Dangerously Warm Northern Gulf of Mexico SST

Fig. 1-2: Current Gulf of Mexico SST and anomalies.

Fig. 3-4: Current North Atlantic SSTA and 30-day SSTA change.

Discussion: The northern Gulf of Mexico SST pattern has warmed to 85-88F (29-31C) in June (Fig. 1). Daily SSTA analysis reveals these values are 3-4C warmer than normal (Fig. 2). During the recent (2016-21) North Atlantic basin active tropical cyclone period when seasonal tropical storm average has exceeded 19 (normal is near 14), tropical cyclones moving into the western or northern Gulf of Mexico across 87F/31C SST (Harvey, Michael, Laura, Delta and Ida) have transitioned into category-4 major hurricanes just-before making landfall. The early season aggressive warming in the northern Gulf of Mexico caused by the super-hot early summer thermal pattern across the Gulf States is very concerning.

In the main development region (MDR) for hurricanes located in-between the eastern Caribbean Sea and Cape Verde Islands, the tropical North Atlantic index (TNA) has warmed to +0.42 which is trending into a very supportive regime for tropical cyclone development despite the early stages of the season. However, the North Atlantic basin has cooled to near normal during June despite the warm northern Gulf and outer tropics (Fig. 3). During the past 30 days, aggressive cooling has occurred off the U.S. East Coast near and east of the Gulf Stream and also across the subtropics (Fig. 4). The cooler SST off the East Coast is attributed to above normal cloudiness associated with an upper trough while up-welling of cool waters due to stronger than normal easterlies south of a strong Azores high-pressure system has cooled the subtropics.

Global SST forecast models (CFS V2, ECMWF, IMME) indicate a robust warm western Northern Atlantic for upcoming hurricane season. The cooling off the U.S. Atlantic Seaboard is a bit of a surprise. However, the MDR and northern Gulf of Mexico are trending into robust warm signatures early!