Still more questions than answers...(4-19-12)
We are still watching with great interest the potential for a late season Nor’easter along the East Coast next Monday. The models have been tracking two jet stream disturbances across the country and merging (or ‘phasing’) them by Sunday night creating a storm along the coast. Check out my blog from two nights ago to read more about these disturbances.There are still differences in the models as to how these disturbances interact and ultimately where along the coast a storm forms and how strong it is. In one camp you have the American models (the NAM and the GFS) which at least through their runs Thursday merged these disturbances later in time resulting in a storm that would be too far east to impact us significantly here in central New York. I’ve included a forecast map for the GFS valid Monday morning.
In the other camp are the foreign models (European and UKMET) which merge these two disturbances over the mid Atlantic with a very deep low near New York City Monday morning and a mix of precipitation over central New York (lower elevation rain, higher elevation snow)This scenario painted by the foreign models would point to a heavy wet snow over higher elevations of central New York during the first part of the day Monday. However, with such differences from the models plus the fact it is such a late season storm and temperatures will be borderline our confidence in the outcome is still on the low side. One of the reasons the confidence is so low is that the pieces ( the disturbances) to this potential storm are well to the west of us and far apart from each other. One of those disturbances at this hour (Thursday evening) remains over the Pacific Ocean where data that would detect that feature is sparse. In other words, we don’t truly know the strength of this disturbance. However, during Friday this disturbance will come ashore in British Columbia and will start travelling through the denser upper air network of North America. At that point the models should have a much better idea of this disturbance and we should (in theory) start to get more consistency. In fact, over the past few winters we’ve seen changes in the model’s output as a disturbance travels over eastern Asia then over the vast Pacific Ocean then back over land again in North America. Until this latest disturbance is over North American soil projecting where any storm COULD be on Monday is just speculation.
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