Update – 2009 Hurricane Forecast

17 05 2009

hurricane-ike-batters-cubaAccording to a report from Reuters (Jim Loney, May 13th), Colorado State University hurricane forecaster William Gray may reduce his next Atlantic season forecast because sea temperatures are cooling and a week El Nino may appear by late summer.  “Things are looking better and better for fewer storms,” Gray told Reuters in an interview at the Florida Governor’s Hurricane Conference in Fort Lauderdale.

“Off the west African coast there’s colder water. There’s increasing high pressure in the Azores Islands that typically makes the trade winds stronger,” he said.  In April, Gray’s team predicted the six-month Atlantic hurricane season, which starts on June 1, would see 12 tropical storms, of which six would become hurricanes and two would reach “major” status of Category 3 or higher on the five-step Saffir-Simpson scale of hurricane intensity.

The pioneering forecaster said if his research team lowers the forecast, it would likely drop to 11 storms. The new forecast is scheduled for release on June 2.  The April forecast was already reduced from one issued in December, when the CSU team called for 14 tropical storms, including seven hurricanes and three major hurricanes. 

Gray said sea surface temperatures in parts of the Atlantic were clearly cooling. Where they were about 0.1 degree Celsius above average last fall, they are now about 0.3 degrees Celsius below average, he said.  Hurricanes draw energy from warm water, so cooler temperatures bode well for fewer and possibly weaker storms.

The prospect of an El Nino event — a warming of eastern Pacific waters that can suppress hurricane activity in the Atlantic by increasing storm-wrecking wind shear — could be a key element in the outlook for the 2009 season, Gray said.  “We’re watching that carefully. About half the models are forecasting a weak El Nino by this late summer and the other half aren’t,” he said.

“But it’s getting warmer (in the eastern Pacific) and perhaps the effect of that is to cause westerly winds to blow over the Caribbean.”  The hurricane forecasting pioneer, now 79 years old, issued his first formal seasonal prediction in 1984.  Some of his recent forecasts have been well off target. But the CSU predictions, along with those of the U.S. National Oceanic and Atmospheric Administration, private forecasters AccuWeather and Tropical Storm Risk and others are closely watched by energy, insurance and commodities markets.



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