Severe Weather Experience

Welcome to the Severe Weather Experience. Everything you need to know about severe weather is here, from how you prepare, to how it forms. WCIA is proud to present this website to help educate and prepare our viewers for central Illinois’ severe weather.

 

Scroll down to follow the Severe Weather Experience story.  We hope you enjoy and come back to visit in the future as well!

 

 

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Tornadoes

A Tornado is a violently rotating column of air extending from the base of a thunderstorm the surface of the earth. These mysterious storms can be very destructive, especially when they form in populated areas. Tornadoes inspire countless meteorologists and scientists to study their awe-inspiring power; therefore much of the mystery surrounding these storms has been removed. The following information will cover what we’ve learned about these amazing storms.

 

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How Tornadoes Form

Tornadoes usually form during the presence of a Severe Thunderstorm. This is because severe storms are already very turbulent with their air movement. A key component in creating a tornado is having a strong updraft – a rising current of warm, moist air and wind shear – change of wind direction and speed with height.

Tornadoes are the result of ideal conditions necessary to create them and the thunderstorms which produce them. First off, we need an abundant supply of low level moisture to contribute to the development of a thunderstorm. Once that moisture is present we need a “trigger”, or lifting mechanism, such as a cold front to lift that moist air into the atmosphere. As the air rises, it becomes saturated, forming a cloud which may go on to become a thunderstorm cloud (Cumulonimbus Cloud), if the atmosphere is unstable enough. An unstable atmosphere is a term you may hear a lot during the severe weather season. This means that the temperature decreases rapidly with height, or that cool/dry air will be above warm moist air.  Lastly, tornadoes form in areas where winds at all levels of the atmosphere are strong and turn clockwise with height.

A change in wind direction and an increase in wind speed with height create a horizontal spinning effect near the surface. The storm’s updraft can tap into this horizontal spin. If this happens, that horizontal spin will become vertical, causing an area of rotation within the storm. Many powerful and violent tornadoes form within this area of rotation.

 

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The Science Behind Tornadoes

Tornado Damage

Tornadoes can cause serious damage to populated areas, therefore they’re rated based on the damage they leave behind. Some of them could even be strong enough to damage “well built” structures like schools and office buildings. Here’s a breakdown of the damage ratings and the tornadoes that usually cause the damage.

The Enhanced Fujita Scale is currently used to assess storm damage.

EF Rating Wind Speeds Damage Category Damage Examples
EF-0 65-85MPH Minor
  • Shingles Removed
  • Gutters Damaged
  • Branches Off of Trees
  • Shallow Rooted Trees Toppled
EF-1 86-110MPH Moderate
  • Significant Roof Damage
  • Windows Broken
  • Exterior Doors Damaged or Lost
  • Mobile Homes Overturned or Badly Damaged
EF-2 111-135MPH Considerable
  • Roof Torn Off
  • Homes Shifted Off Foundation
  • Mobile Homes Destroyed
  • Large Trees Snapped or Uprooted
  • Cars Tossed
EF-3 136-165MPH Severe
  • Entire Storied of Homes Destroyed
  • Significant Damage to Large Buildings
  • Weak Foundations Blown Away
  • Trees Begin to Lose Bark
EF-4 166-200MPH Extreme
  • Homes Leveled
  • Cars Thrown Significant Distances
  • Top Stories of Masonry Buildings Collapsed
EF-5 200+MPH Massive/Incredible
  • Homes Swept Away
  • Critical Damage to Reinforce Concrete Structures
  • High Rise Buildings Sustain Severe Structural Damage
  • Trees are Completely Debarked and Stripped of Branches

How to Prepare for a Tornado

Here are a few tips on how to prepare for a tornado:

  • Put a plan in place with your family and other members of your household.
  • Have a place of shelter.  It should be the interior of a home, away from windows, and preferably in a bathroom.
  • Have an emergency kit read and put it in your place of shelter.

Include in your kit:

  • Water (3 Gallons per person)
  • Food – non perishable
  • Flashlight
  • Battery-powered radio
  • Extra Batteries
  • First Aid Kit
  • Medications
  • Multi-purpose tool
  • Sanitation & personal hygiene items
  • Copies of personal documents
  • Cell phone with chargers
  • Family & Emergency contact information
  • Extra Cash
  • Keep trees and shrubbery trimmed.  This will make them more wind resistant.

 

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If you are in a…

Tornado Watches & Warnings

A Tornado Watch means that conditions are favorable for severe thunderstorms, and if they form, they could produce a tornado.

