THUNDERSTORMS make lightning, thunder & sometimes severe weather.
Rising air, called an updraft, lifts moisture into the air to form clouds. When the clouds bubble upward and build in one area, water droplets grow within the cloud. These types of clouds are "Cumulus" because the water 'accumulates' in one spot.
Water droplets rising in the updraft freeze and combine with ice crystals far above the ground. When these particles get heavy they fall and melt on the way down. The updraft then carries them back up to repeat the process over and over until the particles become heavy enough to fall to the ground as rain. If the updraft is very strong the particles can fall to the ground still frozen as hail.
When the storm produces rain, lightning and thunder, the cloud is a "Cumulonimbus." As the rain falls it drags cold air out of the thunderstorm as a downdraft. After 10 to 20 minutes the single thunderstorm weakens and dissipates. Most thunderstorms seem to last longer than 20 minutes. That's because many storms are really clusters of individual thunderstorm 'cells' that grow and die one after the other. At times, thunderstorms last for hours as they produce new cells and feed each other with moisture and wind. When thunderstorms move together as a line it is known as a squall line. Sometimes these lines become very powerful and last for many hours as a derecho.
A thunderstorm is severe when it produces violent and hazardous weather which is one or more of the following: wind over 58mph; hail that is 1" or larger, or tornadoes. Notice that lightning does not make a storm severe but it makes all thunderstorms dangerous.
When you see a severe thunderstorm go inside for shelter and find out what's happening. You must have a plan of action. Keep up with the forecast. There is almost always advance notice of potential severe weather on TV, your weather radio, and from the Storm Prediction Center
The safest place in buildings is the basement or lowest floor, unless there is flooding.
Other safe places are small interior rooms, without windows on the lowest floor.
In houses or high-rises, closets, bathrooms, and stairwells can be shelter.
Avoid windows and move away from walls that are adjacent to outside.
In extreme cases, cover your head and body with blankets or get underneath a mattress to protect yourself from flying debris. You can also get into a bathtub but avoid ones with sliding glass doors unless you remove the doors.
Don't use plumbing and don't touch appliances that are connected by wire or metal to the outside of the building because a close lightning strike can send electricity into the building.
To protect expensive or sensitive electronics, you can unplug them but be concerned for your safety first.
If you are outdoors when severe weather approaches, get inside.
You can find shelter from lightning inside a vehicle but don't go into a vehicle when strong winds or tornadoes are possible.
If no building is nearby you can find shelter by getting into a low area and lying flat if a tornado is approaching.
Get out of and away from water.
Avoid metal fences, train tracks, power lines and tall isolated objects.
Make sure you know what county you live in so that when a Watch or Warning is issued you'll be ready.
Tune to News 5 to see what's happening, and get a NOAA Weather Radio to give you important information, even if you lose electricity.
Lightning happens in regular and severe thunderstorms. Because it's so common, many people don't see lightning as a threat. While any lightning is a danger, lightning is not a measure for severe thunderstorms. You must treat all thunderstorms as dangerous due to lightning.
As a thunderstorm develops, positive charges are carried upward to the higher parts of the cloud. The negative charges stay mainly in the bottom of the storm where temperatures are warmer. Beneath the thunderstorm, on the ground, positive charges prevail. When the difference between the positive and negative charges grows large, a lightning discharge occurs to try to balance the charges.
Lightning tends to seek tall or metal objects but it can strike low areas, water, and non-metal objects. Once lightning strikes something, it can travel through wet soil, water, wires, cables and pipes. There is no way to know exactly when or where it will strike so you must be cautious and follow safety rules.
Don't get caught outdoors. Move inside.
If caught outdoors, get inside of a hard-top vehicle, or crouch low on the ground away from tall isolated objects. There's no guarantee that crouching will help you so running to a permanent building or hard-topped vehicle is good advice.
Don't hide under tall isolated trees or near power lines, fences, heavy machinery, water, or train tracks.
Don't use a phone with cord during lightning.
Listen to your weather radio to find out if storms my be severe.
Don't shower or use other plumbing in lightning storms.
More than 80% of lightning victims are men who stay outdoors rather than going inside. Many of these men are campers, golfers, boaters and fishermen, or men who do yard work or roof work. There's a special lightning safety webpage just for kids. Visit the National Lightning Safety Institute or the Lightning Protection Institute for more safety information. Find plenty of general lightning information from the National Weather Service.
