Friday, December 2, 2011

Overview of December 3-5 Snowstorm and December 5-7 Snowstorm

0z NAM interpretation of 2 pieces of energy
The two lows are outlined above with implemented snowfall totals by hour 84 from the new 0z NAM model. The GFS is nowhere near this solution, so we will have to watch to see which one is the correct predictor. A full discussion will be issued tomorrow. You can bet on that, unlike the one we failed to issue a couple days ago.

December 5-7 Snow Event (South Plains, Midwest, Ohio Valley Affected)

The Storm Prediction Center's SREF ensemble group is projecting snow to occur in the South Plains into the Midwest and Ohio Valley.
A storm system currently in the Southwest will drift eastward and disperse into a weak wave of energy that will travel on a NNE path from New Mexico. This weak wave will move into Wisconsin and put down some snow accumulations in that area. Left behind will be a bulk of the energy. This other piece of energy will eject on a more NE based path as a cold air blast following the first wave of energy will modify the path of the storm. The cold air will be pushing the storm track on a more southerly position as the cold air mass fights for control of the Southeast, where a ridge will be positioned. As this second wave of energy ejects, snow is expected to fall in New Mexico, Texas and Oklahoma. As this system moves along the track we have designated, it appears that snowfall amounts will decrease. It is either that or the issue of the SREF timeframe being too short for this storm.
SREF Individual Members Projected Low Pressure Centers at Hour 87 (last possible timeframe for SREF)
Above is a spaghetti chart of where individual models are projecting the low pressure center to be. As you can see, the consensus is to have the low close to where the first map's storm track is. There are other members that are quicker with this storm and show up on this map in Indiana, while other members go south into Louisiana. We will keep with the consensus at this point and monitor later SREF runs for additional information.

12z ECMWF Backs Off December 9-12 MW/GL/OV Storm

Notes: MW= Midwest, GL= Great Lakes, OV= Ohio Valley.

The ECMWF has backed off the idea of a storm system in the Midwest/Great Lakes/Ohio Valley, and judging by teleconnections, this storm my come through yet. The PNA is forecasted to go neutral/positive (good for winter storms), the AO is projected to fall (good for storms) and the NAO may go negative as well (good for cold). While these teleconnections are not in necessarily ideal territory for storms, a strong storm like the one projected could still occur.
We will continue to watch the models for any sign of this storm returning to the model's vision soon.