NATIONAL STORM SUMMARY

 

AUGUST 2010

 

1^st-7^th…Scattered storms moved into the Midwest on Monday, as a low pressure system pushed a warm front into the region. Flow around the system pulled moisture in from the Gulf of Mexico, and allowed for scattered showers and thunderstorms to stretch from the Central and Northern Plains into the Midwest. Some of these storms turned severe with strong winds and heavy rainfall. Many areas in the Dakotas saw around an inch of rain, while parts of Michigan, Iowa, and Wisconsin also saw rainfall totals near an inch. Early Monday morning, severe storms swept through Norfolk, Nebraska and brought 3.22 inches of rain, 1.98 inches of that fell in 1 hour. Due to these slow moving and repetitive storms, floods remain a concern in the Upper and Mid-Mississippi River Valley. Highs remained in the 80s across most of the North-Central US. Some storms also developed in the Northeast as the eastern edge of the front stretched into the region from the Midwest. This brought overcast skies with light sprinkles, but northern New York state saw some thunderstorms with quarter size hail reported in Beekmantown.

Active weather developed across portions of the Midwest on Wednesday as a nearly stationary front reached across the Central Great Basin through the Central Plains and into the Ohio Valley and the Upper Great Lakes. Clusters of showers and thunderstorms developed near the boundary through the afternoon. Waves of low pressure along the boundary supported chances of severe thunderstorms from the Mid-Mississippi Valley through the Ohio Valley. Damaging winds gusts up to 66 mph were reported in northeastern Illinois, southeastern Michigan, Indiana, and Ohio. Incidents of quarter to golf ball sized hail (1.00 to 1.75 inches in diameter) were also reported in central Ohio. In the West, a low pressure trough triggered scattered showers and thunderstorms throughout portions of the Central Great Basin as it trekked northeastward from northern Utah toward Wyoming. Moderate instability created the potential for severe weather activity in eastern Wyoming with chances of large hail and damaging winds.

Scattered storms persisted in the Southeast on Friday. A stationary front pushed into the Southeast, and stretched from the Mid-Atlantic states and into the Southeast and Southern Plains. This front pulled in ample moisture from the Gulf of Mexico and allowed for thunderstorms to develop. Some of these storms turned severe with strong winds, and heavy downpours. Wind gusts at 64 mph were reported in Seaside, North Carolina, while 1.76 inches fell in Whiteville, North Caroline.

 

8^th-14^th…Cloudy skies covered the much of the north-central Gulf of Mexico on Wednesday as the very broad and elongated Tropical Depression Five became centered at about 150 nautical miles southeast of the mouth of the Mississippi River. The depression continued to move northwestward toward southeastern Louisiana with maximum sustained winds of 25 knots and gusts to 35 knots. Bands of showers and thunderstorms developed around the periphery of the depression but remained limited in the center. Outer rain bands affected the eastern and north-central Gulf through the afternoon. In the West, a fairly strong boundary moved from the Pacific Northwest into parts of the Intermountain West and the Northern High Plains with chances of showers and thunderstorms. Meanwhile, monsoon moisture sparked isolated showers and thunderstorms in the Southwest, while low clouds and fog lined areas of the West Coast.

A second wave of violent weather roared across the Washington region late Thursday, dumping rain and hail and whipping up dangerous winds only twelve hours after a similar line of storms brought havoc to the area in the morning. Violent downpours from gusty thunderstorms drenched areas already soaked from the morning's deluge, and the National Weather Service issued a series of tornado and flash flood warnings from northern Maryland, through the District, to as far south a Richmond. The day left a landscape of inundated streets, downed trees and tens of thousands of power outages over a huge swath of the region. Shortly after 7 a.m., with the temperature already in the low 80s and the humidity in the upper 70s, the sky grew as dark as doom and then cut loose, as a 60-mile-long squall line sliced through region from the suburbs of Baltimore to just south of the District. Almost an inch and a half of rain was dumped across the area in roughly an hour, forecasters said. The torrent flooded streets across the area, at one point carrying a minivan on a 15-foot wall of water a quarter-mile along Rock Creek in Northwest Washington, while the driver fled and then clung for his life to a fence. In Montgomery County, stranded motorists reportedly took to the roofs of their vehicles as muddy water inundated an area around Viers Mill Road and Connecticut Avenue. Canal Road in the District became a lake, witnesses said, as did Rhode Island Avenue, and Route 1, in Beltsville. In Chevy Chase, the downpour brought down a tree that punched through a roof and showered debris on an infant sleeping in his crib. The child was unhurt.

And in Gaithersburg, rescue workers responded to a report of a tree that had fallen through the roof of an apartment building in the 500 block of Frederick Avenue. Workers found that the tree had damaged a common stairway, so they used 24-foot ladders to rescue residents. No serious injuries were reported, but two people were taken to an area hospital with injuries that were not believed to be life-threatening, according to initial reports from Capt. Oscar Garcia, a spokesman for the Montgomery County Fire and Rescue Service. A search for trapped residents was undertaken, but authorities believe everyone is out of the building.

Elsewhere, fire and rescue workers were busy throughout the county responding to reports of storm-related damage, Garcia said. Across the area, tens of thousands of people were again without power Thursday -- more than 100,000 at the height of the storm, according to local utilities. Pepco said it could be days before all power was restored.

"This has been a very extreme summer," said Dan Stillman of the Capital Weather Gang, noting that there were no 100-degree days last summer and only 21 days when the temperature reached 90. Stillman said the heat extremes might not be entirely to blame for the severe weather.

