Tropical weather analysis - July 6, 2010

Invest 96L

Invest 96L continues to be persistent. As of this evening, it appears to be located across the northern Yucatan Peninsula about 60 miles east of Merida. This is based on shortwave infrared satellite animations as well as recent surface observations. The estimated center position, based on the above, is 20N 89W. Convection is currently minimal near the estimated center position, though this is undoubtedly because it is currently overland. What's interesting to me, however, is that satellite loops finally indicate the development of upper-level outflow.

This recent development and expansion of upper-level outflow is no doubt associated with a well-defined upper-level anticyclone that, while not directly atop the center, is at least close enough to ventilate the system, rather than shear it. The system appears to be moving WNW at the moment. This motion could continue for the next 6-12 hours, but after that, I expect a turn back to the NW. That should continue until after 48 hours, at which point the ridge could rebuild to the north and force a more WNW component of motion. The models have shifted considerably southward today, and thus I am forced to do the same. Unfortunately, this puts south Texas and northeast Mexico back in the bullseye, after having just dealt with Hurricane Alex, which generated considerable flooding that is still ongoing.

The models still appear to be too quick in bringing this system into the USA (or Mexico), generally bringing it inland in about 48 hours. I will forecast a landfall in the USA/Mexico in about 60 hours. This is based on CIMSS steering analysis, which does not appear to be as quick as the models are saying. This system should emerge into the southern Gulf of Mexico sometime tomorrow morning.

Upper-level winds still appear to be marginally conducive for some development of this system over the next couple of days, but the overall environment across the Gulf of Mexico will certainly not be anticyclonic. The NHC is giving this system a 40% chance of becoming a tropical cyclone within the next 48 hours. This is a reasonable forecast. I still think that this has a decent chance of becoming the season's second named storm, though at this point it no longer appears as if it will become a hurricane, because of the southward shift in the models today. It will instead pass over Alex's cold wake, generated south of 25N, which will tend to inhibit any rapid intensification. Hence, I expect only gradual intensification, assuming the system forms at all.

I forecast a landfall somewhere across south Texas in 60 hours, though it is difficult to pinpoint the exact location within that vicinity. Interests from northeast Mexico to southeast Texas should continue to carefully monitor the progress of this system over the next couple of days. In the meantime, locally heavy rainfall will continue overspreading portions of the Yucatan Peninsula, western Cuba, and the Cayman Islands over the next day or so.

Eastern Caribbean tropical wave

A tropical wave moving westward across the eastern Caribbean Sea is very disorganized, and upper-level winds are forecast to remain unfavorable for tropical cyclogenesis as the wave moves W to WNW at 15 to 20 kt over the next several days. This will be my final mention of this system unless some drastic changes are noted.

Bahamas/western Atlantic system

A disorganized area of showers and thunderstorms located from the Bahamas eastward for several hundred miles is associated with the remnants of an old cold front (now a trough). Upper-level winds are forecast to become more conducive for development as the system moves little over the next couple of days. Eventually, the system could move NE. The GFS continues to hint at development of this feature.