Scientists still see 16 storms, nine hurricanes
Warmer than average sea temperatures, lower than average sea level pressures and the lack of an El Niño in the tropical Pacific Ocean are likely to combine to produce an active peak portion of the Atlantic Basin hurricane season.
Colorado State University scientists Phil Klotzbach and William Gray issued their adjusted 2011 Atlantic hurricane season forecast on Wednesday, sticking to the same numbers they predicted in April and June of this year. Using a variety of statistical and analog forecasting methods, the duo sees the formation of 16 named storms, nine hurricanes and five major hurricanes of Category 3 or above.
Those figures are all significantly above the official US-National Hurricane Center seasonal averages of 11 named storms, six hurricanes and two major hurricanes.
One uncertainty that Klotzbach and Gray cited in their April and June forecasts was whether a warming trend in the tropical Pacific Ocean would continue enough to bring on the onset of an El Niño, a cyclical weather phenomenon known to suppress the formation and strengthening of tropical cyclones in the Atlantic Basin. The scientists said that the warming trend has abated.
“We are reasonably confident that we will have near neutral [El Niño] conditions for the remainder of this year’s hurricane season,” their report stated.
In addition, Klotzbach and Gray estimate the probability of a landfall of a major hurricane in the United States and major hurricane activity in the Caribbean to be well above the long-period average.
According to National Hurricane Center climatology statistics, the average date for the formation of the first hurricane in the Atlantic Basin is 10 August, and the average date for the first major hurricane is 4 September.
Although hurricane season officially starts 1 June, the average number of tropical cyclones that form in June and July is less than one for each month. In August, however, wind sheer in the Atlantic Basin decreases, bringing a sharp increase in the average number of named storms and hurricanes.
The peak of the Atlantic hurricane season occurs on 10 September, but the average numbers of storms stays relatively high until the third week of October, at which point it sharply decreases. However, late season tropical cyclone activity until the second week of November is still higher than early season activity, especially in the area of the western Caribbean.