Hurricanes

Hurricane Preparedness

Prepare to evacuate if advised to do so by the governor or elected officials through radio or television announcements. Plan to evacuate as early as possible before hurricane gale-force winds and storm surges force road closings. Leaving early may also help you to avoid massive traffic jams encountered during late evacuation efforts. Listen to the radio and/or television for evacuation and sheltering information.

STORM ADVISORIES ARE ISSUED AS FOLLOWS:

TROPICAL STORM WATCH: Tropical storm conditions are possible in the specified area of the watch, usually within 48 hours.
TROPICAL STORM WARNING: Tropical storm conditions are expected in the specified area of the warning, usually within 36 hours.
HURRICANE WATCH: Hurricane conditions are possible in the specified area of the watch, usually within 48 hours.
HURRICANE WARNING: Hurricane conditions are expected in the specified area of the warning, usually within 36 hours.

Saffir-Simpson Hurricane Wind Scale

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane's sustained wind speed. This scale estimates potential property damage. Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage. Category 1 and 2 storms are still dangerous, however, and require preventative measures.

1

Sustained Winds: 74-95 mph
Storm surge: 4 to 5 feet

Very dangerous winds will produce some damage: Well-constructed framed homes could have damage to roof, shingles, vinyl siding, and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles will likely result in power outages that could last a few to several days.

2

Sustained Winds: 96-110 mph
Storm surge: 6 to 8 feet

Extremely dangerous winds will cause extensive damage: Well-constructed framed homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks.

3

(Major)

Sustained Winds: 111-129 mph
Storm surge: 9 to 12 feet

Extreme damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.

4

(Major)

Sustained Winds: 130-156 mph
Storm surge: 13 - 18 feet

Devastating damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months.

5

(Major)

Sustained Winds: 157 mph or higher
Storm surge: 18 feet or higher

Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.

Hurricane Intensity Scale (Wind and Storm Surge Damage)

Saffir-Simpson Hurricane Wind Scale. Click on image for a larger view.

Storm Surge

The storm surge is water that is pushed onto shore by a hurricane. It is rarely a “wall of water” as often claimed, but rather a rise of water that can be as rapid as several feet in just a few minutes. The storm surge moves with the forward speed of the hurricane— typically 10-15 mph. This wind-driven water moving at 10-15 mph has tremendous power. A cubic yard of sea water weighs 1,728 pounds — almost a ton. A one-foot deep storm surge can sweep your car off the road, and as little as a six-inch surge can sweep you off your feet. The storm surge can begin to rise a day before the storm hits, cutting off escape routes when low-lying highways are flooded. The storm surge depends greatly upon the size and intensity of a hurricane, the angle at which it approaches the shore, how fast the hurricane is moving, coastal features such as bays and estuaries, and the width and slope of the continental shelf. A shallow slope will potentially produce a greater storm surge than a steep shelf. Louisiana’s Coastline has a very wide and shallow continental shelf.