Washington, D.C. will not avoid Hurricane Sandy: latest storm scenarios

There’s virtually no chance the Washington, D.C. region will avoid the wrath of Hurricane Sandy entirely. The only question remaining is: how bad will it be?

As we’ve stressed for days, the local impact depends on the exact track of the storm. The range of possible tracks has narrowed some, but not nearly enough to provide a single, confident forecast. So we present three scenarios.

Link: Why We Cannot Be More Specific as to Locations (Mike Smith, AccuWeather)

The scenarios are: 1) direct hit (worst case), 2) almost direct hit and 3) indirect hit. There are major differences in these scenarios. Significantly, in scenario 3, the worst wind and rain starts up to 36-48 hours after the worst wind and rain in scenario 1. In all scenarios, windy, inclement conditions would batter the region for an extended period of time.

Scenario 1: Worst case, landfall from Virginia Beach to the Delmarva (1 in 3 chance)

The worst case scenario involves the storm coming ashore between Virginia Beach and Delaware and then moving west towards Washington, D.C or just to its south. Typically, the worst storm impacts occur in the northeast part of the storm and a large part of the region would fall into this section in this scenario.

The European model - which is the best computer model out there - has shown a simulation like this (or slightly north) for numerous consecutive runs.

In this scenario, we expect the following:

* Rain likely begins late Saturday night or early Sunday morning and increases in intensity during the day. Winds also gradually pick up, becoming very gusty by evening.

* The heaviest rain and strongest winds occur late Sunday night into Monday night, with widespread power outages. Peak sustained winds from 45-60 mph and gusts over 60 mph possible.

* Winds remain strong into Tuesday, gusting over 40 mph frequently.

* Rain and wind slowly taper off late Tuesday or Wednesday.

* Rainfall totals of at least 4-8”. Widespread flooding occurs in low lying areas and rivers/creeks/streams.

* Severe, possible historic coastal flooding for Maryland, Delaware beaches. The National Weather Service in Philadelphia cautions: “A ten foot storm tide (surge + astronomical tide) is possible along the Atlantic Coast and in the Delaware Bay based on where the storm center comes ashore. This would result in record coastal flooding in some areas.”

* If the storm track far enough south, close to Virginia Beach, a storm surge could push up the Chesapeake Bay into the Potomac, causing flooding Old Town, Georgetown, and Annapolis.

* Crippling snow possible at high elevations of southwest Virginia and West Virginia.

Graphic indicates significant river flooding possible from Sandy (National Weather Service)

* Rain showers develop Sunday and Sunday night as winds slowly ramps up.

* Heaviest rain and strongest winds occur Monday into early Tuesday.

* Peak sustained winds from 40-50 mph and gusts over 50 mph possible with significant power outages.

* Rain totals of at least 3-6”. Flooding occurs in low lying areas and rivers/creeks/streams.

* Major to severe coastal flooding.

* Crippling snow possible at high elevations of southwest Virginia and West Virginia.

Scenario 3: Indirect hit, landfall between northern New Jersey and southern New England (1 in 3 chance)

In this scenario, Sandy would make landfall somewhere between northern New Jersey and southern New England. This is the worst case scenario for New York City. Sandy would then bend back to the southwest some, eventually spreading wind and rain into the D.C. region but significantly later than in Scenario 1.

I should stress that while this is the least severe scenario, a transitioning storm often has very heavy rain and possibly intense winds mixing down on the western side where you get frontal formation.

What we might expect:

* Chance of showers Sunday, Sunday night and Monday and becoming becoming breezy. But frankly, not a lot may be happening during this period of time.

* Steadier rain develops Monday night, possibly heavy at times. Winds also pick-up, becoming strongest Monday night into Tuesday , gusting over 45 mph at times, sustained at 30-45 mph. Scattered power outages.

* Wind and rain diminishes by late Wednesday

* Rainfall totals of at least 2-4”. Some flooding in low lying areas and creeks/streams.

* Significant to severe coastal flooding for Maryland, Delaware beaches.

* Snow possible at high elevations of western Maryland and eastern West Virginia, possibly 6-12” or more Monday into early Wednesday.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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