Subtropical Storm Alpha (1972)

Subtropical Storm Alpha

Subtropical Storm (SSHWS/NWS)
Satellite image of the subtropical storm northeast of Florida
Formed	May 23, 1972
Dissipated	May 29, 1972
Highest winds	1-minute sustained: 70 mph (110 km/h)
Lowest pressure	991 mbar (hPa); 29.26 inHg
Fatalities	2 total
Damage	$100,000 (1972 USD)
Areas affected	Southeastern United States
Part of the 1972 Atlantic hurricane season

Subtropical Storm Alpha (also called Alfa) was a rare off-season subtropical cyclone that hit Georgia in May 1972. It developed from a previously non-tropical cyclone in the western Atlantic Ocean, and initially it moved northeastward off the Carolinas. The storm turned southwestward due to a building ridge, and concurrently it intensified to become Subtropical Storm Alpha. It later moved ashore near Savannah, and it finally dissipated in the northeast Gulf of Mexico on May 29. It produced wave action and moderate rainfall along the coast. Damage totaled over $100,000 (1972 USD), and there were two associated deaths.

Throughout May 1972, a series of weak troughs moved across the eastern United States. In the third week of the month, an upper-level cutoff low developed along one of these troughs, located southeast of the United States and removed from the Westerlies. The origins of Alpha were from a surface low northeast of Florida, associated with the larger-scale, cold core upper low. It organized, and late on May 23 it could be classified as a subtropical depression, east of the Georgia/South Carolina border. While southeast of Hatteras, North Carolina, a developing ridge blocked its northeast motion, and so it slowed to turn to the southeast. On May 25, a small, intense low-level center organized rapidly, and by the next day it attained gale force winds, by which time the storm turned southwestward. At 1600 UTC on May 26, the National Hurricane Center initiated advisories on Subtropical Cyclone Alpha, when the storm was about 225 miles south of Cape Hatteras. Around that time, it reached its peak winds of 70 mph (110 km/h).

On its first advisory, there was disagreement among forecast models regarding its eventual track, with projected tracks deviating from a Georgia landfall to a track northeastward out to sea. Alpha was also a climatological outlier at the time; the NHC HURRAN model, which was based on previous storms with similar characteristics, found no analogs for the storm. Subtropical Storm Alpha was initially well-defined as it moved southwestward. The very small center was located along the eastern edge of the convection, while low-level cloud bands formed east of the center. At the time, the temperature structure was more typical of a winter storm, although it was expected to become more like a subtropical storm typical during the summer months. The winds decreased steadily as it turned more westward on May 27, and the heavy rainfall persisted mostly to the north and west of the center.