Wednesday, February 22, 2012

12z ECMWF Shows Superstorm in East Coast- But Will it Happen?

This is the 12z ECMWF at hour 192, displaying 850mb temperatures and sea level pressure. We can see a very strong storm system on the East Coast at hour 192. There is a lot of cold air in place over the entire Northeast so that significant (1 foot+) snow accumulations would be almost guaranteed.

But will it happen?


I say no. The same ECMWF model run that is showing this superstorm is also showing a major positive NAO (North Atlantic Oscillation). A positive NAO will essentially make a ridge that diverts any storms away from the East Coast. Just simply using that, it is easy to see why this ECMWF run is flawed.
Other than the NAO, The Pacific North American Pattern (PNA) will be in a raging negative phase, indicating the likelihood of a ridge in the East and storm systems in the West half of the country.

Clipper System to Bring Up to 9 Inches of Snow to Wisconsin

The 12z NAM model is predicting a fairly strong clipper system hitting central Wisconsin in the next couple days. The image above shows 3 hour snowfall accumulations at 9:00 PM CST tomorrow. Up to 3 inches of snow in 3 hours is pretty much an inch of snow per hour, which is actually a pretty good rate.

Total snow accumulations look to be up to 9 inches, with widespread amounts of 2 to 6 inches. Now, a local model that I glanced over did show snow accumulations of up to 4 inches coming in for the Chicago area.
It does indeed look like that the NAM model is too far north with this system after analyzing HPC-made forecasts.

That said, you can see the correct forecast by taking the snowfall strip, moving it south into central Illinois and central Iowa, and deducting 1-2 inches from all amounts as the NAM typically overestimates snowfall amounts by a couple inches.


Long Range Maps Indicative of Southeast Ridge Returning

Here we have a map for 11 days out made using past analogues of similar situations. What is shown here are 500mb height anomalies. In the Southeast, there is a fairly large red area, indicating that the infamous Southeast Ridge may be returning.

The Southeast Ridge is a ridge of high pressure that is infamous for diverting storm systems away from the East Coast. What I am seeing here is the likely end of winter for the East Coast with this possible Southeast Ridge re-emergence.

Storm systems diverted away from the East Coast usually hit the Ohio Valley and/or the Midwest and Lower Great Lakes.

This is indeed long range, but will be something to closely watch as this could have major implications going into the end of February and beginning of March.



Okay everyone, once again this cold is downing me with Round 2.
No posting for the rest of today- I feel like junk.

Have a good day.