La Nina No More…

It came and it went. What am I talking about? LA NINA! This past Friday, the Climate Prediction Center (CPC) issued a discussion stating that La Nina conditions had weakened and that we were no longer dealing with La Nina (in the weather community, we call this ‘ENSO-Neutral'”).

The graphic above tells us 2 things, the top graphic shows the temperatures of the ocean water, the bottom graphic tells us the departure from normal that the sea temperatures are. La Nina is considered the cooling of the Pacific Ocean waters and from July 2010 to June 2011, it was present. However, the trend had been weakening and just last week, the ocean temperatures across the Nino regions had returned to normal status. So, was La Nina the root cause for our wacky weather? Not all the way, but it certainly played a big role. So, what could we possibly contribute La Nina to?

For starters, we could likely say that La Nina played a role in the drought.

Storm systems during a La Nina period tend to favor the Northern United States and The Rocky Mountains. (there is still a lot of snow in The Rockies). Of course, the drought monitor above is current, but at one point, it looked much much worse than it is now.

The above graphic shows a typical La Nina weather pattern, which would explain the reason for the drought across Oklahoma and the wetness across The Mountains and now, the flooding across The Mississippi River.A large block high pressure across The Pacific and a displacement in the jet-stream left us with a lot of wind, and a lot of fire weather.

As for the severe weather we experienced this past spring from Oklahoma and to the east. It has not been proven that La Nina seasons lead to higher than normal tornadoes, but it is something that is being studied closely. But, if La Nina does produce higher than normal tornado counts, then this year will likely be studied very closely. According to The Storm Prediction Center, there have been 66 tornadoes in Oklahoma, which would be about 12 above normal. But, the real story comes from the national report on tornadoes where 1500 tornadoes were reported so far, a number that is about 800 above normal.

So, now that La Nina has been considered “officially over”, what can we expect now? For starters, the outlook is somewhat fuzzy. Nina conditions are rarely felt during the summer months. But, should we remain in a neutral phase by the winter, then it should lead to a normal winter here in Oklahoma. However, with 6 months still to go, a lot can change. Only time we tell.




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