Thursday, May 14, 2009

AccuWeather cuts 2009 Atlantic hurricane forecast. And: Bill Gray May do the Same

Two from Reuters:
Private forecaster on Thursday cut its forecast for this year's Atlantic Hurricane season, which begins June 1, to 10 named storms from the 12 it predicted in March.

AccuWeather forecast six of the storms will be hurricanes, down from eight predicted in March, with two of them rated category 3 or stronger on the five-step Saffir-Simpson scale.

AccuWeather's forecast is the latest of several to predict a less active hurricane season than in 2008, when hurricanes Gustav and Ike shut offshore oil and natural gas production platforms in the Gulf of Mexico and refineries in Louisiana and Texas.

Forecasts from AccuWeather and the company's Chief Long-Range and Hurricane Forecaster Joe Bastardi are closely watched in energy markets....MORE


Colorado State University hurricane forecaster Bill Gray said on Wednesday he may reduce his next Atlantic season forecast because sea temperatures are cooling and a weak El Nino may appear by late summer.

The pioneering forecaster told Reuters if his research team lowers the forecast, it would likely drop from the 12 tropical storms predicted in April to 11.

The CSU team had already reduced the forecast from the 14 storms it predicted in December....

A month ago we posted Hurricane Forecast Reduced ( "Remarkable Cooling in the Atlantic ...") with commentary and a March temperature anomaly map from StormX:
...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....
Here's the latest anomaly from Unisys Weather:

Current Sea Surface Temperature Anomaly Plot

Here are the tables of monthly values for the AMO and the PDO. One quick note, the El Nino-Southern Oscillation (ENSO) is distinct from the PDO but the PDO cool phase appears to correlate with a 2:1 La Nina/El Nino ratio whereas the warm phase correlates with twice as many El Nino's. Here is the current Oceanic Nino Index.
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