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Western US weather expert

What Is Up with La Nina?/2011 Pacific Hurricane Season

5/05/2011, 12:50:53 AM

It’s been awhile since I updated you on what is happening with La Nina. Well, today is the day I do just that.

La Nina continues to weaken, and this trend is expected to persist into the summer heading to a ENSO-Neutral condition. During the last four weeks, sea surface temperatures were below average between 170E and 140W while they have gone above normal in the eastern Pacific.

Computer models have continued to be consistent with this trend into summer.

After that, there is uncertainty. While computer model averages keep ENSO-neutral conditions through the end of the year, individual models show everything from weak La Nina to weak El Nino conditions occurring, so there is some uncertainty about this time period.

It does seem likely that current La Nina conditions will continue to have a major impact on the weather in the U.S. for the next few months. This will probably mean below-normal temperatures and above-normal precipitation across a large part of the Northern states and below-normal precipitation and above-normal temperatures in the South. The exception to this in the West may be coastal California which will be more greatly impacted by local cooler sea surface temperatures than other places in California and the Southwest.

How about the eastern Pacific hurricane season? With waters warming in the eastern equatorial Pacific it seems highly likely that we are going to have a much more active 2011 than 2010. First, here are the averages are for the this region.

Saying it’s going to be a more active year than last year is not really saying much. Last year was a very quiet year, about as quiet as it can get. There were only seven named storms with just three making it to hurricane status. In 2009, it was a pretty normal year with 17 storms, seven hurricanes. It is my thought that this year will end up being pretty close to average. With La Nina continuing to weaken and my expectation of a more normal monsoon season in the Southwest than last year (albeit maybe late in getting going), should all combine to help develop more storms.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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Western US weather expert