Severe ThunderstormsEven without a tornado, a severe thunderstorm can be a damaging and life threatening event. Deaths and injuries occasionally occur from strong thunderstorm winds. Thunderstorms also accounted for millions of dollars in property damage. Also large hail can be responsible for tremendous property damage.
EXACTLY WHAT IS A "SEVERE" THUNDERSTORM?
The National Weather Service defines a thunderstorm as "SEVERE" when wind speeds reach 58 mph or stronger and/or hail is produced that is 3/4 inch in diameter or larger and/or a tornado is produced.
Downward rushing currents of air, or downdrafts, occur along the leading edge of almost all thunderstorms and along the trailing edge as well, in some cases. This process, the same that can bring a welcome cooling breeze on a hot summer day, can also produce winds as damaging as those of a tornado. Strong localized downdrafts are called "downbursts", These intense concentrations of sinking air fan out upon striking the earth's surface and produce damaging winds. They may be accompanied by a "roaring sound". Thunderstorms that produce downbursts typically produce several in succession of various sizes and intensities. There may be a well defined damage path similar to that of a tornado or concentrated damage may occur in one spot.
Downdraft winds from thunderstorms often reach destructive force in Ohio. These damaging winds area called "straight-line winds", and can have winds speeds up to 60 mph...and can even reach or exceed 100 mph on occasion. What makes these winds so damaging is the rapid increase in local wind speeds when downbursts strike. Winds that rapidly jump from 10 to 60 mph can produce more damage than sustained 60 mph wind. Frequently, damage that is attributed to tornadoes is actually due to the straight-line winds of a downburst. In Ohio the frequent occurence of downburst winds makes it imperative that the threat of non-tornadic severe thunderstorms be taken seriously as severe thunderstorms with tornadoes.
Large hailstones can develop within strong thunderstorm updrafts. The stronger the updraft is, the larger the stones that can be held up in the updraft without falling to the ground. Severe thunderstorm in Ohio usually produce hailstones one inch in diameter or smaller. A few of the storms produce golfball to baseball size hailstones which cause substantial damage. The most severe thunderstorm across the country have been known to produce up to grapefruit size hailstones.
The potential for deaths, injuries, and damage from severe thunderstorms makes it imperative that our preparedness plans include thunderstorm safety and that we heed Severe Thunderstorm Warnings.
Just like Tornado Watches or Tornado Warnings, watches and warnings are issued for areas threatened by severe thunderstorms.
WHAT TO LISTEN FOR
SEVERE THUNDERSTORM WATCH: conditions are favorable for severe thunderstorms to develop in or close to the watch area. Be ready to seek shelter if a storm approaches or a warning is issued for your area.
SEVERE THUNDERSTORM WARNING: a severe thunderstorm is indicated by radar, or reported by a reliable source. Move to a safe place immediately and stay away from windows.
Summertime is the peak season for one of the nation’s deadliest weather phenomena - lightning. According to the National Weather Service, 27 people in the United States were killed by lightning strikes in 2008. Forty-five people were struck and killed by lightning in 2007.
Of those who were killed by lightning in 2007,
- 98% were outside
- 89% were male
- 30% were males between the ages of 20 and 25 years
- 25% were standing under a tree
- 25% of the deaths occurred on or near water
When Thunder Roars, Go Indoors!
Watch for Developing Thunderstorms. Thunderstorms are most likely to develop on spring or summer days but can occur year round. As the sun heats the air, pockets of warmer air start to rise and cumulus clouds form. Continued heating can cause these clouds to grow vertically into towering cumulus clouds, often the first sign of a developing thunderstorm.
An Approaching Thunderstorm: When to Seek Shelter. Lightning can strike as far as 10 miles away from where it is raining. That’s about the distance you can hear thunder. If you can hear thunder, you are within striking distance. Seek shelter immediately! When thunder roars, go indoors!
Outdoor Activities – Minimize the Risk of Being Struck. Most lightning deaths and injuries occur in the summer. During organized outdoor sporting events, coaches, camp counselors and other adults must stop activities at the first clap of thunder to ensure that everyone has time to get to a large building or enclosed vehicle. Leaders of outdoor events should have a written emergency plan that all staff are aware of and enforce.
Indoor Activities – Things to Avoid. While inside, stay off land lines or corded phones, computers and other electrical equipment that put you in direct contact with electricity. Stay away from indoor and outdoor pools, bathtubs, showers, and other plumbing. Buy surge suppressors for key equipment. Install ground fault protectors on circuits near water or outdoors. When inside, wait 30 minutes after the last sound of thunder and lightning before going out again.
Helping a Lightning Strike Victim. If a person is struck by lightning, call 911 and get medical care immediately. Cardiac arrest and irregularities, burns and nerve damage are common injuries when people are struck by lightning. You are not in physical danger when helping a lightning victim. Knowing first aid measures, which include cardiopulmonary resuscitation (CPR), can help lightning-strike victims survive. American Red Cross chapters and local fire departments often offer first aid and CPR classes.
Summary: Lightning is dangerous. By knowing what to do during severe weather incidents, you can greatly increase your safety and the safety of those around you. At the first clap of thunder, go inside a preferably large building or fully enclosed vehicle and wait 30 minutes after the last sound of thunder and lightning before going back outside. Remember: When thunder roars, go indoors!
Shelter from Thunder and Lightning Storms Safe Shelter from Storms - A house or other substantial building offers the best protection from lightning. For a shelter to provide adequate protection from lightning, it must contain a mechanism for conducting the electrical current from the point of contact to the ground. These mechanisms may be on the outside of the structure, or contained within the walls of the structure, or a combination of the two. On the outside, lightning can travel along the outer shell of the building or follow metal gutters and downspouts to the ground. Inside, lightning can follow conductors such as electrical wiring, plumbing and telephone lines to the ground.
Unsafe Sheltering - Unless specifically designed to be lightning safe, small structures do little, if anything to protect people from lightning. Many small, open shelters on golf courses, parks and athletic fields are designed to protect people from rain and sun, but not lightning. A shelter that does not contain plumbing or wiring throughout, or some other mechanism for grounding from the roof to the ground is not safe. Small wooden, vinyl or metal sheds offer little or no protection from lightning and should be avoided during thunderstorms.
Protect Your Pets - Outside dog houses are not lightning-safe. Dogs that are chained to trees or wire runners can easily fall victim to lightning strikes. You may want to consider bringing your pets inside the home or garage during thunderstorms.
RESOURCES FOR MORE INFORMATION
- Ohio Committee for Severe Weather Awareness
- NOAA Lightning Safety
- The National Weather Service - Cleveland Forecast Office