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Tornadoes

 

 

Earth's fiercest winds are found swirling around the black heart of a strong tornado.  These powerful whirls can obliterate houses, hurtle cars hundreds of yards, and instantly take the life of anyone caught in the path unprepared.  Each year hundreds of tornadoes strike U.S. soil, more than in any other nation in the world.

Governor Steve Beshear has declared March 2010 as Severe Storms Awareness Month in Kentucky.  Now is the time to take stock of your ability to receive storm warnings, determine what procedures you will follow when severe weather strikes, and how you will respond when disaster hits your neighborhood. 

Click on the links below for more information about one of the deadliest phenomena to threaten Kentucky:  the tornado.

Kentucky Tornado Statistics and Climatology Recent Major Kentucky Tornadoes
Statewide Tornado Drill March 2! Safety Rules
Tornado FAQ Tornado Terms and Definitions
Helpful Links  


Kentucky Tornado Statistics and Climatology

Since 1953 Kentucky has averaged about 12 tornadoes per year, four of which are EF2 or stronger.  In 2009 more than two dozen twisters spun across the state, mostly in western and central sections.

The most likely time of year for tornadoes in Kentucky is April through June, though there is a secondary peak in activity in the fall as well.  However, tornadoes can occur at any time of year, as was shown recently on January 2, 2006, January 29, 2008, and February 5-6, 2008.

The most usual time of day for tornado activity in Kentucky is between 3pm and 9pm.  If conditions are right, however, tornadoes can happen at any time of day or night.  On February 6, 2008 an EF3 tornado killed four people in Allen County at 1:45 in the morning.

Tornadoes typically travel from southwest to northeast, though they are capable of moving in any direction.  On April 4, 1892 a tornado moved due north in Logan County, and on May 6, 1971 a tornado traveled southward through Danville in Boyle County.

Most tornadoes, about 69%, are weak.  Moderate tornadoes account for 29% of all tornadoes, and strong ones are only about 2%.  However, strong tornadoes result in 70% of all tornado deaths.

 

Recent Major Kentucky Tornadoes

Kentucky's strongest tornado so far in the 21st Century was an 800 yard wide F4 twister that caused $31 million in damage across Hopkins County on November 15, 2005.  Peak winds in the storm were around 220 mph as it leveled several houses on the north side of Earlington.  This tornado caused more injuries than any other Kentucky tornado in the past decade, with 40, but there were no fatalities.

The most expensive tornado of the past ten years was the Owensboro tornado of January 3, 2000, which casued $64,000,000 in damages.  Kentucky Weslyan College suffered damage to 12 of its buildings.  Across the city well over a thousand structures were damaged, and Owensboro was declared a Federal disaster area.  Fortunately there were no fatalities.

Fourteen people have lost their lives to Kentucky tornadoes since 2000.  The deadliest tornado killed four people in Allen County on February 6, 2008.

It's interesting to note that all three of these terrible tornadoes occurred during non-traditional times of year.  In other words, instead of happening in the springtime, they took place in January, February, and November!

 

Statewide Tornado Drill March 2! 

On Tuesday, March 2, at 10:07am EST/9:07am CST, the National Weather Service will conduct a statewide test tornado drill that will activate NOAA Weather Radios and broadcast media, allowing schools, businesses, and all citizens across the Commonwealth to participate. 

We strongly encourage you to join in this tornado drill, no matter where you are:  at home, work, school, or on the road.  It is imperative that you know what you will do when a tornado threatens you, and to practice that plan now, while the weather is quiet.  When a destructive tornado is bearing down on you it's too late to develop a safety plan!  You need to know exactly what you will do in the event of an emergency, and also what your family and co-workers should do.

Scroll down for some suggested tornado safety rules.

 

Safety Rules

Before the Storm:

  If a Warning is issued or if threatening weather approaches:

  • In a building, move to a pre-designated shelter, which should be near the center of the lowest floor available, away from windows. Interior hallways and bathrooms work well.
  • If you are caught outdoors, seek shelter in a basement, shelter, or sturdy building.  If you cannot quickly walk to a shelter:
    • Immediately get into a vehicle, buckle your seat belt and try to drive to the closest sturdy shelter.  
    • If flying debris hits your vehicle while you are driving, pull over and park.

