Active hurricane season fueled by unusually warm water and light steering winds

Weather

COLUMBUS (WCMH) — The 2020 Atlantic hurricane season has produced nine named storms through early August. Hurricane Isaias, which formed on July 29, broke the previous record for the earliest ninth named storm (Aug. 7, 2005–Irene).

NOAA’s Climate Prediction Center updated its seasonal tropical storm forecast by an average of six storms, to between 19 and 24 named storms through the remainder of the year, including 7 to 11 hurricanes, with 74 mph sustained winds or greater.

Three to six storms potentially could reach major hurricane status (Category 3 or higher, with winds of 111 mph-plus on the Saffir-Simpson Hurricane Wind Scale). Earlier in the week, Colorado State University (CSU) issued an upgraded forecast for 24 named storms, higher than previously expected.

Hurricane forecasters look at a number of factors that allow storms to develop and intensify, as tropical waves move west off of Africa across the tropical Atlantic. Near-record weak vertical wind shear in the Caribbean, weak easterly trade winds, very warm warm in the Atlantic Basin, and a stronger West African monsoon are favorable conditions that are likely to extend into autumn.

A neutral or weak La Nina season (cooler-than-normal water in the eastern equatorial Pacific) diminishes wind strength in the western Atlantic Basin and low-level convergence, which is more favorable for storm organization.

Extensive warmer-than-normal sea surface temperatures supply heat and moisture, which allows storms to maintain strength approaching the U.S. Since 1995, the warm phase of the Atlantic Multidecadal Oscillation climate system has contributed to more active hurricane years.

The Atlantic tropical storm season runs from June 1 to November 30, although the first named storm of the season has formed in May every year from 2015 to 2020. The seasons of 1995 and 2010-2012 produced 19 named storms in the Atlantic Basin. The most active year was 2005, when 28 storms were observed.

About 95 percent of tropical storms that develop in the Atlantic Basin storm season occur between mid-August and late October, so there is concern for more landfalls in the midst of the ongoing pandemic during an active year.

If we reach a total of 21 named storms (Wilfred, since the letters Q and U are not on the list), the National Hurricane Center (NHC) will dip into the Greek alphabet, which has only happened in 2005.

Stay tuned for storm updates and all the latest weather information on NBC4 and through our mobile weather app, and on NBC4i.com/weather.

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