexico. In fact, dissipation of Richard well before "landfall" can be expected. However, Central America and the Yucatan Peninsula may not be so fortunate. The GFDL brings Richard up to Category 4 strength before it slams it into northeastern Belize in about 66-72 hours.
Interests in Honduras, Belize, the Yucatan Peninsula should closely follow the progress of this system over the next several days. Richard could also pose a long-range rainfall threat for from the central Texas to southwest Louisiana coasts, and interests in those areas should also follow the progress of Richard over the next few days.
Again, I want to reiterate that the US is unlikely to see anything more than a little bit of rain from Richard's remnants. Richard will NOT be an organized tropical system by the time it reaches any of the aforementioned areas. However, the rainfall could be locally heavy depending on how moist the environment gets with the approach of said cold front. Tropical systems are notorious for entraining moisture into approaching cold fronts, which can in turn create some serious rainfall and associated flood potential.
Since these areas are in a drought though, the rainfall is unlikely to cause significant flooding problems for Texas and Louisiana.
The most likely target for Richard's Central American landfall is Belize, and for its US landfall, western Louisiana, near Cameron.
Watches and warnings
A HURRICANE WATCH IS IN EFFECT FOR...
* HONDURAS FROM THE NICARAGUA/HONDURAS BORDER WESTWARD TO LIMON AND
THE BAY ISLANDS
* EAST COAST OF MEXICO FROM PUNTA GRUESA TO CHETUMAL
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* HONDURAS FROM THE NICARAGUA/HONDURAS BORDER WESTWARD TO LIMON AND
THE BAY ISLANDS
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* HONDURAS FROM WEST OF LIMON TO THE GUATEMALA BORDER.
* BELIZE
Invest 90L
A strong tropical wave is located near the Cape Verde Islands. This wave has been dubbed "Invest 90L" by the National Hurricane Center. The associated shower activity has become a little better organized, but upper-level winds are only marginally conducive for development, and a less favorable upper wind environment is forecast over the next 12-24 hours. Indeed, southwesterly shear is rapidly approaching the system.
This system does not pose a threat to any land areas, and can be expected to move NW to NNW throughout the forecast period.
Elsewhere
Elsewhere in the tropics, the GFS and ECMWF are indicating that tropical cyclogenesis might occur in the eastern Caribbean in about 7-10 days. This could occur as the ITCZ lifts northward with the approach of the upward MJO.
Since the GFS has been particularly fluent in sniffing out long-range storms this year, I would not discount this possibility at all. However, upper-level winds will not be particularly favorable for development over that part of the Caribbean, so no significant intensification should be expected if this system does form.
Tropical Storm Richard is slowly intensifying. As of the most recent NHC advisory, here is the latest information on Richard:
Wind: 45 mph, with higher gusts
Movement: W at 5 mph
Pressure: 1005 mb
Location: 16.2°N 81.7°W
Category: Tropical storm
Visible satellite animations suggest that the center is located underneath the mass of deep convection, but the imagery also suggests some vertical shearing over the system. However, there are some indications that this shear is lessening. Additionally, Richard's cyclonic circulation appears to be wrapping some stratocumulus clouds into the western semicircle. Indeed, the latest run of the SHIPS model places 700-500 mb relative humidity values at only 59%, suggesting a very dry mid-level airmass. Finally, Richard's overall circulation envelope appears to be a bit elongated, as evidenced by low-cloud motions observed on satellite imagery. These factors should prevent any rapid intensification of Richard for now.
The dry air and shear notwithstanding, Richard certainly has the potential to become a formidable hurricane over the next several days, as upper-level winds are forecast to be quite favorable for intensification. There are also some indications on water vapor imagery that the very dry airmass is gradually moistening, and high cloud motions derived from satellite imagery imply a lessening of the aforementioned vertical shear.
I expect continued slow intensification of Richard over the next 18 hours, with a more steady rate of strengthening thereafter. However, the potential certainly exists for Richard to rapidly intensify beyond that time, given the very high oceanic heat content located across the western Caribbean Sea, and the light vertical shear profiles forecast.
I expect that by 24 hours, Richard will have become a hurricane.
Richard is currently located in a col region between a developing anticyclone across the Gulf of Mexico and a very potent longwave trough over the western and central Atlantic. This synoptic scale setup indicates that Richard will move only slowly in the short-term. Some erratic motion cannot be ruled out, as well.