A Tornado Warning means a severe thunderstorm has developed and has either produced a tornado or radar has indicated intense low level rotation in the presence of atmospheric conditions conducive to tornado development.

 

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Tornadoes By The Numbers

Gifford, Illinois

Strong Winds

Damaging Winds

The criteria for damaging winds are 58 miles per hour or greater at the surface. Although tornadoes get all the recognition for causing damage, don’t let damaging winds sneak up on you. Just like tornadoes, these winds can also be created by severe thunderstorms and cause a lot of damage. At times this damage can be so close to tornadoes, that the National Weather Service has difficulty determining between the two during damage surveys.

 

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How Damaging Winds Form

Strong winds are created by an area of rain-cooled air thru (Evaporative Cooling) held up by the storm’s updraft. This is the same setup that usually creates hail, as well. Since cold/dry air is very dense or heavy, it will eventually fall to the surface at a high rate of speed. Once it hits the ground, the winds will spread out in all directions producing strong winds called straight line winds or downburst. Unlike tornados, winds from a downburst are directed outwards from the point where it hits land. Dry downbursts are associated with thunderstorms with small amounts of rain, while wet downbursts are created by thunderstorms with high amounts of rainfall. Wet downbursts are usually the cause of torrential rains and flash flooding.

Damaging winds can also be the result of that same cold pool of air increasing in size and elongating. Sometimes this could cause fast moving upper level winds to create an inflow of air known as the rear-inflow jet, behind the thunderstorm. This fast moving current aloft will hit the storm’s updraft, but instead of going through the updraft, it tilts downwards towards the surface, bringing very gusty winds with it. This will cause the storm’s updraft to tilt as well, allowing the thunderstorm to live longer and expand outward. This cold air accumulating beneath the storm strengthens the gust front, causing it to take on a bow like shape. The resulting acceleration and forward motion of the gust front subsequently forces warm & moist air upward creating more storms, and if this process repeats itself, a Derecho could result.

 

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Downbursts

Variations

Derecho: The criteria for severe winds are 58 miles per hour or greater at the surface. In a Derecho, these winds can travel a distance of at least 250 miles (400 km) or greater – ahead & along a squall line. A Derecho’s wind can last up to 30 minutes or longer. Due to the length of time these winds are sustained, they can cause considerable damage over a large area.

 

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Severe Thunderstorm Watches & Warnings

A Severe Thunderstorm Watch means that conditions are favorable for severe thunderstorms capable of producing large hail (1” in diameter) and winds up 58+ mph.

A Severe Thunderstorm Warning means a severe thunderstorm has developed and has either produced large hail (1” in diameter), winds up 58+ mph or both. These warnings could also be upgraded to a Tornado Warning, since severe thunderstorms can produce a tornado.

emergencypreparednesskit

 

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How To Prepare For Damaging Winds

Put a plan in place with your family and other members of your household.  Have a place of shelter.  It should be the interior of a home, away from windows, and preferably in a bathroom.  Have an emergency kit read and put it in your place of shelter.

Include the following in your kit:

  • Water (3 Gallons per person
  • Food – non perishable
  • Flashlight
  • Battery-powered radio
  • Extra Batteries
  • First Aid Kit
  • Medications
  • Multi-purpose tool
  • Sanitation & personal hygiene items
  • Copies of personal documents
  • Cell phone with chargers
  • Family & Emergency contact information
  • Extra Cash
  • Keep trees and shrubbery trimmed.  This will make them more wind resistant.

 

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Flash Flooding

Believe it or not, the majority of storm related deaths occur from flash flooding.  Most people don’t realize that just a few inches of fast moving water can sweep you off your feet or even move your car.  Typically, flash floods are caused by slow moving thunderstorms, or thunderstorms that move repeatedly over the same area.  However, ice floating in a river or debris can restrict water flow along the river and cause a flash flood.

 

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Definition Of A Flash Flood

A flash flood is defined as a flood that rises quite quickly or with no advanced warning.  This is usually the result of intense rainfall over a small area.

Compare this to a typical flood, which rises slowly along major streams and rivers.  These types of floods are due to multiple heavy rain events or snow melt.  Also, typical floods will last for days, even months and typically only affect agricultural lands.

