Thursday, 26 September 2013

Long Range Lookout: Technical Discussion

Couple interesting factors showing up...

Relative AAM tendency is on the rise, meaning the Gulf of Alaska trough is coming back into play with a +EPO/WPO couplet dominating the next two weeks. Euro weeklies indicating the potential for this feature to stick around well into october. 
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Need to keep a very close eye on this. If the GOA vortex continues to be a factor as we head into late october/november it could very well come into play by winter.

Current SLP pattern since september 1st has a lack of greenland blocking and strong AK trough
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Current SLP pattern looks fairly similar to september 2011 which preceded a winter with a very strong AK vortex.
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I am in no way saying that this winter will be anything like 2011-12, just pointing out some similarities. In fall of 2011 we saw a large pickup in solar activity. This helped cool the stratosphere and raise 500mb height anoms in the tropics. Poleward propagating +AAM, Indian Ocean tropical forcing, a raging hadley cell and a cooling stratosphere did not bode well for blocking and helped force troughiness around AK. The good news is that Solar activity is expected to drop off over the next few weeks which should make the pattern more supportive of a -NAO/AO. 

Solar forecast can be found here:

The AAM forecast is also expected to head the other way with negative anomalies favoured near 30N:
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Another positive is that the MJO wave has been remaining predominantly in the el nino phases over the summer with very weak propagation into phases 2-5. Whether this continues remains to be seen as the Indian Ocean has warmed over the last month in tandem with ENSO. 
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