Models are split into two camps: the first set, comprised of the CMC, NOGAPS, and UKMET forecast a much weaker Richard. As a result, a shortwave trough and associated cold front that is forecast by the models to branch off from the base of a longwave trough over the high plains/upper midwest in about three days has little appreciable effect on the cyclone. Should this scenario verify, Richard would move into Central America in about two to three days, and eventually into northeast Mexico or south Texas. In fact, the CMC and NOGAPS even lose Richard's circulation over the rugged terrain of Central America.
The latter set of models, comprised of the GFS, HWRF, GFDL, and ECMWF, forecast a deeper, more vertically respectable Richard to respond more significantly to the trough. As a result, these models have Richard turning NW to NNW in about four days toward a developing weakness in the ridge due to a southward movement of said trough toward the Gulf Coast states. In this scenario, Richard would expected to be in the eastern Bay of Campeche in the Gulf of Mexico at that time.
Given current trends, which suggests slow organization (but Richard is still undoubtedly struggling), as well as the forecast of an improving upper wind and thermodynamic environment, which appears to be happening as we speak, I will side with the latter camp.
This track tends to agree pretty well with the NHC's current one, although I am a bit farther to the east of their forecast track at days four and five.
Richard does not pose a significant threat to the United States, as vertical shear profiles are forecast to be quite unfavorable across the Gulf of Mexico. In fact, dissipation of Richard well before "landfall" can be expected. However, Central America and the Yucatan Peninsula may not be so fortunate. The GFDL brings Richard up to Category 4 strength before it slams it into northeastern Belize in about 66-72 hours.
Interests in Honduras, Belize, the Yucatan Peninsula should closely follow the progress of this system over the next several days. Richard could also pose a long-range rainfall threat for from the central Texas to southwest Louisiana coasts, and interests in those areas should also follow the progress of Richard over the next few days.
Again, I want to reiterate that the US is unlikely to see anything more than a little bit of rain from Richard's remnants. Richard will NOT be an organized tropical system by the time it reaches any of the aforementioned areas. However, the rainfall could be locally heavy depending on how moist the environment gets with the approach of said cold front. Tropical systems are notorious for entraining moisture into approaching cold fronts, which can in turn create some serious rainfall and associated flood potential.
Since these areas are in a drought though, the rainfall is unlikely to cause significant flooding problems for Texas and Louisiana.
The most likely target for Richard's Central American landfall is Belize, and for its US landfall, western Louisiana, near Cameron.
Watches and warnings
A HURRICANE WATCH IS IN EFFECT FOR...
* HONDURAS FROM THE NICARAGUA/HONDURAS BORDER WESTWARD TO LIMON AND
THE BAY ISLANDS
* EAST COAST OF MEXICO FROM PUNTA GRUESA TO CHETUMAL
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* HONDURAS FROM THE NICARAGUA/HONDURAS BORDER WESTWARD TO LIMON AND
THE BAY ISLANDS
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* HONDURAS FROM WEST OF LIMON TO THE GUATEMALA BORDER.
* BELIZE
Invest 90L
A strong tropical wave is located near the Cape Verde Islands. This wave has been dubbed "Invest 90L" by the National Hurricane Center. The associated shower activity has become a little better organized, but upper-level winds are only marginally conducive for development, and a less favorable upper wind environment is forecast over the next 12-24 hours. Indeed, southwesterly shear is rapidly approaching the system.
This system does not pose a threat to any land areas, and can be expected to move NW to NNW throughout the forecast period.
Elsewhere
Elsewhere in the tropics, the GFS and ECMWF are indicating that tropical cyclogenesis might occur in the eastern Caribbean in about 7-10 days. This could occur as the ITCZ lifts northward with the approach of the upward MJO.
Since the GFS has been particularly fluent in sniffing out long-range storms this year, I would not discount this possibility at all. However, upper-level winds will not be particularly favorable for development over that part of the Caribbean, so no significant intensification should be expected if this system does form.
