The Atlantic should be a lot quieter than last year with 11 total named storms forecast for the 2012 season as opposed to last year’s 19, but the number of storms to reach hurricane strength (category 1 & 2 on the Saffir-Simpson scale) is expected to be similar to last year. Hurricanes that reach “Major” status (category 3 and up on the Saffir-Simpson scale) is forecast to be 2 this year. Meanwhile, storms that reach tropical storm status should be nearly half of last year’s total. There are a couple of factors that will play important roles in the 2012 Atlantic Hurricane Season including the following:
1. Anomalously cold water in the Tropical Atlantic inhibiting tropical cyclone genesis and intensification.
2. Likely development of El Niño in late Summer/Fall which increases vertical shear and also inhibits storm formation and intensification
WTI has identified 2 years with similar atmospheric and oceanic conditions to 2012 which were incorporated into the WTI model to forecast patterns and tendencies of tropical systems this year. These similar years were 1979 and 2009. Tropical cyclones that form during the 2012 Atlantic Season will tend to follow similar tracks and result in a similar amount of activity to both of these years. In 2009, there were 9 named storms, 2 of which were major hurricanes, 1 reached hurricane status, and 6 reached tropical storm status; in 1979 there were 8 named storms, 2 major hurricanes, 3 hurricanes and 3 tropical storms.
WTI expects the first storm of the season to crop up in July with the bulk of the storm activity over by the end of September. Keep in mind that a storm or two is not out of the question after September and it only takes one land-falling storm to make a huge impact on an area.
The Central Gulf Coast from the East Texas Coast through about the Florida Panhandle will run the highest risk of a land-falling tropical system. Meanwhile, a moderate risk of a land-falling storm will encompass the Southeast coast from about Fort Lauderdale, FL to Charleston, SC. Elsewhere, WTI has lower confidence of a land-falling storm.
Water temperatures in the Eastern Atlantic Ocean are anomalously cool right now. The expectation is for these cool, sea surface temperatures to migrate westward and reach the Caribbean by June. For this reason, we expect that the first storm of the season will hold off until July as the cooler water will inhibit tropical cyclone growth at the very beginning of the season which starts June 1st. Conversely, very warm waters in the Gulf of Mexico will feed storms and contribute to making this a high risk area for storms.
The La Niña (cooler than normal Equatorial Pacific sea surface temperatures) that brought an active season in 2011 has mostly dissipated as sea surface temperatures (SSTs) have turned warmer. In figure 4, the previous 4 weeks of Equatorial Pacific SST anomalies show that warmer areas are increasing in coverage and magnitude while cooler areas are decreasing, especially in the eastern Pacific. El Niño (warmer than normal Equatorial Pacific SSTs) is likely later this Summer or Fall and this will inhibit tropical system development in the Atlantic Ocean by increasing vertical wind shear (a killer for tropical systems) and lowers the chance of a major hurricane. WTI anticipates that the 2012 Hurricane Season will be front-loaded with most of the activity occurring from July until September. As the season progresses, the likelihood of El Niño increases, thus, the environment will be less favorable for cyclone development later in the season.
Both of WTI’s analog years, 1979 and 2009, exhibited similar scenarios to 2012 with a developing El Niño and are considered to be reliable indicators for this year’s season. Expect a near to below normal season for named storms in the Atlantic with a nearly normal to below-normal probability of a storm striking the U.S. The highest risk will be in the Central Gulf Coast, while the area from Fort Lauderdale, FL to Charleston, SC runs a moderate risk of a strike. Remember, it takes only 1 storm to cause a major impact to an area.
Last year the season totals were 19 named storms, 4 major hurricanes, 3 hurricanes, 12 tropical storms, and 3 U.S. land-falling storms. As cautioned in Weather Trends’ report last year, the Carolina coast received a land-falling storm, Hurricane Irene, the most infamous storm of the season. Irene made landfall in NC, NJ, and NY in late August before racing up through New England and Canada. Irene’s impacts included: 41 casualties in the U.S., widespread damage to homes, flooding, and long-lasting power outages from the Carolinas through New England. Tropical Storm Lee made landfall in Louisiana on the heels of Irene’s departure and the remnants from Lee caused flooding from the Gulf Coast through the Mid-Atlantic resulting in some of the region’s most severe flooding in history. Tropical Storm Don was the first land-falling storm of the season which struck S. TX in late July. However, soon after landfall the storm dissipated as it encountered wind shear and very dry air from drought-stricken areas of NE Mexico and S. TX.