Mobile Government

HURRICANE PREPAREDNESS


Terminology and Acronyms

CATEGORY ONE HURRICANE: Winds 74-95 mph or storm surge 4-5 feet above normal. No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage.

CATEGORY TWO HURRICANE: Winds 96-110 mph or storm surge 6-8 feet above normal. Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of the storm center. Small craft in unprotected anchorages break moorings.

CATEGORY THREE HURRICANE: Winds 111-130 mph or storm surge 9-12 feet above normal. Some structural damage to small residences and utility buildings with a minor amount of curtain wall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet may be flooded inland 8 miles or more. Hurricane Opal, which hit NW Florida and Alabama in 1995 and resulted in nearly $3 billion in damage, is an example of a Category 3 Hurricane.

CATEGORY FOUR HURRICANE: Winds 131-155 mph or storm surge 13-18 feet above normal. More extensive curtain wall failures with some complete roof structure failure on small residences. Major erosion of beach areas. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet above sea level may be flooded inland as far as 6 miles. Hurricane Andrew, which hit SE Florida and SE Louisiana in 1992 and resulted in over $26 billion in damage, is an example of a Category 4 Hurricane.

CATEGORY FIVE HURRICANE: Winds greater than 155 mph or storm surge greater than 18 feet above normal. Complete roof failure on many residences and industrial buildings. Some complete building failure with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5-10 miles of the shoreline may be required. Hurricane Camille, which hit Mississippi and SE Louisiana in 1969 and resulted in the deaths of 256 people, is an example of a Category 5 Hurricane.

EMERGENCY MANAGEMENT: Organized analysis, planning, decision making, and assignment of available resources to mitigate, prepare for, respond to, and recover from the effects of all hazards.

EMERGENCY OPERATIONS CENTER (EOC): A pre-designated facility established by an agency or jurisdiction to coordinate the overall agency or jurisdictional response and support to an agency. Mobile’s EOC is located on McGregor Avenue near Spring Hill Avenue.

EVACUATION: Once notified by Mobile County EMA, citizens should begin evacuation by those zones specified in the evacuation order. There are four evacuation zones in Mobile County

FEDERAL EMERGENCY MANAGEMENT AGENCY: The Federal agency created in 1979 to provide a single point of accountability for Federal activities related to disaster mitigation and emergency preparedness, response, and recovery.

FLASH FLOOD: A flood that crests in a short period of time and is often characterized by high velocity flow. It is often the result of heavy rainfall in a localized area.

FLASH FLOOD WATCH: A flash flood is possible in the area; stay alert.

FLASH FLOOD WARNING: A flash flood is imminent; take immediate action.

GALE FORCE WINDS: Winds with a speed from 32 to 63 mph.

HAZARD MITIGATION: Actions taken to prevent disasters or to reduce the damage caused by hazards that cannot be avoided.

HIGH WIND WARNING: Sustained winds of 40 mph or greater, or winds gusting to 58 mph or greater which are either expected or observed regardless of duration. Will be issued for inland areas, away from the coast, where hurricane force conditions are not expected.

HURRICANE: Also tropical cyclone. A storm with pronounced rotary circulation and constant wind speed of 74 mph or more.


Effects Of High Winds Wind Speed
Large branches are in motion. 25 - 31 mph
Whole trees are in motion. 32 - 38 mph
Twigs break off trees; wind impedes walking. 39 - 54 mph
Shallow rooted trees are pushed over. 55 - 72 mph
Roof surfaces are peeled off; windows are broken. 73 - 112 mph
Whole roofs are torn off; large trees are uprooted. 113+ mph

Hurricanes are further classified by the Saffir-Simpson Scale:
Category Winds (mph) Central Pressure(millibars) Storm Surge Damage
1 74 - 95 > 979 4 - 5 ft. minimal
2 96 - 110 965 - 979 6 - 8 ft. moderate
3 111 - 130 945 - 964 9 - 12 ft. extensive
4 131 - 155 920 - 944 13 - 18 ft. extreme
5 155 + < 920 18 + ft. catastrophic

HURRICANE SEASON: Begins June 1st and ends November 30th. Most active time in the Atlantic Ocean is in August and September.

HURRICANE WARNING: Issued when hurricane conditions are expected in a specified coastal area in 24 hours or less. Hurricane conditions include winds of 74 mph and/or dangerously high tides and waves. Actions for protection of life and property should begin immediately when the warning is issued.

HURRICANE WATCH: Issued for a coastal area when there is a threat of hurricane conditions.  Hurricane conditions are possible within 36 hours in the specified area of the Watch.  During a hurricane watch, prepare to take immediate action to protect your family and property in case a hurricane warning is issued.

HURRICANE WATCH AND WARNING AREAS: The National Hurricane Center is responsible for selecting warning areas based on the probability that a hurricane will make landfall within a given area. Before selecting a warning area, hurricane forecasters consult and analyze several computer models to determine the storm's probable course. Then, because most storm damage occurs in an approximate 125-mile swath, forecasters select a warning area of approximately 300 miles in length to ensure that the potentially threatened population has been warned.

SMALL CRAFT CAUTIONARY STATEMENTS: When a tropical cyclone threatens a coastal area, small craft operators are advised to remain in port or not to venture into open sea.

STORM SURGE: An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the storm. A hurricane's greatest destructive force is the storm surge. As a hurricane moves toward the coast, mean water levels may increase 18 feet or more. The greatest storm surge is located in a hurricane's northeast quadrant. As a hurricane makes landfall, this storm surge is pushed onshore, causing severe flooding and destruction. The waves of the surge can undermine waterfront structures, wash out roadbeds, destroy ships, and cause drowning.

STRIKE PROBABILITY FORECASTS: The National Hurricane Center's strike probability forecasts present the percentage chance that the center of a tropical cyclone will pass within 65 miles of a specific location.


Forecast Period Maximum Probability
72 hours 10%
48 hours 13 - 18%
36 hours 20 - 25%
24 hours 35 - 50%
12 hours 60 - 80%

TROPICAL DEPRESSION: Rotary circulation at surface, highest constant wind speed 38 mph.

TROPICAL DISTURBANCE: A moving area of thunderstorms in the Tropics that maintains its identity for 24 hours or more.

TROPICAL STORM: Distinct rotary circulation, constant wind speed ranges from 39-73 mph.

TROPICAL STORM WATCH: An announcement that a tropical storm or tropical storm conditions poses a threat to coastal areas generally within 36 hours. A tropical storm watch should normally not be issued if the system is forecast to attain hurricane strength.

TROPICAL STORM WARNING: A warning for tropical storm conditions including winds within the range of 39-73 mph which are expected in a specified coastal area within 24 hours or less.

TROPICAL WAVE: A trough or cyclonic curvature in the easterly trade winds.



ACRONYMS:

DHEC
Dept. of Health and Environmental Control

EOC
Emergency Operations Center

FEMA
Federal Emergency Management Agency

GIS
Geographic Information System

NHC
National Hurricane Center

NOAA
National Oceanic Atmospheric Admin.