The first tropical cyclone of the 2018 Atlantic hurricane season has a chance to form late next week – and may lead to a messy Memorial Day weekend for Florida and the Southeastern United States, regardless of development. A Central American Gyre (CAG) and a Convectively Coupled Kelvin Wave (CCKW) are expected to increase convection over the Western Caribbean Sea, leading to the formation of a broad area of low pressure.

The low pressure area is expected to be pulled northward by a trough over the Southeastern United States, and may develop into a tropical or subtropical cyclone during this time. If something does develop, it should be heavily sheared, with most of the heaviest precipitation and the strongest winds east of the center. Global models predict the low may deepen off the coast of the southeastern United States by next weekend as it loses tropical characteristics. The primary threat with this system, regardless of development, is heavy rain and flooding in areas that have already been receiving significant rainfall. I expect strong westerly wind shear to limit significant strengthening, and it is highly unlikely that this system will develop into a hurricane. In fact, it would not be surprising if the system never develops a sufficiently well defined circulation to be classified as a tropical or subtropical cyclone.

The 12z GFS, ECMWF, and CMC models all predicted a broad area of low pressure would develop by late next week, but the potential track of this system remains uncertain. The 12z GFS is farther east, and predicts that a weak closed low would develop near southwestern Florida by late next week (possibly not even a tropical cyclone). The 12z ECMWF is farther west and stronger, predicting a moderate tropical storm would make landfall in the Florida Panhandle by next Saturday. The 12z CMC is somewhat between the two solutions, but only shows a broad area of low pressure moving over west-central Florida rather than a tropical or subtropical cyclone. The CMC model prediction is somewhat questionable because it develops a tropical cyclone over the eastern Pacific, which is most likely a false alarm since no other models are predicting development there.

This setup looks fairly typical for early season Atlantic tropical cyclones, and needs to be watched. I currently give 10-day development chances of 40%. The first name on the Atlantic naming list is Alberto. I will be back with another post tomorrow.