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July 2005: Windstorm Preparation Guide

Severe windstorm studies have shown that storm-related damage can be prevented or minimized. The keys to this are windstorm preparation planning in advance of the storm and organized action during and after the storm. A hurricane is a severe tropical storm that forms in the ocean. Hurricanes need warm tropical oceans, moisture and light winds above them. If the proper conditions last long enough, a hurricane can produce violent winds, incredible waves, torrential rains and floods. Hurricanes rotate in a counterclockwise direction around an "eye." A tropical storm becomes a hurricane when winds hit 74 mph. There are on average six hurricanes each year in the Atlantic Ocean; over a three-year period, approximately five hurricanes strike the United States coastline from Texas to Maine. The Atlantic Ocean hurricane season runs from June 1 through November 30. The East Pacific hurricane season runs from May 15 through November 30, with peak activity happening during the months of July through September.

It's never too late to start making a plan. Start planning as soon as possible. This guide offers suggestions that you can work into your plan to minimize windstorm-related damages. If you need assistance in developing a plan or would like someone to double check your current plan, contact Risk Logic Inc.

Windstorm Preparation Prior to the Storm

The ideal emergency action plan should include the following:

Impending Storm

A hurricane watch indicates the possibility that you could experience hurricane conditions within 36 hours. This watch should trigger your emergency action plan. A hurricane warning indicates that sustained winds of at least 74 mph are expected within 24 hours or less. Once this warning has been issued, you should be in the process of completing protective actions and deciding the safest location to be during the storm. Use the advance warning to begin taking action consistently with your emergency plan.

The following steps will be helpful:

During The Storm

Emergency response personnel should stay at the facility only if safe to do so. When hurricanes move onto land, the heavy rain, strong winds and heavy waves can damage buildings, trees and cars. The heavy waves are called a storm surge. Storm surge is very dangerous and a major reason why you MUST stay away from the ocean during a hurricane.

The following steps will be helpful:

After The Storm

Hurricane and Cyclone Categories

(The following category descriptions are based on hurricane wind speeds.) Category

Category
Hurricane
Cyclone
1
74 to 95 mph (120 to 153 km/h)
less than 78 mph (125 km/h)
2
96 to 110 mph (154 to 177 km/h)
78 to 106 mph (126 to 170 km/h)
3
111 to 130 mph (179 to 209 km/h)
107 to 140 mph (171 to 225 km/h)
4
131 to 155 mph (211 to 249 km/h)
141 to 174 mph (226 to 280 km/h)
5
Greater than 155 mph (249 km/h
Greater than 174 mph (280 km/h)

Category 1

Possible storm surge 4 to 5 ft. (1.2 to 1.5 m) above normal. Damage primarily to shrubbery, tree foliage and unanchored mobile homes. No real damage to other structures. Some damage to poorly constructed signs. Low-lying coastal roads inundated, minor pier damage, some small craft in exposed anchorage torn from moorings.

Category 2

Storm surge of 6 to 8 ft (1.8 to 2.4 m) above normal. Some trees blown down. Major damage to exposed mobile homes. Extensive damage to poorly constructed signs. Some damage to roofing materials of buildings. Coastal roads and low-lying escape routes inland cut by rising water two to four hours before arrival of windstorm center. Considerable damage to piers. Marinas flooded. Small craft in unprotected anchorages torn from moorings. Evacuation of some shoreline residences and low-lying islands required.

Category 3

Possible storm surge 9 to 12 ft (2.7 to 3.6 m) above normal. Limbs torn from trees and large trees blown down. Practically all poorly constructed signs blown down. Damage to roofing materials of buildings, some window and door damage. Mobile homes destroyed. Serious flooding at coast and many smaller structures near coast destroyed. Larger structures near coast damaged by battering waves and floating debris. Low-lying escape routes inland cut by rising water three to five hours before windstorm center arrives. Flat terrain 5 ft (1.5 m) or less above sea level flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences within several blocks of shoreline possibly required.

Category 4

Storm surge 13 to 18 ft (4 to 5.5 m) above normal. Flat terrain 10 ft (3 m) or less above sea level flooded inland as far as 6 miles (9.6 km). Shrubs and trees blown down, all signs down. Extensive damage to inadequately installed roofing materials, windows and doors. Complete failure of roofs on many small residences. Complete destruction of mobile homes. Major damage to lower floors of structures near shore due to flooding and battering of waves and floating devices. Low-lying escape routes inland cut by rising water three to five hours before windstorm center arrives. Major erosion of beaches. Massive evacuation of all residences within 500 yards (457 m) of shore possibly required, and of single-story residences on low ground within 2 miles (3.2 km) of shore.

Category 5

Storm surge greater than 18 ft (5.5 m) above normal. Shrubs and trees blown down, considerable damage to roofs of buildings; all signs blown down. Very severe and extensive damage to windows and doors. Complete failure of roofs of many residences and inadequately designed industrial buildings. Extensive shattering of glass in windows and doors. Some complete building failures. Small buildings overturned or blown away. Complete destruction of mobile homes. Major damage to lower floors of all structures less than 15 ft (4.6 m) above sea level within 500 yards (457 m) of shore. Low-lying escape routes inland cut by rising water three to five hours before windstorm center arrives. Massive evacuation of residential areas on low ground within 5 to 10 miles (8 to 16 km) of shore possibly required.

Acknowledgements:

FMRC "Protecting Your Facility Against Windstorms"

FMRC "Severe Windstorm Planning Guide"