What a (Forecasted) Storm!

12z Euro SLP/QPF 192 Hour Forecast

These are the kind of 12z model runs that get your attention!

I blogged a bit about the potential tropical system brewing in the Caribbean yesterday with the GGEM run that slammed the extra tropical transitioning storm into Washington, D.C. as a hurricane. Unusual to say the least!  To the left is the 12z European run that takes Sandy just off the southeastern U.S. and takes an abrupt left hook into eastern Pennsylvania. Every so often we see these kinds of extreme model solutions in the 7 to 10 day time frame and they almost never verify. Today, most of our global models jumped on the superstorm bandwagon but at this point the odds of the storm occurring seem quite low.

12z GFS SLP/QPF 216 Hour Forecast

The 12z GFS may be the most extreme weather porn of the day with over 12″ of rain across the state (a 1-in-100 year event in its own right) with the storm remaining offshore then getting captured by a digging trough over the Great Lakes. The storm, which appears to be near or at hurricane strength, stalls off the New England coast, does a loop, and then exits stage right. This is about as likely as a foot of snow in October in downtown Hartford – a one in 100+ year event.

All of these wacky solutions are due to a monster block that develops in the jet stream downstream of Sandy.

12z op GFS 500mb Heights and Height Anomalies (in m) / Courtesy Alan Huffman http://raleighwx.americanwx.com/models/12zgfs.html

A huge rex block over Greenland transitions to a large omega block over the west Atlantic which essentially seals the storm’s escape hatch. The blocking over the north Atlantic keeps Sandy from recurving. This assumes that Sandy isn’t able to sneak underneath the ridging out toward Bermuda which is what the 18z op GFS shows. This also assumes Sandy can develop in the Caribbean and meander north of Cuba and Hispaniola – at this point it looks pretty disorganized.

IR Satellite Image 00z / Courtesy: NOAA

The most likely scenario is a storm that’s no big deal here in Connecticut. To get a hurricane-like storm up the coast in October is very rare. To get a hurricane that interacts just perfectly with the jet stream to strengthen as it moves toward the northeast is very rare. To get a hurricane that is absorbed by a digging trough and is flung northwest into the northeastern U.S. is exceptionally rare.

While these solutions are fun to look at they’re unlikely to verify. Numerical weather prediction quickly breaks down past day 7. We see extreme and wacky solutions every once in a while in forecasts more than a week out most of which never come to pass.

192 Hour 12z Euro 500mb height and vorticity

With extremely anomalous downstream blocking over the north Atlantic which morphs into a large omega block over the north Atlantic I think we’ll see some type of storm. Odds are it won’t be Sandy but rather something else that develops (a la 18z GFS?). It’s possible a separate storm will entrain some of Sandy’s moisture so we could see indirect impacts even if the storm scoots to the east.

We’ll have to see how things play out over the next few days. No reason to be concerned – at this point these model solutions are a novelty. But the weather pattern is forecast to be a little funky and a lot anomalous so we’ll have to watch things closely.

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2 thoughts on “What a (Forecasted) Storm!

  1. Your sister stations are predicting the end of the world… To many variables have to come into play to make this “superstorm II” happen. Lets just hope, CL&P as well as the State of CT take this seriously and put plans into place to prevent what happened last October. This would be one great drill for both entities. If I recall their was plenty of warning last year for both and a lot of finger pointing after the fact. Point is, what is to be is to be. Lets prepare in any event and keep a eye turned. History does not need to repeat itself this time around.

  2. Pingback: PERFECT STORM? « The Burning Platform

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