Wednesday, October 13, 2010
Tropical weather analysis - October 13, 2010
Paula
Extremely tiny Hurricane Paula has weakened steadily throughout the day today, and is now only a Category 1 hurricane. Here is the latest information on this system as of the 11:00 PM CDT advisory from the National Hurricane Center:
Wind: 80 mph, with higher gusts
Movement: NE at 3 mph
Pressure: 993 mb
Location: 21.9°N 85.4°W
Category: 1 (Saffir-Simpson Hurricane Wind Scale)
Analysis of infrared satellite animations suggest that Paula's circulation might be becoming somewhat exposed along the southwestern edge of the CDO. Indeed, high cloud motions observed on said imagery indicate that the hurricane is experiencing southwesterly vertical shear associated with a mid- to upper-level trough and associated cold front currently draped across the central Gulf of Mexico. CIMSS analysis indicates that this shear is prohibitively strong, at 30 kt.
Upper-level outflow is nonexistent to the southwest and quickly going in that direction on the western side as a consequence of the aforementioned shear.
Paula should continue to gradually spin down due to continued southwesterly then westerly vertical shear, and it would not surprise me at all to see Paula dissipate in as little as 36 hours if it manages to track directly over the mountainous terrain of Cuba. Since I suspect Paula will track just north of the Cuban coast after passing the hurricane warning area, I will not forecast such rapid dissipation at this time, but I do expect that Paula will have dissipated by 60 hours.
Analysis of water vapor imagery implies that Paula is already embedded within the mid-latitude southwesterly flow associated with the aforementioned trough. As such, the hurricane is now recurving, albeit at a painfully slow forward motion for the time being, as the approach of said trough has briefly weakened the steering currents surrounding the storm, as is usually the case just prior to and just after recurvature.
Based on various steering data I've analyzed, both real time and forecast, it appears that the trough responsible for Paula's current recurvature will not be strong enough to fully recurve Paula out to sea. All of the models, with the exception of the GFDL, which loses Paula north of Hispaniola in five days, suggest that that a severely weakened or dissipated Paula will eventually move southward back into the western Caribbean Sea underneath the northerly flow associated with the backside of the trough, which is forecast to eventually become a powerful Nor'easter.
Some, such as the NOGAPS, go even further and forecast Paula, or its remnants, to move NW into the southern Gulf of Mexico along the southwestern periphery of a building ridge across the Gulf of Mexico in about five days or so.
Needless to say, confidence in the forecast track beyond two days is not high.
Right now, I my forecast track is just a bit to the south (about 75-100 miles) of the 18z GFDL for the first 48 hours, and just north of NHC's current forecast track during that time.
After 48 hours, my forecast track agrees pretty strongly with that of the NHC, albeit a tad farther westward at the end of the forecast period.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCE OF PINAR DEL RIO
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCES OF LA HABANA AND CUIDAD DE LA HABANA
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE FLORIDA KEYS FROM CRAIG KEY WESTWARD...INCLUDING THE DRY
TORTUGAS
Heavy rainfall in excess of 4 to 8 inches, with locally higher amounts, are possible across portions of western and central Cuba over the next couple of days, along with sustained hurricane force winds along the western and extreme west-central sections of the country, and residents in those areas should closely monitor the progress of Paula over the next couple days.
A storm surge in excess of 3 to 6 feet is possible across extreme western Cuba, which will be accompanied by large, destructive waves.
Elsewhere
Elsewhere in the tropics, most of the global models are indicating another tropical cyclone will develop in the Caribbean, this one north of Panama. The time frame is about a week, which, though still quite far out, is one where we need to start paying attention, especially given the model consensus with this.
The GFS suggests that an anticyclonic environment will develop across the southwest Caribbean at about that time, so this will need to be watched closely.
Extremely tiny Hurricane Paula has weakened steadily throughout the day today, and is now only a Category 1 hurricane. Here is the latest information on this system as of the 11:00 PM CDT advisory from the National Hurricane Center:
Wind: 80 mph, with higher gusts
Movement: NE at 3 mph
Pressure: 993 mb
Location: 21.9°N 85.4°W
Category: 1 (Saffir-Simpson Hurricane Wind Scale)
Analysis of infrared satellite animations suggest that Paula's circulation might be becoming somewhat exposed along the southwestern edge of the CDO. Indeed, high cloud motions observed on said imagery indicate that the hurricane is experiencing southwesterly vertical shear associated with a mid- to upper-level trough and associated cold front currently draped across the central Gulf of Mexico. CIMSS analysis indicates that this shear is prohibitively strong, at 30 kt.
