Tropical weather analysis - June 22, 2012
Invest 96L
A large tropical disturbance located over the southeastern Gulf of Mexico ("96L") is producing a widespread area of precipitation to the east, but the western side continues to struggle amidst unfavorable upper-level winds, and the system as a whole remains disorganized.
Figure 1. Latest infrared satellite image of Invest 96L. Image credit: NOAA
Convection is slowly wrapping, however, so 96L is definitely trying to organize. In fact, the overall circulation appears a little tighter today than yesterday, and this is supported by analysis of satellite imagery as well as real-time vorticity data from UW-CIMSS. This fact notwithstanding, there remains little sense to deny the continued broad nature of the circulation. This should at least slow development in the near-term. Westerly shear also continues to inhibit development, and while there are indications on water vapor imagery that this shear is decreasing, it is going to be a gradual process, not a rapid one, and the global models have been too quick to move the shear over 96L. SHIPS doesn't show the shear decreasing much, but considering the 18z run was a little more lenient, and there are actual signs of a more favorable upper environment, I do not have a proclivity toward belief in this regard.
I still anticipate this low to become a tropical depression and eventually, a tropical storm. A hurricane is still possible, but the GFS suggests an upper air pattern over the Gulf that is not quite as anticyclonic as we'd like if we want to get a hurricane out of this system. On the other hand, none the global models show anything less than a slow-moving large circulation traversing the central Gulf of Mexico. Given the enormous size of the circulation already preexisting with the system, one possible outcome is for the latent heat release to generate a more substantial, well-defined anticyclone atop the circulation, which would help the system strengthen, possibly to hurricane strength. The longer the system remains in the Gulf, the more favorable the upper-level flow will become.
The track forecast is anything but straightforward. Water vapor imagery shows a distinct mid-level ridge over the central United States, with a weakness downstream over the western Atlantic. The ridge is gradually shifting eastward and flattening out as a developing trough over the western United States pivots eastward. The global models show this ridge more or less remaining in place between two troughs -- one over the west, and one over the east. This is where the biggest forecast challenge arises, and what has still yet to be resolved within the models. The GFS continues to insist on a strike on the Florida west coast near Tampa, while the ECMWF has been consistent in tracking the system toward the lower to central Texas coast. I've mentioned for several days now, particularly yesterday, that I don't buy the sharp, almost immediate recurve toward Florida considering the time of year. In addition, for the GFS solution to verify, the trough over the western Atlantic would have to be in the process of picking up the system now, which it is not.
I still do not know where this system will ultimately make landfall, but interests along the entire Gulf Coast should follow the progress of this disturbance. I still don't think western Florida is at the risk the GFS claims it is. I really want to place the Texas coast at greatest risk given the model trends in that direction. A stall near the northern Gulf Coast before heading toward the Texas coast underneath the central US ridge is also possible. Another trough is forecast to arrive on the US west coast by Tuesday, which, if it moves faster than predicted, could bend the track more to the east. At the very least, much of the Gulf Coast could receive some heavy rains, and possibly gusty winds as well.
A reconnaissance aircraft is scheduled to investigate this system tomorrow, if necessary. Although today's flight was canceled due to the disorganized nature of the system, I suspect they will fly tomorrow. Hopefully, a NOAA G-IV synoptic surveillance mission will be launched, and help to resolve some of the track issues within the global models.
Probability of development in 48 hours: 80%
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