      Now you have the following options as a last resort:
    • If you can safely get lower than the level of the roadway, exit your car and lie in that area, covering your head with your hands.
    • If there is no ditch available, stay in the car with the seat belt on. Cover your head and try to get below the level of the windows.
  • Mobile homes, even if tied down, offer NO protection from tornadoes and should be abandoned immediately.
  • Occasionally, tornadoes develop so rapidly that advance warning is simply not possible. Remain vigilant and alert for signs of an approaching tornado, even if there is no warning in effect.

YOU must make the decision to seek shelter before the storm arrives. It could be the most important decision you will ever make.

 Tornado Safety in Schools 

  • Develop a severe weather action plan while the weather is calm
  • Each school should be inspected and tornado shelter areas designated by a registered engineer or architect. Basements offer the best protection. Schools without basements should use interior rooms and hallways on the lowest floor and away from windows.
  • Those responsible for activating the plan should monitor weather information from NOAA Weather Radio.
  • If the school's alarm system relies on electricity, have a compressed air horn or megaphone to activate the alarm in case of power failure.
  • Keep children at school beyond regular hours if threatening weather is expected. Children are safer at school than in a bus or car. Students should not be sent home if severe weather is approaching. This strategy was put into use during the January 2, 2006 Elizabethtown tornado.
  • Lunches or assemblies in large rooms should be delayed if severe weather is anticipated. Gymnasiums, cafeterias, and auditoriums offer no protection from tornado-strength winds.

Hospitals, nursing homes, and other institutions should develop a similar plan

 YOU can prepare for the possibility of a tornado by learning the safest places to seek shelter when at home, work, school, or outdoors. You should also understand basic weather terms and danger signs related to tornadoes. Your chances of staying safe during a tornado are greater if you have a plan for you and your family, and practice the plan.

A DISASTER SUPPLIES KIT SHOULD INCLUDE:

  • A 3-day supply of water (one gallon per person per day) and food that won't spoil
  • one change of clothing and footwear per person
  • one blanket or sleeping bag per person
  • a first-aid kit, including prescription medicines
  • emergency tools, including a battery-powered NOAA Weather Radio and a portable radio, flashlight, and plenty of extra batteries
  • an extra set of car keys and a credit card or cash
  • special items for infant, elderly, or disabled family members

 

Tornado FAQ

  What is a tornado? A tornado is "a violently rotating column of air, pendant from a cumuliform cloud, often (but not always) visible as a funnel cloud, and in contact with the ground." Literally, in order for a vortex to be classified as a tornado, it must be in contact with the ground and the cloud base. It is well-known that a tornado may not have a visible funnel.

What's the difference between a funnel cloud and a tornado? What is a funnel cloud? In a tornado, a damaging circulation is on the ground -- whether or not the cloud is. A true funnel cloud rotates, but has no ground contact, and is not doing damage. If it is a low-hanging cloud with no rotation, it is not a funnel cloud. Still, since a funnel cloud might quickly become a tornado (remember rotation!), it should be reported by spotters.

Does hail always come before the tornado? Rain? Lightning? Utter silence? Not necessarily, for any of those. Rain, wind, lightning, and hail characteristics vary from storm to storm, from one hour to the next, and even with the direction the storm is moving with respect to the observer. While large hail can indicate the presence of an unusually dangerous thunderstorm, and can happen before a tornado, don't depend on it. Hail, or any particular pattern of rain, lightning or calmness, is not a reliable predictor of tornado threat.

