The Atlantic hurricane season officially starts on June 1, but we could see a tropical or subtropical depression form in the Gulf of Mexico by Wednesday off the coast of the Florida Panhandle. An upper-level trough of low pressure currently over the western Gulf of Mexico will move east and become a closed-off upper-level low-pressure system that will stall out over the eastern Gulf over the weekend, bringing heavy rains to much of Florida. As this low meanders over the warm waters of the Gulf of Mexico on Sunday through Wednesday, the low has the potential to gradually acquire tropical characteristics and become warm-cored, potentially transforming into a tropical or subtropical depression. Sea surface temperatures (SSTs) off the coast of the Florida Panhandle are near 25°C (77°F)—a little cooler than is typically needed to see a tropical depression form, but plenty warm enough to support the formation of a subtropical depression.
The Friday morning operational runs of our top three models for predicting tropical cyclone genesis—the European, GFS, and UKMET models—did not predict that a tropical or subtropical cyclone would form in the Gulf of Mexico early next week. However, there was some support for this idea from the 0Z Friday ensemble runs of the GFS and European models, according to a custom forecast tool supplied to WU by cfanclimate.com. About 20% of the 50 members of the European model predicted that a tropical or subtropical depression could form by Wednesday in the Gulf, as did more than 50% of the 20 members of the GFS model. The National Hurricane Center was not giving this system any odds of development on Friday morning in their Tropical Weather Outlook, but I give this system 5-day odds of development of 10%.
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| Figure 2. Sea surface temperatures (SSTs) off the coast of the Florida Panhandle are near 25°C (77°F)—a little cooler than is typically needed to see a tropical depression form, but plenty warm enough to support formation of a subtropical depression. SSTs in the Western Caribbean are near 28°C (82°F)—plenty warm enough to support a hurricane. Image credit: Levi Cowan, tropicaltidbits.com. |
The GFS model has also been predicting during much of the past week that an area of disturbed weather over Central America could act as the seed to get a tropical storm spinning in the Western Caribbean 7 – 12 days from now. Water temperatures there are near 28°C (82°F)—plenty warm enough to support a hurricane. The subtropical jet stream—which is typically located over the Caribbean in May, creating high wind shear that interferes with hurricane development—is predicted to lift northwards by late in the week, creating conditions favorable for tropical cyclone genesis. However, the long-range runs of the European model have not been supporting this idea, and this is too far in the future to make reliable genesis forecasts. Thus, the GFS forecasts of a tropical storm in the Caribbean in 7 – 12 days should be viewed at this point as interesting, but improbable.
