Adding to the chorus of forecasters calling for a busy Atlantic hurricane season, experts at the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center said Tuesday they are projecting a 75% chance that the 2007 Atlantic hurricane season will be above normal, while WSI Corp. agreed -- showing the ongoing active hurricane era remains strong despite the "aberration" that was the 2006 season.
"For the 2007 Atlantic hurricane season, NOAA scientists predict 13 to 17 named storms, with seven to 10 becoming hurricanes, of which three to five could become major hurricanes of Category 3 strength or higher," said Conrad C. Lautenbacher, undersecretary of commerce for oceans and atmosphere and NOAA administrator.
NOAA said an average Atlantic hurricane season brings 11 named storms, with six becoming hurricanes, including two major hurricanes, while some other forecasters put the seasonal long-term averages at 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes.
Andover, MA-based WSI said it expects the tropical season to have 15 named storms, eight hurricanes, and four intense hurricanes. The forecaster said the main drivers of the expected active season are:
"The 2006 tropical season was surprisingly inactive, considering the relative warmth of the tropical Atlantic Ocean," said Todd Crawford, WSI seasonal forecaster. "The historical record shows that 2006 was a bit of an aberration in this regard, and we feel that the continued warm ocean temperatures tilts the odds strongly towards an active season in 2007. Further, our seasonal temperature models depict a warm summer in the Southeast. If this occurs, the stronger-than-normal Atlantic subtropical ridge should act to steer more storms into the Gulf of Mexico than in a typical year."
Earlier this month, AccuWeather Chief Hurricane Forecaster Joe Bastardi said that as many as seven storms -- of an expected 13-14 named storms -- could strike the U.S. coast during the 2007 Atlantic hurricane season. Three or more of the season's storms are likely to be Category 3 or greater on the Saffir/Simpson scale (see Daily GPI, May 9).
The Colorado State University (CSU) hurricane forecast team led by Phil Klotzbach and William Gray and London-based Tropical Storm Risk (TSR) have also called for more active than normal storm activity this year. TSR is forecasting 2007 Atlantic basin and U.S. landfalling tropical cyclone activity will be about 75% above the 1950-2006 norm, the highest March forecast for activity in any year since the forecaster began issuing real-time forecasts in 1984 (see Daily GPI, March 22). TSR is forecasting that 17 tropical storms will form, which includes nine hurricanes and four Category 3-5 storms. Five storms, including two hurricanes, are expected to make U.S. landfall, the TSR estimated.
Upping its December prediction, the CSU team has said the U.S. Atlantic basin will likely experience a very active hurricane season in 2007 with an increased probability of a major hurricane making U.S. landfall (see Daily GPI, April 4). CSU anticipates 17 named storms with nine of those expected to become hurricanes, of which five are expected to develop into intense or major hurricanes.
NOAA said Tuesday that climate patterns responsible for the expected above-normal 2007 hurricane activity continue to be the ongoing multi-decadal signal, which is the set of ocean and atmospheric conditions that spawn increased Atlantic hurricane activity, warmer-than-normal sea surface temperatures in the Atlantic Ocean and the El Nino/La Nina cycle.
Last year, seasonal hurricane predictions proved to be too high when an unexpected El Nino rapidly developed and created a hostile environment for Atlantic storms to form and strengthen (see Daily GPI, Dec. 1, 2006). When storms did develop, steering currents kept most of them over the open water in the middle of the Atlantic.
"There is some uncertainty this year as to whether or not La Nina will form, and if it does how strong it will be," said Gerry Bell, lead seasonal hurricane forecaster at the NOAA Climate Prediction Center. "The Climate Prediction Center is indicating that La Nina could form in the next one to three months. If La Nina develops, storm activity will likely be in the upper end of the predicted range, or perhaps even higher depending on how strong La Nina becomes. Even if La Nina does not develop, the conditions associated with the ongoing active hurricane era still favor an above-normal season."
Bell also noted that preseason storms, such as Subtropical Storm Andrea in early May, are not an indicator of the hurricane season ahead. "With or without Andrea, NOAA's forecast is for an above-normal season."
"With expectations for an active season, it is critically important that people who live in East and Gulf coastal areas as well as the Caribbean be prepared," said Bill Proenza, NOAA National Hurricane Center director. "Now is the time to update your hurricane plan, not when the storm is bearing down on you."
While the Atlantic hurricane season runs from June 1 through Nov. 30, the peak activity occurs from August through October. The NOAA Climate Prediction Center will issue an updated seasonal forecast in August just prior to the historical peak of the season.
WSI's next full seasonal forecast package, which will include both an update on the current tropical season as well as expectations for late summer temperatures, will be issued on June 19.
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