AdriansWeather.com
Tracking the Eye of the Storm
Hurricanes
A hurricane is one of nature's most destructive forces.
It is a whirling windstorm of enormous power, with winds that have reached a constant speed of 74 miles per hour or more. The eye of a storm is usually 20-30 miles wide and may extend over 400 miles. The dangers of a storm include torrential rains, high winds and storm surges. A hurricane can last for 2 weeks or more over open water and can run a path across the entire length of the Eastern Seaboard.
The 74- to 160-mile per hour winds of a hurricane can extend inland for hundreds of miles. Hurricanes can spawn tornadoes, which add to the destructiveness of the storm. Floods and flash floods generated by torrential rains also cause damage and loss of life. Following a hurricane, inland streams and rivers can flood and trigger landslides.
Even more dangerous than the high winds of a hurricane is the storm surge-- a dome of ocean water that can be 20 feet at its peak and 50 to 100 miles wide. The surge can devastate coastal communities as it sweeps ashore. Nine out of 10 hurricane fatalities are attributable to the storm surge.
The Primary Hazards of a Hurricane are:
Storm Surge High Winds Debris Tornadoes Rain/Flooding.
CONDITIONS WHICH MUST BE PRESENT
Low-pressure system
Warm temperatures over the Ocean
Moist environment (precipitation)
Tropical wind patterns over the equator
SEASON
The Atlantic Hurricane Season begins June 1 and ends November 30 of each year.
An "early" hurricane occurs in first three months of season, i.e. June - August while a "late" hurricane occurs in the last three months of the season, i.e. September - November.
Historically, the most active time for hurricane development is mid-August through mid-October.
The winter hurricane threat is virtually non-existent. Since 1886, only 3 hurricanes have been officially recorded during the month of December and only 1 during the month of January.
STRENGTH and INTENSITY
The strongest hurricane recorded was the Florida Keys Storm of 1935. 500 people killed from the Category 5 storm.
The largest storms recorded were the Category 5 Labor Day Storm of 1935, which killed 400 in Florida and Hurricane Camille that hit Louisiana and Mississippi in 1969. Camille caused a 25-foot storm surge, killed 256 and caused flooding all the way to New England.
In general, hurricanes lose about 1/2 of their intensity in the 12 hours after landfall.
STORM SURGE
Hugo, which hit North and South Carolina in 1989, had a 20 foot storm surge and caused damages in the amount of $7 million.
Storm surge, the raising of the ocean water along with the storm tide, is the leading killing element during hurricanes.
Storm Surge. Storm surge is a large dome of water often 50 to 100 miles wide that sweeps across the coastline near where a hurricane makes landfall. The surge of high water topped by waves is devastating. The stronger the hurricane and the shallower the offshore water, the higher the surge will be. Along the immediate coast, storm surge is the greatest threat to life and property.
STORM TIDE
If the storm surge arrives at the same time as the high tide, the water height will be even greater. The storm tide is the combination of the storm surge and the normal astronomical tide.
HEAVY RAINS/FLOODS
Widespread torrential rains often in excess of 6 inches can produce deadly and destructive floods. This is the major threat to areas well inland.
WINDS
Hurricane-force winds, 74 mph or more, can destroy poorly constructed buildings and mobile homes. Debris, such as signs, roofing material, siding, and small items left outside, become flying missiles in hurricanes. Winds often stay above hurricane strength well inland.
TORNADOES
Hurricanes also produce tornadoes, which add to the hurricane's destructive power. These tornadoes most often occur in thunderstorms embedded in rain bands well away from the center of the hurricane. However, they can also occur near the eyewall.
CHARACTERISTICS
Hurricane winds in the Northern Hemisphere circulate in a counterclockwise motion around the hurricane's center or "eye," while hurricane winds in the Southern Hemisphere circulate clockwise. Natural phenomena, which affect a storm, include temperature of the water, the gulfstream, and steering wind currents.
