Revising their predictions on the eve of the official start to hurricane season, Colorado State University's William M. Gray and Philip J. Klotzbach said the 2005 hurricane activity in the Atlantic Basin is now expected to be "well-above average," an upgrade from their early April prediction for an "above-average" hurricane season (see NGI, April 4). Hurricane season officially runs from June 1 to November 20.
"We foresee a well above-average hurricane season for the Atlantic basin in 2005. Also, an above-average probability of U.S. major hurricane landfall is anticipated," the researchers said. "We have adjusted our forecast upward from our early April forecast as it now appears unlikely that El Nino conditions will develop this summer."
As part of the revision, the study predicts there will now be 15 named storms this season in the Atlantic, two more than the 13 that were predicted in April and four more than the 11 named storms on record from 2004. The number of actual hurricanes also increased by one from April to eight, which is also two more hurricanes than the 2004 hurricane season saw. Hurricane days went from the April forecast of 35 days to the end of May prediction of 45 days, which is 20 days more than experienced in 2004.
The researchers also upgraded the amount of intense hurricanes expected from three to four. Last year saw three. As a result, intense hurricane days increased from the April prediction of seven to 11, which is five more than seen in 2004.
Looking at the Saffir-Simpson scale of hurricane strength, the researchers said the probability of at least one major (category 3, 4 or 5) hurricane making landfall on the entire U.S. coastline was 77%, which is significantly above the 52% probability over the past century. Other landfall probabilities include:
"Information obtained through late May 2005 indicates that the 2005 Atlantic hurricane season will be a very active one," the researchers said. "We estimate that 2005 will have about 15 named storms (average is 9.6), 8 hurricanes (average is 5.9), 75 named storm days (average is 49.1), 45 hurricane days (average is 24.5), 4 intense (category 3-4-5) hurricanes (average is 2.3) and 11 intense hurricane days (average is 5.0). We expect Atlantic basin Net Tropical Cyclone (NTC) activity in 2005 to be about 170% of the long-term average. The probability of U.S. major hurricane landfall is estimated to be 150% of the long-period average. We expect this year to continue the past-decade trend of above-average hurricane seasons."
The researchers said this late May forecast is based on a newly devised extended range statistical forecast procedure which utilizes 55 years of past global reanalysis data. Analog predictors are also utilized. "We have increased our forecast from our early April prediction due to continued Atlantic Ocean warming and a decreased likelihood of the development of an El Nino this summer/fall," they said. "Conditions in the Atlantic are very favorable for an active hurricane season."
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