The 2020 Atlantic hurricane season officially began today, though two tropical storms had already formed – Arthur and Bertha. Arthur strengthened into a moderately strong tropical storm off the coast of the North Carolina Outer Banks, while Bertha unexpectedly developed and made landfall in South Carolina. Invest 92L nearly developed into a subtropical cyclone early Saturday morning, but was unable to do so. However, Invest 93L has developed into Tropical Depression Three. TD Three, associated with the remnants of eastern Pacific Tropical Storm Amanda, is gradually getting better organized, and an Air Force Hurricane Hunter aircraft is scheduled to visit the depression late Tuesday morning. If 93L gains maximum sustained winds of 39 mph, it will be named Cristobal. The current earliest third named storm record is held by Tropical Storm Colin (2016), which developed on June 5. TD Three is very likely to break that record. TD Three is the first June Atlantic tropical cyclone since Cindy in 2017, and the earliest tropical cyclone to develop over the Bay of Campeche on record. In addition, TD Three is the first Atlantic tropical cyclone to be active on June 1, the first official day of hurricane season, since Tropical Storm Barry in 2007.

As of 4:00 p.m. CDT (5:00 p.m. EDT) Monday, Tropical Depression Three was centered near 19.6°N 91.2°W, and was moving west-northwestward at about 7 mph. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1007 mb. TD Three faces a highly uncertain future. The 12Z Thursday GFS and ECMWF operational model runs all predicted that the depression would make landfall and move into Veracruz, Mexico by Thursday. The GFS and ECMWF show what appears to be a separate tropical cyclone developing over the central Gulf Mexico in about five days. The GFS and ECMWF show this new tropical cyclone remaining a large, sloppy tropical storm. They also are both in agreement of a sharp turn to the west late in the forecast period, towards Texas. It appears likely there will be some sort of tropical feature to affect Texas and/or Louisiana 6-7 days from now, but it is unclear if it will be TD Three or a new system. However, the HWRF model, as well as many ensembles from the European EPS suite, predicted that Three would remain over water. It is worth noting that the HWRF, as well as many EPS members that keep Three over water bring it up to hurricane strength. The last Atlantic hurricane to form in the month of June was Chris in 2012, and the last hurricane to make landfall in the United States during June was Bonnie in 1986. The future of TD Three hinges largely on whether it moves inland into Mexico or remains over the Bay of Campeche.

Based on the 18z run of the SHIPS model, environmental conditions over the Bay of Campeche are conducive for intensification. Sea surface temperatures were warmer than 29°C (84.2°F), and wind shear was relatively light (less than 20 knots). The mid-levels of the atmosphere were also very moist, with relative humidity values near 80 percent at 700-500 mb. The large size of the depression as well as its monsoonal nature could act to slow intensification, though. The ECMWF model shows significant intensification during the next 48 hours, bringing TD Three to strong tropical storm strength prior to moving it inland into Mexico. If TD Three moves inland into Veracruz as suggested by the operational GFS and ECMWF, it will likely dissipate quickly due to the mountainous terrain of central Mexico.

Regardless of how much the depression strengthens, heavy rainfall is a major threat to southern Mexico, Honduras, Guatemala and El Salvador. A Tropical Storm Warning is currently in effect from Campeche, Mexico to Puerto de Veracruz, Mexico. Rain accumulations of up to 10-15 inches are possible over Veracruz from TD Three.

I will be back with an update on TD Three tomorrow. This is a very uncertain situation.