Thursday, July 12, 2012

Tired of the heat?
Then let's talk about Winter!

6:35 AM EDT 7/12 (Forecaster Mike & Advisor Foot) - So when would you like for us to start giving you the inside scoop on winter? Could there ever be a repeat of 09-10, and if so, are there climate indicators that give early clues about the winter ahead? New readers may not be aware of our Winter Stormcast Team, which has quite the track record for snowfall forecasting in recent years I'm told. One little winter forecast indicator they follow is Arctic Sea Ice decline in summer and recovery starting in September.

For students and teachers aggravated at the paltry snowfall this past winter year, the recently released NOAA Climate Report shows us just how big an impact the loss of Arctic Sea Ice can have on large scale climate here in the U.S. 

ANALYSIS - Our team examined this latest graphic from the National Snow & Ice Data Center, and then did a comparison of the Sea Ice decline levels in the years noted to the snowfall at BWI for the following winter, and here's our question for you. Do you see a correlation between the two? Why is it that 2008 sea ice decline was not much different than 2009, but the 09-10 winter was heads and tails more catastrophic for Maryland than 2008 despite such a tiny difference in Sea Ice levels? The answer may lie in the data for El Nino vs. La Nina! 
The latest Sea Surface Temperature Anomaly in the Pacific as of July 9, 2012 from NOAA
EL NINO/LA NINA - While the results can never be blamed on one single long range signal, El Nino vs. La Nina is always a very important consideration. With a large amount of sea ice through the summer of 2009, we headed into the winter season with strong El Nino conditions in place – much warmer than normal temperatures in the equatorial Pacific. However, the year before was bringing cooler than average temperatures in the Pacific, but it would need to have been cool longer in order to be considered an official La Nina event that year. Still La Nina conditions persisted through the fall and winter that year, which was a sharp contrast to the El Nino a year later.

HOW 2010 GOES AGAINST THE GRAIN - Also, you may be wondering how 2010 fits in here. As you can see from the graphic, sea ice in 2010 was at its record lowest at this point two years ago. However, many of you may remember that 2010-2011 was the Baltimore “snow-hole” winter, where BWI was still able to reach near average. That was also the record breaking year throughout much of the country in terms of snowfall, and this may seem to go against everything else because of the low sea ice present and a Moderate La Nina in place. That year, typically hostile conditions for snow were completely overridden by another group of short range signals, the NAO and AO, which you may hear us discuss.

AND THIS YEAR? - Now where does 2012 fit into all of this? As you can see on the graphic, the sea ice through June is pretty low. The National Snow and Ice Data Center reports that June 2012 saw the record steepest drop in sea ice for the month of June. On the other hand, the La Nina that struck for both winters 2010-11 and 2011-12 has waned and we currently have neutral conditions in place. This may not be the case by the winter though, and we are keeping a very close eye on all of these signals, and more beyond the El Nino/La Nina and the sea ice heading closer to the season!

The extent of Sea Ice as of July 10, 2012. 

While it's not an precisely scientific technique to compare just 6 recent years to each other, it is interesting to point out how much higher the 2009 Arctic Sea Ice levels were  in the summer than all others in the most current data set. In future reports, we will be detailing a much larger swath of data sets across several disciplines in Earth Systems Science related to winter weather indicators.

Our bottom line right now: If you want a lot of snow this winter, better cheer on that sea ice... it's got a lot of fast refreezing to do come fall to make up for the approximately 5.6 million square kilometers of loss observed since its peak in March 2012! 

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