Friday, September 1, 2006

Hello, Ernesto ... the Rain and Wind Arrive

11:59pm Update: The Flash Flood Watch has expired. Another .25"-.75" as rain tapers overnight. Look for steadier showers to end by the 6-9am range, and winds dying down to 15mph (with some occasional gusts) for the bulk of the day tomorrow. Maybe a few breaks in the clouds during the late afternoon and high temps near 75. -Dan Stillman
5:30pm Update: A band of heavy showers just east of Upper Marlboro and Bowie is moving northward.
4:15pm Update: National reported a wind gust of 46 mph (40 kt) in the past hour. Total rainfall is just under 1". Rain has ended at Norfolk.


A Flash Flood Watch continues in effect through late tonight for most of Maryland, DC, central and northern Virginia, and the eastern panhandle of West Virginia. A Wind Advisory is also in effect. Click on your county above for details. CapitalWeather continues to call for a storm total of 2-5" in the metro area, probably the lower end of that range for DC and points west, before tapering tonight.

Ernesto was downgraded this morning to a tropical depression, and the last National Hurricane Center advisory was issued at 11am. The heaviest rain so far in the Maryland, DC, Virginia region has been in the Tidewater area, where Norfolk has picked up nearly 9" since 2am this morning. Official amounts in the immediate Washington metro area were near 2/3" as of early afternoon. Light to moderate rain will continue this afternoon. As the storm moves northward, some heavy rain bands will rotate northwestward into the area, especially east of I-95. Some wind gusts with these could exceed 40 mph, possibly causing some tree damage and power outages.

Scroll down to Camden's earlier post for more details, the latest radar, a storm total forecast map, and the extended outlook through the holiday weekend. Let us know what's happening in your area using the comments link at the bottom of this post, and stay tuned to's continuing coverage of this developing event.

Thursday, August 31, 2006

DC Braces for Heavy Rain Event;
Ernesto Strengthens Approaching Carolinas


Cloudy, cool. As Tropical Storm Ernesto nears the Carolina coast, a Flash Flood Watch is in effect through late Friday night for most of Maryland, DC, central and northern Virginia, and the eastern panhandle of West Virginia. Click on your county above for details. A state of emergency has been declared for the state of Virginia to allow deployment of the National Guard and other resources. For the latest satellite/radar loop from WUSA-TV9, click here.
[Note that the hurricance "warning" in the WaPo article linked above is bogus as of post time; it is in fact a watch.]

Those clouds you're seeing this afternoon are from a frontal system that stretches through the Carolinas, but radar and satellite images show the beginnings of a merger between that system and the outer fringes of Ernesto to the south. Temperatures are generally between 70° and 75° throughout the metro region this afternoon. The relatively drier northeasterly wind over the Mid Atlantic area has kept precipitation today confined mainly to southern Virginia southward.

Tonight and Tomorrow

Ernesto's rain and wind arrives. Tonight will be cloudy and cool with an increasing breeze, lows in the low to mid 60s, and a 40% chance of a few scattered showers through midnight. By morning, the chance of showers increases to 70% and with more coverage. Rain will be steadier and heavier during the day tomorrow with a chance of some thunderstorms and winds in the 15-25mph range. Highs will be in the upper 60s to near 70. In his post below, Josh has more details on the possible timeline for Ernesto impacts on the metro area, as well as the forecast through the holiday weekend and next week.

Tropical Topics

Ernesto regained strength over the Atlantic overnight and was a strong tropical storm with maximum winds of 70 mph by early this afternoon. It remained at that strength at the 5pm advisory. The storm is headed for landfall tonight near the North Carolina/South Carolina border. As it moves northward, the track will be deflected to the west by a strong high pressure area now centered in eastern Canada. This will also slow down the forward progress of the storm and enhance the precipitation in some parts of the Mid Atlantic area. Paradoxically, it's the relative weakness of the storm which will help increase precipitation amounts by preventing it from barreling off to the north as stronger tropical systems frequently do when they reach middle latitudes.

There is still some disagreement between models on the placement of the heaviest precipitation. The global model from this morning has the precipitation bullseye near the mouth of the Chesapeake Bay, but this afternoon's North American model puts the heaviest amounts from central Virginia to eastern North Carolina with a very sharp cutoff to the northeast. This model has amounts generally less than an inch through Saturday night north and east of the Potomac.

Stay tuned to's continuing coverage of this developing event.

Wednesday, August 30, 2006

Eagerly Eyeing Ernesto


Cloudy, cool. A Flash Flood Watch is in effect from Thursday afternoon through late Friday night for most of Maryland west of the Bay, DC, central and northern Virginia, and the eastern panhandle of West Virginia. Click on your county above for details. (And don't forget to check your gutters, since they've had plenty of time to collect debris over the last several weeks.)

Under cloudy skies and a northeasterly breeze, this afternoon's official Washington temperatures have failed to reach the 82° observed at 1am last night. In the southern portion of the metro region, however, low 80s and even a few mid 80s have been seen at Fredericksburg, Stafford, Culpeper, Manassas, and Winchester.

Radar shows some light to moderate showers and some heavier thunderstorms from eastern West Virginia southeastward to north of Richmond on I-95 and toward the Northern Neck of Virginia. These are moving generally northeastward toward the metro area.

