This is an excerpt from EERE Network News, a weekly electronic newsletter.

June 04, 2008

Atlantic Hurricane Season Likely to be Above Normal

The Atlantic hurricane season started on June 1st, and it's likely to be an above-normal one, according to the National Oceanic and Atmospheric Administration (NOAA). Experts at NOAA's Climate Prediction Center (CPC) say there's a 65% chance that the Atlantic hurricane season will be above normal. The CPC is projecting 12-16 named storms, with 6-9 becoming hurricanes, of which 2-5 could reach Category 3 or higher. An average season has 11 named storms, including 6 hurricanes, of which 2 reach Category 3 or higher. The season already has one named storm, as Tropical Storm Arthur formed off the coast of Belize on May 31, then quickly headed inland, dissipating by June 2. See the NOAA press release and the archive of bulletins on Tropical Storm Arthur from the National Hurricane Center.

NOAA's projection is generally backed up by other forecasters. On June 3, the team at Colorado State University (CSU) released their latest forecast, which projects 15 named storms, 8 hurricanes, and 4 intense hurricanes. The CSU team estimates a 69% chance of landfall of a major hurricane somewhere on the U.S. coast this year. Among private company forecasters, WeatherBug predicts 10-12 named storms, 4-6 hurricanes, and 2-4 major hurricanes. See the CSU press release and forecast (PDF 68 KB) and the WeatherBug press release. Download Adobe Reader.

So what happened last year, when an active season was predicted, but the season was actually below normal, with only one Category 1 hurricane making landfall on U.S. soil? According to NOAA's CPC, although La Niña was strengthening during the season, it did not reduce the vertical wind shear in the area where tropical storms typically develop. Vertical wind shear (faster winds at higher elevations) tends to inhibit tropical storm development. Atmospheric conditions over eastern North America also inhibited tropical storm development. This year, there's a slight chance that El Niño conditions could develop later in the season, inhibiting hurricane formation and causing the projections to be high once again. Currently, however, the sea surface temperatures are above normal in the eastern tropical Atlantic Ocean and wind shear is low, and both factors point to an above-normal season. See the CPC forecast.