Maybe SOMEthing to Hang a Winter Outlook Hat On, Finally.

November 23rd, 2012 at 3:27 pm by under 4 Warn Weather

Thanks to Tom Niziol, who forwarded to me an interview with winter outlook researcher and forecaster, Judah Cohen. The interview was conducted by a private sector meteorologist, who works for a group called The Capital Weather Gang, in Washington. They are regular contributors to the Washington Post. Surprisingly, Dr. Cohen has partially “spilled the beans” in a public way early in the season. While part of the interview’s focus centers on D.C., much of what he discusses is relevant to the NE as well.

A couple of important notes before you hop on the link, please. Cohen and his group have developed a new index on how to look at October Siberian snowfall; the Snowfall Advance Index, or SAI. He now correlates a faster rate of snow accumulation  with a -AO more than with just a monthly anomaly. It is clear that this professional (me) and some of you weather hobbyists have not been interpreting the Rutgers Global Snow Lab data (which he mentions) the way Cohen does. As for this year, despite what we saw on the Rutgers site, the SAI is favorable for a colder than average winter in the east and NE, and a more -AO/NAO. I think many of my fellow fans of wintry weather will be greatly encouraged by much of what he says here.

Another note: Cohen does not generally go into detailed precipitation outlooks. I would remind you all again that the “Snowmaggedon” winter of 2009-2010 left Buffalo with only 74 inches of snow. That record negative AO brought us cold, but not that much snow. So in MY opinion, we still can’t extrapolate much on snowfall from this hopeful outlook, except to say that both statistical odds and expected pattern dominance would favor more snow than last winter. The statistical side of that is an easy call. The pattern dominance is a predictive call.

And 2 puzzles: Cohen and a few others seem to enjoy treating the NAO and AO as if they were virtually identical, and virtually a single index. I can’t say I agree with that. There are parallels, but I have seen periods in which one was highly negative and the other wasn’t. Clearly, the majority of forecasters still go with 2 indices. Cohen may be favoring his approach to simplify matters for clients and the public…I don’t know.

The other puzzle is why he never mentions the MJO, nor does The Capital Weather Gang. The MJO is recognized by CPC as playing a role in temperature anomalies during the winter season. There is a highly suggestive body of evidence that its anomalous behavior last year was a very significant forcing mechanism in “defeating” la nina climatology over much of the northern latitudes of the U.S. And, when I asked Dr. Kerry Emanuel of MIT about this in August (one of the most accomplished meteorological scholars we have), he agreed it was a good hypothesis.

Now that I’ve said my piece, here’s the interview: http://wapo.st/WxMLXq

Please use the link in my first comment for ease.

481 Responses to “Maybe SOMEthing to Hang a Winter Outlook Hat On, Finally.”

  1. Don Paul says:

    That’s correct, he does not issue a snowfall forecast. It can be inferred that when the AO is strongly negative, the storm track along the east coast becomes more active, and that snowfall becomes more abundant, as per 2009-2010 and 2010-2011. It’s more difficult to make such a case for the Great Lakes for excessive snowfall, unless a prevalent storm track develops which favors polar air reaching us on a more SWly boundary lyr flow.

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