Thursday, May 21, 2009

Summer Climate Outlook

The Climate Prediction Center issued its Summer Climate Outlook for June, July, and August 2009 this morning. These three-month outlooks are usually heavily influenced by what is going on with the El Nino Southern Oscillation (ENSO) cycle. However, in the Spring this year, the Equatorial Pacific transitioned from La Nina conditions to ENSO neutral, meaning that there are no significant anomalies of sea surface temperatures in that region, either much warmer or much cooler than average. So in the absence of a strong climate driver like El Nino or La Nina, forecasters must rely on recent trends in precipitation and heavily on climate model output for a long-term outlook.

Here is the national temperature outlook for June-August 2009, where the blue shades indicate below-average temperatures and the orange shades indicate above-average temperatures. The Commonwealth has a chance of warmer-than-average temperatures for the Summer months this year.





As for precipitation, most of the country has equal chances (EC) of being either wetter or drier than average this Summer, including Virginia. The green shades indicate wetter than average conditions, while the orange shades indicate drier than average conditions.


In other words...this Summer's outlook just might be any one's guess in the absence of an obvious influence like El Nino or La Nina. This is pretty much what a slew of computer models "think" will happen.
--Carrie

Update Thursday Mid-day:
NOAA also announced its 2009 Atlantic Hurricane Season Outlook this morning, and they are predicting an average hurricane season, which means there is a good chance for "nine to 14 named storms, of which four to seven could become hurricanes, including one to three major hurricanes (Category 3, 4 or 5)." Again, because of the absence of an El Nino or La Nina, there is no significant, possible driving influence on hurricane formation or inhibition. Basically NOAA is saying it is important to be prepared for tropical cyclones if you live within a couple hundred miles of the coast (remember, there is the flooding threat from heavy rain that exists from tropical systems moving inland). For more on how to be prepared for hurricane season, click here.
--Carrie