"You could easily get the kind of storms we've gotten when you have summer temperatures that are pretty warm and not quite as hot," he said.

The day began ominously. At Reagan National Airport, the temperature was reported as 82 degrees shortly after dawn. The humidity was more than a steamy 70 percent. And the morning sky over much of the Washington area was dark and still, as if with the pent-up gloom of weeks of heat and irritation. About 7:15 am, the sky erupted in torrential thunderstorms that deluged parts of the area in the midst of the morning rush.

Streets flooded. Trees came crashing down. Power went out. Parts of the Metro system were hobbled, and traffic in some places crawled to a halt amid rivers of muddy water. Rain -- an inch and a half in an hour -- was the main culprit. It was dumped by a 60-mile-long squall line that reached from just outside Baltimore to the District. Flash floods across the area stranded motorists atop their cars. More than 100,000 people lost power, local utilities said, and Pepco said repairs could again take days. Among other things, the morning's hour-long deluge brought a tree down on a house in Chevy Chase, showering an infant in a crib with debris. Robert Anderson and his wife, Betsy, ran upstairs to find Jaymes, their two 2-month-old son, in his crib covered with parts of the tree, the ceiling, and hunks of slate roofing, brick and insulation. There were delays on Metro, as the Cleveland Park and Forest Glen stations were temporarily closed. There were also delays at local airports, as aircraft had to wait out the passing squall lines. And roads were closed by high water and fallen debris across the area. In Montgomery County, stranded motorists were described as taking to the roofs of their vehicles as muddy water inundated an area around Veirs Mill Road and Connecticut Avenue. Canal Road NW became a lake, witnesses said, as did Rhode Island Avenue in the District and Route 1 in Beltsville. Shady Grove Adventist Hospital in Rockville had to reschedule surgeries after flooding in its waiting rooms and surgical services area, and United Medical Center in Southeast Washington had to rely on generators for most of the morning when the hospital lost power for several hours.  In Gaithersburg, rescue workers responded to a report of a tree that had fallen through the roof of an apartment building in the 500 block of Frederick Avenue. Workers found that the tree had damaged a common stairway, so they used 24-foot ladders to rescue residents. No life-threatening injuries were reported, but two people were taken to a hospital. As the day went on, amid mounting heat and humidity and the still unstable atmosphere, the second wave of weather cooked up and spawned fast-moving storms that galloped across the area from north to south.  Forecasters said the "backdoor" cold front that slipped into the area from the northeast and stalled here was partly to blame for Thursday's unsettled atmosphere.

Scattered storms swept through the Northern Plains and Upper Midwest on Friday, while rain persisted in the Southeast. A low pressure system skirted along the Canadian border which created a cold front that stretched southward into the Northern US. The system has kicked up scattered showers and thunderstorms, some of which turned severe with heavy rain and strong winds. Heaviest rainfall hit Minnesota with 2.76 inches reported in Glencoe, while Minneapolis saw 2.59 inches of rain. Strong winds blew down multiple trees in Tomah and Wilton, Wisconsin, with gusts up to 69 mph. To the south, the remnants of Tropical Depression Five lingered over the northern Gulf of Mexico and continued pushing ample moisture onshore over the Gulf states. This allowed for rain and thunderstorms to persist from Louisiana to the panhandle of Florida. Storm totals since Wednesday range between 3-5 inches. On Friday, Hammond, Louisiana saw a mid-day total of 2.05 inches.

 

15^th-21^st…Active weather continued throughout the eastern half of the nation on Wednesday. A frontal boundary associated with a low pressure system centered over Hudson Bay, Canada became stalled across the northern tier of the Midwest. The disturbance sparked areas of scattered showers and thunderstorms in the Dakotas, northern Minnesota, northern Wisconsin, and the western portions of the Michigan Upper Peninsula. Increased instability along the front lead to chances of severe weather activity with hail and possible tornadoes from the Northern Plains through the Upper Great Lakes. Thus far, quarter sized hail (1.00 inch in diameter) was reported in Wilkin County, Minnesota. Meanwhile, more active weather developed in the southeastern quadrant of the nation as another frontal boundary extended from the Mid-Atlantic through the Southern Plains. Ample moisture from the Gulf of Mexico heightened instability along the front and aided in producing scattered showers, locally heavy rainfall, and thunderstorms through the afternoon. Prolonged periods of rainfall created chances of flooding and flash flooding from southeastern Louisiana northeastward through the western areas of Virginia and North Carolina.

 

22^nd-28^th…A warm swept through the Midwest, which kicked up severe weather on Friday. The system developed from a low pressure system that moved off the Rockies and into the Northern Plains and Upper Midwest. Flow around the system pulled in warm and moist air from the South, which created a front that triggered showers and thunderstorms over Minnesota, Iowa, and Illinois. Most areas saw 1-2 inches of rain, while hail was reported in Mercer and Kennan, Wisconsin. Strong winds developed south of this system, with signs blown down in St. Clair, Missouri and wind gusts up to 70 mph in Smithville, Missouri. Northern Minnesota saw the heaviest rainfall with 2.13 inches reported in Bemidji. Scattered showers and thunderstorms persisted across the Southeast, as a front lingered on Friday. A stationary front extended off the coast of the Mid-Atlantic states and stretched into the northern Gulf of Mexico. This system has hovered over the region for the past few days, thus, flooding problems threatened many areas. Rainfall totals along the front ranged from a half of an inch to nearly 2 inches. Biloxi, Mississippi saw 2.26 inches of rain associated, while Pensacola, Florida saw 1.68 inches of rain.

 

Jim G. Munley, jr.
http://www.jimmunleywx.com