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Posted at 05:00 AM ET, 08/27/2011

Forecast: Rain and wind inbound as Hurricane Irene impacts the East Coast

Hurricane Tracking Center with Tweets from NHC
Live updates: Follow the storm all day
Tropical Storm Warning for most of D.C. metro area
Flash Flood watch for most of D.C. metro area
Tornado Watch until 8 p.m. Calvert, St Marys (and bay)
Hurricane Warning for Va/Md/De beaches | Storm surge/wave info
Irene: Are You Prepared?
Live webcams of East Coast beaches


Ocean City webcam picture from this morning. (ocbound.com)
10 a.m. Update: Moderate to heavy rain covers Southern Maryland and east across the Chesapeake Bay to the De/Md/Va beaches. Already 3” of rain, as estimated by Doppler radar, has fallen near Chincoteague, Va. The rain is just starting to arrive from the east and southeast across the southern suburbs of D.C., and will continue to make inroads west and north across the area over the next couple hours.

Now is a good time for Washingtonians to prepare for the potential of low-end tropical-storm force winds, possible power outages, and some minor to moderate flooding especially in low-lying areas this evening or overnight by: charging your cell phone, locating batteries for flashlights and radios, securing loose items outside and clearing gutters.

Meanwhile, here’s a recent dispatch from a Post reporter in Duck, N.C.: “Heavy rain and gusting winds above 70 miles per hour are battering the Northern Outer Banks at 10 a.m. Here in Duck, a house built to withstand 125 mph winds has begun to shudder as the eye of Hurricane Irene draws near. Currituck Sound, outside our windows, has nearly dried up as winds have driven the water to the south.”

8 a.m. Update: A weakening but large Hurricane Irene made landfall near Cape Lookout, N.C., around 7:30 a.m. as a category 1 storm with maximum sustained winds near 85 mph. The National Hurricane Center reports a wind gust to 84 mph at Cape Hatteras, N.C., with a sustained wind of 59 mph. A more impressive report indicates a sustained wind of 90 mph and gust to 110 mph at Cedar Island Ferry Terminal.

Closer to home, rain has overspread the Va/Md/De beaches and is moving into Southern Maryland. Just an isolated shower in the metro area next 1-2 hours - so take this time to secure loose items outside - before rain chances increase. Conditions should really start to go downhill by late afternoon, with the worst rain and winds and probably some power outages this evening and overnight. That said, this looks no worse than a moderate impact event locally, with major impacts from the Chesapeake Bay eastward.

From 5 a.m. ...

Today's Daily Digit
 
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EXPRESS FORECAST

Today: Morning showers, then increasingly windy and rainy. Upper 70s to low 80s. | Tonight: Rain and strong winds. Rain decreasing late at night. Upper 60s to low 70s. | Tomorrow: Morning rain? Partly to mostly sunny and breezy. Mid-80s. | Get Express Forecast by E-mail

FORECAST IN DETAIL

Where will Irene rank in D.C. hurricane folklore? Perhaps not on the “top 5,” but it’s looking notable one way or another. If you have any interest in staying dry while doing anything outside, better get to it early. Otherwise, you’ll be dodging both increasing threats for rain and wind. Given the lines at stores on Friday, I’m guessing many of us are planning on spending a weekend indoors. If you have not prepared, particularly for power outages, please do so early!

Today (Saturday): We may see some rain-free times early in the day, or not. The first bands of Irene should wander up from the southeast, but they may initially be slow in heading north and west. Even by sunrise, places southeast could be dealing with more consistent activity. These bands slowly advance into and through the area from south to north as the day progresses. It won’t rain all the time, but when it does, it will often be torrential. Winds increase from 10-15 mph early to 20-30 mph late -- with higher gusts. The “worst of it” may begin to arrive late day, but it looks to target the evening and afterward. With the clouds and rain around, temperatures should struggle to get any further than the upper 70s to low 80s. Confidence: Low-Medium


Maximum winds during the duration of Irene.
Tonight: By late evening Irene should be centered somewhere near the NC/Va shoreline as conditions continue to go downhill in this area. Bands of rain, some very intense and potentially containing severe weather, mix with increasing winds. Sustained winds as high (or higher?) as 40 mph or so accompany stronger gusts across much of the area -- windiest east. Rain eventually tapers during the overnight and heading into dawn as continued strong north winds behind Irene help send what little cooler air is up there to the south. This should help lows get into the upper 60s to low 70s around dawn.


Storm-total rainfall forecast.
Before all is said and done, expect anywhere from about 1.5-4.5” across the west to 2.5-6” across the east. Higher totals potentially intermix in places that see multiple rounds of heavy rain. These totals can bring about some flooding, particularly in low-lying areas and places which receive a lot of rain in a short period. Additionally, saturated soil combined with wind is likely to lead to a number of power outages, and that risk may continue as the rain winds down and into the morning. Confidence: Low-Medium

Keep reading storm surge info, both locally and at the beaches, and the forecast through a much calmer beginning of next week...

Tomorrow (Sunday): The rain and clouds from Irene should be departing with sunrise, so the weekend might not be a total loss! North and northwest winds won’t be helpful for any cleanup necessary in the storm’s wake, and they may persist through the day, diminishing from about 20-30 mph after sunrise to 5-10 mph and falling heading into the evening. Highs should reach the mid-80s at least, though places like downtown might hit the upper 80s. Confidence: Medium

Tomorrow night: After our hurricane nightmare, this is a winning forecast. Ready? Mostly clear, with temperatures dipping into the 50s in the suburbs and perhaps as far as the low 60s downtown. A northwest breeze almost feels like calm conditions. Confidence: Medium-High

A LOOK AHEAD

When I wrote this up, I jumped straight to Monday and Tuesday. A much easier forecast and much more pleasant weather! After 50 of 90+ in D.C., these are the types of days that make that move into September (almost) and October so brilliant. Lots of sun mixes with mild humidity levels to send temperatures into the mid-80s both days -- perhaps a touch warmer for Tuesday. We may just keep an eye on a little moisture over the South to see if it tries to creep north for clouds and such. Confidence: Medium-High

IRENE COASTAL FLOODING CONCERNS

Will there be tidal flooding?

According to the National Weather Service: “FORECASTED TRACK OF IRENE SUGGESTS THAT MINOR TO MODERATE FLOODING IS POSSIBLE DURING THIS TIME.”

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 2-5 feet. This storm also coincides with astronomical high tide which makes the threat more acute. 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 still a big deal. The National Weather Service warns that waves could reach up to near 20 feet, with storm surges of 3-7 feet possible. These values have diminished slightly with a weaker storm, but not enough to not be a concern. 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. A storm as large as Irene tends to increase the amount of water pushed ashore. You can check out storm surge probabilities for yourself, though note that NWS is predicting a higher storm surge than that tool suggests.

By and  |  05:00 AM ET, 08/27/2011

Categories:  Forecasts, Tropical Weather

 
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