Impressive Early 2013 Pattern Shift Continues

[bluewave]

The impressive early 2013 pattern shift continues. Early in 2013 we saw a reversal of the

+EPO regime of 2010-2012 to a -EPO pattern. The 2010-2012 period featured a nearly

continuous +EPO phase which kept temperatures around NYC Metro well above normal.

Several records for AO and NAO blocking were set during this interval. The last Atlantic

side blocking record was set during the transition process when the AO set an all time

lowest record for the month in March 2013 of -3.185. Since that time the temperatures around

our area have been cooler relative to what was experienced from 2010-2012. Records

for NE Pacific blocking followed since that time. The shift to less blocking and lower

pressures over the North Atlantic has weakened the AMO from the very strong levels

that were common from 2010-2012. So the shift to more impressive EPO region blocking

than NAO and AO continues to this day.

 

 

 

 

 

 

 

 

 

[Isotherm]

Now the one remaining pattern is to couple the two signals such that strong blocking dominates both the NPAC and NATL this winter.

[bluewave]

Now the one remaining pattern is to couple the two signals such that strong blocking dominates both the NPAC and NATL this winter.

 

Yeah, that would be something to see. It was just a really impressive transfer of record blocking from the Atlantic

side around Greenland to the Northeast Pacific from 2010 to 2013. I plotted out the long term 500 mb heights

around Greenland on the top and the Northeast Pacific south of Alaska on the bottom. They were historic

events for each location.

 

Greenland area 500 mb heights

 

 

Northeast Pacific south of Alaska 500 mb heights

 

[Yanksfan]

Now the one remaining pattern is to couple the two signals such that strong blocking dominates both the NPAC and NATL this winter.

Better yet, how about a Rex Block pattern along with an El Nino. 

[Isotherm]

Yeah, that would be something to see. It was just a really impressive transfer of record blocking from the Atlantic

side around Greenland to the Northeast Pacific from 2010 to 2013. I plotted out the long term 500 mb heights

around Greenland on the top and the Northeast Pacific south of Alaska on the bottom. They were historic

events for each location.

 

Greenland area 500 mb heights

 

G.png

 

Northeast Pacific south of Alaska 500 mb heights

 

P.png

 

 

 

Yeah the 2010-present period has undoubtedly been historic in terms of the extreme / anomalous pressure patterns across the northern hemisphere, from record -AO/NAO blocking in the early part of the decade to long duration EPO blocking since 2013.

 

It doesn't happen all that often, that is, the coupling of strong -EPO and -AO/NAO blocking, but when it does, the results are certainly historic.

 

Two examples of winters in which high latitude blocking dominated in both the NPAC and NATL/Arctic were 1976-77 and 1977-78.

 

One can see the resultant H5 pattern is about as good as it gets cold / snow wise in the East.

 

 

 

[Weathergun]

The +PDO is on fire. Despite long-range guidance may show, I don't think -EPO/+PNA patterns aren't are going away, anytime soon. The -NAO:

 

 

[Yanksfan]

The +PDO is on fire. Despite long-range guidance may show, I don't think -EPO/+PNA patterns aren't are going away, anytime soon. The -NAO:

 

 

I think we will see this winter predominately a -EPO/ +PNA regime, with occasional brief breakdowns- (reloading) of the overall pattern.

[bluewave]

The cooler temperatures after the pattern change in early 2013 are obvious for NYC.

 

 

NYC annual temperature departures and high and low temperatures for the year since 2010:

 

Year.....departure....high....low

 

2010....+1.8............103.....13

2011....+1.5............104......6

2012....+2.4............100.....13

2013....+0.4.............98.......11

2014.....-1.4..............92.......4.......through August

[NEG NAO]

Now the one remaining pattern is to couple the two signals such that strong blocking dominates both the NPAC and NATL this winter.

I have my doubts about the NAO staying mainly negative this winter after its performance the last week when it has all of a sudden spiked to positive levels not seen in a long time after being mainly negative since last spring- and the NAO forecast is for it to remain mainly positve the next couple of weeks -it is possible we are entering a 6 month period of mainly positive - since we have just exited a 6 month period of mainly negative - just have to wait and see as trying to predict what will happen with it this winter is next to impossible ....

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao_index_mrf.shtml