Hurricane X

When a storm threatens, the National Hurricane Center will begin issuing a map illustrating the potential storm surge threat with possible inundation levels.

A key to being properly prepared when a hurricane or tropical storm threatens is appreciating the risks for your specific location or residence. The three major risks from an approaching storm will be:

• The expected storm surge/inundation levels;

• The projected intensity, size and impact area of the storm’s wind field; and

• The safety and feasibility of any evacuation route and location.

For the first risk, you should have a good idea of the base elevation of your place of residence, as well as some understanding of what inundation levels (the amount of water above ground in a storm surge/tide) are expected in your area. For example, if you are situated at an 8-foot elevation and a 10-foot storm surge is expected, you can expect about 2 feet of inundation, or water above ground.

Fortunately, the National Hurricane Center is developing new tools to help you understand what this threat may be in your location for any given storm.

When a storm threatens, the National Hurricane Center will begin issuing a map illustrating the potential storm surge threat with possible inundation levels.

For example, with the hypothetical storm “Hurricane X,” in the illustration, water levels greater than 9 feet above ground level would be possible over sections of Pelican Island and low lying areas on Galveston Island and the adjacent mainland. Such high water levels also might be expected in the upper parts of the bay and over a very large area from the Bolivar Peninsula to Sabine Pass and the Beaumont-Port Arthur areas.

Water levels greater than 3-6 feet would be widespread on much of Galveston Island and parts of Galveston County around the western areas of Galveston Bay.

If you live in a ground-level structure in any of these areas, there’s a good chance that you may be flooded with this storm.

If you are in a raised structure (pier and beam or on stilts), your chances of flooding will depend on how high your structure is raised above the ground and the expected water levels at your location.

The second risk factor you need to assess in deciding what to do as a storm approaches is the expected winds in your area and how well designed your residence or place of refuge is to withstand such winds. Unfortunately, many homes in Galveston County were built before codes were established and are not designed to withstand winds likely to be encountered in Category 3 to 5 hurricanes.

For warning purposes, the National Hurricane Center provides a surface wind field chart showing the extent of hurricane and tropical force storm winds in a storm. It also will issue a specific Saffir-Simpson scale for the storm outlining the expected damage for those in and near the eye-wall of the hurricane.

If your location will be near or in the eyewall of a hurricane strong enough to cause major structural damage, you may want to consider evacuation and/or relocation to a stronger building.

Living or sheltering inland over Galveston County may not ensure safety from high winds and tornadoes, especially in a major storm. Even a Category 3 storm could bring winds in excess of 100 mph more than 50 miles inland from the coast and wind gusts of 80-100 mph more than 100 miles inland. Be sure you understand the intensity of the impending storm, its projected wind field and path, and the ability of your structure to withstand the winds likely in your area.

Finally, if you do evacuate, try to consider the storm’s projected path after landfall in considering your route and place of shelter. The strongest winds, most tornadoes and the heaviest rains occur most frequently near the center and to the right of the center.

Hurricane Carla in 1961 took 100 mph winds nearly 150 miles inland and 150 mph winds close to 80 miles inland from the coast. Hurricane Rita brought widespread damage to inland areas of the Piney Woods of East Texas. Hurricane Allen in 1980 spawned flash floods and tornadoes in the San Antonio area, parts of the Hill Country and even as far west as Del Rio.

Recognizing the probable path of the storm when choosing a place of refuge could help you avoid the error of “jumping out of the pan into the fire.”

Stan Blazyk’s “Weather Wise” blog appears at galvnews.com.

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