Severe Thunderstorms – Vulnerability Assessment

Radar Image Lubbock, TX – 17 May 2010[2]

Severe Thunderstorm vulnerability depends on the incidence of and societal exposure to them for a particular location. The greatest potential for severe weather develops in geographical regions that are subject to warm, humid air at low levels, while dry, conditionally unstable air prevails aloft and are most likely to occur in the spring and summer and during the afternoon and evening. The following U.S. geographical areas are characterized by the various thunderstorm patterns:[1]

  • Southeast – Thunderstorms occur most frequently over the Florida peninsula and in other parts of the Southeast.
  • Great Plains and Midwest – The most severe weather threat from thunderstorms extends from Texas to southern Minnesota along the Great Plains and midwestern United States.
  • Colorado and Southwest – The thunderstorms that form in Colorado, Arizona, and New Mexico are due to orographic lifting—ascending airflow caused by the Rocky Mountains.
  • West Coast – Few thunderstorms occur along the west coast of the United States because this region is frequently influenced by cooler, maritime air masses that suppress convectional uplift over land.

Severe Thunderstorm Vulnerability Assessment Questions

To assess your vulnerability to the threat of a Severe Thunderstorm to your family and property, perform an assessment to determine if you have knowledge of, are prepared and/or have a plan by answering the following questions:

General All-Hazard Questions:

  • Have you determined the disaster risks in your locale and the hazards that accompany them?
  • Do you know the emergency warning signals and alert notifications used in your community?
  • Have you instructed family members how to shut off water, gas and electricity to your house?
  • Have you made the necessary property preparations to reduce the damage from the hazard?
  • Do you have a backup generator in case of a prolonged power failure?
  • Have you purchased insurance (property, health, life, and/or hazard type)?
  • Have you made the necessary financial arrangements in case of a sudden evacuation and power outage that shuts down local ATMs and banks?
  • have you organized important documents and records and stored them in a portable lock box or safe-deposit box?
  • Have you performed a home inventory video taping the contents stored them in a portable lock box or safe-deposit box?
  • Does your family have an established Emergency Communication Plan and evacuation plan in place and asked an out-of-state person to serve as the “family contact”?
  • Have you assembled a shelter-in-place Emergency Supplies Kit in case you have to shelter at home and you are without power?
  • Have you assembled a mobile Emergency Supplies Kit that can serve as a “grab and go” bag?
  • Are you or someone in your family trained in first aid and CPR?
  • Have you made they necessary preparations and arrangements for pets, seniors, and the disabled?
  • Have you familiarized yourself with the emergency plans of your family member’s employment building, school, day care center, or nursing home?

Hazard Specific Questions:

  • Do you understand the difference between a severe thunderstorm watch and a severe thunderstorm warning?
  • Do you understand why electrical equipment, telephones and plumbing are all dangerous during a thunderstorm?
  • Have you installed electric surge protectors and battery backup devices.
  • Have you selected a safe place in your home for household members to gather during a thunderstorm? This should be away from windows, skylights and glass doors that could be broken by strong winds or hail.
  • Have you made a list of items to bring inside in the event of a severe thunderstorm?
  • Have you made trees and shrubbery more wind resistant by keeping them trimmed and removing damaged branches?
  • Have you protected your animals by ensuring that any outside buildings that house them are protected in the same way as your home?
  • Have you consulted your local fire department about installing lightning rods?

Severe Thunderstorm Density Vulnerability Map

This density map displays the annual Severe Thunderstorm Watch frequency in the United States by county, 1999 to 2008.[3]