Upper-level outflow is nonexistent to the southwest and quickly going in that direction on the western side as a consequence of the aforementioned shear.
Paula should continue to gradually spin down due to continued southwesterly then westerly vertical shear, and it would not surprise me at all to see Paula dissipate in as little as 36 hours if it manages to track directly over the mountainous terrain of Cuba. Since I suspect Paula will track just north of the Cuban coast after passing the hurricane warning area, I will not forecast such rapid dissipation at this time, but I do expect that Paula will have dissipated by 60 hours.
Analysis of water vapor imagery implies that Paula is already embedded within the mid-latitude southwesterly flow associated with the aforementioned trough. As such, the hurricane is now recurving, albeit at a painfully slow forward motion for the time being, as the approach of said trough has briefly weakened the steering currents surrounding the storm, as is usually the case just prior to and just after recurvature.
Based on various steering data I've analyzed, both real time and forecast, it appears that the trough responsible for Paula's current recurvature will not be strong enough to fully recurve Paula out to sea. All of the models, with the exception of the GFDL, which loses Paula north of Hispaniola in five days, suggest that that a severely weakened or dissipated Paula will eventually move southward back into the western Caribbean Sea underneath the northerly flow associated with the backside of the trough, which is forecast to eventually become a powerful Nor'easter.
Some, such as the NOGAPS, go even further and forecast Paula, or its remnants, to move NW into the southern Gulf of Mexico along the southwestern periphery of a building ridge across the Gulf of Mexico in about five days or so.
Needless to say, confidence in the forecast track beyond two days is not high.
Right now, I my forecast track is just a bit to the south (about 75-100 miles) of the 18z GFDL for the first 48 hours, and just north of NHC's current forecast track during that time.
After 48 hours, my forecast track agrees pretty strongly with that of the NHC, albeit a tad farther westward at the end of the forecast period.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCE OF PINAR DEL RIO
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCES OF LA HABANA AND CUIDAD DE LA HABANA
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE FLORIDA KEYS FROM CRAIG KEY WESTWARD...INCLUDING THE DRY
TORTUGAS
Heavy rainfall in excess of 4 to 8 inches, with locally higher amounts, are possible across portions of western and central Cuba over the next couple of days, along with sustained hurricane force winds along the western and extreme west-central sections of the country, and residents in those areas should closely monitor the progress of Paula over the next couple days.
A storm surge in excess of 3 to 6 feet is possible across extreme western Cuba, which will be accompanied by large, destructive waves.
Elsewhere
Elsewhere in the tropics, most of the global models are indicating another tropical cyclone will develop in the Caribbean, this one north of Panama. The time frame is about a week, which, though still quite far out, is one where we need to start paying attention, especially given the model consensus with this.
The GFS suggests that an anticyclonic environment will develop across the southwest Caribbean at about that time, so this will need to be watched closely.
Tuesday, October 12, 2010
Tropical weather analysis - October 12, 2010
Paula
Hurricane Paula became a Category 2 hurricane early this afternoon. As of the latest NHC advisory (7:00 PM CDT), here is the latest information on Paula:
Wind: 100 mph, with higher gusts
Movement: N at 9 mph
Pressure: 981 mb
Location: 19.6°N 86.0°W
Category: 2 (Saffir-Simpson Hurricane Wind Scale)
Infrared satellite animations show that Paula is a very small but well-organized hurricane, with a well-defined poleward (north) and equatorial (west) outflow channels due to an amplifying upper trough currently moving across the deep south. However, outflow remains quite restricted to the east, and particularly to the south, due to 20 kt of southerly vertical wind shear analyzed by University of Wisconsin CIMSS. This shear is being induced by a well-defined mid- to upper-level ridge to the east.
An eye is not currently present using conventional satellite imagery, but it was earlier, and all indications are that Paula has maintained her strength over the last couple of hours.
Doppler radar out of Cancun, Mexico shows that Paula has a very small eye, and earlier reconnaissance reports indicates that the eye is no more than, say, 10-15 miles wide. Indeed, if I hadn't been forecasting these systems for three years, I would not, as a layman, be able to readily tell just where Paula's eye is using the aforementioned radar imagery.
I've never seen a Caribbean hurricane as small as Paula, except for perhaps Hurricane Iris in 2001, and even that's iffy since the latter had a larger radius of tropical storm force winds.
