Blizzard of 2013 – Friday Morning Update

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Here’s the blizzard! A beautiful looking storm is streaming north with snow ready to overspread Long Island by 6:30 and moving ashore here in Connecticut shortly after 7:00.

There still remains uncertainty with whether or not this storm will be a mere “major” storm with widespread 12″+ snows or will it enter the pantheon of historic storms with widespread 20″+ totals. There are several reasons for the uncertainty including the influence that large thunderstorms off the coast of North Carolina will have on the eventual track.

Here are the updated snow probabilities. I have changed very little other than to bump up northeast Connecticut and New Haven’s probabilities slightly. I think the forecast from the NWS in Boston of 2+ feet statewide is too bullish at this point. In fact for any specific location I have the odds of >24″ of snow generally 25% or less (which is actually quite high for any snowstorm).

chart_3 (1)

Here’s the bottom line

  • 15″-25″ of snow statewide. It’s possible someone in southern New England gets 30″-36″ of snow but it’s too early to say where that will be or if it will occur.
  • Wind gusts to 60 m.p.h. in southeastern Connecticut and 40-50 m.p.h. elsewhere will result in isolated to scattered power outages. Not a huge deal but some people will be in the dark.
  • Blizzard conditions (wind gusts >35 m.p.h. and visibility <1/4 mile) will be possible in parts of the state.
  • The storm begins as light snow after 8 a.m. A steadier and heavier snow overspreads the state after noon.
  • The heaviest snow will be during the evening and overnight when snowfall rates may approach 3″ or 4″ an hour.
  • Travel will be difficult so stay off the roads if you can.
  • A period of mixing with sleet is possible in coastal Connecticut but it’s possible that this remains an all snow event in many areas including New Haven.

Technical Discussion

The embarrassing run of modeling for U.S. numerical weather prediction continues. Just hours before snow starts falling here’s the difference between the 6z GFS and 6z NAM QPF forecasts.

QPF

No question that the NAM is a garbage model. It’s of limited use to anyone. The GFS, however, has been pretty inconsistent with this storm altogether. The European has been much more reliable and consistent over the last 5 days.

The GFS shows no stall with this storm off of the Cape and keeps it trucking northeast. In addition, it appears to be suffering from some convective feedback with the thunderstorms over the Gulf Stream. This may be resulting in a track too far offshore.

The NAM, on the other hand, is about as wild a weather porn run as you’ll see. A widespread 20″-40″ across southern New England.

The more measured, and consistent, solution has been found with the ECMWF and the SREF. I like this blend of global model with non-hydrostatic short range ensembling. Blend with the best of both worlds! The SREF shows generally 1.5″ to 2.25″ of QPF and is fairly close to the Euro. Run with it friends!

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