La Nina 2010 - 2011

[Chris Carter]

Hearing word that the strongest La Nina in about 55 years is poised to poke its ugly head in winter this year. I was wondering if anyone else had heard this or could pull up any information of what winter was like way back then.

I seemed to find that the lowest La Nina index occurred in 1973, but 1955 (55 years ago) was not too far behind this. I believe the strongest index in 1973 was -2.1 for the months of NovDecJan, 3 months before that it was -2.0. Which brings me to 1955 when the index was -2.0 for JanFebMar. Compare those readings to the more current La Nina's we have had over the past 10 - 15 years where the indexes were -1.4 to -1.6. If La Nina does get as strong as its predicted to get, just how bad is this going to affect this upcoming winter? Will it do a complete 180 like El Nino did last year?

 

[Wes Carter]

I'm currently reading about La Nina and it's affects on severe weather in the Southeast and have found some good information that I'm trying to cram into my limited mind and make sense of.

NOAA has a good site for ENSO information if you want to dig a bit and look at data from past years. According to their data, the Southeastern US through Texas and Eastern New Mexico can expect warmer than normal conditions in a La Nina winter. The Pacific Northwest and northern states however normally get cooler temperatures.

The Gulf Coast and Great Plains normally get dryer than normal conditions. I'm assuming this is because of the shift in the jet stream down into Mexico and up through the central US, cutting off the Gulf of Mexico moisture and instead bringing dry air up from Mexico.

There are some other maps and charts I'm trying to make sense of here.

As you stated before, the winter of 1973/1974 appears to be when the strongest La Nina conditions were present as indicated in this chart.

And we all know that 1974 is a very historical year for tornadic activity.

If you are interested in the effects of La Nina in the Southern States, Fred Gossage wrote an interesting article about his take on the upcoming winter. La Nina conditions have historically provided more severe weather to the Southeastern US, especially Mississippi, Alabama, and Tennessee.

I'd love to hear what some of the more knowledgeable and experienced chasers have to say about this. I'm glad you started this thread.

 

[jdrenken]

Here is the graph you posted with 2010's MEI...

It goes quite a bit deeper than what y'all have discussed also. Don't forget the teleconnections. PDO, NAO, AMO, AAO, AO, PNA...all of them have a link.

Something else to consider is also how you go from one extreme to the other. For instance, in 1973, we were coming out of a strong El Nino that turned into a strong La Nina going into the winter.

1972 JAS reading was +1.3
2009 JAS reading was .8

1973 JAS reading was -1.3
2010 JAS reading was -1.0