How Can La Nina Impact the U.S.

On February 28, scientists with the government`s Climate Prediction Center announced that La Nina conditions were developing over the tropical Pacific as the 2006-2007 El Nino fades away.

La Nina is the periodic cooling of ocean waters in the east-central equatorial Pacific, which like its cousin El Nino, can impact weather patterns across the U.S.

This La Nina is still in its formative stages, so forecasters and scientists stress that it is too early to know how it will affect the weather patterns over the next six months.

However, past La Nina winters have produced some of the following effects:

• Hurricane Activity in the Atlantic tends to be above-normal with activity below normal in the Pacific
• The chances of the U.S. experiencing a hurricane increase substantially during La Nina
• The northerly jet stream keeps the southern U.S. drier and warmer than normal. Prolonged droughts are possible. The Ohio Valley, central Appalachians and Mid-Atlantic experience less days of below-freezing high temperatures.
• A more northerly Pacific jet stream brings more storms into the Northwest and Canada`s British Columbia. Winter time rainfall and mountain snow is more frequent and total accumulations trend higher.
• Storm track across the U.S. tend to take a northern track across the central U.S., bringing increased precipitation and more large swings in the temperatures to the eastern Plains, Great Lakes and Ohio Valley.
• Seasonal snowfall totals for much of the Mid-Atlantic, southern and central Appalachians and the Northeast Coast is significantly lower during a La Nina winter.
• Cold pools of air tend to dive south out of the Arctic and into the Northwest, northern Rockies and northern Plains.

To learn more about La Nina from the Climate Prediction Center`s website, click the link to the left of this story.

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