Thursday, November 26, 2015

Under Pressure In New England

Weather map from Thursday morning shows extremely
strong high pressure over eastern Canada
and New England.  
For most of us in New England, Wednesday afternoon and evening's weather seemed unremarkable.

Skies were a bit clearer than they often are in November, and it was a bit warmer than normal. Kinda hazy, too. But surely there was no extreme weather going on, right?

Au contraire! The atmospheric pressure in eastern New England especially was the highest on record for November in many towns.

You can be forgiven for not noticing. Weather patterns are made up of areas of high air pressure, which usually brings fair weather, and low pressure, where there's storminess.

The high pressure system over eastern New England Wednesday was particularly strong, causing the records to fall.

Barometric readings in places like Providence, Boston and Bangor, Maine were around 1045 millibars or around 30.85 inches of mercury.

If there was anything unusual about this high pressure system, other than the strength of it, was the fact it wasn't an Arctic high pressure.

When there's near record high pressure, especially in the cold season, it's usually caused by an intense blast of Arctic air from the North Pole.

This high had polar air, which modified in the mid-latitudes as it crossed the nation. Then, over the Northeast and eastern Canada, the high strengthened to its near record peak.

The high pressure is helping shunt storminess in the middle of the country to the west of New England, toward the Great Lakes.

Since there is a big contrast between the strong high, and the low pressure out west, it'll get windy today, especially in western New England. (If there's a strong difference in pressure across a region, it tends to get windy)

But it will be warm, and when the tail end of the western storm finally reaches New England as the high moves away, only some fairly light rain showers will come through Friday night. With maybe a few snow showers Saturday.

For a record weather event, conditions on the ground do seem pretty blase.

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