Monday, April 20, 2009

Hurricane Forecast Reduced ( "Remarkable Cooling in the Atlantic ...")

From Reuters:
The 2009 Atlantic hurricane season will produce 11 tropical storms, of which six will become hurricanes, WSI Corp predicted Monday.

The Andover, Massachusetts, private forecaster reduced its forecast from the one it issued in December, when it said the six-month season starting on June 1 would see 13 tropical storms, including seven hurricanes.

The lower forecast was due to cooler water temperatures in the tropical Atlantic Ocean and a fading La Nina cool-water event in the eastern Pacific, the forecaster said.

WSI predicted that two of the six hurricanes would be "major" storms of Category 3 or higher on the five-step Saffir-Simpson scale of hurricane intensity. Such storms are the most destructive type, with sustained winds winds of greater than 110 miles per hour (177 km per hour).

Another prominent storm forecaster, Colorado State University, also reduced its forecast recently....MORE
Back in March the folks at StormX had a post with a couple maps that show the Sea Surface Temperature anomaly change graphically:

Remarkable Cooling in the Atlantic May Decrease 2009 Hurricane Activity

...A cooler Atlantic may impact the upcoming hurricane season, as cooler ocean temperatures inhibit storm development. In 2005, when the AMO was near its peak warming, the most active Atlantic hurricane season on record occurred with 27 named storms. Between 2005 and 2009, there have been significant changes in Atlantic Sea Surface Temperature (SST) anomalies.

The Atlantic Multidecadal Oscillation Index has been developed by scientists to track surface temperature changes in the Atlantic. This index is correlated with tropical storm frequency; high index values indicate a warmer ocean and more tropical storms, and low index values indicate a cooler ocean and less tropical storm activity. In February 2009, the index reached a value of -0.11, the lowest observation since November 1996....
See also:

US Climate Update: Driest Start to Year on Record
...*Note: Although the AMO is in it's warm phase, the monthly sea surface temperature anomaly is currently negative. This happens. During the 30-year warm phase of the PDO that ended in September 2007, there were months in which the anomaly fluctuated in the opposite (cooler) direction. The east coast drought appears closer to the historical record for -AMO/-PDO. It should break when the AMO anomaly rises. This stuff is so exceedingly complex that it is probably impossible to model with any degree of resolution (granularity), it is more about shading the odds in one direction or another. If you want certainty, go rig a market (or something)....
More on the Possibility of a Hurricane Striking New York City
Atlantic Hurricane Season Will Be Less Active, AccuWeather Says