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Frequently Asked Questions (FAQ)  E-mail
Sunday, 12 April 2009 23:43

1) What Exactly Is a Tornado?
2) Can there be more than one tornado at a time, or another tornado after the first one?
3) Is a Twister the Same as a Tornado?
4) Where Do the Most Tornadoes Occur? Where is Tornado Alley?
5) Is There a Tornado Season?
6) How Are Tornadoes Measured? What does it mean when they say the tornado was an F5?
7) They Say the Sky Turns Green Before a Tornado. Is This True?
8) Why Do Tornadoes Always Hit Mobile Home Parks?
9) I live in a mobile home, is it safe during severe weather?
10) If You Are Not Near a Storm Shelter or Cellar When a Tornado Approaches, What's the Best Thing to Do?
11) What is the difference between a Thunderstorm Watch and a Thunderstorm Warning?
12) What is the difference between a Tornado Watch and a Tornado Warning?
13) I heard my friend say if we are driving we would be safer in the car, is this true?
14) If Storm Chasers can use cars to get closer, then why can't I use a car to get away?
15) Do you chase storms like they did in the movie "Twister"?
16) What is a WX (Weather) radio or what is NOAA Weather radio?
17) What does WX mean anyway?
18) Why do you people put your lives in danger and chase storms?
19) What states have the most tornadoes?
20) How fast do tornadoes travel?
21) Can I hide under an overpass like they did in that video?
22) How much do you get paid to chase storms?
23) I want to be a storm chaser for a career. How do I do that?

1) What exactly is a tornado?

A tornado is a violently rotating column of air between a cloud and Earth, touching both (although not always visibly). When conditions are right, a thunderstorm can spin out one or more tornadoes. There must be moisture in the low to middle levels of the atmosphere, air that is rising from the ground and strong enough to keep rising, and a "lifting force" that causes the air to begin rising. (This can happen when air near the ground is warmed.) As air rises, it cools, and the moisture in it begins to condense, forming a cloud. If the lifting force is strong enough and the air has enough moisture, this cloud can tower more than 50,000 feet. The updraft can carry winds upward of 100 mph. Tornadoes can form in this updraft. Falling rain or hail pulls air down to form downdrafts. Since the tornado is in rising air, the wind around it is flowing into the tornado. Damaging winds can hit hundreds of yards from the tornado's vortex.

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2) Can there be more than one tornado at a time, or more after the first one?

Tornadoes can come one at a time or in clusters, and they can vary greatly in length, width, direction of travel, and speed. They can leave a path 50 yards to more than a mile wide. They may touch down for seconds or remain in contact with the ground for much longer periods, although the average is about 15 minutes. Occasionally, one storm can become what is known as cyclic, and can produce a number of tornadoes one after the other, in some cases while the last one is still on the ground. Sometimes, there might even be a storm behind the first storm that can also produce tornadoes. Scientists are studying tornadoes so that they can more accurately predict what conditions create them and thus improve warning techniques.

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3) Is a twister the same as a tornado?

The term twister has been used for some smaller tornadoes, and some people use the term interchangeably with tornado. Meteorologists frown on such usage.

As early as the late 1500s, "twister" referred to someone who spins thread or cord. The twisting strands of a rope very much resemble the spiraling motion of air in a tornadic vortex, but the name "twister" was apparently not applied to tornadoes until 1897, when this sentence appeared in a magazine article: "Kansas is a favorite spot of the 'twisters' as the Westerns [sic] playfully term their windy enemy, the tornado." It is probable that "twister" came to mean "tornado" in the same way that other common words have taken on special meanings related to thunderstorms, for example, "anvil," "tower," "vault," "funnel," "echo," and "lid."

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4) Where do most tornadoes occur? Where is tornado alley?

The United States has the highest incidence of tornadoes worldwide, with around 1000 occurring every year. The country's unique geography brings together polar air from Canada, tropical air from the Gulf of Mexico, and dry air from the Southwest to clash in the middle of the country, producing thunderstorms and the tornadoes they spawn. Tornadoes have hit all 50 U.S. States, but some states have tornadoes more often than others. Oklahoma, Texas, and Florida are the leading candidates. Frequent thunderstorms in western Florida contribute significantly to the number of tornadoes there, but the tornadoes tend to be relatively weak. Fewer thunderstorms occur in the central Great Plains, but tornadoes spawn there frequently because of the low-level wind shears in that part of the country.

