Emergency Management

The intensity of a landfalling hurricane is expressed in terms of categories that relate wind speeds and potential damage. According to the Saffir-Simpson Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in higher categories. A Category 4 hurricane would have winds between 131 and 155 mph and, on the average, would usually be expected to cause 100 times the damage of the Category 1 storm. Depending on circumstances, less intense storms may still be strong enough to produce damage, particularly in areas that have not prepared in advance.

Tropical storm-force winds are strong enough to be dangerous to those caught in them. For this reason, emergency managers plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds.

Hurricane-force winds can easily destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material, and small items left outside become flying missiles in hurricanes. Extensive damage to trees, towers, water and underground utility lines (from uprooted trees), and fallen poles cause considerable disruption.

High-rise buildings are also vulnerable to hurricane-force winds, particularly at the higher levels since wind speed tends to increase with height. Recent research suggests you should stay below the tenth floor, but still above any floors at risk for flooding. It is not uncommon for high-rise buildings to suffer a great deal of damage due to windows being blown out. Consequently, the areas around these buildings can be very dangerous.

The strongest winds usually occur in the right side of the eyewall of the hurricane. Wind speed usually decreases significantly within 12 hours after landfall. Nonetheless, winds can stay above hurricane strength well inland. Hurricane Hugo (1989), for example, battered Charlotte, North Carolina (which is 175 miles inland) with gusts to nearly 100 mph.

The Inland High Wind Model can be used by emergency managers to estimate how far inland strong winds extend. The inland wind estimates can only be made shortly before landfall when the windfield forecast errors are relatively small. This information is most useful in the decision-making process to decide which people might be most vulnerable to high winds at inland locations.

QUESTIONS TO ASK YOUR COMMUNITY LEADERS
Does your community building code set standards that will help buildings withstand winds in a major hurricane?

Do your shelter facilities include long-span roofs or unreinforced masonry walls (such as gymnasiums) that are vulnerable in high winds?

Saffir-Simpson Hurricane Scale

Tropical Storm
Winds 39-73 mph

Category 1 Hurricane – winds 74-95 mph (64-82 kt)
No real damage to buildings. Damage to unanchored mobile homes. Some damage to poorly constructed signs. Also, some coastal flooding and minor pier damage.
– Examples: Irene 1999 and Allison 1995

Category 2 Hurricane – winds 96-110 mph (83-95 kt)
Some damage to building roofs, doors and windows. Considerable damage to mobile homes. Flooding damages piers and small craft in unprotected moorings may break their moorings. Some trees blown down.
– Examples: Bonnie 1998, Georges(FL & LA) 1998 and Gloria 1985

Category 3 Hurricane – winds 111-130 mph (96-113 kt)
Some structural damage to small residences and utility buildings. Large trees blown down. Mobile homes and poorly built signs destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain may be flooded well inland.
– Examples: Keith 2000, Fran 1996, Opal 1995, Alicia 1983 and Betsy 1965

Category 4 Hurricane – winds 131-155 mph (114-135 kt)
More extensive curtainwall failures with some complete roof structure failure on small residences. Major erosion of beach areas. Terrain may be flooded well inland.
– Examples: Hugo 1989 and Donna 1960

Category 5 Hurricane – winds 156 mph and up (135+ kt)
Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Flooding causes major damage to lower floors of all structures near the shoreline. Massive evacuation of residential areas may be required.
– Examples: Andrew(FL) 1992, Camille 1969 and Labor Day 1935

Hurricanes can also produce tornadoes that add to the storm’s destructive power. Tornadoes are most likely to occur in the right-front quadrant of the hurricane. However, they are also often found elsewhere embedded in the rainbands, well away from the center of the hurricane.

Some hurricanes seem to produce no tornadoes, while others develop multiple ones. Studies have shown that more than half of the landfalling hurricanes produce at least one tornado; Hurricane Buelah (1967) spawned 141 according to one study. In general, tornadoes associated with hurricanes are less intense than those that occur in the Great Plains (see the Fujita Intensity Scale below). Nonetheless, the effects of tornadoes, added to the larger area of hurricane-force winds, can produce substantial damage.

