EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
313 PM EDT THU OCT 25 2012
VALID 12Z SUN OCT 28 2012 - 12Z THU NOV 01 2012
...HIGH IMPACT MERGING OF ENERGETIC SYSTEMS ANTICIPATED OFF THE
MID ATLANTIC COAST...
DESPITE A MODEST CLUSTER OF OUTLYING DETERMINISTIC SOLUTIONS AND ENSEMBLE MEMBERS FROM THE VARIOUS MODELING CENTERS, THE LION'S SHARE OF GUIDANCE INDICATES THAT THE CIRCULATION ASSOCIATED WITH HURRICANE SANDY WILL PASS CLOSE ENOUGH TO THE AMPLIFYING POLAR TROUGH OVER THE EASTERN UNITED STATES TO BECOME INCORPORATED INTO A HYBRID VORTEX OVER THE MID ATLANTIC AND NORTHEAST NEXT TUESDAY. THE HIGH DEGREE OF BLOCKING FROM EASTERN NORTH AMERICA ACROSS THE ENTIRE ATLANTIC BASIN IS EXPECTED TO ALLOW THIS UNUSUAL MERGER TO TAKE PLACE, AND ONCE THE COMBINED GYRE MATERIALIZES, IT SHOULD SETTLE BACK TOWARD THE INTERIOR NORTHEAST THROUGH HALLOWEEN, INVITING PERHAPS A GHOULISH NICKNAME FOR THE CYCLONE ALONG THE LINES OF "FRANKENSTORM", AN ALLUSION TO MARY SHELLEY'S GOTHIC CREATURE OF SYNTHESIZED ELEMENTS.
"Blocking" refers to the effect of high pressure to the north of the two low pressure systems preventing them from moving toward the northeast in this case. Here is what the potential interaction looks like on the upper air forecast charts.
|This is the forecast 500 millibar map for 2:00 p.m. EDT Monday, October 29, 2012.|
There are several reasons East Coast residents should be taking notice. Hurricane Sandy will be drawing large amounts of moisture from the Atlantic inland, setting the stage for widespread flooding. The polar trough approaching from the west will be accompanied by cold air which help maintain some intensity of Sandy, even after she loses tropical characteristics. In addition, the storm will be moving very slowly because of the blocking high to the northeast. The large difference in pressure between the blocking high and the cyclone will produce sustained high winds that will damage trees and power lines.That means East Coast residents will be dealing with this for not just hours, but days. As of 11:00 p.m. EDT on October 25th. the expected forecast track of Hurricane Sandy will bring her ashore somewhere in southern New Jersey Tuesday morning.
For the latest updates on Hurricane Sandy see the National Hurricane Center website. Be sure to check your local NWS office website for updated forecasts for your specific area.