How many LA NINA events have we had in the past 25 years and are we currently in one now?

Question

that would be awesome if you explained this to me! ;) thankks much

Answer 1

La Nina's are characterized by below normal sea-surface temperatures in the Pacific Ocean.  4 regions of the Pacific are designated for monitoring El Nino/La Nina.  Typically, the combination of two of these regions, named Nino 3.4, is used officially to determine the presence of La Nina.  The Climate Prediction Center classifies an event as a La Nina if the sea-surface temperatures for the Nino 3.4 region are 0.5 degrees Celcius or more below normal.  

Since 1983, there have been 5 La Ninas, although one could argue that two of those events were actually the same event, as temperatures in the Nino 3.4 region only briefly were less than 0.5 degrees below normal.  

We are currently in a La Nina and have been since Summer 2007.  Sea-surface temperatures between February and April of 2008 in the Nino 3.4 region were 1.1 degrees below normal.