Thunderstorms that precede a cold front are generally stronger and more likely to reach severe proportions than localized thunderstorms associated with tropical air masses. A few things must happen in the earth's atmosphere in order for a thunderstorm to become severe. By definition, a severe thunderstorm is a thunderstorm that contains any one or more of the following three weather conditions:
Supercell thunderstorms are fierce and can sometimes discharge a number of tornadoes. They are tremendously powerful and well-organized, containing rotating columns of rising air.
These storms are capable of maintaining severe thunderstorm strength for hours. They can also produce dangerous straight line winds, large hail and torrential rain. Sometimes these storms spawn particularly strong tornadoes.
Frequently, a severe thunderstorm develops as part of a cold front associated with strong jet stream winds in the upper levels of the troposphere. Spurred on by the jet stream, this line of severe thunderstorms is called a squall line. Bow echoes associated with squall lines or mesoscale convective systems can produce widespread damage.
A downburst is a severe localized wind blasting down from a thunderstorm. These strong downward currents are classified by meteorologists as microbursts if the downburst covers an area less than 2.5 miles in diameter and as macrobursts if the downburst covers an area of at least 2.5 miles in diameter.
Wind shear is any sudden change of speed or direction in wind flow. Since a microburst is a sudden vertical drop of air, it produces considerable wind shear.
Some thunderstorms can be seen approaching, while others hit without warning. It is important to learn and recognize the danger signs and to plan ahead.
Check for hazards in the yard. Dead or rotting trees and branches can fall during a severe thunderstorm and cause injury and damage.
Make sure that all family members know how to respond after a thunderstorm. Teach family members how and when to turn off gas, electricity and water.
Teach children how and when to call 9-1-1, police, fire department, and which radio station to tune for emergency information.
Severe thunderstorm watches and warnings: A severe thunderstorm watch is issued by the National Weather Service when the weather conditions are such that a severe thunderstorm (damaging winds 58 miles per hour or more, or hail three-fourths of an inch in diameter or greater) is likely to develop. This is the time to locate a safe place in the home and tell family members to watch the sky and listen to the radio or television for more information. A severe thunderstorm warning is issued when a severe thunderstorm has been sighted or indicated by weather radar. At this point, the danger is very serious and everyone should go to a safe place, turn on a battery-operated radio or television, and wait for the "all clear" by the authorities.
Learn how to respond to a tornado and flash flood. Tornadoes are spawned by thunderstorms and flash flooding can occur with thunderstorms. When a "severe thunderstorm warning" is issued, review what actions to take under a "tornado warning" or a "flash flood warning."
Develop an emergency communication plan. In case family members are separated from one another during a thunderstorm (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together.
Ask an out-of-state relative or friend to serve as the "family contact". After a disaster, it's often easier to call long distance. Make sure everyone knows the name, address, and phone number of the contact person.
Contact your local emergency management office or American Red Cross chapter for more information on thunderstorms and lightning.
If in a car:
Estimating the distance from a thunderstorm: Because light travels much faster than sound, lightning flashes can be seen long before the resulting thunder is heard. Estimate the number of miles you are from a thunderstorm by counting the number of seconds between a flash of lightning and the next clap of thunder. Divide this number by five.
Important: You are in danger from lightning if you can hear thunder. Knowing how far away a storm is does not mean that you're in danger only when the storm is overhead.
Hail: Hail is produced by many strong thunderstorms. Hail can be smaller than a pea or as large as a softball and can be very destructive to plants and crops. In a hailstorm, take cover immediately. Pets and livestock are particularly vulnerable to hail, so bring animals into a shelter.
Check for injuries. A person who has been struck by lightning does not carry an electrical charge that can shock other people. If the victim is burned, provide first aid and call emergency medical assistance immediately. Look for burns where lightning entered and exited the body. If the strike cause the victim's heart and breathing to stop, give cardiopulmonary resuscitation (CPR) until medical professionals arrive and take over.
Remember to help your neighbors who may require special assistance infants, elderly people, and people with disabilities.
Report downed utility wires.
Drive only if necessary. Debris and washed-out roads may make driving dangerous.
For more information on mitigation, contact our office.