Tonight and Tomorrow

Cool, some showers likely. Tonight will be cloudy and cool with a 50% chance of showers, especially in the southern and western suburbs this evening, and lows in the low to mid 60s. Tomorrow will be cloudy with a 40% of showers and highs in the low 70s.

Scroll down to Dan's post below for the outlook through the holiday weekend, and look for Larson's Long-Range later.

Tropical Topics

Ernesto continued to weaken over southern Florida last night and was declared tropically depressed this morning; peak winds were only 35 mph at 2pm and again at 5pm. Some strengthening is possible as it re-emerges over the Atlantic, so tropical storm warnings have been extended along the northern Florida, Georgia, and Carolina coasts as far as Cape Lookout, NC.

The main threat from this storm is clearly heavy rain rather than wind, although winds will increase as it moves northward and a stronger pressure gradient develops with a "blocking" high pressure area to the north. Although the exact path of the center of such a weak circulation is not that significant, recent forecasts have tended to push the track westward over the mountains as it approaches our latitude. Models are notoriously unreliable in forecasting amounts of this kind of convective precipitation, but some areas are definitely going to be very wet. The most likely locations for the heaviest rain are from central North Carolina through central Virginia and westward to the eastern slopes of the Blue Ridge.

Tuesday, August 29, 2006

The Importance of Being Ernesto


Muggy. A tornado watch is in effect to the northeast of the immediate DC area until 8pm. Nearby areas affected in Maryland include Baltimore City/County as well as Anne Arundel and Howard Counties.

Temperatures in the low to mid 90s and dewpoints as high as the mid 70s have pushed some heat index readings over 100 in the Washington metro area this afternoon. After holding at 91° with a southerly river breeze, the National Airport temperature popped up to 94° at 4pm with a more westerly wind direction.

Despite the juicy conditions and a weak low pressure area to the north, regional radar is not very impressive so far. A few very isolated showers had popped up by mid afternoon, mainly to the north and east of the Beltway. The heavier activity was just east of the Blue Ridge and south of I-66 in Virginia. This area has now moved eastward to I-95 south of the Beltway. Technically, the area's 2-week-plus rainless streak was broken by the 0.01" which fell around 6am this morning, but there are probably very few lawns which would be convinced of that.

Tonight and Tomorrow

Chance of thunderstorms, then cooler and less humid. There is a 40% chance of showers and thunderstorms through this evening. Lows will be in the lower 70s in the city, near 70° in the cooler 'burbs, with gradually decreasing humidity. Tomorrow will be cooler and less humid with highs in the low 80s.

The outlook for the rest of the week and weekend is strongly dependent on the interaction of a northward-moving Ernesto with a high pressure area building to the north. Dan will update the outlook in his post tomorrow.

Tropical Topics

Ernesto has maintained relatively minimal tropical storm strength (45 mph at 5pm) today moving northwestward across the Florida Straits, although it has been looking more respectable on radar and satellite imagery. At mid afternoon, radar showed outer rainbands from the storm reaching across the Florida Keys northward as far as Naples and Fort Lauderdale. There is a slight chance of strengthening before landfall in south Florida, but the storm has a better chance of getting back to hurricane strength after re-emerging over the Atlantic before making the next landfall in the Carolinas.

The storm's possible effects on the DC region have varied in the last 24 hours between missing most of the rain because the storm moves offshore from the Outer Banks to missing most of the rain because the remnants move west of the mountains. The latest track has now veered somewhat to the east again, closer to the local area. Stay tuned as the situation continues to develop.

Monday, August 28, 2006

Ernestly Waiting for Rain


Muggy. After missing by 1° on each of the weekend days, the official Washington temperature rose to 90° this afternoon for the 14th time this month, well over the 30-year average of 10.1 days of 90° or more in August. To the south, mid 90s were common in central and southern Virginia. Meanwhile, an area of showers and thunderstorms advancing toward D.C. and vicinity from the west threatens to end our dry spell as a mainly stationary front tries to work its way southward from the Mason-Dixon line.

Tonight and Tomorrow

More mugginess. There is a 30% chance of showers or thunderstorms through early evening and a 40% chance the rest of the night. Lows will be in the mid 70s in urban areas down to near 70° in the cooler 'burbs. Tomorrow will again be warm and humid with highs in the upper 80s to near 90° and a 40% chance of showers or thunderstorms.

Scroll down to Jason's post below for the outlook through the weekend.

Tropical Topics

The disruption to Tropical Storm Ernesto's circulation by the mountains of Haiti and then Cuba plus the inability to fly reconnaissance over Cuba have made it hard to pin down the storm's track, but it is now emerging back over warm waters north of eastern Cuba. The current forecast track brings it northward as a tropical storm along the southeastern coast of Florida Wednesday morning. The following track is quite uncertain. The 2pm forecast which had the storm moving back out to sea after brushing the Outer Banks has been replaced at 5pm with a more westerly path which brings the remnants of the storm as a depression up through central Virginia and a little to the west of the DC metro area late Friday. This could help bring some much-needed rain to the area. Stay tuned in the next several days as the situation becomes clearer.

Broadcast News

Spike Lee's documentary on Katrina, "When the Levees Broke" is being rebroadcast tomorrow night, the anniversary of Katrina, at 8pm.

Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.