Thursday, May 28, 2009

WSI Updated 2009 Hurricane Forecast;. And: El Nino odds rising with warming Pacific

With the start of the 2009 hurricane season on Monday we are welcoming Dr. Jeff Masters' Wunderblog back to the blogroll.
As we have for the last couple years we will supplement his thinking with the Houston Chronicle's SciGuy for action in the Gulf and the Sun-Sentinal's Storm Center for Florida. Of course we'll also be drawing off NOAA and the National Hurricane Center.

For now, it appears that the P&C insurers will make money. That of course could change any day but it's the way to shade the betting.
From the WSI press release:
WSI Corporation's updated 2009 hurricane season forecast continues to call for 11 named storms, 6 hurricanes, and 2 intense hurricanes (category 3 or greater).

Ocean temperatures in the tropical Atlantic are cooler, relative to normal, than at any time since 1994
These forecast numbers are the same as the previous WSI forecast issued in April due to a continuation of relatively cool tropical Atlantic Ocean temperatures and a trend towards El Nino conditions in the tropical Pacific. The 2009 forecast numbers are quite close to the long-term (1950-2008) average of 9.8 named storms, 6.0 hurricanes, and 2.5 intense hurricanes, but are significantly lower than the numbers from the relatively active seasons of the past 15 years.

The 2009 WSI tropical forecast comes on the heels of a very successful 2008 forecast. The WSI December forecast values of 14 named storms, 7 hurricanes, and 3 intense hurricanes were slightly smaller than the final observed 2008 values of 16/8/5. The subsequent updates improved the forecast further, as the April 2008 updated forecast values of 14 named storms, 8 hurricanes, and 4 intense hurricanes were the most accurate amongst the publicly-available forecasts issued last spring.

"Ocean temperatures in the tropical Atlantic are cooler, relative to normal, than at any time since 1994," said WSI seasonal forecaster Dr. Todd Crawford. "Further, the recent La Nina event has now ended and a trend towards El Nino conditions has begun, and because of this we expect at least slightly above-normal wind shear in the tropical Atlantic this season. Neither the cooler tropical Atlantic nor the expected wind shear conditions are enabling for tropical activity this year. While we have persisted our forecast numbers in response to the latest information, future changes to our forecast are more likely to be towards smaller numbers than larger numbers.">>>MORE

From Reuters:

The chances of a 2009 El Nino, a warming of eastern Pacific waters that often brings drought to Australia's farmlands, has risen and is above a 20 percent probability, the Australian Bureau of Meteorology said on Thursday.

International climate models are now predicting a warming of the Pacific Ocean," said the bureau.

"The average of the forecasts from each of these five models predict El Nino conditions being established by the southern spring, and by mid-winter in four of them," said the bureau in its latest report.

"With this higher predictability and better agreement between the forecasts, the probability of the development of an El Nino event in 2009 is now much higher than one month ago and it is significantly higher than the climatological probability of about 20 percent."

The possibility of a drier spring could reduce estimates of Australia's 2009/10 wheat crop, now being planted....MORE

Regular readers may remember this map and commentary from May 14's "AccuWeather cuts 2009 Atlantic hurricane forecast. And: Bill Gray May do the Same":

Here's the latest anomaly map 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

See also April 20's "Hurricane Forecast Reduced ( "Remarkable Cooling in the Atlantic ...")"