Tropical weather analysis - June 20, 2010

Began writing at approximately 10:19 PM eastern

Invest 92L

Invest 92L is no more. Strong upper-level winds, dry air, and land interaction have all but destroyed the system. It appeared very early this morning, as per doppler radar loops from San Juan, Puerto Rico, along with CIMSS vorticity data, that 92L was trying to form a new center underneath the deepest convection, which was located southwest of Ponce at that time. However, this did not materialize. Doppler radar animations out of San Juan still indicate a large amount of moisture in the vicinity. However, this precipitation is more likely associated with a tropical wave currently stretching from northeastern Venezuela northward to the Leeward Islands, rather than 92L.

In any case, this moisture is located well to the east of the wave axis of 92L, which is currently devoid of deep convection. There is no organization to these showers, as evidenced by not only doppler radar data, but also infrared satellite loops. There is also very little in the way of low-level vorticity associated with this system, and indeed, 92L's convection (which, again, is displaced well to the east of the very weak wave axis) appears to be becoming increasingly and rapidly influenced by the large area of moisture currently evident across the eastern Caribbean.

Given that there is currently no model support at all for 92L, and the fact that most of the models foresee the aforementioned area of moisture, associated with a westward-moving tropical wave, becoming the dominant system, I do not expect any significant development of 92L.

The wave (92L's wave), as per the 1800 UTC NHC surface analysis map, currently extends along 22N 73W to 11N 75W, and is moving W near 15 kt, embedded within the low-level easterlies, the signature of the tropics. Based on water vapor animations, 12z steering from PSU, and the current low-level steering wind flow, as per University of Wisconsin CIMSS, I expect 92L continue to moving W at around 10 to 15 kt for the next 12 to 18 hours, after which a WNW movement should begin, across western or central Cuba.

92L still appears quite poised to enter the Gulf of Mexico, but at this point, it appears that 92L's structure is much too disrupted to ever reinvigorate. Indeed, I have been giving this system only a low chance, 20%, to ultimately develop into a tropical depression in the Gulf of Mexico, but given recent structural trends, I will have to lower that probability to only 5%.

At this point, it does not appear likely that 92L will pose a significant threat to any land areas as a tropical cyclone, though it may produce occasional locally heavy rainfall across portions of western and central Cuba, the northern Yucatan Peninsula, and eventually, portions of northeastern Mexico and southern and central Texas over the next several days.

Unless conditions significantly change, this will be my final mention of 92L. It was a tenacious system, to be sure.

Windward Islands tropical wave

The aforementioned tropical wave is the one we really need to keep a watchful eye on. This system might ultimately entrain some moisture from an area of disturbed weather currently located near Nicaragua, as well as from another tropical wave currently along 45W. The 12z NOGAPS, the 12z ECMWF, and the 12z CMC were all developing this wave, and had it in the Yucatan Channel at 144 hours. The NOGAPS and ECMWF had it between western Cuba and the Yucatan Peninsula at this time, while the CMC tracked it westward across the Yucatan Peninsula, and then into the Gulf of Mexico.

The 18z GFS predicts a largely anticyclonic environment across much of the Caribbean beginning in about 72 hours, and eventually brings this favorable environment into much of the Gulf of Mexico, where this potential system appears likely to eventually end up. Residents from Mexico to Florida should carefully monitor the progress of this wave over the next several days. It should be noted that the ECMWF has been consistent in making this system a hurricane in the Gulf of Mexico, though this is highly uncertain at this time.

The most useful forecast I can give for this system at the moment is that it has a far greater chance to develop than 92L ever did. The NHC is currently giving this system a 10% chance of becoming a tropical cyclone in the next 48 hours, due to moderate westerly shear, and this is a reasonable forecast. This shear should let up by around 72 hours, at which point we will need to monitor this system for potential tropical development.

In the meantime, expect this system to oscillate between W and WNW at around 10 to 15 kt over the next several days, though the direction should be mostly WNW.