Yet another May tropical storm has formed over the Atlantic, this time rather unexpectedly. On Wednesday morning, Invest 91L developed a new circulation center underneath the convection mass, and 91L rapidly developed into Tropical Storm Bertha. Bertha has already moved inland into South Carolina, and weakening has already begun. Bertha is the Atlantic’s second tropical storm, approximately two months ahead of climatology. Bertha’s formation makes 2020 the first season since 2016 to feature two pre-season tropical cyclones, and the first season since 2012 to feature two named storms during May. Despite May not being considered part of the Atlantic hurricane season, Bertha is the 11th tropical or subtropical cyclone to form in the Atlantic during May since 2007. However, none of these May tropical cyclones have reached hurricane strength.

As of 2:00 p.m. EDT Wednesday, Tropical Depression Bertha was centered near 33.7°N 80.2°W, and was moving north-northwestward at about 15 mph. Maximum sustained winds were 30 knots (35 mph), with an estimated minimum pressure of 1007 mb. Bertha made landfall near Mount Pleasant, South Carolina at 9:30 a.m. EDT Wednesday, with maximum sustained winds of 45 knots (50 mph), with an estimated minimum pressure of 1004 mb. The National Hurricane Center (NHC) did not well anticipate the genesis of Bertha, initiating advisories just over an hour before landfall. Since Bertha is already inland, Bertha should weaken further, and will likely dissipate by Thursday evening. A Tropical Storm Warnings have been discontinued. However, Bertha is still expected to produce rainfall totals of 2-4 inches across the eastern Carolinas, with isolated totals of greater than 8 inches in some areas.

Eastern Pacific’s first named storm this weekend

The eastern Pacific is still yet to see its first named storm – but that could change this weekend. The National Hurricane Center is monitoring a trough of low pressure over the far eastern Pacific. The NHC gives this system a 30 percent chance of development within 48 hours, and an 80 percent chance within five days. The development of this system appears to be associated with a Central American Gyre (CAG). The exact track of systems like these are tricky to forecast, because it is unclear if and where a center will form. It is possible a tropical storm may make landfall in southern Mexico, Guatemala or El Salvador late this weekend. If this system becomes a tropical storm it will be named Amanda.