Colorado State University -- By Philip J. Klotzbach and William M. Gray:  We foresee a very active hurricane season in 2010. We have increased our forecast from early April, due to a combination of a transition from El Niño to currently-observed neutral conditions and the continuation of unusually warm tropical Atlantic sea surface temperatures. We anticipate a well above-average probability of United States and Caribbean major hurricane landfall. All factors are lining up for a very active 2010 hurricane season.

Information obtained through May 2010 indicates that the 2010 Atlantic hurricane season will be much more active than the average 1950-2000 season. We estimate that 2010 will have about 10 hurricanes (average is 5.9), 18 named storms (average is 9.6), 90 named storm days (average is 49.1), 40 hurricane days (average is 24.5), 5 major (Category 3-4-5) hurricanes (average is 2.3) and 13 major hurricane days (average is 5.0). The probability of U.S. major hurricane landfall and Caribbean major hurricane activity is estimated to be well above its long-period average. We expect Atlantic basin Net Tropical Cyclone (NTC) activity in 2010 to be approximately 195 percent of the long-term average. We have increased our seasonal forecast from early April.

This forecast is based on an extended-range early June statistical prediction scheme that utilizes 58 years of past data. Analog predictors are also utilized. The influence of El Niño conditions is implicit in these predictor fields, and therefore we do not utilize a specific ENSO forecast as a predictor.

We expect that the current trend from El Niño to neutral conditions will persist and that weak La Niña conditions will develop by the most active portion of this year’s hurricane season (August-October). The expected trend towards weak La Niña conditions should lead to reduced levels of vertical wind shear compared with what was witnessed
in 2009. Another reason for our forecast increase is due to the persistence of anomalously warm sea surface temperatures in both the tropical and North Atlantic. Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season. Another factor in our forecast increase is the weaker-than-normal Azores High that prevailed during April-May. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons. Another important factor is that we are in the midst of a multi-decadal era of more major hurricane activity. Major hurricanes cause 80-85 percent of normalized hurricane damage.

We are also debuting a hurricane forecast for activity in the Caribbean Basin. This forecast is based on a statistical prediction scheme that utilizes 60 years of past data. This model is predicting a very active season for the Caribbean.

How will the Gulf oil spill impact a hurricane?
We do not anticipate that the oil spill will have any noticeable impact on tropical cyclone intensity or frequency. The strong winds of a tropical storm or hurricane should sufficiently mix the oil and water that there should be no noticeable alterations in broad-scale evaporation and sensible and latent heat flux.

What impact will a hurricane have on the Gulf oil spill?
This depends on the storm’s track in relation to the oil spill. If the storm tracks to the west of the oil, there is the potential that the counter-clockwise circulation of the hurricane could drive some of the oil further towards the U.S. Gulf Coast. Alternatively, a storm tracking to the east of the oil could push the oil further offshore. But, little is understood about the interaction of tropical cyclones and oil.



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