 

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The Danger Of Flash Floods

As mentioned before, flash flooding is the leading cause of deaths due to thunderstorms.  Nearly half of all flash flooding deaths are vehicle related because most people don’t realize a few inches of fast moving water can move your car.  In many cases, people ignore barriers blocking flooded areas or knowingly drive into a flooded area.  It’s because of this that the National Weather Service started the “Turn Around, Don’t Drown” campaign.

 

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Flash Flooding Can Be Dangerous

Flash Flood Watches and Warnings

Flash flood watches are typically issued before rainfall (usually in the form of storms) starts to fall.  Some leading factors to issuing a flash flood watch would be:  forecasted rainfall is heavier than what runoff can support, rapid snowmelt with heavy rainfall, saturated soil ahead of heavy rainfall.  Typically, the watches cover large areas for long amounts of time.

Flash flood warnings are issued when flash flooding is occurring, or likely occurring.  The National Weather Service issues these warnings if they have a report of flash flooding occurring, if radar indicates that rainfall amounts have exceeded what runoff can handle, or if a levee or dam is near failure.  Warnings are issued for small areas or large areas, typically for several hours.

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Flash Floods By The Numbers

127 – The national average of flood deaths per year.

6 Inches – The amount of fast moving water needed to knock you off your feet.

 

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The Damage Of A Flash Flood

Flash flooding typically recedes with little damage.  However, in some instances, homes can be damaged by water from quickly rising waters.  Also, in instances that cover the roadways, water can create potholes or even washout the road completely.  However, as said before, flash flooding does most of its damage by putting people in harm’s way.

 

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Hail

Thunderstorms often form chunks of ice that make their way to the ground.  We call this hail and it causes more than $1 billion in crop and property damage each year.  As we will show you in the pages below, hail forms because of the strong updrafts in a storm.  The hail stones can fall at speeds of over 100 mph.

 

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The Sound of Hail

How The Ice Forms

Thunderstorms are very dynamic.  There’s wind going, up and down, as well as rain being pushed around by that wind.  A large part of a thunderstorm’s development is the updraft.

The thunderstorm’s updraft is an area of rising warm and moist air.  As the warm, moist air rises, it begins to cool to the point the water condensates and a cloud forms.  As the cloud continues to cool, it will eventually form drops of water and those drops will start to fall due to gravity.

If the drops of water fall all the way to the surface of the earth, then it is just rain.  However, those drops will sometimes meet up with the same updraft that created them.  This will push the raindrop back into the cloud.  Often, the higher parts (above around 15,000 ft.) of the clouds are below freezing.  As the raindrop enters this area it will freeze into a small chunk of ice.

This process will repeat itself many times, with the ice falling again and the updraft pushing it above the freezing line.  Each time it falls below the freezing line, the small chunk of ice picks up more water.  When it returns above the freezing line, it becomes a bit of a bigger chunk of ice.  The process will continue many times until the updraft becomes weaker or the weight of the ice is too much for the updraft to support.

 

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Severe Thunderstorm Watches and Warnings

Hail can cause serious property damage as well as injury if a person doesn’t have proper shelter.  Therefore, the National Weather Service does issue severe thunderstorm warnings for times when hail is greater than 1”.  That’s about the size of a quarter and is the point at which damage can occur.

Severe thunderstorm warnings are issued when the National Weather Service believes, or has confirmed that a thunderstorm is producing severe hail or damaging winds.  Warnings are issued for small areas, usually about the size of a county.  However, they may cover small parts of several counties as well.  Also, a severe thunderstorm warning is issued for a short amount of time, typically less than 1 hour.

Severe thunderstorm watches are issued for much larger areas for the possibility of damaging winds or hail.  Areas outlined by watches can cover a state or several states.  Typically, they are in effect for several hours, sometimes as many as 12.

 

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Hail By The Numbers

$1 Billion – Crop and property damage each year.

100 mph – speed of the large hail stones.

1” – the size in which hail becomes large enough to do damage.

The largest hail stone:

  • 8” in Diameter
  • 18.625” in circumference
  • 1.9375 lbs
  • 160 – 180 mph:  The estimated updraft strength

$2 Billion – Costliest single hailstorm.

Hailstone Size

Measurement (Inches) Updraft Speed (mph)

bb

<1/4 Less than 24

Pea

¼

24

Marble

½

35

Dime

7/10

38

Penny

¾

40

Nickel

7/8

46

Quarter 1

49

Half Dollar

1 ¼

54

Walnut

1 ½

60

Golf ball

1 ¾

64

Hen egg

2

69

Tennis ball

2 ½

77

Baseball

2 ¾

81

Tea Cup

3

84

Grapefruit

4

98

Softball 4 ½

103

 

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How To Prepare For Hail

Preparing for hail is a bit different than preparing for other severe weather events.  Hail typically only affects the exterior of buildings.  So assuming you have shelter away from windows, you should be safe from hail.  However, because hail is a just one of two dangerous threats that severe thunderstorms bring, it is a good idea to treat a hailstorm the same as other severe thunderstorms, as we’ll review below.

