Thursday, 19 June 2014

Early Thoughts on Winter

Few comparisons I made on twitter this morning, using an ONI base state between +0.7 and +1.5c. All el nino/-QBO years are on the right with nino/+QBO years on the left. We should be in a -QBO shear phase this DJF nearing the -QBO peak late winter. Note how the -QBO years tend to have a pretty strong -NAO block with lower heights surrounding the block and a -SAM/+PDO state in the means. Whether solar activity increases or decreases heading into winter will be very important as you run the risk of ending up similar to 91-92 although it's definitely not a guarantee either way.

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The PDO dataset is also pretty interesting with the positive years on the right. I am expecting the PDO to remain positive through next winter as the nino continues to gradually strengthen. This is consistent with the NMME/JAMSTEC suite's. Note how PNA and EPO ridging is stronger in the +PDO years and the state of the NPAC is completely opposite. This tends to favour areas further SE for the heavy snow's(mid atlantic and southern parts of the Northeast) as it takes any nina component out of the pattern.

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The few things i'll be monitoring besides solar:

1) Positioning of the NPAC warm pool. If it can retrograde, look for the storm track to want to shift further west. If it continues to shift East into a more classic +PDO horseshoe position, as I am expecting, the mid atlantic will be more favoured in terms of storm track/snow interests.

2) The warm SST's off the east coast tend to pump up a stronger SE ridge like 51-52 saw in the December-January period. 

3) Keeping an eye on the positioning of the nino. Currently favouring a slightly west based nino although it could very well end up providing more basin wide like forcing.

4) We just came out of a long lasting la nina period. ONI spikes coming after at least a double nina look like this with no ENSO sorting:
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5) SLP pattern across N Siberia in October. This goes hand in hand with SAI feedbacks, which looks at snow cover growth in october over southern siberia.

Below are Positive AO El nino december heights at 250mb with Oct SLP anoms on the left. Notice the negative SLP anomaly across N Siberia and the response across North America.
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-AO years are completely opposite in December. 8 of those 10 +AO December years remained persistent with a +AO in January as well. In feb it mattered little as troughiness still dominated over the northeast/great lakes. Any questions about the upcoming winter? Feel free to shoot me a question in the comment section below or you tweet me @blizzardof96.

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  1. Hey do these early predictions give an indication that the the GTA could see higher snowfall next winter?

    1. Higher then this winter... probably not. Around the 150cm mark is definitely possible so long as trimonthly ONI index stays AOB +1.0c. If this can couple w/ a -AO, warmth off the SE coast and not too much of an overwhelming N atlantic block(-AMO helps with this) it should be a very interesting winter.