Sunday, 7 October 2012

La Nada analogs, is El Nino dead or reloading?

Latest MEI update shows a large dip which can be expected due to the cooling of the ENSO regions and pop in the SOI values in September.
Notice the pop in the SOI recently to slightly positive. Current SOI values:

 ENSO region 3.4 cooled to +0.2 and nino 4 is at +0.4. Notice the warmest water centred west towards the dateline with a cool plume along the equator in most of the ENSO regions. A quote from Klaus Wolter the MEI founder shows the possibility of another surge of warmth in nino 3.4 and 4 "The burgeoning El Niño event of 2012 may have already run its course, considering an overall environment that appears to favor La Niña conditions since 2006. Or it could get a "second wind" if a currently evolving westerly wind burst northeast of New Guinea manages to penetrate south and east to the equatorial central Pacific. In either case, it would be unprecedented to see a switch back to La Niña before 2013."

The wind flow pattern across the region shows that westerly wind burst near 150 east which may help to move the warm pool westwards helping the el nino.
The cross section shows the warm pool between 160E and 140W:
My thoughts are leaning towards more of a weak el nino with nino 3.4 anomolies near +0.5 but a positive neutral winter is definitely in the cards as well which is why i constructed an analog set based on some la nada years that best represented my thinking on this winter and were positive neutral winters. This set is very close to my thinking with warm condition over the northwest, cool conditions over the southwest, south central and then colder conditions as you get further east. I think coldest departures may end up further south but i really like the look of this temperature outlook which is close to what i have out for this winter. I think the cold in the dakota's is a bit overdone but a slightly below normal year is possible. I have normal across most of the midwest and northern plains. I like the look for chicago as well. I don't agree with the wetter signal that i am getting on these years in the pacific northwest because i believe that the southern jet will track south into california and northern mexico as opposed to the pacific northwest. I would switch the wet anomalies from washington to california. I feel that on the precipitation analogs it is too dry across the great lakes and ohio valley although the area with the driest anomalies just SW of chicago may end up right. It may end up slightly below normal across the eastern great lakes but right now i don't believe that this is the case. I think too wet across the northern plains and interior northwest and feel pretty confident on that.  I believe the interior southeast will average above normal for precipitation.

One thing to remember is in la nada winters other indicies such as the nao, ao, QBO and PNA play a larger role in the overall pattern across north america. This means that if a la nada occurs and the NAO and AO end up negative(which is favoured this year) we are in store for some serious cold. Don't be fooled warm neutral years can pack a punch. 

The cold may also be reinforced by the QBO and stratospheric warming events.

The last east QBO warm La Nada that occurred is one of my analog years 2003-04 and look what happened in the stratosphere and at the surface.
December started off warmer but as the stratospheric warming events occurred frigid temperatures and high latitude blocking  overruled in january. January was tied for boston's 2nd coldest ever with an average temperature of 20.7F and was NYC 7th coldest january ever with an average temperature of 24.7F. 

No comments:

Post a Comment