Tropical weather analysis - June 23, 2010

Began writing at approximately 7:30 PM eastern

Invest 93L continues to struggle. This was not totally unexpected, however, as I had predicted last night that this would happen throughout a portion of today. The last of the visible satellite animations suggest that the broad and poorly defined surface center -- if it can even be accurately referred to as such -- is located at 18N 79W. There also appears to be several other vorticity maximums embedded within the broad cyclonic gyre associated with this system. It appears that the anticyclone, which was practically atop 93L last night appears to have shifted a bit westward today, and its axis is now located southwest of Jamaica.

This appears to be producing 20 kt of westerly shear across the estimated center position. This would at least partially explain 93L's current disorganization, as satellite loops show that the system's associated convection is not well organized, and is instead displaced to the east of the estimated "surface center".

The biggest change I have noted with 93L today is pressure falls, with several land stations, and even one oceanic station, "Station 42057", reporting significant pressure falls. Surface pressures are rising to the east, within the convective mass affecting Hispaniola, indicating that 93L's competing influence may finally be starting to gradually dissipate. Should this indeed be occurring, it should finally allow 93L to "breathe", so to speak.However, I do suspect that any development will be slow to occur with 93L, and we will not see tropical cyclogenesis until tomorrow night at the very earliest. 93L is currently moving W at 10 to 15 kt.

I expect oscillations between W and WNW over the next day or so. At that point, 93L could either not strengthen significantly, if at all, and head W into the Yucatan Peninsula and dissipate, or it could strengthen and continue WNW into the southern Gulf of Mexico, following the mid-level atmospheric flow. It continues to be very difficult to accurately predict this system, and given recent model trends calling for a much weaker storm or even dissipation, I am also going to be less bullish than I was this time yesterday.

However, I do still expect this system to be deep enough to follow the mid-level flow and eventually move across the southern and central Gulf of Mexico. The eventual landfall location of this system in the Gulf of Mexico, assuming it makes it there, is highly uncertain. Texas does appear to be at greater risk than it was this time yesterday, simply because the system is being slow to organize. Residents from Mexico to Florida, with emphasis along the entire Texas coast and much of the Louisiana coast, should carefully monitor the progress of this system over the next several days.

The GFS abates the current westerly shear in about 18 hours, giving way to more favorable northerlies. It also stalls the anticyclone in the Yucatan Channel from 36 to 84 hours. This is critical, because 93L might be able to catch up with the anticyclone and establish itself underneath it during this time, which would greatly assist in development. Even if it doesn't, the flow along the eastern periphery of the anticyclone will be N, NE, and then it will veer to the E. This upper flow pattern is much more conducive to intensification than the currently westerly flow aloft, which is also being generated by the aforementioned anticyclone.

Bottom line is, conditions appear conducive for steady development as the system enters the western Caribbean in about 18 hours. The GFS suggests that the westerly shear I mentioned last night, that was supposed to be blowing across the central and northern Gulf of Mexico, won't be present throughout the forecast period. Should this hold true, and 93L remain intact long enough to reach the Gulf of Mexico, we need to keep a very watchful eye on this situation.

I do not foresee this system becoming a major hurricane at this point, or even a Category 2. I expect, if it holds together, a Category 1 hurricane, but not until it reaches the central Gulf of Mexico.