Blizzard of 2013 – Thursday Evening Nemo Update

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15″-25″ of snow with gusty winds will make the blizzard of 2013 one to remember. A beautiful phase between the Polar jet and sub tropical jet will result in a powerful nor’easter just off the coast. The storm will stall and do a loop-de-loop off of Cape Cod which is a characteristic of some of our most powerful and memorable storms.

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.
  • 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

Here’s the 15z SREF plume for BDL which shows a mean QPF of about 2″. This matches well with the European model (though is a bit less) and is a bit higher than the GFS. Each line here represents an ensemble member’s forecast with the black line representing the mean.

Screen shot 2013-02-07 at 8.02.15 PM

 

There still remains uncertainty as to whether the blizzard of 2013 will be an historic storm or a more pedestrian (yet major) snowstorm. The two questions that remain are

  • Whether the southern stream disturbance (which is firing impressive convection and being modulated by strong latent heat release and PV generation) will truck east a bit and stay farther offshore.
  • How mesoscale banding (and associated subsidence) will modulate snowfall totals.

To answer question one here’s a look at the 18z GFS and 18z NAM 700mb height and RH forecast for 00z Saturday. Notice the NAM (which actually agrees with the Euro) is much closer to the coast with the center of the 700mb low than the GFS. The GFS – off the coast of Nantucket – is too far east for monster snow totals here in Connecticut.

700MB

The second point, about mesoscale snow bands, is just about impossible to pin down ahead of time. Given the strong frontogenesis and -EPV signal we know there will be strong banding and the potential for 3″ or 4″ per hour rates but where and how transient those bands are remains to be seen. 

Enjoy the storm! I’ll see you on Twitter and I’ll be on WNPR tomorrow around 7:10 a.m.

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3 thoughts on “Blizzard of 2013 – Thursday Evening Nemo Update

  1. Ryan, I don’t claim to understand much of the technical stuff, but I very much appreciate your enthusiasm for weather and for talking and teaching about weather. Keep up the great work!
    Peter W.

  2. Great job. Would be nice for us to have a place to go to explain some of the technical info. There is certainly little of this on the Weather Channel anymore since they are more concerned with fluff rather than details. And suggestions of places find definitions such as mesoscale and QPF? Also have not heard any talk of the barometric pressures in these storm nor if they will actually join up and where.

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