Steering analysis from CIMSS indicate that Paula is moving northward under the influence of the aforementioned anticyclone to the east.
Once this shear gets into the core, then rapid weakening is possible, given the hurricane's small size. Shear is forecast to gradually increase over the next 24 hours, and beyond that time, rapidly increase. However, shear should be light enough over the next 12 hours or so to allow a little more intensification of Paula. I will not go as high as the current NHC intensity forecast, however. Instead, I'll go up to 90 kt/105 mph, though it would not be surprising given current trends if Paula has already peaked.
After 24 hours, the shear will increase dramatically, as previously noted, and will also veer from southerly to southwesterly by 36-48 hours, and remain that way throughout the forecast period. This, combined with the likelihood of dry air entrainment from the Gulf of Mexico, along with interaction with the Cuban landmass, suggests that Paula may not even last five days as a tropical cyclone.
In fact, some of the models, including the reliable ECMWF, insist on losing Paula's circulation over the next 1-3 days or have a severely weakened tropical cyclone meandering in the northwest Caribbean Sea for several days, and this is a possible scenario. However, I feel that Paula will maintain enough vertical depth to feel the effects of the trough currently moving across the deep south.
One important development in the synoptic scale steering pattern that has transpired over the last 12 hours or so is that the aforementioned deep-layer trough and accompanying cold front has transitioned from a meridional flow to a more zonal one.
This is evident by analysis of water vapor imagery, mid-level steering from PSU's e-wall, and finally, CIMSS real-time steering data.
This suggests that Paula may move north for a little bit longer than was earlier anticipated, and as a result, I would expect a slight northward shift in the NHC forecast track at 11:00 PM. Nothing drastic, mind you, just a slight northward shift. South Florida is still very likely to avoid a landfall from this storm, and the Florida Keys probably will too. Nevertheless, interests in those areas should still monitor the progress of Paula closely over the next several days.
The current transition to a more zonal flow notwithstanding, Paula should still ultimately miss the US and generally follow the NHC's forecast track, since all of the global models foresee the trough reamplifying over the next day or two as it moves across the southeast United States.
Right now, I agree pretty strongly with the NHC's current forecast track, though I am a little bit further north of it after 24 hours and beyond.
Interests in the Yucatan Peninsula, the Cayman Islands, western and central Cuba, the Florida Keys, south Florida, and the Bahamas should closely follow the progress of Paula over the next several days.
In the meantime, heavy, flooding rains are possible across the eastern portion of the Yucatan Peninsula and western Cuba over the next day or two, along with the likelihood of sustained tropical storm force winds for the former and sustained hurricane force winds for the latter.
The eastern Yucatan Peninsula can expect sustained tropical storm force winds throughout the morning tomorrow, with western Cuba experiencing those winds Wednesday afternoon. Hurricane force sustained winds are likely across western Cuba Wednesday night and into Thursday morning.
Additionally, storm surge flooding will be a serious concern for those areas, as well.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA GRUESA NORTHWARD TO CABO CATOCHE...
INCLUDING COZUMEL
* THE PROVINCE OF PINAR DEL RIO CUBA
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM CABO CATOCHE TO SAN FELIPE
Hurricane Paula became a Category 2 hurricane early this afternoon. As of the latest NHC advisory (7:00 PM CDT), here is the latest information on Paula:
Wind: 100 mph, with higher gusts
Movement: N at 9 mph
Pressure: 981 mb
Location: 19.6°N 86.0°W
Category: 2 (Saffir-Simpson Hurricane Wind Scale)
Infrared satellite animations show that Paula is a very small but well-organized hurricane, with a well-defined poleward (north) and equatorial (west) outflow channels due to an amplifying upper trough currently moving across the deep south. However, outflow remains quite restricted to the east, and particularly to the south, due to 20 kt of southerly vertical wind shear analyzed by University of Wisconsin CIMSS. This shear is being induced by a well-defined mid- to upper-level ridge to the east.
An eye is not currently present using conventional satellite imagery, but it was earlier, and all indications are that Paula has maintained her strength over the last couple of hours.
Doppler radar out of Cancun, Mexico shows that Paula has a very small eye, and earlier reconnaissance reports indicates that the eye is no more than, say, 10-15 miles wide. Indeed, if I hadn't been forecasting these systems for three years, I would not, as a layman, be able to readily tell just where Paula's eye is using the aforementioned radar imagery.
