What Happened to all the Snow?   
       
   Jan. 19, 2012: Winter seems to have been on hold this year in some parts of   
   the United States. Snowfall has been scarce so far in places that were   
   overwhelmed with the white stuff by the same time last year.   
       
   California dog driver Tony Phillips poses with his new sled near Mammoth   
   Mountain. In winter 2011 this spot was covered by several feet of snow; in   
   2012 it is bare dirt. [video] Here's a prime example. "The Mammoth Mountain   
   ski resort in the Sierras of California got more than 200 inches of snow last   
   December," says NASA climatologist Bill Patzert of the Jet Propulsion   
   Laboratory. "This December they got less than 10 inches."   
       
   Temperatures have flip-flopped too. There were 583 new heat records broken in   
   the first five days of January in the US.   
       
   "It's 86 degrees in Los Angeles today [Wednesday, January 4th]," says Patzert.   
   "Everyone thinks it's July! In fact, it's warmer today in LA than it was on   
   July 4th last year. And it's been in the 60s and 70 even in the Dakotas   
   lately."   
       
   On January 5th in Bismark, North Dakota, it was 62 -- a marked departure from   
   their average 23 degrees for that day. It was 66 in Denver, Colorado, where   
   it's usually in the low 40s on that date.   
       
   What's going on? Patzert identifies two culprits: La Ni¤a and the Arctic   
   Oscillation.   
       
   First of all," he explains, "we are experiencing a La Ni¤a pattern of sea   
   surface temperatures in the Pacific Ocean. This pushes the jet stream and the   
   cold arctic air northward."   
       
   "On top of that, this year's Arctic Oscillation has been stronger."   
       
   The Arctic Oscillation is a see-sawing pressure difference between the Arctic   
   and lower latitudes.  When the pressure difference is high, a whirlpool of air   
   forms around the North Pole. Last year, the whirlpool motion was weaker,   
   allowing cold air to escape from the polar regions and head southward to the   
   US.   
       
   "This year the whirlpool has been more forceful, corralling the cold air and   
   keeping it nearer the pole. That has reinforced the La Ni¤a impact."   
       
   http://nsidc.org/arcticmet/patterns/arctic_oscillation.html   
       
   (left) Effects of the positive phase of the arctic oscillation; (right)   
   effects of the negative phase of the arctic oscillation (Figures courtesy of   
   J. Wallace, University of Washington)   
       
   While the corralling action of the Arctic Oscillation has kept snow away from   
   parts of the contiguous United States, it has brought extra snow to places   
   inside the whirlpool.   
       
   "The strong positive AO has kept the Jet Stream north," says Patzert.   
   "Snow-delivering storm tracks are pounding Alaska."   
       
   Cordova, a small coastal town about 150 miles east of Anchorage, has been   
   especially hard hit. More than 18 feet of snow has fallen so far this winter.   
   Snow dumps are full, roads have turned into one-lane "snow canyons," and   
   National Guardsmen have been sent in to help residents dig out.   
       
   Even heartbroken snow-lovers of the lower 48 don't want that much white stuff.   
   But they'd like some.   
       
   "Be patient," advises Patzert. "We haven't gotten to the heart of winter. Hold   
   off on selling the new dogsled. There's plenty of time for snow. It ain't over   
   till the Siberian Huskies sing."   
       
   So far in the winter of 2011-2012, the "AO Index" has been mostly positive,   
   signaling a strong Arctic Oscillation. "Compare this to last year's negative   
   AO Index and you can see the difference between the two winters," notes   
   Patzert.   
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   The Arctic Oscillation and Arctic Weather Patterns -- from the National Snow   
   and Ice Data Center   
       
   NOAA's La Nina page -- basic information about the El Nino/La Nina phenomenon     
       
   To see one key difference between this winter and last winter, compare the the   
   Arctic Oscillation Index, 2010 vs. 2011.   
       
   Yes, huskies do sing.  Dr. Tony Phillips' sled team serenades the clouds for   
   snow in Jan. 2012.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.73   
    * Origin: NCS BBS (1:3828/7)