Wednesday, September 14, 2011

La Nina Returns?

NOAA has put out a La Nina Advisory for the 2011 winter season. That's right folks, La Nina appears to have re-developed and is here to stay a bit longer than first thought.

What exactly does La Nina mean, you may be asking? It essentially is a cooling of Sea Surface Temperatures (SST) in the central and eastern portions of the tropical Pacific Ocean. The set up has warmer than average SST's over the western Pacific and cooler than average SST's in the central and eastern Pacific. La Nina typically occurs ever 3-5 years but consecutive episodes occur nearly 50% of the time, according to the NOAA Climate Prediction Center. While La Nina stems from the anomalies of SST's, its impacts go way beyond ocean temperatures.

Sea Surface Temperatures showing a cooler eastern Pacific which signals a La Nina return. Via NOAA CPC.
Winter of 2010 in the United States was a record-setting one. High snowfall totals lead to record Spring flooding and severe weather that was off the charts! The exceptional drought that is on-going in the South...yup, put that one on La Nina. Wichita Falls, TX became the first location with 100 days at or above 100 degrees this year! So the news that La Nina has reformed does not offer much in the way of relief.

What can we expect for winter 2011? Average La Nina winters cause wetter than normal conditions here in the Pacific Northwest and can often expect cooler than average temperatures, too. La Nina doesn't offer much drought relief during the winter months either for those in the South and Southwest,
“This means drought is likely to continue in the drought-stricken states of Texas, Oklahoma and New Mexico,” said Mike Halpert, deputy director of the Climate Prediction Center.  
Typical La Nina setup
Beyond the upcoming winter, it is tough to tell just how long and strong La Nina will be. Should it last into next Summer, it could mean another active hurricane season. During the 2010-11 La Nina conditions, forecasters predicted a very active tropics with 14-19 named tropical storms. As of today, we are sitting at 14 named storms this season. Pretty good, huh? With those cold waters in the Pacific, oceans try to balance out by warming up the tropical Atlantic waters to above average temperatures. So, if La Nina lingers around for another Summer, things could be active again.

With La Nina's anticipated return, records could fall again this winter. That would not be welcome news to most.

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