The naming of storm has a unique history. Early on, storms were named for the location they hit or a particular day they made landfall, i.e. the Labor Day Hurricane. In 1950, the first Hurricane name was Easy that hit the coast of Florida. In 1953, the Department of Defense started the named of hurricanes by a numeric naming, i.e. Able, Baker, Charlie, etc. After three years, this was abandoned and alphabetical naming of storms using female names was implemented.
Hurricanes form in the Atlantic Ocean, Gulf of Mexico, Indian Ocean, Caribbean Sea and Pacific Ocean.
The National Weather Service's Tropical Prediction Center (National Hurricane Center) tracks storms during the hurricane season. Historically, they have tracked up to 76 systems during a season. Most hurricanes travel from Cape Verde, Africa but only 1 of 10 systems becomes a named tropical storm.
STORM STATISTICS
On average, 100 tropical disturbances develop each year between May and November over the Atlantic Ocean. Half of these begin over Africa near the Cape Verde Islands.
About 25 of these disturbances develop into tropical depressions.
Out of these 25 tropical depressions, 10 become tropical storms.
Out of these remaining 10 storms, only 6 become hurricanes.
Of these 6 hurricanes, 2 are likely to strike the coast of the United States.
DEATHS
The deadliest hurricane in U.S. history was at Galveston Island, Texas storm of 1900, estimated to be a Category 4 storm. This storm claimed more than 6,000 deaths and is noted as the worst natural disaster in our country's history. The storm surge was 16 feet.
Eighteen of the 54 direct deaths attributed to Hurricane Andrew occurred during the recovery phase. Of those identified, eight were stress-induced heart attacks, three were either people falling in damaged buildings or hit by debris while cleaning up, and two were children who died in fires in damaged homes.
Nationwide, hurricanes annually account for an average of 17 deaths while flooding deaths average 147 per year.
COSTS
Hurricane Katrina was the costliest and one of the five deadliest hurricanes in the history of the United States. It was the sixth-strongest Atlantic hurricane ever recorded and the third-strongest hurricane on record that made landfall in the United States. Katrina formed on August 23 during the 2005 Atlantic hurricane season and caused devastation along much of the north-central Gulf Coast. The most severe loss of life and property damage occurred in New Orleans, Louisiana, which flooded as the levee system catastrophically failed, in many cases hours after the storm had moved inland. The hurricane caused severe destruction across the entire Mississippi coast and into Alabama, as far as 100 miles (160 km) from the storm's center. Katrina was the eleventh tropical storm, fifth hurricane, third major hurricane, and second Category 5 hurricane of the 2005 Atlantic season.Damages were estimated to be around $86 billion (2007 USD).
WHERE DO HURRICANES COME FROM?
In the eastern Pacific, hurricanes begin forming by mid-May, while in the Atlantic, Caribbean, and Gulf of Mexico, hurricane development starts in June. For the United States, the peak hurricane threat exists from mid-August to late October although the official hurricane season extends through November. Over other parts of the world, such as the western Pacific, hurricanes can occur year-round.
Developing hurricanes gather heat and energy through contact with warm ocean waters. The addition of moisture by evaporation from the sea surface powers them like giant heat engines.
With the exception of a few disturbances which originate in the Gulf of Mexico, tropical disturbances usually approach from the south and east.
Forecasters sometimes mention the Leeward and the Winward Islands. The WINWARD Islands include Dominica, St. Lucia, St. Vincent & the Grenadines, and Grenada. The LEEWARD Islands include Montserrat, Antigua, Barbuda, St. Kitts, Nevis, Anguilla, and the Virgin Islands, among others.
The Saffir-Simpson Hurricane Intensity Scale
Hurricanes vary in intensity. Storms may start out as just a tropical "wave" (an area of low pressure) and then become better organized and grow in strength. When a storm's sustained winds reach 74 miles-per-hour, it is then classified as a Category 1 hurricane.
Meteorologists use the Saffir-Simpson Hurricane Intensity Scale to categorize storms, based upon their wind speed and pressure.
CLICK HERE for a more detailed information on the hurricane categories.