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DANGEROUS FLOODING EXPECTED WITH HURRICANE ISABEL

(See the NOAA National Hurricane Center for the latest information on this storm. Complete advisories are posted at 11 a.m., 5 p.m., 11 p.m. and 5 a.m. All times are Eastern. Advisories are posted more frequently as the storm nears the USA mainland.)

NOAA over head satellite image of Hurricane Isabel beginning to lash the U.S. mainland with its powerful winds taken on Sept. 17, 2003, at 5:15 p.m. EDT.Sept. 17, 2003 ó A wet spring and summer for much of the East Coast has set the stage for Hurricane Isabel to cause significant flooding. Heavy rains are expected in the Mid-Atlantic region which is particularly moist. The Potomac, Susquehanna and Delaware River basins, as well as smaller streams in New Jersey, Delaware, and eastern portions of Maryland, Virginia and North Carolina bear watching. (Click NOAA over head satellite image for larger view of Hurricane Isabel beginning to lash the U.S. mainland with its powerful winds taken on Sept. 17, 2003, at 5:15 p.m. EDT. Click here for high resolution version, which is a large file. Please credit “NOAA.”)

Since June, locations from the Carolinas northward into Pennsylvania have recorded from 20 percent more than normal precipitation in Columbia, S.C., to almost double normal amounts in the Scranton/Wilkes Barre area of northeastern Pennsylvania. Currently soils are quite wet and streams in the mid-Atlantic area are running higher than normal. As a result, precipitation from Isabel will quickly run off, filling low areas on its way to rivers and streams. With rivers already at high levels, heavy rain could cause significant river flooding.

The public tends to overlook the greater danger of flooding and focus on storm surge devouring coastal areas or trees and telephone poles toppled by winds. What most people don’t realize is that over the last 30 years, more than half of all hurricane fatalities are due to inland flooding.

Already, heavy rain has caused record flooding at a number of locations in eastern Pennsylvania and northern Delaware, including the Lackawaxen River in northeastern Pennsylvania, the Schuylkill River in Philadelphia, West Brandywine Creek in southeastern Pennsylvania, and the Christina River in northern Delaware.

With Hurricane Isabel losing punch and being downgraded from a Category 5 hurricane, NOAA forecasters are concerned that there may be a perception that Isabel is not a dangerous storm, but history shows clearly that any tropical cyclone can be dangerous.

In 2001, Tropical Storm Allison wreaked havoc in the Houston area. Intense rain combined with a slow, meandering motion resulted in as much as 36 inches of rain. Flooding caused by Allison took at least 20 lives. Other notable examples of deadly inland flooding due to "weak" systems include Tropical Storm Alberto (1994), which caused flooding in Georgia that killed more than 30 people, and the remnants of Hurricane Agnes (1972), which first made landfall in the Florida panhandle but caused flooding that killed more than 100 people in the mid-Atlantic region, with almost half of the fatalities in Pennsylvania.

The tragedy of these flooding deaths is the fact that many of them were preventable. Statistics show that most flood fatalities involve people driving their vehicles into harm’s way. As little as two feet of moving water can sweep away most vehicles—even SUVs. While it may appear that water over a road is not deep, even if you are familiar with the area, there is no way of knowing whether the road has been washed away. The inconvenience of being delayed is clearly preferable to losing your life or putting the lives of rescuers at risk. Because of this, NOAA’s advice is to “Turn around, don’t drown.”

Isabel, like many hurricanes, will probably cause both power outages and flooding. Even if you lose power, as long as you are not in imminent danger, avoid leaving your residence if you have to travel through flooded areas—wait for guidance from local authorities. Flood danger information is also available online.

Max Mayfield, director of the NOAA Hurricane Center in Miami, Fla., notes that "We’ve done such a good job of communicating the dangers of winds and storm surge that accompany hurricanes that flooding in now the number one cause of hurricane fatalities. Our challenge is to get the word out that inland flooding, in some cases far removed from where the storms come ashore, can pose serious danger."

