January 6, 2005

New Low 


Surface weather maps can be deceptive. Right now, the latest surface maps show a low pressure center over Toronto with an occluded front extending down to a triple point in central Pennsylvania. A triple point is where an occluded front, cold front and warm front all intersect.

Generally, low pressure centers like to re-form at triple points. But not as much as they prefer to re-form near the Gulf Stream east of New England. That's why, this time of the year, when low pressure centers get near the coast, they frequently transfer energy to an environment that is more favorable for development--generally along the coast between Virginia and Maine.

Right now, while the low center is back over Toronto, most of the precipitation has moved east of a line extending from New York City to Burlington, VT. This was the first clue that a low pressure center was about to form east of New England, since that's where the energy is heading.

A look at the latest surface observations confirmed this suspicion. The lowest pressure in New England is at Nantucket, where a gusty southeasterly wind is bringing in mild air. This is a classic sign that something is getting going off of Cape Cod. Meanwhile, pressures at Western New England reporting stations such as Danbury, CT and Pittsfield, MA are actually rising.

What does this mean in plain English? A dramatically declining chance of steady precipitation for New York City and a period of gusty northeasterly winds for southeastern Massachusetts. As usual, I'd rather be here.

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