Cooler ocean temperatures ‘suppressing’ North Atlantic hurricane development: Willis Re

Hurricane forecasters are predicting “below-average hurricane activity for the remainder of the 2014,” due in part to cooler-than-average ocean temperatures on part of the north Atlantic, Willis Re. Inc. suggested in a recent report.

“U.S. landfall probability estimates continue to be low this year, though caution should be exercised due to a recent run of poor U.S. landfall forecasts,” Willis Re said in its 2014 Atlantic Hurricane Season Outlook, released Aug. 15.

The report referred to several predictions, from organizations including Colorado State University, the U.S. National Oceanic and Atmospheric Administration Climate Prediction Center, Weather Services International and Tropical Storm Risk, a service affiliated with University College London and sponsored by Aon Benfield and Crawford & Company.

“As we enter the peak of the hurricane season the storms to watch will be those that develop in the far eastern Atlantic just off the African coast since these have greater potential to become major hurricanes on their long track towards the U.S.” Willis Re stated in the outlook. “However, so far the cooler than normal sea surface temperatures and dry air aloft has been suppressing development.”

Willis Re, the reinsurance intermediary operated by London-based brokerage Willis Group Holdings plc, included a table listing forecasts of named storms, hurricanes and major hurricanes.

The range in the forecast numbers of named Atlantic storms, from the sources cited by Willis Re, is 8.6 to 12.0, with an average of 10.2. The typical number is 12, Willis Re noted, adding the “typical number” of “major” hurricanes (category 3 through 5 on the Saffir-Simpson scale) is 2, whereas the average forecast for this year is 1.5.

Willis Re included an image of NOAA’s sea surface temperature anomaly, which is a satellite image taken from a radiometer, which essentially determines the temperature of the ocean surface by detecting radiation. The colour-coded image depicts the difference between the temperature the day the image was taken to the average. The image included in the Willis Re hurricane season outlook, taken Aug. 14, showed cooler-than-normal ocean surface temperatures over part of the Atlantic, mostly south of the 20th parallel.

“This year, waters over the breeding ground of the most intense hurricanes remain slightly cooler than normal,” Willis Re noted. “Given the tremendous inertia of the oceans, it is likely that these cooler waters will persist throughout the hurricane season and suppress intense hurricane development.”