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June 2012

96L to Become Debby and Bring Rain to East-Central Gulf Coast Regardless of Track

   Posted by Levi at 4:55pm on June 22, 2012

Invest 96L, what promises to be one of the greatest forecasting challenges this season, continues to slowly organize north of the Yucatan Peninsula this morning. The only significant batch of convection associated with it is removed east of the center over the Yucatan Channel. A new lobe of low pressure will likely develop within the broader circulation close to this area of convection and move northward during the next 24-36 hours, eventually dragging the rest of the broad circulation with it. Consolidation of the system will be slow, but it should steadily organize with time as it moves slowly northward to a position southeast of New Orleans during the next 2 days.

By Sunday, 96L will likely stall and not move much for a little while as it decides which way to go. The models are still split on whether 96L will move northeast across Florida into a trough over the eastern seaboard, or whether it will be captured by the Texas ridge and brought westward. I am still of the mind that the westward track is what will eventually occur, with a track taking what should be Debby into southern Texas or northern Mexico. Yesterday more of the global models came back into agreement with this idea, and last night’s 0z runs of the ECMWF, UKMET, and CMC all support that track. However, the ensemble means reveal a very low-confidence forecast, with the ensemble members spread from coast to coast across the Gulf of Mexico with 96L’s future track. Thus, there is still no real consensus, and the models are still deciding what to do with the system. As I mentioned yesterday, the trough that will be over the western U.S. coast makes me wary of the idea that the eastern trough can exert a strong influence over the central Gulf of Mexico in the face of the big Texas ridge between the two troughs. It is also difficult for such a trough to drag such a large monsoonal low northeast out of the deep tropics. While more models currently support my forecast, the northeast track into Florida cannot be discounted, and regardless of track, heavy rains will be spreading through Florida and likely the central gulf coast as well during the next 3-4 days.

96L will take its time strengthening due to its size, and a track into Florida likely wouldn’t give it enough time to become more than a moderate tropical storm. However, if 96L stalls in the central gulf and then takes my track westward, it may have enough time to take advantage of lower wind shear and become stronger, possibly becoming a hurricane in the western gulf, but not much can be known about the peak intensity of this storm until it has developed and we have more confidence in its track and timing. For now, the entire gulf coast should keep a close eye on this system.

We shall see what happens!

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