Thunderstorms and Lightning

The Johnson County area is affected on an average by 40-60 thunderstorm days per year. The typical thunderstorm is 15 miles in diameter and lasts an average of thirty minutes. All thunderstorms are dangerous. The offspring of thunderstorms are strong winds, lightning, hail, heavy rain, flash floods and flooding, downbursts, and tornadoes.

Only about 10% of storms that occur each year in the United States are classified as severe. The National Weather Service considers a thunderstorm severe if it produces hail at least ¾ inch in diameter, winds 58 mph or higher, or tornadoes.

Thunderstorms frequently occur in the late afternoon and at night in the Plains States. Although they are most likely to happen in the spring and summer months, they can occur year-round and at all hours.

SEVERE THUNDERSTORM (or TORNADO) WATCH: Watches are issued by the Storm Prediction Center in Norman, Oklahoma when the threat appears. Watches are issued to heighten public awareness anywhere from 2-6 hrs before severe weather may develop in a specific geographic area that may include 30,000 square miles.

SEVERE THUNDERSTORM (or TORNADO) WARNING: Warnings are issued by the Weather Service Forecast Office in their area of responsibility when the threat poses an imminent danger to life and property to those in the path of the storm. A warning is issued based on information reported by spotters or indicated by radar. The WSFO serving our area is at Pleasant Hill, Missouri.

Lightning occurs with all thunderstorms and is the result of a sudden discharge of the electrical potential between the positive and negative charges generated in a thunderstorm. Lightning produces an electric charge or current that generates an enormous amount of heat - up to 50,000 degrees Fahrenheit. The rapid heating and cooling of the air near the lightning channel causes a shock wave that results in thunder. More deaths are attributed to lightning each year than tornadoes and hurricanes combined. Most lightning deaths and injuries occur when people are caught outdoors.

A cloud to ground lightning strike begins as an invisible channel of electrically charged air moving from the cloud toward the ground. When one channel nears an object on the ground, a powerful surge of electricity

Lightning Myths

• If it is not raining, there is no danger from lightning.   
• The rubber soles of shoes and tires on a car will protect you from a lightning strike.   
• People struck by lightning carry an electrical charge and should not be touched.   
• "Heat lightning" occurs after very hot summer days and poses no threat.

Lightning Facts

• Lightning often strikes outside of heavy rain and may occur as far as ten miles away from any rainfall.    
• Rubber-soled shoes and rubber tire provide NO protection from lightning. However, the steel frame of a hard-topped vehicle provides increased protection if you are not touching metal. Although you may be injured if lightning strikes your car, you are much safer inside a vehicle than outside.    
• Lightning-strike victims carry no electrical charge and should be assessed and treated immediately for injuries or need for resuscitation.   
• What is referred to as "heat lightning" is actually lightning from a thunderstorm too far away for thunder to be heard. However, the storm may be moving in your direction.

Thunderstorms and Lightning Safety:

• Remember: if you can hear thunder, go to a sturdy building or car immediately. Do not take shelter in small sheds, under isolated trees, or in convertible automobiles.    
• If lightning is occurring and a sturdy shelter is not available, get inside a hard top vehicle and keep the windows up.    
• Telephone lines and metal pipes can conduct electricity. Unplug appliances not necessary for obtaining weather information. Avoid using the telephone or any electrical appliance. Use phones only in an emergency. Turn off air conditioners. Power surges from lightning can overload compressors, damage electrical appliances, and cause fires.    
• Do not take a bath or a shower.    
• Get to higher ground if flash flooding or flooding is possible. Once flooding begins, abandon cars and climb to higher ground. Do not attempt to drive through water. (Most flash flood deaths occur in automobiles.)

 

If Caught Outdoors and No Shelter Is Nearby...

• Find a low spot away from trees, fences, and poles. Make sure the place you pick is not subject to flooding.    
• If you are in the woods, take shelter under shorter trees.    
• If you feel your skin tingle or your hair stand on end, squat low to the ground on the balls of your feet. Place your hands on your knees with your head between them. Make yourself the smallest target possible, and minimize your contact with the ground.    
• If you are boating or swimming, get to land and find shelter immediately!

The 30-30 Rule

Use the 30-30 rule where visibility is good and there is nothing obstructing your view of the thunderstorm. When you see lightning, count the time until you hear thunder.

If that time is 30 seconds or less, the thunderstorm is within 6 miles of you and is dangerous. Seek shelter immediately. The threat of lightning continues for much longer period than most people realize. Wait at least 30 minutes after the last clap of thunder before leaving shelter. Don't be fooled by sunshine or blue sky!