Most of the damage from a hail storm can be prevented if you prepare ahead of time.  Making sure your car has shelter will keep the dings away.  Get lawn and patio furniture inside.  Also, make sure pets and animals have a shelter that will withstand a hailstone.  It may be a good idea to make a list of items that you need to bring in before a storm.

 

Here are a few tips on how to prepare for any storm or tornado

-Put a plan in place with your family and other members of your household.

-Have a place of shelter.  It should be the interior of a home, away from windows, and preferably in a bathroom.

-Have an emergency kit read and put it in your place of shelter.

Include the following in your kit:

-Water (3 Gallons per person

-Food – non perishable

Flashlight

Battery-powered radio

-Extra Batteries

-First Aid Kit

-Medications

-Multi-purpose tool

-Sanitation & personal hygiene items

-Copies of personal documents

-Cell phone with chargers

-Family & Emergency contact information

-Extra Cash

-Keep trees and shrubbery trimmed.  This will make them more wind resistant.

 

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The Damage

Most of hail’s damage is done to objects that can’t be brought inside.  Crops take the brunt of the damage as hail can shred both corn and soybean plants.  Homes typically see a lot of damage to roofs and gutters.  However, at times, windows can be broken if the hail is driven by wind.

 

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Lightning

Many of Mother Nature’s weather hazards are predicted well in advance. Lightning is one of those killers that cannot be forecasted. It kills many people each year and continues to be a game stopper for outdoor events. It is hard to forecast, but easy to understand how it forms and how to stay safe when it storms.

 

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How The Spark Forms

Clouds are made of tiny particles of ice and rain. As a thunderstorm cloud grows, these particles bump up against each other and form charges within the cloud. The lighter ice particles obtain a positive charge and hang in the top of the cloud. The heavier ice particles obtain a negative charge and hang in the lower part of the cloud. A slight positive charge then forms at the bottom of the cloud. A positive charge forms at the ground due to the overwhelming negative charge in the cloud. As the top of the cloud expands a positive charge forms which leads to a negative charge at the ground around the cloud. Lightning can strike between opposite charges within the cloud, or between the cloud and the ground.

Thunder is formed as the air rapidly expands as it is heated quickly by the lightning.

 

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Important Lightning Fact

Lightning is 5 times hotter than the surface of the sun.

Derick Fabert, WCIA3 Chief Meteorologist

What happens when the body is struck by lightning?

 


 

What happens if you are holding something while struck by lightning?

 


 

What happens if you are near someone who is struck by lightning?

 


 

What do you do if you are with someone who is struck by lightning?

 

 

Lack Of Warnings For Lightning

Due to the unpredictability of lightning, there are no warnings for specific lightning strikes. Severe thunderstorms can be warned, but not individual lightning strikes. Lightning can strike even from a thunderstorm that isn’t severe thunderstorm warned.

Some people fall victim to what is called “the bolt from the blue.” This is when lightning strikes under a blue sky.  This is possible when the lightning travels a long distance away from the cloud. Lightning detectors have measured lightning almost 50 miles away from a thundercloud. With such a long distance lightning can travel, it is possible to get hit by lightning even if you aren’t directly beneath the storm cloud.

 

 

Let’s Talk About Lightning

Can you predict lightning?

 


 

What is a lightning rod?

 


 

What do you do if you are outside during a lightning storm?

 


 

What do you do if you are inside during a lightning storm?

 

 

Lightning Quote

When Thunder Roars, Go Indoors

Derick Fabert, WCIA3 Chief Meteorologist

How To Prepare For Lightning

If you hear thunder you are close enough to a storm to be struck by lightning. Immediately move indoors and stay away from the doors and windows.  Do not touch concrete walls or floors. Stay away from plumbing and electricity.

If there is no sturdy building nearby, get in a car with a metal shell and roll up the windows.

If stuck outside move to the lowest ground. Do not lie flat on the ground. Do not stand under a tree. Get off water.

If someone is struck by lightning move them to a safe area and call 911. Use an AED or start CPR.