Brett Anderson

Update on La Nina and the Upcoming Summer

4/29/2011, 3:15:47 AM

As of the third week of April, a WEAK La Nina currently exists in the equatorial Pacific. La Nina is projected to weaken slowly, and we should be looking at near-neutral conditions by mid-May, according to the International Research Institute for Climate and Society.

The image below shows the sea surface temperature anomalies back in early January, when there was a moderate to strong La Nina. Note the expanse of colder-than-normal water along the equatorial Pacific.


The second image below is the most recent sea surface temperature anomaly. You can see there is much less coverage of cool anomalies along the Pacific equator, while above-normal pockets have shown up in the far Eastern Pacific.


The NOAA image below shows the most recent trend of sea surface water temperature anomalies over the Pacific since March. You can see most of the equatorial Pacific continues to have a positive trend.

590x408_04261346_picture 2

Here is the latest model consensus forecast from the International Research Institute. Clearly, the consensus is for near-neutral conditions this summer and fall; however, strong easterlies, which are associated with LA Nina, remain across the region, and the SOI is still well above normal, which means that despite neutral conditions in the equatorial Pacific, La Nina-type influences on global weather patterns will likely persist into early summer, according to the IRI.

Image courtesy of the IRI.


Note: La Nina is -0.5 and below, near neutral is -0.5 to 0.5, El Nino is 0.5 and above.


Based on current modeling and La Nina, projections it looks like a there will be a continuation of cooler weather across much of southern Canada for the rest of this spring, while severe weather will be widespread from the Mississippi Valley to the Middle Atlantic and Southeast U.S. into early June.

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


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