This map gives a graphical idea of tornado occurrences based on Storm Prediction Center statistics. Click on it for a larger view.
The American Meteorology Society's Glossary of Weather and Climate defines Tornado Alley as: "The area of the United States in which tornadoes are most frequent. It encompasses the great lowland areas of the Mississippi, the Ohio, and lower Missouri River Valleys. Although no state is entirely free of tornadoes, they are most frequent in the Plains area between the Rocky Mountains and Appalachians."

 

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5) Is there a tornado season?

The combination of conditions that cause tornadoes is common across the southern United States in the late winter and early spring. As the season goes on, tornadoes are likely to occur farther and farther north in the plains states and the Midwest. April and May tornadoes are common in the South as well as in those more northern areas. Often a large storm system can create tornado conditions for several days in a row.

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6) How is a tornado measured? What does it mean when they say the tornado was an F5?

The Fujita scale, developed by the late Dr. T. Theodore Fujita at the University of Chicago, ranks tornadoes from F0 to F5, with F0 indicating a tornado that does light damage and has wind speeds up to 73 mph. An F5 tornado does incredible damage and has wind speeds greater than 261 mph. Only 2 percent of tornadoes reach the F5 level. It is VERY important to note that the Fujita scale is based on OBSERVED DAMAGE, and not recorded or estimated wind speeds.

The most widely used method worldwide, for over three decades, was the F-scale developed by Dr. T. Theodore Fujita at the University of Chicago. In the U.S., and probably elsewhere within a few years, the new Enhanced F-scale is becoming the standard for assessing tornado damage. In Britain, there is a scale similar to the original F-scale but with more divisions; for more info, go to the TORRO scale website. In both original F- and TORRO-scales, the wind speeds are based on calculations of the Beaufort wind scale and have never been scientifically verified in real tornadoes. Enhanced F-scale winds are derived from engineering guidelines but still are only judgmental estimates. Because:

  1. Nobody knows the "true" wind speeds at ground level in most tornadoes, and
  2. The amount of wind needed to do similar-looking damage can vary greatly, even from block to block or building to building,

...damage rating is (at best) an exercise in educated guessing. Even experienced damage-survey meteorologists and wind engineers can and often do disagree among themselves on a tornado's strength.


An EF5 tornado can do incredible damage and has winds speeds estimated greater than 200 mph! Only a very small percentage of all rated tornadoes are ever believed to reach the EF5 level. IMPORTANT NOTE ABOUT ENHANCED F-SCALE WINDS: The Enhanced F-scale still is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. Standard measurements are taken by weather stations in open exposures, using a directly measured, "one minute mile" speed. The rating in no way reflects on the visual appearance of a tornado. Small tornadoes can still produce catastrophic damage.

There are some various modifiers for estimating the tornado damage, but here is the basic new scale.

Basic Enhanced F Scale for Tornado Damage

FUJITA SCALE DERIVED EF SCALE OPERATIONAL EF SCALE
F Number Fastest 1/4-mile (mph) 3 Second Gust (mph) EF Number 3 Second Gust (mph) EF Number 3 Second Gust (mph)
0 40-72 45-78 0 65-85 0 65-85
1 73-112 79-117 1 86-109 1 86-110
2 113-157 118-161 2 110-137 2 111-135
3 158-207 162-209 3 138-167 3 136-165
4 208-260 210-261 4 168-199 4 166-200
5 261-318 262-317 5 200-234 5 Over 200

A note about the F6 rating: While this rating was part of the original F-scale, there was never a tornado in history rated an F6. There is some misinformation going around that the Oklahoma City tornado on May 3, 1999 was an F6. This is not true! It was rated by the National Weather Service after extensive surveys of the damage path to be an F5. In fact, much of the F5 damage was found in area that had measured winds in the F2-F4 range. It is theorized this was due to the large amounts of wind blown debris adding to the damage. The F6 rating myth has come about by a few journalists that spoke uninformed early after the event and rumor has propagated the myth since. Doppler on Wheels units did record radar estimated 318 mph winds in the tornado vortex, about halfway up the tornado.

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7) They say the sky turns green before the tornado, is this true?