See real-time lightning strikes around the country from the US Lightning Protection Network.
The heat from lightning can actually turn dry, sandy soil into branching tubes of glass. These fragile items are called fulgurites and they form in the ground.
Tornadoes come from severe thunderstorms. They are one of the most frightening, feared forces of nature and we do get them, along with their weaker cousins- waterspouts. Over a thousand tornadoes are recorded annually in the US. Most of them are not deadly or long lasting but a few can be catastrophic. The Tornado Project is a good place to learn more.
A tornado is a violently rotating column of air, from a severe thunderstorm, that is in contact with the ground. The winds can range from under 100mph to over 250 mph. On average, most tornadoes move from southwest to northeast at around 30mph. They last for only a few minutes and generally are not devastating. However, every tornado is different and must be treated with caution. Because of the isolated yet deadly nature of some tornadoes, we put extra effort into informing you of them by breaking into our programs on News 5.
There's much we don't know about tornadoes. We do believe that tornadoes are started when winds blow in different directions across each other creating a shear and a spinning tube of air. The tube begins horizontally but it is tilted upward and into a thunderstorm by the updraft. The updraft causes the tube to stretch upward and spin faster as it becomes smaller. This leads to a funnel cloud and then a tornado. The Storm Prediction Center has a long list of tornado FAQ.
When the conditions that might lead to tornadoes from severe thunderstorms are seen on weather charts, satellite and radar, a Tornado Watch is issued by the Storm Prediction Center in conjunction with the National Weather Service. AWatch means that severe thunderstorms that may produce tornadoes are likely. The Watch lasts from 4 to 6 hours and covers a large area of a state or several states. It means you must watch the sky and stay alert.
When a tornado is sighted or imminent, a Tornado Warning is issued from your local National Weather Service office. This tells you to immediately go into your action plan. While Watches usually come ahead of Warnings, along the Gulf Coast, we commonly have Warnings issued without Watches. Tornado Warnings cover individual counties and they last from 30 minutes to an hour.
Remember the safety rules. Get indoors to a basement, interior stairwell, or small, interior room on the lowest floor. Don't use elevators. Crouch down and cover yourself. Don't try to outrun a tornado in a vehicle unless you are positive you will be safe and successful.
People who have experienced tornadoes say that the sky turned green or very dark before the storm. Hail has often been reported right before a tornado. Some people say that there was an eerie calm right before the storm followed by 20 seconds of incredible noise, like that of a freight train. There is no one pattern that comes with a tornado. In fact, some tornadoes are invisible when the air is very dry or when there is no debris to pick up.
Tornadoes are ranked or rated by the damage they do using now an enhanced Fujita Scale. The EF Scale goes from 0 to 5 but it is only a scale of damage. It cannot be used just based on the size or look of a tornado as it happens. Even when Doppler radar measures a wind speed in a supercell thunderstorm producing a tornado the damage may vary because the radar can only measure wind above the ground, not at the ground where the damage would be don.
If you live in a low lying area or a community that has flooded in the past you must be prepared for flooding again. Even people who live in areas where the terrain is flat have to be cautious. Flash flooding is a rapid flood caused by thunderstorms that drop a lot of rain in one spot or into an area where all the water drains to one spot.
When powerful thunderstorms produce intense rains sometimes a Flash Flood Watch will be issued by the National Weather Service. At News 5 we let you know by displaying a map in the corner of the screen with the counties in the Watch. If the situation worsens then a Flash Flood Warning is issued for specific counties or areas.
In flash flooding you must not try to drive through water that is moving across roads. You have no way of knowing how deep it is or how fast it is moving. As little as two feet of moving water can lift a car and push it into deeper water where you can drown. The rule when you see deep water is turn around, don't drown. There's a whole lot more on this from the National Weather Service.
When people become trapped it is important to get professional help to rescue them. Even a strong swimmer cannot swim against swiftly moving water.
Flash flooding is extremely dangerous at night because it is difficult for motorists to see water in roadways as well as to determine if the road has been washed away. There is now an annual Flood Safety Week where we all pay extra attention to the dangers of deep moving water.
When you think storm safety consider strengthening the building you live or work in. Find excellent tips and instructions from FLASH, the Federal Alliance for Safe Homes.
How much do you know? Don't be one of the many people injured or killed by severe weather because of misunderstanding. Check out the links below to storm safety information and then check NOAA for much more information.
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