NOAA WEATHER STATS OF AREAS ALONG THE EASTERN SEABOARD;
RECENT CONDITIONS AND CONDITIONS PRESENT DURING HURRICANE FLOYD IN 1999

LEGACY OF HURRICANE FLOYD

In 1999, Hurricane Floyd made landfall on Sept. 16 near Cape Fear, N.C., with winds to 105 mph—Category 2 on the Saffir-Simpson hurricane scale. Crossing eastern North Carolina and Virginia, Floyd weakened to a tropical storm. Its center moved offshore along the coasts of the Delmarva Peninsula and New Jersey, and then, on Sept. 17, it moved over Long Island and New England where it became extratropical.

Rainfall totals were large, and combined with saturated ground water levels from recent
previous rain events, the result was an inland flood disaster. There were 56 deaths in the United States (and one in the Bahamas), most due to drowning from fresh water floods. This made Floyd the deadliest U.S. hurricane since Agnes of 1972. Rainfall totals were as high as 15 to 20 inches over portions of eastern North Carolina and Virginia, 12 to 14 inches over portions of Maryland, Delaware, and New Jersey, 4-7 inches over eastern Pennsylvania and southeastern New York, and up to 11 inches over portions of New England. Maximum storm surge water levels reached as high as 9 to 10 feet above normal tide levels along the North Carolina coast. Total damage estimates range from $3 billion to more than $6 billion dollars.

Floyd's track was close in proximity to all of the U.S. East Coast and required hurricane warnings from south Florida to Massachusetts, excluding the New York City metropolitan area, which was under a tropical storm warning. The last hurricane to require warnings for as large an area was Hurricane Donna in 1960.

January-June 2003 (8 months):

Virginia — record wettest (21st driest in 1999)
Maryland — record wettest (25th driest in 1999)
North Carolina and South Carolina — 2nd wettest (21st and 15th driest in 1999, respectively)
West Virginia — 3rd wettest (8th driest in 1999)
Georgia — 5th wettest (15th driest in 1999)
Florida 6th wettest (28th driest in 1999)

June-August 2003 (3 months/summer):
Pennsylvania & West Virginia — 2nd wettest (17th and 3rd driest in 1999 respectively)
Alabama — 3rd wettest
Virginia — 5th wettest (12th driest in 1999)
Georgia — 7th wettest
North Carolina — 8th wettest (16th driest in 1999)
South Carolina — 9th wettest (7th driest)

March—August 2003 (6 months)
Virginia and South Carolina — record wet (12th and 7th driest in 1999 respectively)
Alabama, Georgia., North Carolina — 2nd wettest (Alabama — near normal, Georgia.— 9th driest , North Carolina —12th driest)
West Virginia and Maryland — 4th wettest (5th and 10th driest respectively)
Florida and Pennsylvania — 5th wettest. — (Fla., near normal, Pa., — 17th driest)

September— August 2003 (12 months):
Alabama, Georgia, South Carolina, North Carolina, Virginia — record wet
Florida, Maryland, Pennsylvania, Delaware — 2nd wettest
New Jersey — 6th wettest

September—August 1999 (12 months)
Georgia — 19th driest
South Carolina — 21st driest
North Carolina — 12th driest
Virginia and Maryland — 4th driest
Delaware — 9th driest
New Jersey — 15th driest
Pennsylvania — 17th driest
Entire remainder of East Coast, except Florida, was dry, too.

***These data are all based on 109 years of record keeping by the NOAA Climatic Data Center in Asheville, N.C., except the 12-month data, which are from 108 years of record keeping (1895-present). The NOAA Climatic Data Center is the world’s largest reservoir of archived climate and weather data.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nationís coastal and marine resources. NOAA is part of the U.S. Department of Commerce.

Relevant Web Sites
Significant River Flood Outlook

NOAA Inland Flooding Information

NOAA River Forecast Centers

NOAA Flood Products

Media Contact:
Susan Weaver, NOAA National Weather Service, (301) 713-0622 or John Leslie, NOAA Satellites and Information Service, (301) 457-5005