Clouds often take on a greenish hue before severe storms, but this is most often associated with hail. Hail is usually part of a tornado-bearing storm. Another thought is that these very tall, dense storms are most likely not letting in any sunlight, so the greenish tint may be a reflection of Earth's green foliage, although this theory has been tested to be rather unlikely. Some other studies have determined that the most likely cause of the "green clouds" is in fact the clouds themselves, filtering out certain other wavelengths of the light spectrum. There are ongoing studies on this.

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8) Why do tornadoes always hit mobile home parks?

Tornadoes DO NOT hit mobile homes more frequently than they hit other structures. Fact is that mobile homes are more vulnerable to tornado damage. Mobile homes can easily be overturned by strong wind gusts. In addition, their thin walls make them susceptible to windblown debris. Mobile homes also do not have cellars in which to seek shelter. Residents of mobile home parks in tornado-prone areas should NEVER attempt to remain in their homes when a tornado approaches. Many parks have designated community shelters, and those that don't, should!

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9) I live in a mobile home, is it safe during severe weather?

Absolutely not!! Tornadoes are not the only threat to mobile homes! While even a small tornado can tear up a mobile home, regular severe thunderstorms also can produce straight-lined winds, often as high as 100 mph or more. These winds can roll a mobile home in an instant, especially if they are not well anchored, and many are not. When severe weather threatens, it is best to find another place to ride it out. NEVER try to ride out a tornado in a mobile home!!

Just in case you need a visual reason, check out these pictures of some left over mobile homes. These were struck by only F2 tornados!

10) If You Are Not Near a Storm Shelter or Cellar When a Tornado Approaches, What's the Best Thing to Do?

The normal lead time for tornado warnings is no more than 20 minutes, and typically a lot less than that, so sometimes there aren't a lot of options when a sturdy shelter is not nearby. Tornadoes harm people primarily through flying debris. Being outdoors when a tornado strikes poses a threat if there are many things nearby that could go flying through the air, so it's best to be in an open field if possible. Other good, but not great, places are a ditch or under a bridge (not an elevated overpass). It's usually a bad idea to stay in your car or to get into a car to get away from a tornado, especially in urban areas. Cars can become death traps in these storms, as they can be flung about by high winds or crushed by debris. That said, if your are out in open country and you spot a tornado and believe it is coming to you, if it’s not nearly on top of you already, you should be able to outrun it by moving at a right angle to it’s movement. Usually south or east in most storms will work if you are east or north of the tornado respectively.

Indoors, a small room in the interior of your home, such as a closet or bathroom, offers the best protection next to a cellar. The key is to stay away from windows and put as many walls as possible between yourself and the outside. If you do not have an interior room, take shelter in a room farthest from the approaching tornado, typically, the east side.

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11) What is the difference between a Thunderstorm Watch and a Thunderstorm Warning?

Thunderstorm Watches are issued in a wide area by the Storm Prediction Center in Norman, OK. Special Forecasters there continually watch all sorts of data to see where the next "hot spot" might be. When they determine an area is especially at risk for severe storms, they will issue a watch (watch box) for that area, often covering several hundred square miles. A thunderstorm watch does not mean that severe storms are definite, but you should keep tabs on the weather, because things can change quickly. A Thunderstorm Watch means that conditions in and near the watch area are prone to Severe Thunderstorm development. If a Thunderstorm Watch is issued for your area, you should start thinking about what you severe weather safety plans are, just in case.

A Severe Thunderstorm Warning is issued by your local National Weather Service office. They do this when a storm in their County Warning Area (CWA) is doing something severe such as high winds, heavy rain or large hail. Generally speaking, WARNINGS are issued one county at a time, and for shorter duration, typically 30 minutes to an hour.

A thunderstorm warning can be issued regardless of whether a thunderstorm watch was in effect or not.

If a Severe Thunderstorm Warning is issued, you should take your preplanned precautions. Don't be outside if at all possible. Do get out of mobile homes and go to a preplanned safer place. Stay away from windows and doors. You can expect heavy rains, large hail, frequent cloud-to-ground lightning, and high winds.

Also remember that thunderstorms can and occasionally do produce tornados, often with little or no warning.

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12) What is the difference between a Tornado Watch and a Tornado Warning?

