Yesterday I attended the 80-minute U.S. Winter Forecast 2011-2012 presentation here at AccuWeather, given by lead long-range forecaster Paul Pastelok. Based on the power point he showed and the discussion in the room, I'd like to add a few "insider" points that may be more relevant to the weather enthusiast community than what's stated in our public news story, which gives complete information broken down into regions.
The headline is this: The worst of the winter, with colder-than-usual temps and heavier-than-normal snow will be from the northern Plains through the interior Northeast (west of Apps).
It will be "back to reality" for the I-95 corridor, with less snow than the last two years. Fewer Nor'easters and those that come will have changeover from, and to, rain that will lessen snow totals. This could also be the year of the "westward shift" where the models initially show an east coast storm which backs into the Midwest before it happens.
We are making specific predictions for estimated seasonal snowfall for four major cities, as shown below (but note that this is an estimate, when looking at recent analog years, the range for NYC was 10-35". Seasonal snowfall prediction is nearly impossible... one 50-mile shift on any storm can ruin a forecast and this is even worse for areas that have little average snowfall where one storm can double it.
Additional points for this area:
- Most of the non-lake-effect snow will come from clippers and cutters.- Lake-effect snow will come fast and furious starting in mid-November- The harsh winter may start for the East in mid to late November and not let up until the end of January.- It could be even colder than the -3 to -5 which we are projecting in the Northern Plains
- We may add a "much above normal" snowfall area from Chicago to Detroit and Cleveland later this Fall
For the Southeast, the big story is going to be the severe weather, once again, starting in February in the Deep South and areas further north that got the ice in January. Read our Southeast story for more. Additional points:
- Florida had some cold spells last winter, despite La Nina, so we think that could happen again
- Because of severe weather that occurred in past analog years (the Super Tuesday 2008 outbreak and the February EF-4 tornado in 2009), we expect widespread severe weather outbreaks in February.- The expected path for severe weather may be further north than what happened last Spring, missing populated areas.
- December: Very cold west of a line from Albany to Charlestown, WV to Memphis. The east will get shots of cold air, and possible snow around the holidays. Even Florida could get some cold shots, which you wouldn't normally expect during La Nina, but happened last year.
- January: Coldest areas continue to be cold; southeast warms up. Ice storms frequent from Oklahoma to Tennessee. The worst of the winter for the Northeast will be late Dec - early Jan with a few big storms in the Midwest.
- February: The flip to warmer weather will start (if it didn't already in late January) with a warm-up in the Southeast and Mid-Atlantic, perhaps very warm. The worst of the winter will be over for most of the East Coast.
- Our recent Analog years are 2008-2009 (double weighted), 2007-08,1996-97, 1999-00, 2000-01. Look to your snowfall totals those years, esp. 2008-2009, to get an idea of what we expect this year.- Our confidence in this forecast is higher than average, but the big risk is the turnaround in the weather we are predicting for late Jan. or early Feb. for the East and South. If this doesn't happen, the Mid-Atlantic and Northeast could end up below normal for the season.- We are going into a strengthening La Nina which we believe will be moderate at about -0.9
- We don't think the CFS model's current forecast makes any sense. It should end up dry where it says it will be cold.- Sea Ice extent is important because when you lose ice, there is more water exposed; air is warmer than normal in Fall which changes wind patterns in Eastern Canada. That could setup blocking which cause unexpected extremes but we can't predict where yet.- The sea ice this Summer/Fall (up until a couple weeks ago) was riding as low as the record-low 2007 coverage, which means the lakes may not get cold (or in the case of Lake Erie, freeze, corrected per Mr. Peachey's comment), shutting off the lake-effect snow, until very late. Therefore, heavy lake-effect starts early and lasts longer than usual.
Is it really possible to predict the weather 6 months out? Absolutely, as I said last year, there are several things you can go on, including 1.) Indexes such as La Nina, NAO, etc. 2.) Computer forecast models that go out months in advance such as the CFS and European. 3.) Historical comparisons ("analogs") of years which had similar weather leading up to winter.
DISCLAIMER: Since I am not part of the Long-Range forecast team, these predictions are expressed as best as I can based on what they've said, and may not read word-for-word with our official forecast. Use with caution.
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