North Atlantic Basin Reginal SSTA Trends

Discussion: The Main Development Region (MDR) for North Atlantic hurricanes is located between 5N and 23N latitude in-between the Caribbean Sea and northwest coast of Africa (Fig. 1). Currently, the SSTA in this region is a marginally warm +0.31C. There is little change the past 2 weeks but this value has warmed modestly (+0.24) during the past 30 days. The outlooks is for slight marginal warming in September.

In the Caribbean Sea the basin average is +0.22C which is barely marginally warm (Fig. 2). However, the 14-day change is the warmest for the entire North Atlantic at +0.46C. During early-to-middle summer, a tropical upper tropospheric trough (TUTT) was present across the western Caribbean Sea. This feature combined with stronger than normal trade winds kept SSTA near normal. However, the upper shear has weakened and trade winds are not as strong and additional warming is expected in September.

In the Gulf of Mexico, the basin SSTA is +0.22C with most of the anomalous warmth in the northeast sector (Fig. 3). The 7-day change indicates the warmer change is entirely in the northeast Gulf. This zone is a favored area for tropical development/intensification in September.

In the western North Atlantic basin, the SSTA average remains a robust +0.65C (Fig. 4). However, the very warm signature is not as warm as mid-summer. During the past 14 days the basin has cooled 0.14C lead by stunning cooler changes off the U.S. East Coast (Fig. 5). The cooler waters are caused by the coastal counter-current to the Gulf Stream.

Fig. 1: The main development region (MDR) for North Atlantic hurricanes in-between the Caribbean Sea and northwest coast of Africa SSTA.

Fig. 2: The Caribbean Sea basin SSTA regime.

Fig. 3: The Gulf of Mexico basin SSTA regime.

Fig. 4: The western North Atlantic basin SSTA regime.

Fig. 5: The dramatic cooling of SSTA off the U.S. East Coast.