North Atlantic Tropics Are Cooling

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After robust warming in the North Atlantic tropics as defined by tropical North Atlantic index in 2017 and a major contributor to the active hurricane season last year the tropics have cooled significantly the past 2 months.

North Atlantic is cooling, dramatically cooler in tropics

Discussion: During the past 2 months the tropical North Atlantic has cooled dramatically (to below normal). The most dramatic cooling is off the northwest coast Africa where increased trade winds are up-welling cooler subsurface water. The basin-wide regime is cooler than last autumn but steady in the neutral to weak warm phase the past couple months.  The Atlantic multi-decadal oscillation covering the entire North Atlantic Basin is marginally warm while the tropical North Atlantic index is cool (Fig. 1).

Fig. 1: NOAA monthly Atlantic multi-decadal oscillation and tropical North Atlantic index for the past 12 months indicates sudden cooling.

Fig. 2: The North Atlantic basin averages slightly warmer than normal thanks to a warm bias in the western basin while the subtropics/tropics are cool.

Fig. 3: The 30-day change of SSTA across the North Atlantic basin is cooler central and east basin while western basin is warmer.