National Hurricane Preparedness Week 2012 runs from May 27 through June 2
History teaches that a lack of hurricane awareness and preparation are common threads among all major hurricane disasters. By knowing your vulnerability and what actions you should take, you can reduce the effects of a hurricane disaster.
Hurricane hazards come in many forms, including: storm surge, heavy rainfall, inland flooding, high winds, tornadoes and rip currents. The National Weather Service is responsible for protecting life and property through issuance of timely watches and warnings, but it is essential that your family be ready before a storm approaches. Furthermore, mariners should be aware of special safety precautions when confronted with a hurricane.
Download the Tropical Cyclone Preparedness Guide at www.weather.gov/os/hurricane/resources/TropicalCyclones11.pdf. But remember, this is only a guide. The first and most important thing anyone should do when facing a hurricane threat is to use common sense.
Storm surge and storm tide
Storm surge and large waves produced by hurricanes pose the greatest threat to life and property along the coast.
Storm surge is an abnormal rise of water generated by a storm’s winds. Storm surge can reach heights well over 20 feet and can span hundreds of miles of coastline.
Storm tide is the water level rise during a storm due to the combination of storm surge and the astronomical tide.
The destructive power of storm surge and large battering waves can result in loss of life, buildings destroyed, beach and dune erosion and road and bridge damage along the coast. Storm surge can travel several miles inland. In estuaries and bayous, salt water intrusion endangers public health and the environment.
Heavy rainfall and inland flooding
Tropical cyclones often produce widespread, torrential rains in excess of six inches, which may result in deadly and destructive floods. In fact, flooding is the major threat from tropical cyclones for people living inland. Flash flooding, defined as a rapid rise in water levels, can occur quickly due to intense rainfall. Longer term flooding on rivers and streams can persist for several days after the storm.
Rainfall amounts are not directly related to the strength of tropical cyclones, but rather to the speed and size of the storm, as well as the geography of the area. Slower moving and larger storms produce more rainfall. In addition, mountainous terrain enhances rainfall from a tropical cyclone.
The strong winds of a tropical cyclone can cause dangerous waves that pose a significant hazard to mariners and coastal residents and visitors. When the waves break along the coast, they can produce deadly rip currents – even at large distances from the storm.
Rip currents are channeled currents of water flowing away from shore, usually extending past the line of breaking waves, that can pull even the strongest swimmers away from shore.
In 2008, despite the fact that Hurricane Bertha was more than a 1,000 miles offshore, the storm resulted in rip currents that killed three people along the New Jersey coast and required 1,500 lifeguard rescues in Ocean City, Md. over a one week period.
In 2009, all six deaths in the United States directly attributable to tropical cyclones occurred as the result of drowning from large waves or strong rip currents.
To find out more information about rip currents, visit www.ripcurrents.noaa.gov.
Hurricanes and tropical storms can also produce tornadoes. 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. Usually, tornadoes produced by tropical cyclones are relatively weak and short-lived, but they still pose a significant threat.
Tropical cyclone climatology
A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has a closed low-level circulation. Tropical cyclones rotate counterclockwise in the Northern Hemisphere. They are classified as follows:
Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less.
Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots).
Hurricane: A tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher. In the Western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale.
Atlantic and Eastern Pacific climatology
The Atlantic hurricane season runs from June 1 to Nov. 30, and the Eastern Pacific hurricane season runs from May 15 to Nov. 30. The Atlantic basin includes the Atlantic Ocean, Caribbean Sea and Gulf of Mexico. The Eastern Pacific basin extends to 140°W.