Sandy: a potential billion-dollar storm
for the mid-Atlantic, New England, and Canada
The latest set of 12Z (8 am EDT) model runs are in, and they portray an increased risk to the U.S. and Canadian East Coasts for early next week. The GFS model, which had been showing that Sandy would head to the northeast out to sea, now has changed its tune, and predicts that Sandy will double back and hit Maine on Tuesday evening. The ECMWF model, which has been very consistent in its handling of Sandy, now has the storm hitting Delaware on Monday afternoon. These models are predicting that Sandy will get caught up by the trough approaching the Eastern U.S., which will inject a large amount of energy into the storm, converting it to a powerful subtropical storm with a central pressure below 960 mb and sustained winds of 60 - 70 mph. Winds of this strength would
likely cause massive power outages, as trees still in leaf take out power lines. Also of great concern are Sandy's rains. Given that ocean temperatures along the Northeast U.S. coast are about
5°F above average, there will be an unusually large amount of water vapor available to make heavy rain. If the trough of low pressure approaching the East Coast taps into the large reservoir of cold air over Canada and pulls down a significant amount of Arctic air, as predicted, the potential exists for the unusually moist air from Sandy to collide with this cold air from Canada and unleash the heaviest October rains ever recorded in the Northeast U.S.
Another huge concern is storm surge flooding. Sandy is expected to have tropical storm-force winds that extend out more than 300 miles from the center, which will drive a much larger storm surge than its winds would ordinarily suggest. The
full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding.
There remains a lot of model uncertainty on where Sandy might go, and I still give a 30% chance that the storm will have a minimal impact on the U.S. An extra set of balloon-borne radiosondes is going to be launched at 2 pm EDT on Thursday all across the U.S., which should help tomorrow evening's model runs make better forecasts of where Sandy might go. Extra radiosondes will be launched every 6 hours through Saturday afternoon.
Jeff Masters
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Originally Posted by PaulConventionWV
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