I've never seen a Caribbean hurricane as small as Paula, except for perhaps Hurricane Iris in 2001, and even that's iffy since the latter had a larger radius of tropical storm force winds.
Steering analysis from CIMSS indicate that Paula is moving northward under the influence of the aforementioned anticyclone to the east.
Once this shear gets into the core, then rapid weakening is possible, given the hurricane's small size. Shear is forecast to gradually increase over the next 24 hours, and beyond that time, rapidly increase. However, shear should be light enough over the next 12 hours or so to allow a little more intensification of Paula. I will not go as high as the current NHC intensity forecast, however. Instead, I'll go up to 90 kt/105 mph, though it would not be surprising given current trends if Paula has already peaked.
After 24 hours, the shear will increase dramatically, as previously noted, and will also veer from southerly to southwesterly by 36-48 hours, and remain that way throughout the forecast period. This, combined with the likelihood of dry air entrainment from the Gulf of Mexico, along with interaction with the Cuban landmass, suggests that Paula may not even last five days as a tropical cyclone.
In fact, some of the models, including the reliable ECMWF, insist on losing Paula's circulation over the next 1-3 days or have a severely weakened tropical cyclone meandering in the northwest Caribbean Sea for several days, and this is a possible scenario. However, I feel that Paula will maintain enough vertical depth to feel the effects of the trough currently moving across the deep south.
One important development in the synoptic scale steering pattern that has transpired over the last 12 hours or so is that the aforementioned deep-layer trough and accompanying cold front has transitioned from a meridional flow to a more zonal one.
This is evident by analysis of water vapor imagery, mid-level steering from PSU's e-wall, and finally, CIMSS real-time steering data.
This suggests that Paula may move north for a little bit longer than was earlier anticipated, and as a result, I would expect a slight northward shift in the NHC forecast track at 11:00 PM. Nothing drastic, mind you, just a slight northward shift. South Florida is still very likely to avoid a landfall from this storm, and the Florida Keys probably will too. Nevertheless, interests in those areas should still monitor the progress of Paula closely over the next several days.
The current transition to a more zonal flow notwithstanding, Paula should still ultimately miss the US and generally follow the NHC's forecast track, since all of the global models foresee the trough reamplifying over the next day or two as it moves across the southeast United States.
Right now, I agree pretty strongly with the NHC's current forecast track, though I am a little bit further north of it after 24 hours and beyond.
Interests in the Yucatan Peninsula, the Cayman Islands, western and central Cuba, the Florida Keys, south Florida, and the Bahamas should closely follow the progress of Paula over the next several days.
In the meantime, heavy, flooding rains are possible across the eastern portion of the Yucatan Peninsula and western Cuba over the next day or two, along with the likelihood of sustained tropical storm force winds for the former and sustained hurricane force winds for the latter.
The eastern Yucatan Peninsula can expect sustained tropical storm force winds throughout the morning tomorrow, with western Cuba experiencing those winds Wednesday afternoon. Hurricane force sustained winds are likely across western Cuba Wednesday night and into Thursday morning.
Additionally, storm surge flooding will be a serious concern for those areas, as well.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA GRUESA NORTHWARD TO CABO CATOCHE...
INCLUDING COZUMEL
* THE PROVINCE OF PINAR DEL RIO CUBA
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM CABO CATOCHE TO SAN FELIPE
Monday, October 11, 2010
Tropical weather analysis - October 11, 2010
Paula
Tropical Storm Paula formed this afternoon in the western Caribbean, east of Honduras. As of the latest NHC advisory (11:00 PM EDT), here is the latest information on Paula:
Wind: 70 mph, with higher gusts
Movement: NW at 10 mph
Pressure: 994 mb
Location: 16.8N 84.6W
Category: Tropical storm
Infrared satellite imagery indicates that Paula is a healthy and intensifying tropical cyclone, with very cold convection over the center and what appears to be the early stages of an eyewall wrapping cyclonically around the center. However, an eye or warm spot is not yet evident using conventional satellite imagery. Unfortunately, there have been no recent microwave satellite passes over the center of the cyclone to confirm this suspicion.
Regardless, it is quite obvious that Paula is an intensifying tropical cyclone. The storm has managed to develop a well-defined poleward and equatorial outflow channel, namely along the northern and western semicircles. Indeed, outflow is also becoming apparent to the south of the center. It remains restricted to the east due to weak southeasterly shear induced by an upper-level high pressure system centered near northwestern Colombia.
