Ex-TD 4 May Regenerate Near the Bahamas - Pay Attention Gulf of Mexico DUers

[malaise]

https://www.wunderground.com/cat6/ex-td-4-may-regenerate-near-bahamas
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A renewed burst of showers and thunderstorms (convection) developed early Monday around the remnants of Tropical Depression 4, located several hundred miles east of the Bahamas. This depression originated on Wednesday in the central tropical Atlantic with a sizable low-level circulation, but widespread dry air associated with the Saharan Air Layer torpedoed TD 4’s ability to generate convection and develop further. NHC terminated TD 4 on Friday, but it now appears possible that TD 4 may be springing back to life. Satellite loops of the system (which were reinitiated on Monday under the name 04L) illustrate the vivid burst of convection over the last few hours.

Michael Ventrice (The Weather Company) believes the new lease on life may be the result of 04L having moved north of 20°N latitude. Across the deep Atlantic tropics, he says, the system was being tamped down by the effects related to the suppressed phase of a convectively coupled Kelvin wave—a large, slow-moving atmospheric wave that can enhance or detract from hurricane formation in the deep tropics. Now that 04L is beyond the Kelvin wave’s direct influence, Ventrice believes it may have a better chance of strengthening.

It will take until this evening before computer models have fully incorporated the regrowth of 04L into their forecasts, but the European model from last night (0Z Monday) was already indicating some support for modest redevelopment. Most of the 50 members of the European ensemble run from 0Z Monday bring 04L to depression strength, and about a third of the ensembles produce a tropical storm, though only one of the 50 generates a hurricane. The ensemble is in close agreement on a westward track through the Bahamas in about 3-4 days, with much greater track divergence thereafter—solutions range from a track toward the Texas coast to an East Coast hugger that reaches Newfoundland!

Interestingly, only 2 of 20 GFS ensemble members take 04L to tropical storm strength, and even those dissipate 04L before it clears the Bahamas. The GFS tends to produce more hurricanes overall than the European model, so the discrepancy in this direction is a bit unusual. The last several runs of the UKMET model have not supported redevelopment of 04L in the Bahamas, although the model has favored at least some redevelopment into a tropical depression or tropical storm after 04L passes into the eastern Gulf of Mexico late this week. Tonight’s 0Z Tuesday model runs should be able to incorporate 04L’s growth spurt, so it will be interesting to see if the GFS comes on board. The 12Z Monday run of the SHIPS statistical model shows that 04L will continue to struggle with dry air (mid-level relative humidities of only around 50% for the next several days). However, wind shear will be gradually dropping from around 15 knots on Monday to less than 10 knots by Wednesday, and warm sea-surface temperatures of 28-29°C (82-84°F) would certainly support development. The Hurricane Hunters are now scheduled to investigate the system on Tuesday.