Virginia coast could face historic storm surge

Virginia coast could face historic storm surge:
Storm Introduction:
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea level. Low pressure at the center of a weather system also has a small secondary effect, as can the bathymetry of the body of water. It is this combined effect of low pressure and persistent wind over a shallow water body which is the most common cause of storm surge flooding problems. The term "storm surge" in casual (non-scientific) use is storm tide.Along the coast, storm surge is often the greatest threat to life and property from a hurricane. In the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall. Hurricane Katrina (2005) is a prime example of the damage and devastation that can be caused by surge. At least 1500 persons lost their lives during Katrina and many of those deaths occurred directly, or indirectly, as a result of storm surge.
Virginia coast:
Storm surge estimates are rising, which means worse flooding for parts of Norfolk and Portsmouth as Hurricane Irene bears down on Virginia, according to Gov. Bob McDonnell.We are still right in the line of fire,” McDonnell said in an interview with MSNBC. “We've got two or four hours now we're expecting the worst part of the storm, the highest winds.The storm surge estimates have gone up in the last hour to now 5 to 7 feet, which means that some of the areas of Norfolk and Portsmouth will actually have 9 feet above mean low water mark, so it's going to be significant flooding in those areas.“We're still expecting as much as 12 inches of rain and maybe as high as 15 in some areas.”McDonnell said Virginia is up to about 650,000 customers out of power “which means about 1.5 million people, so it's a significant event (and) we expect more of that.”Virginians “have largely heeded the mandatory evacuation orders that we gave earlier,” he said.And they're staying off the roads, which is just great.

Storm Surge

New York City storm surge:
In an unprecedented move, New York City is evacuating nearly 400,000 residents of low-lying sections of Manhattan, Brooklyn, and Queens. Just as unprecedented, the city's airports and subways are being shut down, and Con Ed is warning that if it has to cut electricity to Wall Street, it could take three days to restore it

Storm Details:
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea level. Low pressure at the center of a weather system also has a small secondary effect, as can the bathymetry of the body of water. It is this combined effect of low pressure and persistent wind over a shallow water body which is the most common cause of storm surge flooding problems. The term "storm surge" in casual (non-scientific) use is storm tide; that is, it refers to the rise of water associated with the storm, plus tide, wave run-up, and freshwater flooding. When referencing storm surge height, it is important to clarify the usage, as well as the reference point. National Hurricane Center tropical cyclone reports reference storm surge as water height above predicted astronomical tide level, and storm tide as water height above NGVD-29. Most casualties during a tropical cyclone occur during the storm surge.
 

 How high will the flood waters go?
The National Hurricane Center warned that hurricane Irene was still expected to arrive in New York Sunday night at or near hurricane strength.The big concern: Storm surge.The Miami-based National Hurricane Center has forecast a storm surge of up to 8 feet for Long Island and metropolitan New York when Irene passes, Reuters reports.Storm surge is caused primarily by strong winds pushing on the surface of the water, creating a higher than normal tide. Other factors contributing to storm surge can be large amounts of rain, and in this case, a full moon on Sunday.Higher than normal astronomical tides are occurring this weekend," said Daniel Brown, a meteorologist for NOAA's National Hurricane Center. "Coastal and river flooding will be highest in areas where the peak surge occurs around the time of high tide."A storm surge model developed by MIT, shows that areas around Manhattan, including lower Manhattan, could show a surge of four feet on top of the high tide.Another model by The Stony Brook Storm Surge Research Group at the State University of New York, offers an interactive map that's updated every 12 hours. It indicates that the peak surge for The Battery is at 5:15 am Sunday. If you click on the buoys on the map around New York, you can see the surge charted in specific areas over the next 12 hours.The Stony Brook site advises that this is a research model still under development and shouldn't be use for evacuation decisions.But clearly NYC officials are taking the storm surge threat seriously.Consolidated Edison said it wouldn't shut down the city's electricity pre-emptively, but could cut power early Sunday in low-lying parts of Manhattan, including to 6,000 homes or businesses south of the Brooklyn Bridge. The area includes New York's Financial District, according to Reuters.Con Ed officials say it could take three days to restore power in lower Manhattan, if power is shut off, reports The New York Daily News.

TornaDo

A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone although the word cyclone is used in meteorology in a wider sense, to name any closed low pressure circulation. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).
Nature's Most Violent Storms:
Adapted from: A PREPAREDNESS GUIDE Including Safety Information for Schools U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Weather Service September 1992 (NOAA, FEMA, The American.
Tornado!
Although tornadoes occur in many parts of the world, these destructive forces of nature are found most frequently in the United States east of the Rocky Mountains during the spring and summer months. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries. A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Once a tornado in Broken Bow, Oklahoma, carried a motel sign 30 miles and dropped it in Arkansas!
What causes tornadoes?
Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.
Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.
Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.
Tornado Variations:
* Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type of tornado is most common along the front range of the Rocky Mountains, the Plains, and the Western States.
* Tornadoes may appear nearly transparent until dust and debris are picked up.
* Occasionally, two or more tornadoes may occur at the same time.
Waterspout:
* Waterspouts are weak tornadoes that form over warm water.
* Waterspouts are most common along the Gulf Coast and southeastern states. In the western United States, they occur with cold late fall or late winter storms, during a time when you least expect tornado development.
* Waterspouts occasionally move inland becoming tornadoes causing damage and injuries.
Tornadoes Take Many Shapes and Sizes:
Weak Tornadoes
* 69% of all tornadoes
* Less than 5% of tornado deaths
* Lifetime 1-10+ minutes
* Winds less than 110 mph
Strong Tornadoes:
* 29% of all tornadoes
* Nearly 30% of all tornado deaths
* May last 20 minutes or longer
* Winds 110-205 mph
Violent Tornadoes:
* Only 2% of all tornadoes
* 70% of all tornado deaths
* Lifetime can exceed 1 hour
* Lifetime can exceed 1 hour.