Wednesday, October 24, 2012

Hurricane Sandy and/or Hybrid to Have Major Impacts on U.S. East Coast

Storm surge is pounding Jamaica at this hour as Hurricane Sandy gathers steam and promises to hit the region hard over the next 12-24 hours.

As of the 2pm EDT advisory from the National Hurricane Center, maximum sustained winds had increased to 80 mph, with the center of the system located about 30 miles South of Kingston, Jamaica.  Movement is toward the North at about 14 mph, and a general motion toward the North is forecast to continue for the next 24-36 hours at least.

Sandy will likely retain hurricane strength as the center moves across eastern Cuba tonight and Thursday morning, heading toward the Bahamas on Thursday night and Friday.

Low level winds and surf are already picking up along the Florida coast, and this trend will continue on an increasing scale through Saturday.  Some of the outer precipitation bands of Sandy will also spread across at least central and eastern Florida late tomorrow through Saturday, bringing locally heavy downpours at times.  

Beyond the Bahamas, all eyes turn toward the remainder of the Eastern seaboard of the United States.  There was quite a divergence among the computer forecast models through yesterday, with some taking the system East and out to sea, and others bringing a "super storm" to New England early next week.

During the last 24 hours, the models have come into better agreement in that the out to sea scenario seems less likely.  The main question now becomes one of the type and magnitude of the system and where exactly it will have the greatest impact along the East Coast early next week.

The European Model has consistently "advertised" a major hit to the Northeast U.S., and that trend has certainly continued through the most recent run early this morning, as shown by the forecast images from that model valid at 8am EDT on Monday and Tuesday, 10/29/12 and 10/30/12, below:

If the above forecasts verify, major impacts would be felt from North Carolina through the Delmarva Peninsula and into southern New England, including the "big cities" of DC Metro, Philly, New York City and Boston.

The European model is no longer the "outlier", as most models now depict the system taking a Westward turn and/or regenerating as an extra-tropical storm and impacting the Northeast:

As you can see, the European model does, however, bring the system on shore further South than most of the remainder of the models, based on the composite plot above.  This wasn't the case until this latest run at 8am EDT today.  It will be interesting to see how the 8pm EDT run this evening compares and whether or not it adjusts the track back to the North.

The U.S. based GFS Model is also forecasting a very strong system to impact the Northeast, but with a "landfall" quite a bit to the North of the latest European run.  The image below is from the latest GFS model run and is valid at 8pm EDT on Tuesday, October 30th, depicting a major storm making "landfall" in southern Maine:

The National Weather Service has ordered all offices that launch weather balloons to increase their frequency to 4 times a day until further notice (they are typically launched twice per day).  This will result in additional data being fed into the U.S. computer models, which will hopefully increase their accuracy, consistency and reliability as the situation unfolds.

As you've probably gathered by reading the above, there still remains much uncertainty as to the exact track of this storm and its impacts on the U.S. for early next week.  With that said, as I mentioned in a post this past Sunday, folks along the Eastern seaboard from the Carolinas through New England are strongly advised to keep a close eye on the progress of this system.  I do not believe it's too early to start planning for the eventuality of having to move a safe distance inland if you live in this region, particularly from the Delmarva peninsula on Northward through Boston.  It would also be a good idea to put together and/or restock items within your severe weather safety kit in this region.

Cold air will also be wrapped into the back side of this system, with heavy snows possible from parts of New York state into Pennsylvania and the Virginia's.  The exact location of the heaviest snow will depend on exactly where the center of the system comes on shore, and when.  This will become more clear over the coming days as well.

We will continue to closely monitor this situation and issue updates as the storm progresses over the coming days.

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