Monday, December 17, 2012

Monday Night Discussion

The modeling over the last two weeks has been very poor. Trends that where shown for a cold and stormy setup for NJ were broken Storms that looked to be a lock in for the east coast have instead cut into the lakes as a result of the model errors.  This threw off my forecasts and I also had a bias based on the trend we saw in November (sandy and two snow events). There are three major drivers of cold stormy weather in the east coast. A negative NAO which is high pressure over Greenland which supports a east cost through and prevents storms from easily escaping to the north from that trough. A positive PNA which is basically a ridge in the west coast which amplifies the through in the east coast more than the NAO alone. And finally a negative AO which is high pressure over the poles which results in general cold over the US. Here is what the models are showing:

AO: Trending Neutral                          NAO: trending neutral to negative

PNA: Trending Negative

You do not need to be a rocket scientist to figure out that these trends do not look good for a snowstorm over NJ over the next two weeks. We had two out of the three over the last week which produced storms and still will produce storms this week, but without the positive PNA (which has been absent all winter) it is very hard to get the trough amplified enough over the east to let a storm ride up the coast. Instead you are seeing these inland great lake storms that leave us on the eastern end , resulting in rain. It is possible to have a snowstorm over our area without a positive PNA but the odds are more stacked against it. The high pressure region over Canada has to set up in a precise spot. Otherwise we have a flat flow in the jet stream which can produce cold but when a storm forms it does not "crank" up. 

So am I throwing in the towel on this winter? Not in any regard. This winter will be nothing like the dry and mild winter we had last year and I believe we will see snowstorms. Over the next two weeks there will be three storms that effect the eastern third of the country- one late this week, one after Christmas, then one on the real long range. As of now however, they look to run into the great lakes leaving us on the warm side. Of course that can always change so keep checking in especially for the post Christmas storm.

 This weekend there is a chance we can see a brief period of snow at the end possibly dropping 1-3 inches. For the big snows I will reiterate we need that positive PNA unless we get lucky and the high pressure sets up in the perfect spot as I mentioned.  Who knows maybe that will happen in the next two weeks, one can make the argument that the pattern is changing so that's why the modeling has been so poor. I do not have enough conviction to make that call at this time. Keep checking in daily and I will keep updating on this pattern- it will be evolving daily. 

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