As we resume Standard Time this morning, Sunday November 7, 2010, the air is colder in Georgia (26° Peachtree) than in Massachusetts (32° Worcester). This happens when the Steering Current high in the sky buckles into 'High Amplitude' flow.
High Amplitude flow features air moving more south to north, and north to south (Zonal Flow is more east to west). Usually we have a combination of the two. But today we have a very deep trough on the east coast, sending that early freeze to The Peach Garden of the United States (quickly, buy some peach futures, the price may jump tomorrow). On the east side of the deep trough we have a cloud stretched from South America to Greenland. That's a Deeep Trough!
Does this remind you at all of late October 1991? Yes, this weather pattern has similarities to the ('No Name') Halloween Hurricane of 1991 (recently named 'Perfect Storm'). On October 27, 1991 a front stalled east of the United States, while Hurricane Grace spun up south of Bermuda. This year the Hurricane name is Tomas. Grace was originally a cold core storm that turned warm core and was about 50 miles south of Bermuda, Tomas is a long lived warm core storm that formed west of Barbados, from an African wave, on October 29. Tomas is 400+ miles south of Bermuda, and has for the third time, strengthened from Tropical Storm to Hurricane.
The satellite image appears to have Tomas embedded in the same front that brought us the heavy rain and wind of last Thursday. Much like what happened in 1991, the old front is absorbing energy from Tomas into a new storm developing east of New England Tonight. Unlike 1991, we have only old cold left from High Pressure over Quebec ( in 1991 very cold air resulted in Blizzard Conditions in Minnesota). This old cold is a limiting factor in how strong our new 2010 storm will get tonight and tomorrow.
We have just enough cold to get a period of snow and sleet late tonight, before a change to rain Monday. Cold is an ingredient in storm development, as warm air rides over the cold, low pressure deepens until the temperature gradient is wiped out, then the storm occludes and spins out. This warmer air is arriving from the north and east, a 'Back Door' warm front!
This will all happen very fast tonight and tomorrow. In fact we may have a period of 'Bombogenesis' near Cape Cod tonight as the central pressure of the new storm drops from 1011 millibars to 996 millibars in 24 hours ending Monday Morning at 7 AM. After that the storm will tend to weaken for a day or two, but may be rejuvenated by slightly colder air from Nova Scotia , and the influx of the heart of Tomas into the storm center on Wednesday.
The net result is heavy wintry mix from east to west tonight, with a 4 hour period of Gale to Storm force wind for early Monday. Then we have bands of moderate to heavy rain spiraling counterclockwise through New England into Tuesday. Rainfall amounts greater than 3" may cause flooding along the shore from Maine to Massachusetts, lighter rain is expected in the west of New England. By Wednesday most of the storm will be at Sea, but that make 6 days in a row of massive fetch waves battering New England during our new moon. Our Beaches are once again being rearranged by nature. Surf will be huge all week long. As for ski season, Killington (8" new last Thurs/Fri) and Sunday River are open, an inch or two new will fall tonight and tomorrow, after that we are too warm to make snow until next weekend. But the Ski Show is coming to Boston, we have that to look forward to.
We also look forward to the Satellite Image of the Atlantic Ocean this week, it may look very much like view from October 31, 1991.