Atlantic warm pool, Caribbean low‐level jet, and their potential impact on Atlantic hurricanes

Abstract

The Atlantic Warm Pool (AWP) is a large body of warm water (warmer than 28.5°C) that appears in the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic during the summer and fall. Located to its northeastern side is the North Atlantic Subtropical High (NASH) that produces the easterly trade winds in the tropics. The trade winds carry moisture from the tropical North Atlantic into the Caribbean Sea where the flow intensifies forming the Caribbean Low‐Level Jet (CLLJ). This paper finds that the easterly CLLJ is maximized in the summer and winter, whereas it is minimized in the fall and spring. The semi‐annual feature of the CLLJ results from the semi‐annual variation of sea level pressure in the Caribbean region associated with the east‐west excursion of the NASH. The AWP's impact is to weaken the summertime NASH, especially at its southwestern edge and thus weaken the easterly CLLJ. The weakening of the easterly CLLJ, in conjunction with the AWP‐induced change of upper‐level wind, reduces the tropospheric vertical wind shear that favors hurricane formation and intensification during August–October.