Wednesday, September 29, 2010

La Niña Influence on U.S. Winter Weather

Headline: La Niña to Influence our Winter Weather Pattern.

As noted in the last posting in the SNR Climate Corner Blog (see link below)
we are currently seeing La Niña conditions in the Pacific Ocean. It is currently a moderate strength La Niña, and it is expected to become a strong La Niña by mid-Winter 2010-11. The attached figure shows the generalized influences on weather and climate in North America for both an El Niño and a La Niña.

Unlike an El Niño which results in a very wet pattern for the southwestern U.S. and Gulf region, the La Niña phase sees the storm track deflected well north to the Pacific Northwest and toward Alaska resulting in very dry and warm conditions across the southwest and Gulf region. Cold air, with much below normal temperatures builds in Canada during the typical La Niña and warm air with above normal temperatures builds across the southern Plains.

La Niña winters in Nebraska are most known for very large swings in temperature as the two air masses, (colder than normal to the north and warmer than normal to the south) battle it out for supremacy. So, don't be surprised if we see some days this winter with record warmth as well as some days with record cold temperatures throughout the region. With drier than normal conditions across the Gulf and a storm track well off to our northwest, Gulf moisture (the primary ingredient for heavy snowfall in our area) should be restricted in our area this coming Winter 2010-11.

Link to La Niña forecast:
http://snrclimatecorner.blogspot.com/2010/09/la-nina-returning-for-winter-2010-11.html),

Link to animation of Ocean surface temperatures (showing the current La Niña):
http://www.elnino.noaa.gov/

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