Upper-level winds appear favorable for Paula to continue intensifying over at least the next 48 hours. Thereafter, increasing southwesterly to southerly vertical shear will begin to impinge upon the system. This, along with a very dry airmass across the Gulf of Mexico, should begin to weaken Paula after 48 hours. The GFDL brings the system to 75 kt near the northeastern Yucatan Peninsula in 36 hours. While this track seems a tad too fast, the model certainly has the right idea in forecasting such a degree of intensification. In fact, for once, I think the GFDL is being too conservative. I'll go a bit higher, and forecast Paula to become an 85 kt Category 2 hurricane in the western Caribbean in about 48 hours.
It is certainly not out of the question that Paula could become a major hurricane over the next two days or so, especially if current trends continue.
Paula is being steered generally NW by a low- mid-level ridge to the east. It is possible, based on analysis of said imagery along with water vapor imagery, that Paula could turn a little to the right over the next couple hours before bending back to a straight NW course.
In the short-term, Paula should continue moving in this general direction, bringing the center in the general direction of the Yucatan Peninsula in the next 36-48 hours. Thereafter, the track forecast becomes quite complicated, and is dependent entirely upon the strength and amplification of a deep-layer trough forecast by the models to move across the southeast United States.
Depending on the model of your choice, the effects of this trough on Paula's motion varies. Some move the cyclone quickly poleward as Paula comes underneath the influence of the deep-layer westerly flow associated with the aforementioned trough, quickly ejecting it toward western Cuba by about 48 hours.
Others foresee Paula slowing to a crawl and either meandering in the western Caribbean Sea for several days, or moving very slowly eastward, never to leave the Caribbean throughout the forecast period (five days).
Right now, my current thinking is that, based upon current intensification trends and water vapor analysis, Paula will move a bit more poleward than some of the models are thinking, as a well-defined weakness is evident at 400 mb due to a shortwave trough currently moving across the Texas/Louisiana area.
This trough should drop a bit more southward over the next 12-18 hours as a well-defined upper-level low located across the central plains has moved quite far to the southeast over the last several hours. Since Paula is intensifying, it will be strong enough to feel this deep-layer trough. And, as a consequence, move more poleward.
For my forecast track, out of respect for the usual reliability of these two global models, as well as given current trends, and of course, the ever-present uncertainty in long-range weather forecasting, particularly with systems such as Paula, I will compromise between the faster GFS and the slower ECMWF.
This comes out to a forecast of Paula moving NW over the next 36-48 hours, toward the eastern Yucatan Peninsula, and then slowing down a bit and moving very slowly eastward, possibly just north of due E during the remainder of the forecast period.
This track is highly uncertain until the synoptic scale situation becomes clearer. Given the uncertainty, interests in Honduras, Belize, the Yucatan Peninsula, Jamaica, the Cayman Islands, western Cuba, south Florida, and the western Bahamas should closely follow the progress of Paula over the next several days.
In the meantime, heavy rainfall is possible across portions of Honduras, Nicaragua, Jamaica, Belize, the Cayman Islands, the Yucatan Peninsula, and western Cuba over the next several days. These rains have the potential to produce life-threatening flash floods and mudslides across these areas.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA GRUESA NORTHWARD TO CABO CATOCHE...
INCLUDING COZUMEL
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF HONDURAS FROM LIMON EASTWARD TO THE
HONDURAS/NICARAGUA BORDER...INCLUDING THE BAY ISLANDS
* THE COAST OF MEXICO FROM CHETUMAL NORTHWARD TO SOUTH OF PUNTA
GRUESA
* THE COAST OF MEXICO FROM CABO CATOCHE TO SAN FELIPE
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE COAST OF BELIZE
Tropical Storm Paula formed this afternoon in the western Caribbean, east of Honduras. As of the latest NHC advisory (11:00 PM EDT), here is the latest information on Paula:
Wind: 70 mph, with higher gusts
Movement: NW at 10 mph
Pressure: 994 mb
Location: 16.8N 84.6W
Category: Tropical storm
Infrared satellite imagery indicates that Paula is a healthy and intensifying tropical cyclone, with very cold convection over the center and what appears to be the early stages of an eyewall wrapping cyclonically around the center. However, an eye or warm spot is not yet evident using conventional satellite imagery. Unfortunately, there have been no recent microwave satellite passes over the center of the cyclone to confirm this suspicion.
