University of Arizona forecasts a below-average Atlantic Hurricane Season

Published: Tuesday, 03 July 2018 06:43

The University of Arizona (UA) forecasting model is predicted a below-average number of hurricanes for the 2018 Atlantic Hurricane Season, which runs to November 30th. UA researchers are predicting four hurricanes, two of which will be major hurricanes. That forecast falls below the median of seven hurricanes with two majors.

The UA prediction is among the lowest of all published forecasts, which include predictions by the National Oceanic and Atmospheric Administration, the London, United Kingdom-based consortium Tropical Storm Risk and other universities.

Last year, the UA's forecast was among the highest - 11 hurricanes with six majors - and came closest to hitting the mark. The 2017 hurricane season ended with 10 hurricanes and six majors, making it the most active since 2005.

"Since we began issuing our annual hurricane prediction in 2014, our average error is 1.5 hurricanes," said Xubin Zeng, director of the UA's Climate Dynamics and Hydrometeorology Center, a professor of atmospheric sciences and the Agnes N. Haury Endowed Chair in Environment in the Department of Hydrology and Atmospheric Sciences at the UA.

A main factor in this year's prediction is the low sea surface temperatures over the Atlantic, where little warming occurred from April to May. The sea surface temperatures were the lowest Zeng and his team have seen since 2014, but similar to long-term average temperatures. The Atlantic Multidecadal Oscillation index in May, which describes multidecadal climate variability in the North Atlantic, was zero, which is below the threshold at which El NiƱo would affect hurricane activity in the UA model.

"These conditions imply an average year for hurricane activities; however, tropical Atlantic Ocean surface easterly wind - from east to west, the so-called trade wind - is stronger than in most years," Zeng said. "This implies a stronger wind shear, which usually reduces hurricane activities. Therefore, together, we predict a slightly below average year for hurricane activities."