Saturday, October 27, 2012

The Dance Begins



The upper-level trough that has been moving through the central part of the U.S. is beginning to affect Hurricane Sandy.  It is moving east and energy will be moving into the base of the trough that will cause to tilt negatively.  Initially this will push the hurricane to the northeast.  However, as the trough gets close and the upper-level winds back, Sandy will turn north and then westward moving inland in the Northeast.

The 500 mb analysis for Friday evening October 26, 2012.  Click on the image for a larger view.  Image Credit: WSI.

Wind shear has been increasing over the hurricane and it is beginning to resemble a hybrid system.  A warm core typical of the tropical cyclone is in place, but the center does not have a ring of thunderstorms surrounding it.  NASA imagery showed the thunderstorms displaced to the north Friday evening.


Satellite image of Hurricane Sandy at 0240z October 27, 2012.  Click on the image for a larger view.  Image Credit: NASA.

The Atlantic Oceanographic and Meteorological Laboratories (AOML) analysis showed that the strongest winds were northwest of the center.  Sandy was still maintaining hurricane strength, but the wind shear over the system has increased.  A shear of 40-50 knots will help weaken to storm Saturday to a tropical storm.  However, the wind field will begin to expand as it continues a transition to an extratropical cyclone.

An analysis of the wind field around the center of Hurricane Sandy at 0130z October 27, 2012.  Click on the image for a larger view.  Image Credit: NOAA/AOML.

Winds will be gusty along the Carolina coast where a Tropical Storm Warning is in effect for Georgetown and Horry counties in South Carolina and for the entire North Carolina coast.  The ECMWF wind analysis indicates that winds will be gusting Saturday to 35 or 40 mph along the South Carolina coast.  Higher gusts are expected along the North Carolina coast.

Forecast of wind gusts for Saturday afternoon from the ECMWF model.  Click on the image for a larger view.  Image Credit: WLTX-TV.

Much of eastern North Carolina will continue to experience high winds until Sandy goes ashore on Tuesday.  Winds will South Carolina will also be brisk as a cold front pushes through the state on Sunday.  It will be windy through Wednesday; however the strongest winds gusts inland may come on Tuesday.  This is will be wind the strongest pressure gradient exists between the extratropical storm and high pressure to the west.

Forecast of wind gusts for Tuesday afternoon from the ECMWF model.  Click on the image for a larger view.  Image Credit: WLTX-TV.

There will be much to learn during the transition to a potential superstorm.  So far the forecasts are on track, but there may be a few surprises.  Stay tuned!