We have no way at present to predict exactly which storms will spawn tornadoes or where they will touch down. The new Doppler radar systems have greatly improved the forecaster’s warning capability, but the technology usually provides lead times from only a few minutes up to about 30 minutes. Consequently, preparedness is critical.

Tornado Facts

• When associated with hurricanes, tornadoes are not usually accompanied by hail or a lot of lightning, clues that citizens in other parts of the country watch for.
• Tornado production can occur for days after landfall when the tropical cyclone remnants maintain an identifiable low pressure circulation.
• They can also develop at any time of the day or night during landfall. However, by 12 hours after landfall, tornadoes tend to occur mainly during daytime hours

Tornado Safety Actions – Homes

• Monitor NOAA Weather Radio.
• When a tornado watch is issued, be prepared to take action.
• When a tornado warning is issued, or a tornado is imminent, move to a small interior room away from windows.
• Consider constructing a tornado safe room in or adjacent to your home

Tornado Safety Actions – Mobile and Manufactured Homes

• Monitor NOAA Weather Radio.
• Have a plan of where to go during a tornado threat—a nearby pre-identified safe structure within walking distance.
• When a tornado watch is issued, be prepared to take action.
• When conditions warrant, move to the pre-identified safe structure.
• If you live in a mobile or manufactured home park, get together with other residents and the park owner/manager to designate safe shelter areas in the park or community.

Tornado Safety Actions – Offices, Condominiums and Hotels

• Monitor NOAA Weather Radio.
• When action is required, take shelter in an interior hallway on a lower floor, closet or small room.
• As a last resort, get under heavy furniture, away from windows.

Fujita Scale

The Fujita scale (F-scale) uses actual damage to determine a tornado’s wind speed

F1 Moderate Tornado
73-112 mph
Peels surface off roofs. Mobile homes overturned. Moving autos pushed off roads.

F2 Significant Tornado
113-157 mph
Considerable damage. Roofs torn off frame houses. Large trees snapped or uprooted. Light-object missiles generated.

F3 Severe Tornado
158-206 mph
Severe damage. Roofs and some walls torn off well constructed homes. Trains overturned. Most trees in forests uprooted. Heavy cars lifted off ground.

F4 Devastating Tornado
207-260 mph
Well-constructed houses leveled. Structures with weak foundations blown off some distance. Cars thrown and large missiles generated.

F5 Incredible Tornado
261-318 mph
Strong frame houses lifted off foundations and disintegrated. Automobile-sized missiles fly through the air in excess of 100 mph. Trees debarked.

• Discuss the type of hazards that could affect your family. Know your home’s vulnerability to storm surge, flooding and wind.
• Locate a safe room or the safest areas in your home for each hurricane hazard. In certain circumstances the safest areas may not be your home but within your community.
• Download “Have a Place to Go” in Microsoft Word Format
• Determine escape routes from your home and places to meet. These should be measured in tens of miles rather than hundreds of miles.
• Have an out-of-state friend as a family contact, so all your family members have a single point of contact.
• Make a plan now for what to do with your pets if you need to evacuate. Post emergency telephone numbers by your phones and make sure your children know how and when to call 911.
• Download Pet Plan in Microsoft Word Format
• Check your insurance coverage – flood damage is not usually covered by homeowners insurance.
• Stock non-perishable emergency supplies and a Disaster Supply Kit.
• Download Disaster Supply Kit in Microsoft Word Format
• Use a NOAA weather radio. Remember to replace its battery every 6 months, as you do with your smoke detectors.
• Take First Aid, CPR and disaster preparedness classes.

• www.weatherbug.com
• www.fema.gov
• www.homelandsecurity.alabama.gov
• ema.alabama.gov
• www.nhc.noaa.gov
• www.weather.com
• www.nhc.noaa.gov
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