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-AO/-PNA Analogs to this winter

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-AO/-PNA Analogs to this winter

Post by Toot on 2012-12-08, 1:39 pm

Seeing most guidance ramp up the negative PNA got me to digging into some data for some analogs as the negative PNA was not expected by me this winter and I still have my doubts that it lasts into January but never the less.. here are some analogs that featured a -PNA and -AO December. Going back to 1950 I could only find four cases

The following analogs were chosen due to both the PNA and AO having a December value of at least -1.00. The winters are 1961/62 1996/97 and 2010/11.

All three of these cases broke down the -AO by Febuary

1961/62 500Mb winter pattern anomaly

The PNA won out that year as January and Febuary went on to feature a negative PNA



1996/97 500Mb winter pattern anomaly

The AO won out that year as January and Febuary featured a positive PNA



2010/11 500mb winter pattern anomaly

No one indice really stands out as winner that year as January feature a highly positive PNA and Febuary featured a negative PNA


The following analog featured a negative PNA of at least -0.50 and a negative AO value of at least -1.00 during the month of December

1978/79

The PNA went on to win out that year as Jan and febuary went on to feature a negative PNA

All four analogs averaged out temperature anomalies for the winter


..........................................................................................................

After looking at those one has to ask..do those really match the pattern the last few months? Not really..only one featured a October..November and December AO value like this fall has. That would be 2010/11 which also featured a VERY Deeply negative AO during the month of December.
As we speak the current -AO sets around -3.00

After looking at the above data...I can only draw one conclusion..the negative AO should continue to overwhelm the pattern into late January and in theory that will help offset possible harsh conditions in the Pacific. That said..its just my opinion when looking at the data and I could very well be wrong.

I might add that 1978/79 and 2010/11 featured a negative NAO during the months of December and January which had MAJOR implications of us being cold or not. As always..the NAO is boss around here!






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Re: -AO/-PNA Analogs to this winter

Post by Toot on 2012-12-08, 2:11 pm

This is what happens when you factor in the negative NAO as these two years featured the -NAO/-AO/-PNA

Another cold anomaly that pretty much proves a -NAO will usually trump the Pacific


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