Ag Weather Forum
Doug Webster DTN Senior Ag Meteorologist

Friday 10/26/12

Rare Weather Situation Building

WOBURN, Mass. (DTN) -- Hurricane Sandy has churned northward through the northern Caribbean, across Cuba, and through the Bahamas during the past three days, leaving in its wake plenty of mayhem. Sandy's story may not yet be finished.

Hurricane Sandy was located off the South Atlantic coast Friday afternoon. The storm has the potential to bring extensive flooding and wind damage to the Mid-Atlantic and Northeast areas of the U.S. during the next week. (Satellite image by NOAA)

While it is quite normal to see tropical cyclones rear their ugly heads across the Caribbean during October and even into November, these storms normally will track northward for a short time before turning harmlessly off to the northeast, into the Atlantic.

Thanks to a large roadblock in the upper atmosphere across the North Atlantic and eastern Canada during the next several days, it appears Hurricane Sandy will not make an escape away from the U.S. East Coast. Blocking high pressure at upper levels from Atlantic Canada to southern Greenland and the North Atlantic as well as a strong upper-level low-pressure area through the east-central Atlantic will combine with a developing upper-level trough through the eastern U.S. to steer the storm into the northeast coast.

The strong upper-level trough diving into the eastern U.S. will likely close off into an upper-level low through the Mid-Atlantic region by Monday and capture Sandy as it moves northeastward then northward through the western Atlantic. Thereafter, as Sandy becomes a very intense post-tropical storm Tuesday, most computer models move the storm northwestward well south of Cape Cod at first and then to the west south of New England to near the New Jersey coast by Tuesday evening.

Thereafter the intense North Atlantic gale is expected to stall briefly before meandering off to the north or northeast across New England or New York state later next week. The aforementioned scenario is quite rare and could even become a historical event before all is said and done. The most recent event with any resemblance would be the now famous "Perfect Storm" of late October 1991.

There were a couple of hurricanes during the past 150 years that have tracked northward toward the Carolinas and then northwestward into the Mid-Atlantic states, most notably Hurricane Hazel in 1954. This storm has potential to outdo all of the above. Sandy is expected to take a track northeastward over the warm Gulf Stream until it reaches a position well east of the Mid-Atlantic Coast. Only then will it be captured and turned to the northwest and west toward the northeast coast. This track will allow the storm to maintain tropical characteristics longer than normal.

By the time Sandy transitions to a post-tropical gale well south of New England Monday night or Tuesday it will then be able to tap into the enormous amount of upper-level jet-stream energy supplied by the developing trough and upper-level low through the Mid-Atlantic states. This transformation could allow post-tropical Sandy to be more intense than the tropical version was when it was moving from Jamaica to Cuba.

The central pressure of the intense gale could produce some all-time low barometer readings for some locations. Computer models are forecasting the central pressure to fall as low as 27.80 inches by Tuesday within this storm.

A major difference from the tropical to the post-tropical Sandy will be the wind field. The strong winds surrounding Hurricane Sandy were mostly within 150 miles of the center. The post tropical version of Sandy should see the gale wind field expand outward to as much as 400 miles in all directions. This is why it is important not to focus on the center of post-tropical Sandy because damaging winds could occur from as far north as Maine to as far south as Cape Hatteras at the same time.

The track of this storm may also bring a significant storm surge and coastal flooding and the associated damage into a large portion of the northeast coast from Maine to New Jersey. Sustained easterly winds could reach as high as 40 to 60 mph along coastal areas with gusts exceeding 75 mph in exposed areas, and this will push ocean waters into the coast. While the exact track of the storm is yet to be set in stone, there appears to be a considerable threat to the New York City area for a large and possibly record storm surge. For this to happen, the post-tropical Sandy would have to track west or northwestward into the central New Jersey coast. A track a little different would probably spare New York City the worst.

The full moon occurs Monday and that only worsens the situation for coastal flooding by adding on a couple of feet of water to the storm surges.

Strong westerly to northwest winds to the south of the storm, possibly through the Chesapeake Bay and Delaware Bay regions, could lead to very low waters at times of low tide. This has been a problem in the past with some notable strong storms.

Other potential problems with this storm will be strong winds across inland areas that could bring down trees and power lines leading to widespread power outages. Heavy rainfall of as much as 2 to 4 inches with local amounts exceeding 6 inches could lead to local flooding early and significant river flooding later on next week. If the current scenario pans out there could be major disruptions to travel throughout a large portion of the Northeast during the early- and mid-week period of next week.

With cold air rushing into the storm as it reaches the northeast coast Tuesday, we can't rule out some snow for portions of the Appalachians from southwest Pennsylvania to West Virginia.

The final track and intensity of post-tropical Sandy is yet to be pinned down, but it does appear with decent certainty that one of the most highly populated portions of the U.S. is going to be dealt a blow of significant proportions from Monday into Wednesday of next week.

Doug Webster can be reached at


Posted at 2:44PM CDT 10/26/12 by Doug Webster
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