Disturbance over the Bahamas Given a Low Chance of Development

The first area of interest has been tagged in the Atlantic basin over the Bahamas, coinciding with the opening of the final and most active month of the off-season: May. The National Hurricane Center is giving it a low chance, near 0%, of forming into a TC over the next 2 days as it treks towards Florida, and a 20% chance through early next week as it moves off the coast of the southeastern United States.

5 Day Graphical Special Tropical Weather Outlook issued at 9:25 EDT on May 1, indicating a low threat of TCG off the southeastern U.S.

The disturbance is currently located over the central Bahamas in the form of a weak, inverted surface trough, which has been producing relatively abundant convection near and east of the trough axis. Last night, a weak vorticity maxima developed north of eastern Cuba on the southern end of the trough. It was not being supported by vigorous convection or located towards the northern tip, where vorticity would be its greatest, so it was a short-lived mesoscale feature, but it has enhanced vorticity and sporadic convective coverage across the trough axis.

Visible imagery of the disturbance in the Bahamas this morning, revealing a broad trough axis and sporadic convection. (GOES-16 MSFC).

An upper-level trough has been present to the north of the disturbance, which was providing sufficient baroclinic forcing and instability, aiding convective development on east side of surface trough. In addition, the southwesterly flow from upper trough and westerly flow over Caribbean Sea has been causing upper divergence as well, allowing convection to blossom. However, this trough is also instigating some westerly shear over the surface trough, which is not allowing the convection to bundle near the trough axis. This has also shoved the mid-level vortex to the east of the trough axis, currently located over the Turks and Caicos Islands.

GFS analysis of the 200mb wind, showing the upper trough northeast of the disturbance. (Tropical Tidbits)

Over time, the upper trough will kick out and flatten, which is beginning to allow mid-level ridging to build over the Carolinas. This will cause shear to temporarily subside, but the disturbance will then begin to progress northwest towards Florida, where it should arrive by tomorrow. This will hinder chances of tropical or subtropical cyclogenesis temporarily. However, as the ridge builds southward and the trough kicks into the southeastern U.S., the system may have a brief window to develop into a tropical or subtropical cyclone as it passes over the Gulf Stream, the only place where SSTs will be adequate enough for development, and as that trough adds baroclinic forcing to the disturbance. The chance remains low for now, but the evolution of the steering and where the storm tracks is crucial to determine if it will develop.

Regardless of development, this system will bring inclement weather to Florida and the the rest of the southeastern U.S. into the weekend. The main, and only, threat will be heavy rains, which may total up to 2″ or higher over the east coast of Florida. Chances of development remain low for now, but keep tabs with the National Hurricane Center for the latest on this disturbance. Hurricane season begins in a month, and this is the first of multiple disturbances that will form into the summer and fall. Make sure you have a plan just in case a storm comes knocking on your doorstep.

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