It appears very likely that the Atlantic’s streak of pre-season tropical activity, which began in 2015, will continue for a sixth year. A trough of low pressure – now designated Invest 90L – is likely to organize into 2020’s first tropical or subtropical cyclone, possibly as soon as Friday evening. An Air Force Reserve Hurricane Hunter aircraft has been tentatively scheduled to investigate 90L on Friday afternoon.

As of 2:40 p.m. EDT Thursday, the National Hurricane Center (NHC) gave 90L a 70 percent chance of development within 48 hours, and an 80 percent chance within five days. If this disturbance organizes into a tropical or subtropical storm with maximum sustained winds of at least 39 miles per hour, it will be named Arthur. This disturbance was designated Invest 90L on Thursday afternoon. As of 18:00 UTC Thursday, Invest 90L was centered near 23.7°N 81.2°W. Maximum sustained winds were 30 knots (35 mph), with an estimated minimum pressure of 1013 mb.

The most likely window for development will be between Friday night and Saturday, as a low pressure center is expected to form over the northwestern Bahamas around this time. The exact location of where the center forms remains uncertain, and more impacts may be felt for Southeastern Florida if the center forms farther west than anticipated. In their 12z Thursday runs, the GFS and ECMWF models developed 90L into a classifiable system. The GFS model is stronger, appearing to develop 90L into a high-end tropical storm with maximum sustained winds of at least 65 mph, while the ECMWF model is much weaker, depicting a weak, broad, likely subtropical storm. The center of the disturbance, if it develops, should remain offshore the United States East Coast. 90L will likely bring some rainfall to Southeastern Florida and maybe the Outer Banks of North Carolina, but significant flooding appears unlikely. However, heavy rainfall in the Bahamas appears likely, with isolated rainfall totals of over 5″ possible in some areas. 90L may produce isolated tropical storm force wind gusts in southeastern Florida and the northwestern Bahamas. It is possible tropical storm watches or warnings may be issued, in which case the National Hurricane Center would initiate Potential Tropical Cyclone advisories.

If 90L develops, it will be the 10th tropical or subtropical cyclone to form in the Atlantic basin during May in the last 13 years. Despite not being officially part of the Atlantic hurricane season, the month of May has had activity in 9 of the last 13 seasons! The National Hurricane Center does not appear as if they will move up the start of hurricane season, since none of the systems in May have reached hurricane strength.

I will be back with an update on 90L tomorrow.