July 23rd, 2015

Impact of SSTs on the 2015 Atlantic Hurricane Season

Posted at 1:00 AM ET

Seasonal outlook providers note the cooler than average sea-surface temperatures (SSTs) in the tropical Atlantic as a key factor for a quiet season.

Indeed, a closer look reveals cooler SSTs in the Atlantic Main Development Region (AMDR). However, on closer inspection, above normal SSTs are found in an area adjacent to the U.S. Florida coast including the Bahamas and northern Caribbean. SSTs are also quite warm in the northern Gulf of Mexico (see figure below).

 hurricane-charts-2015_figure-3

  • Disturbances adjacent to the U.S. mainland, northern Gulf of Mexico and northern Caribbean may find an environment that enables development. This applies both to disturbances that originate in the area and also for “Cape Verde” disturbances arriving from their Atlantic transit, even if they haven’t had a chance to develop.

IMPLICATIONS

In light of the expected El Niño and cooler than average SSTs over the AMDR, some subtle but important factors warrant consideration:

1. The suppressive effects of El Niño are found to be strongest over the deep tropics (1) and “Cape Verde” origin storms, and less pronounced for Gulf origin storms or those of higher latitude.

2. With the moderate El Niño expected this year, tropical development may indeed be suppressed in the deep tropics and for African “Cape Verde” type storms.

3. SSTs are somewhat cooler than normal over the tropical East Atlantic, but not for the waters adjacent to Florida, the northern Caribbean or the northern Gulf of Mexico.

4. Disturbances adjacent to the U.S. mainland and northern Caribbean may find an environment that enables development. This applies both to disturbances that originate in the area, and also for “Cape Verde” disturbances that arrive from their Atlantic transit, even if they have not yet had a chance to develop.

5. Landfalls are influenced by large-scale weather patterns at the time of occurrence, which cannot be forecast beyond a 14-day time frame.

So while this indeed may be a quiet year, the northern Gulf of Mexico and northern Caribbean are areas still to watch closely. Hard experience has reminded us time and again that a single landfalling hurricane can be very impactful, with severe consequences both for those affected, and for the industry at large, regardless of basin activity.

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Note:

1. Kossin, J.P., Camargo, S.J. and Sitkowski, M., 2010: Climate Modulation of North Atlantic Hurricane Tracks. Journal of Climate, 23, 3057-3076.

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