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Tropical Storm Warning most of D.C. metro area
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Irene: Are You Prepared?
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Rainfall potential from Irene

How about the Eastern Shore, including the Va/Md/De beaches? The story is more troubling there, where destructive winds, flooding rain, widespread power outages and a life-threatening storm surge are possible.

How confident are you on this forecast?

Our confidence is not terribly high - probably medium or even just low-to-medium. The reason is because Washington, D.C. is on the western periphery of the rain shield. A slight shift in the track eastward (as hinted by some models last night) would result in very little rain along and west of I-95, including in the District.

Our confidence is higher the Delmarva peninsula will experience very heavy rain and strong winds, especially right along the coast. But even there, small changes in track will mean the difference between a major storm and severe to historic storm.

Could the storm be worse than expected? How bad it could be?

Yes. If the storm takes a track slightly west of the current National Hurricane Center forecast and does not weaken substantially before reaching our latitude, heavier rain (3-6” or more) and stronger winds (up to 50-70 mph gusts) would reach the immediate metro region. That would increase the possibility of flooding and power outages locally.

At the beaches, a stronger storm near the coast would increase the odds of damaging hurricane force winds, and increase the storm surge. Such a scenario would have a huge economic toll on that region.

Could the storm miss?

For areas along and west of I-95, yes. If the storm took a slight jog to the east, little or no rain would fall in the region.

When will the rain begin? Lighter showers might arrive in the morning, but the heavy stuff should wait for later morning/afternoon east of the Bay, and afternoon into evening in the immediate metro area, lasting into Sunday morning. Some flooding due to rain is a decent risk, especially east of I-95 in low-lying areas.

Projected peak sustained wind speeds and wind gusts

Generally up to 30-35 mph sustained (gusts to around 50-60 mph) looks to be range in the D.C. metro area, except lower the further west you go from the District. Right along the Bay and east to the coast, winds may howl to 35-70 mph with gusts up to near 70-90 mph (highest toward the coast). In the metro area, significant scattered power outages are a concern. East of the Bay to the coastline, widespread outages are likely, especially the closer you get to the coast.

Will there be tidal flooding?


Will there be a storm surge up the Chesapeake Bay and into the tidal Potomac?

Southern portions of the Bay are at the greatest risk for a significant storm surge to near 2-4 feet. Elsewhere and for the tidal Potomac, a brief but limited surge is possible, probably around or less than 2 feet.

How big will the storm surge be for the Maryland, Delaware and Virginia Beaches?

Potentially a big deal. The National Weather Service warns that waves could reach up to near 20 feet, with storm surges of 4-8 feet possible. Of all the threats - rain, wind and storm surge - storm surge is the most serious risk and the No. 1 killer and cause of damage in a storm of Irene’s magnitude. Also, a storm as large as Irene tends to increase the amount of water pushed ashore. You can check out storm surge probabilities for yourself with this interactive tool, though note that NWS is predicting a higher storm surge than that tool suggests.

Will Irene be as bad as Isabel?

It depends where you’re talking about. East of the Bay and along the Atlantic coast, Irene may be much worse, with more rain, stronger winds and a larger storm surge for the beaches.

For the Bay and tidal Potomac, Irene shouldn’t be as bad, since predominantly north winds should preclude a major storm surge. Because Isabel passed west of the Bay, winds from the south rushed up the Bay pushing a big surge northbound.

Around D.C., winds should not be as strong as Isabel so we do not expect the widespread power outages (but isolated to significant scattered outages are a concern) unless the storm tracks substantially farther west than current forecast.

How will the storm impact air traffic this weekend? Will my flight be cancelled? Flights may be impacted as early as today as airlines begin to move planes and equipment out of the storm’s path. Delays and cancellations across the mid-Atlantic and Northeast due directly to occurring weather are likely tomorrow afternoon into Sunday night.

Do I need to evacuate?

Follow the advice of local officials. Around the D.C. metro region and Chesapeake Bay, there is no need to evacuate. Evacuation has been recommended or mandated for the Atlantic beaches in Md., De., and Va.

What should I do to prepare?

If you live around D.C., make sure you secure loose items, have batteries in your flashlight, your cellphone charged and a battery-operated radio. You may also want to make sure your gutters are clear.

If you live near the Bay or on the Eastern Shore, you should take preparedness actions very seriously and follow the advice of the National Hurricane Center for developing a disaster family plan and kit.

Also, do not forget about your pets and ensuring their safety.

When will the rain and storminess end?

While the exact timing of Irene is difficult, most guidance suggests skies should gradually clear from south to north Sunday morning into early afternoon. Breezy conditions may continue until Sunday night.

When can I go back to the Maryland, Delaware, and Virginia beaches?

You should not go back to any of the Atlantic beaches (including the Outer Banks and New Jersey shore) until officials say it is safe. Power outages may linger in those locations and the clean-up effort may take days.