What is a multivortex tornado? Multivortex (a.k.a. multiple-vortex) tornadoes contain two or more small, intense subvortices orbiting the center of the larger tornado circulation. When a tornado doesn't contain too much dust and debris, they can sometimes be spectacularly visible. These vortices may form and die within a few seconds. They can happen in all sorts of tornado sizes, from huge "wedge" tornadoes to narrow "rope" tornadoes. Subvortices are the cause of most of the narrow, short, extreme swaths of damage that sometimes arc through tornado tracks. They can leave cycloidal marks in fields

What is the Enhanced F-scale? The Enhanced F-scale (simple table or detailed 95 page PDF) is a much more precise and robust way to assess tornado damage than the original F-Scale. It classifies F0-F5 damage as calibrated by engineers and meteorologists across 28 different types of damage indicators (mainly various kinds of buildings, but also a few other structures as well as trees). The idea is that a "one size fits all" approach just doesn't work in rating tornado damage, and that a tornado scale needs to take into account the typical strengths and weaknesses of different types of construction. This is because the same wind does different things to different kinds of structures. In the Enhanced F-scale, there are different, customized standards for assigning any given F rating to a well built, well anchored wood-frame house compared to a garage, school, skyscraper, unanchored house, barn, factory, utility pole or other type of structure.  As with the original F-scale, the enhanced version rates the tornado as a whole based on most intense damage within the path. There are no plans to systematically re-evaluate historical tornadoes using the Enhanced F-scale.

Big fat tornadoes are the strongest ones, right? Not necessarily. The size or shape of any particular tornado does not say anything conclusive about its strength. Some small "rope" tornadoes still can cause violent damage of EF4 or EF5; and some very large tornadoes over a quarter-mile wide have produced only weak damage equivalent to EF0 to EF1.

What does a tornado sound like? That depends on what it is hitting, its size, intensity, proximity to you, and other factors. The most common tornado sound is a continuous rumble, like a train. Sometimes a tornado produces a loud whooshing sound, like that of a waterfall. Tornadoes which are tearing through densely populated areas may be producing all kinds of loud noises at once, which collectively may make a tremendous roar. Just because you may have heard a loud roar during a damaging storm does not necessarily mean it was a tornado. Any intense thunderstorm wind can produce damage and cause a roar. Also, just because you don't hear a roar that  doesn't mean no tornadoes are nearby.

What is the role of Doppler radar in tornado forecasting? Each NWS forecast office uses output from at least one Doppler radar in the area to help to determine if a warning is needed. Doppler radar signatures can tell warning meteorologists a great deal about a thunderstorm's structure, but usually can't see the tornado itself.  Instead, a radar indicates strong winds blowing toward and away from it in a way that tells forecasters, "An intense circulation probably exists in this storm and a tornado is possible." Possible doesn't mean certain, though. That is why local forecasters must also depend on spotter reports and analysis of the weather situation to make the best-informed warning decisions.

What was the first successful tornado forecast?  The first documented successful tornado forecast by meteorologists was on March 25, 1948, by Air Force Capt. (later Col.) Robert Miller and Major Ernest Fawbush. After they noticed striking similarities in the developing weather pattern to others which produced tornadoes (including the Tinker AFB, OK, tornado several days before), Fawbush and Miller advised their superior officer of a tornado threat in central Oklahoma that evening. A few hours later, despite the tiny odds of a repeat, a second tornado in five days directly hit the base. For more insight into this event, Charlie Crisp has transcribed the late Col. Miller's recollections of the event; and they are now online.

Was tornado forecasting once banned in the U.S.? Yes. Before 1950 the use of the word "tornado" in forecasts was at times strongly discouraged and at other times forbidden, because of a fear that predicting tornadoes may cause panic. As the weather patterns which led to major tornado events became better documented and researched, the mystery behind predicting them began to clear -- a process which still is far from complete, of course. In 1950, the Weather Bureau (today's NWS) revoked the ban (PDF) on mentioning tornadoes in forecasts.

How can a tornado destroy one house and leave the next one almost unscratched? Most of the time, this happens either with multiple-vortex tornadoes or very small, intense single-vortex tornadoes. The winds in most of a multivortex tornado may only be strong enough to do minor damage to a particular house. But one of the smaller embedded subvortices, perhaps only a few dozen feet across, may strike the house next door with winds over 200 mph, causing complete destruction. Also, there can be great differences in construction from one building to the next, so that even in the same wind speed, one may be flattened while the other is barely nicked. For example, a flimsy, unanchored mobile home may be obliterated while all surrounding objects suffer little or no damage.

