An area of low pressure is expected to develop north of the Bahamas on Saturday. This area of low pressure has a medium chance to become the Atlantic’s first subtropical or tropical cyclone of 2020. Although the Atlantic hurricane season does not officially begin until June 1, the month of May has seen a total of 9 subtropical or tropical cyclones form since 2007. These cyclones include Subtropical Storm Andrea (2007), Tropical Storm Arthur (2008), Tropical Depression One (2009), Tropical Storm Alberto (2012), Tropical Storm Beryl (2012), Tropical Storm Ana (2015), Tropical Storm Bonnie (2016), Tropical Storm Alberto (2018) and Subtropical Storm Andrea (2019). If this system becomes a subtropical or tropical storm, it will be named Arthur.

At 10:05 a.m. Tuesday in a Special Tropical Weather Outlook, the National Hurricane Center (NHC) gave the system a near-zero percent chance of development within 48 hours, but a 50 percent chance within five days. The most likely window for development is late Saturday through Monday, when the system will be over warm enough waters for development. However, sea surface temperatures drop to around 24°C (75.2°F) around 30°N. If development occurs, I’d expect it to be fairly weak, and will likely form as a subtropical rather than tropical cyclone. The 00z runs of the GFS, ECMWF, and UKMET models all developed the system into a cyclone, but it is still unclear if it will develop enough tropical characteristics to get classified as a subtropical or tropical cyclone. The most likely scenario is this system moves northeastward without impacting the United States, but the ECMWF model is much farther west than the GFS model. I will be back with an update on this system by Friday.