Regardless, it is quite obvious that Paula is an intensifying tropical cyclone. The storm has managed to develop a well-defined poleward and equatorial outflow channel, namely along the northern and western semicircles. Indeed, outflow is also becoming apparent to the south of the center. It remains restricted to the east due to weak southeasterly shear induced by an upper-level high pressure system centered near northwestern Colombia.
Upper-level winds appear favorable for Paula to continue intensifying over at least the next 48 hours. Thereafter, increasing southwesterly to southerly vertical shear will begin to impinge upon the system. This, along with a very dry airmass across the Gulf of Mexico, should begin to weaken Paula after 48 hours. The GFDL brings the system to 75 kt near the northeastern Yucatan Peninsula in 36 hours. While this track seems a tad too fast, the model certainly has the right idea in forecasting such a degree of intensification. In fact, for once, I think the GFDL is being too conservative. I'll go a bit higher, and forecast Paula to become an 85 kt Category 2 hurricane in the western Caribbean in about 48 hours.
It is certainly not out of the question that Paula could become a major hurricane over the next two days or so, especially if current trends continue.
Paula is being steered generally NW by a low- mid-level ridge to the east. It is possible, based on analysis of said imagery along with water vapor imagery, that Paula could turn a little to the right over the next couple hours before bending back to a straight NW course.
In the short-term, Paula should continue moving in this general direction, bringing the center in the general direction of the Yucatan Peninsula in the next 36-48 hours. Thereafter, the track forecast becomes quite complicated, and is dependent entirely upon the strength and amplification of a deep-layer trough forecast by the models to move across the southeast United States.
Depending on the model of your choice, the effects of this trough on Paula's motion varies. Some move the cyclone quickly poleward as Paula comes underneath the influence of the deep-layer westerly flow associated with the aforementioned trough, quickly ejecting it toward western Cuba by about 48 hours.
Others foresee Paula slowing to a crawl and either meandering in the western Caribbean Sea for several days, or moving very slowly eastward, never to leave the Caribbean throughout the forecast period (five days).
Right now, my current thinking is that, based upon current intensification trends and water vapor analysis, Paula will move a bit more poleward than some of the models are thinking, as a well-defined weakness is evident at 400 mb due to a shortwave trough currently moving across the Texas/Louisiana area.
This trough should drop a bit more southward over the next 12-18 hours as a well-defined upper-level low located across the central plains has moved quite far to the southeast over the last several hours. Since Paula is intensifying, it will be strong enough to feel this deep-layer trough. And, as a consequence, move more poleward.
For my forecast track, out of respect for the usual reliability of these two global models, as well as given current trends, and of course, the ever-present uncertainty in long-range weather forecasting, particularly with systems such as Paula, I will compromise between the faster GFS and the slower ECMWF.
This comes out to a forecast of Paula moving NW over the next 36-48 hours, toward the eastern Yucatan Peninsula, and then slowing down a bit and moving very slowly eastward, possibly just north of due E during the remainder of the forecast period.
This track is highly uncertain until the synoptic scale situation becomes clearer. Given the uncertainty, interests in Honduras, Belize, the Yucatan Peninsula, Jamaica, the Cayman Islands, western Cuba, south Florida, and the western Bahamas should closely follow the progress of Paula over the next several days.
In the meantime, heavy rainfall is possible across portions of Honduras, Nicaragua, Jamaica, Belize, the Cayman Islands, the Yucatan Peninsula, and western Cuba over the next several days. These rains have the potential to produce life-threatening flash floods and mudslides across these areas.
Watches and warnings
A HURRICANE WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA GRUESA NORTHWARD TO CABO CATOCHE...
INCLUDING COZUMEL
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF HONDURAS FROM LIMON EASTWARD TO THE
HONDURAS/NICARAGUA BORDER...INCLUDING THE BAY ISLANDS
* THE COAST OF MEXICO FROM CHETUMAL NORTHWARD TO SOUTH OF PUNTA
GRUESA
* THE COAST OF MEXICO FROM CABO CATOCHE TO SAN FELIPE
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE COAST OF BELIZE
Saturday, October 9, 2010
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