How do tornadoes do some weird things, like drive straw into trees, strip road pavement and drive splinters into bricks? The list of bizarre things attributed to tornadoes is almost endless. Much of it is folklore; but there are some weird scenes in tornado damage. Asphalt pavement may strip when tornado winds sandblast the edges with gravel, eroding the edges and causing chunks to peel loose from the road base. With a specially designed cannon, wind engineers at Texas Tech University have fired boards and other objects at over 100 mph into various types of construction materials, duplicating some of the kinds of "bizarre" effects, such as wood splinters embedded in bricks. Intense winds can bend a tree or other objects, creating cracks in which debris (e.g., straw) becomes lodged before the tree straightens and the crack tightens shut again.

Do mobile homes attract tornadoes? Of course not. It may seem that way, considering most tornado deaths occur in them, and that some of the most graphic reports of tornado damage come from mobile home communities. The reason for this is that mobile homes are, in general, much easier for a tornado to damage and destroy than well-built houses and office buildings. A brief, relatively weak tornado which may have gone undetected in the wilderness can blow a mobile home apart.

Long ago, I was told to open windows to equalize pressure. Now I have heard that's a bad thing to do. Which is right? Opening the windows is absolutely useless, a waste of precious time, and can be very dangerous. Don't do it. You may be injured by flying glass.

I have a basement, and my friend said to go to the southwest corner in a tornado. Is that good? Not necessarily. The SW corner is no safer than any other part of the basement, because walls, floors and furniture can collapse (or be blown) into any corner.  In a basement, the safest place is under a sturdy workbench, mattress or other such protection -- and out from under heavy furniture or appliances resting on top of the floor above.

Does "global warming" cause tornadoes? No. Thunderstorms do. The harder question may be, "Will climate change influence tornado occurrence?" The best answer is: we don't know. According to the National Science and Technology Council's Scientific Assessment on Climate Change, "Trends in other extreme weather events that occur at small spatial scales -- such as tornadoes, hail, lightning, and dust storms -- cannot be determined at the present time due to insufficient evidence." This is because tornadoes are short-fused weather, on the time scale of seconds and minutes, and a space scale of fractions of a mile across. In contrast, climate trends take many years, decades, or millennia, spanning vast areas of the globe. The numerous unknowns dwell in the vast gap between those time and space scales.

Does El Nino cause tornadoes? No. Neither does La Nina. Both are major changes in sea surface temperature in the tropical Pacific which occur over the span of months. U.S. tornadoes happen on the order of seconds and minutes. El Nino does adjust large-scale weather patterns. But between that and tornadoes there are way too many variables to say conclusively what role El Nino (or La Nina) has in changing tornado risk; and it certainly does not directly cause tornadoes.

How do I become a storm spotter? Local National Weather Service offices offer spotter training sessions each year. Contact the office which serves you for info on when and where they conduct these sessions, and how to become a spotter for them. There is also a national spotters' organization, SKYWARN, which can help you learn about storm spotting and get you in contact with spotting experts.

 

Tornado Terms and Definitions

Tornado Warning:  Take shelter now!  A Tornado Warning is issued for an hour or less, for a county or parts of a few counties.  It means that either an actual tornado has been sighted, or radar meteorologists at the National Weather Service have indicated the possibility of a tornado developing very soon.

Tornado Watch:  A watch is issued for several hours and covers states or parts of states.  It means that thunderstorms are expected to develop and some may produce tornadoes.  When a watch is issued, take a moment to review your severe weather action plan, so you'll be able to act quickly and appropriately if a warning is issued for your area.

Tornado:  A violently rotating column of air, extending from a shower or thunderstorm cloud, in contact with the ground.  Tornadoes are extremely dangerous.

Funnel cloud:  A violently rotating column of air, extending from a shower or thunderstorm cloud, not in contact with the ground.  Funnel clouds are harmless, but should be monitored in case they develop into a full-fledged tornado.

Multiple vortex tornado:  A single tornado that has several smaller whirls within the larger circulation.  These small whirls can be very powerful and can destroy one structure while leaving the building next door virtually untouched.

Enhanced Fujita Scale:  A scale for ranking the severity of a tornado, ranging from 0 (weak) to 5 (strong).

 

Helpful Links

National Weather Service Offices:

Storm Prediction Center

General tornado Information, including safety rules

Area Radars:

 

 


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