Sunday, October 28, 2012

2:25pm Sunday: Hurricane Sandy Forecast

Look for a landfall late Monday in Delaware or New Jersey for Hurricane Sandy.

At 2pm EDT, Hurricane Sandy was on predicted course with 75 mph winds and a central barometric pressure 951 millibars.

This is the predicted wind field for 2pm EDT. It compares reasonably well with current weather station measurements if you use it for wind gusts in miles an hour. For example, Norfolk, VA is gusting to 50 mph.

So, how does the wind field change over time?

8am EDT Monday
Due to the falling pressures, the wind speeds are accelerating. Wind gusts above 50 mph are occurring on DelMarVa and into New Jersey. They are just making it to Long Island.

2pm EDT Monday
Barometric pressures are dropping like a rock and wind speeds are spinning up accordingly. The bright orange colors are gusts to about 60 mph with the brown tones above 75 mph. Power failures will be occurring in large numbers and the storm surge will be piling up water.  This would be a record low barometric pressure for the region. Lower pressures (other factors equal) increase wind speeds and raise storm surges.

8pm EDT Monday
Landfall in NJ or Delaware. Winds capable of causing power failures extend from around Portland to Richmond and inland to Harrisburg and, perhaps, Buffalo. Wind gusts of 70 mph develop around DC and Baltimore.  Wind speeds are increasing throughout the eastern Great Lakes region.  The barometric pressure at landfall looks like it will be around 940-942 millibars.

The storm from there moves inland and gradually weakens but may still cause gusts above 50 mph over the eastern Great Lakes region.

The Storm Surge

Let's take a minute to consider what I believe is the under-considered aspect of this storm: The storm surge.  These forecasts do not include wave action which could be an additional 10 to 20 ft. in some areas!

Bridgeport, CT
click to enlarge
You have two models as you can see if you enlarge the graph. Again, keep in mind the water will actually be higher than the 14' above sea level shown due to wave action.

The Battery, NY
This is a higher forecast stage at The Battery than was observed in Irene. If it reaches 11' as forecast moderate to major flooding will result.

Addition at 2:45pm CDT (see below):

Atlantic City, NJ
Major flooding forecast.

I'm concerned that most due not understand the level of threat due to Hurricane Sandy's storm surge.

The posting below, "Finish Preparations" has the rest of the information about snow, etc.

This is going to be the last "comprehensive" update because if you are not wrapping up preparations now, it is going to be too late by the time the next computer model cycle finishes (i.e., darkness and increasing winds).

From this point on, I'm going to "nowcast" the storm (i.e., point out important short-term storm highlights) as it approaches and moves inland.  I'm literally writing this on I-70 crossing the Missouri River near Columbia as Mindy drives us to St. Louis for tomorrow's talks.

Hope you have ready to hunker down for one of Mother Nature's great shows.

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