CPC Issues La Niña Watch

 

 For the last 12-18 months, El Niño has been on our minds.  Cooler and wetter conditions typical of an El Niño pattern were experienced here in the southeast United States this past winter.  Well, it looks like condtions are changing.  On Thursday, June 3, NOAA's Climate Prediction Center (CPC) issued a La Niña Watch.  Click here to read the bulletin.

The question now becomes, why?  Well, a couple of things factor into the CPC making the decision to issue this watch.  Foremost is the change of Sea Surface Temperatures (SSTs) in the Pacific.  As it has been well documented, the oscillations from El Niño to La Niña, and vice versa, are fairly well correlated with changes in the SSTs in the Pacific.  Cooler than normal SSTs indicate the onset of La Niña conditions.  Here are the latest images from the Pacific:

 

 

 

Models are also indicating the transition (numbers from -0.5  or less indicate La Niña conditions):

 

 

 

So, what has happened in central Alabama during La Niña conditions?  Looking at 13 previous summer La Niña's,

 

Birmingham has had

  • 3 below normal seasons
  • 5 near normal seasons
  • 5 above normal seasons


Montgomery has had

  • 2 below normal seasons
  • 5 near normal seasons
  • 6 above normal seasons

 

Autumn trends towards drier than normal in both locations but can be heavily influenced by tropical systems.  Now we have to ask, what does La Niña mean for tropical activity?  Well, it depends on how strong the La Niña conditions become, but typically, La Niña conditions favor tropical development.  Upper level winds that can shear a tropical system apart are usually weaker, which can lead to more development.  On top of that, current SSTs in the Atlantic and Gulf of Mexico are already running warmer than normal:

 

 

 

So, it's still early, but all indications lean towards an active tropical season.  To review NOAA's 2010 Tropical Season Outlook, click here.


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