Ingredients for a Superstorm

All eyes will be focused on the exact track of Hurricane Sandy over the next several days.   Extreme blocking (Negative NAO), a rapidly deepening east coast trough and a very warm gulf stream are all factors that will contribute to what will be one of the more memorable late October storms in the Mid-Atlantic and New England’s history.  Regardless of Sandy’s exact track, the 55 million people in the Northeast Megalopolis can expect widespread high winds, heavy rains, flooding of low-lying areas, a powerful storm surge, coastal flooding and heavy, wet, mountain snow.  

As of Thursday afternoon, the European forecast model tracked Sandy the furthest south into the Del-Mar-Va. The GFS (Global Forecast System) computer model tracked Sandy into the central NJ coastline.  As Sandy nears the Mid-Atlantic coastline, her wind field will expand in size, therefore widespread high winds will lead to power outages across parts of the Washington and Baltimore Areas Monday evening into Wednesday. I would be preparing for widespread tropical storm force winds across the DC Area.  Depending upon Sandy’s exact track, coastal areas should be prepared for hurricane force winds. Please follow the National Hurricane Center’s latest forecasts.

The European Forecast Model continues to be the furthest south in track, taking Sandy into the Del-Mar-Va coastline. (Image courtesy: weatherunderground.com)

GFS forecast model is further north and takes Sandy into the central New Jersey coastline.  (Image courtesy: weatherunderground.com)

The Evolution of a Historic Mega-Storm in the Northeast Megalopolis:

The following images were taken from the October 25, 18z run of the Global Forecast System and paint a ‘general’ picture of the evolution of this upcoming storm.  The devil is always in the details and residents should pay close attention to the official forecasts from the National Hurricane Center as well as the National Weather Service. 

GFS Upper Level Chart from NCEP/NWS/NOAA (I outlined the Blocking High Pressure System/Negative NAO, deep trough (purple line) and Hurricane Sandy (circled in red)

Monday 12 Noon:  Sandy starts to get drawn into the upper level trough as blocking south of Greenland prevents her from moving northeast.  image courtesy: http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller

Tuesday 9 AM:  Sandy is now absorbed into the massive east coast trough.  High winds impact the entire Northeast Megalopolis.  image courtesy: http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller

Tuesday 6PM:  The remnants of Sandy still sits and spins, snow falls in the mountains and heavy rain and wind pelt the big cities. Snow may even mix in across the Baltimore and Washington Areas.  image courtesy: http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller

Halloween (Wednesday at 12 AM):  Upper Level Low (remnants of Sandy) still spinning over the Washington Area with heavy rain and high winds.  Snow continues to fall across the higher elevations.  image courtesy: http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller

Cold air will be feeding into the ‘extratropical remnants’ or “ghost of Sandy” across the Mid-Atlantic.  A powerful jet stream will enhance orographic lift and heavy, wet, snow across the windward facing slopes of the Appalachian mountains.  Snow will likely accumulate at elevations above 2,500 feet.  Several models have hinted at the possibility of 8 to 12 inches of snow accumulating.  The heavy wet snow combined with high winds would cause widespread power outages.  It is also possible that with cold air bleeding into the DC Region, rain may mix with snow at times, even though there will be no accumulations. Temperatures will be raw on Tuesday and Wednesday with highs probably struggling to reach 40 degrees. 

European forecast model showing heavy, wet snowfall accumulations across the West Virginia and Virginia mountains.  Snow may mix in with the rain even across the Washington Area if the ghost of Sandy becomes vertically stacked. (Image courtesy: weatherunderground.com)

Wind Chills in the 10s and 20s may be common across the mountainous terrain early next week. (image courtesy: weatherunderground.com)

Rainfall could approach one foot in portions of the Mid-Atlantic (image courtesy: http://www.hpc.ncep.noaa.gov/)

2 thoughts on “Ingredients for a Superstorm

    • Tim

      Any snow that falls with this system will be on the southwestern flank where the upper level flow will be out of the northwest. Even if Sandy makes landfall in central NJ, the temperatures would be too marginal (40’s) for accumulations on the DC Area. So at most we could see some flakes mixing in in the northwestern suburbs maybe on Tuesday night. Other than that, the main threat for the DC Region is tropical storm force winds (39 to 73 mph)… with higher gusts possible along the Chesapeake Bay and Tidal Potomac.

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