Monday, December 5, 2011

December 15 Potential Snow Event (Ohio Valley Affected)

Left is ECMWF, Right is GFS.
GFS and ECMWF differ on possibility of storm, with GFS
indicating the potential for a winter storm in the Ohio Valley.
The GFS is predicting the potential for a snowstorm in the Ohio Valley in the December 15 timeframe. The GFS and ECMWF differ on this potential. The GFS thinks a low pressure system will be present in the Ohio Valley with the rain/snow line far enough south that many areas of North Ohio, Indiana may receive snow. The ECMWF appears to think that a strong ridge offshore the East Coast will divert the storm system away from the Ohio Valley and probably into Canada.
We will watch for the 0z runs of this storm. As for right now, there's not much else we can figure out.

Rumors of December 12th Indiana Snowstorm Not True

We have heard that some websites were mentioning the potential for a snowstorm on December 12th for Indiana. These are not true. Here's the forecast for December 12 from the 18z GFS.
Bottom Right image is Precipitation.
Top Right image is lows and highs (red line is rain/snow line)
Bottom left image is relative humidities (green means precipitation)
Top Left image is vorticity (red is typical area for low pressures)
As you can see, there is no snow forecasted for Indiana on December 12.
We find it hard to believe that weather enthusiasts would think that there would be a snowstorm on the 12th. We are more inclined to believe that they are referring to the possible December 15-17 Ohio Valley snowstorm. A discussion on this will be issued.

December 7-10 Major Snow Event (Northeast Affected)

18z NAM 84-hour Snow Accumulation
NAM Select Cities Snowfall Accumulation
Middletown, NY: 8-10 inches
Philadelphia, PA: 4-6 inches

The NAM is forecasting a major snow event going into the December 7-10 timeframe, with widespread accumulations over 8 inches possible. What is interesting is how the GFS does not go with this scenario, and does not print nearly the amount of snow shown on the NAM. In fact, the GFS refuses to show any snow for many areas that are forecasted over 8 inches by the NAM.
The ECMWF, meanwhile, does believe that this event will happen, and is actually more aggressive with the low pressure's strength than the NAM is. We will see where the low goes and if this event occurs. I am leaning towards an NAM/ECMWF blend right now.

ECMWF Select Cities Snowfall Accumulation
New York City, NY: 3-5 inches

Where is winter???

It's getting pretty frustrating to see the teleconnections being so unbelievably stubborn right now. In all honesty, if this continues, our winter forecast will have to be revised. Here's the latest.

The NAO is mocking snow lovers with a bouncing ball-like forecast. We see the ensembles pretending to go towards negative territory but then moving positive again, like a bouncing ball. Until the NAO can actually go negative, you won't be seeing huge snows anytime soon.

Here's the gist of the AO: If it goes negative, you can expect temperatures to go down. If it's positive, the cold air won't be coming near the country soon. We see the AO ensembles taunting us with nosediving towards negative, but then shooting up positive again in defiance. This is not a good recipe for winter.

This is a really horrible batch of teleconnections we have here. Until these two indices above go negative, winter will keep stalling. It can only stall for so long before winter ends.
We don't want to vent about how horrible this is, so we are keeping this post to a minimum, explanation-wise.