A Tornado Watch is issued by the forecasters at the Storm Prediction Center in Norman, OK. These forecasters constantly monitor the situation across the US, and when certain conditions are coming together in a given area, a watch may be issued. These watches generally cover several hundred square miles. A Tornado Watch does not mean a tornado is occurring. In fact, thunderstorms may not have even developed yet. It basically means that the watch area is favorable for the development of storms of the type that can produce tornadoes. If a watch is issued for your area, keep tabs on the situation, as it can change quickly, and think about what your severe weather safety plans are, just in case.

A Tornado Warning is issued by your local National Weather Service Forecast Office. If this is issued it means either someone has physically spotted a tornado or rotating wall cloud, or Doppler radar is indicating a storm that might contain a developing tornado.

This is serious! Your life may be in danger. Take immediate cover, do not go outside and look for the tornado.

Get shelter underground if possible, or in the center of a sturdy building, away from windows and doors. Do NOT stay in mobile homes or cars. If caught outside, seek shelter in a ditch, culvert, or low lying area. Do NOT seek shelter under an elevated overpass, you will be seriously injured or killed!

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13) I heard my friend say if we are driving we would be safer in the car, is this true?

No Way!! There are many dangers to you if you were to try to escape during an approaching tornado. Wind propelled debris is the greatest. Also roads are probably going to be littered with all manner of impassable debris, and downed power lines, not to mention other stupid people trying to outrun the storm. All it would take to trap you is one downed line in your path!

That said, if you are out in a rural area, and the tornado is not almost on top of you, you can probably outrun the tornado by driving at a right angle to the tornado. Generally east or south are good options if the tornado is west or north of you respectively.

If you are caught out and absolutely cannot find shelter nearby, find a nearby low-lying area and get into it, away from the car! This may be the only thing to save your life. A strong tornado can crush a car like an aluminum can. Do NOT seek shelter under an elevated overpass! You WILL be seriously injured or killed!

If you must take shelter in a low lying area as a last resort, try and find a concrete culvert or something similar that is enclosed. While it’s been long preached by the National Weather Service to take shelter in a ditch, I have seen far too many ditches FILLED with all manner of deadly debris when a tornado passes for me to genuinely recommend that as an option unless, truly, there is no other option.

Check out the images below and make your own decisions...

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14) If Storm Chasers can use cars to get closer, then why can't I use a car to get away?

Storm chasers have educated themselves thoroughly about where the safe places are and aren't in relation to the movement and behavior of the storm. They usually have cell phones or scanners or ham radios and are in touch with other chasers who are in different locations and have a different view of the storm. They may even have laptop computers and Internet or television access. They may also be in contact with someone who is watching a radar screen, a television weathercast, or in a spotter network. In other words, they have a very good idea about where the tornado is, how intense or violent it may be, in which stage of the life cycle it is, which way it is headed, and how fast it is going. In addition, they may give the tornado a wide berth, sometimes as much as a mile away or more. You must not believe everything you saw in Twister! Chasers aren't nuts. They are very serious about their hobby, and about staying alive to chase again.

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15) Do you chase storms like they did in the movie "Twister"?

The short answer is… NO! No one does, Twister was a movie made for entertainment. It is NOT a documentary. The reality of storm chasing is that it is filled with many hours of preparation, driving, and watching blue skies. If you get to see a tornado 1 out of every 4 chases, you are doing well. Sometimes you are more fortunate to witness more, but it is not common. If we were to try the things they did in the movie in real life, we would most likely have been dead in the first tornado.

No chaser could chase in that manner, and stay alive for long. Twister was loosely based on a research venture the National Severe Storms Laboratory did in 1994 and 1995 in which they had an instrument outfitted 55 gallon drum they tried to put in the path of tornadoes. They were unsuccessful in placing it in front of a tornado, although a lot of good data was gathered overall from the project. It was called Project VORTEX.

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16) What is a WX (Weather) radio or what is NOAA Weather radio? (Now officially known as NOAA All Hazards Radio)

NOAA (National Oceanic and Atmospheric Administration) is the sanctioning government body of the NWS (National Weather Service). They broadcast many of their products via NOAA Weather Radio. This can be picked up by most police scanners by hitting the WX button on newer scanners, or programming the local frequency.

Also you can purchase a weather radio from many retail outlets, Radio Shack being the most common. This radio allows you to listen to their broadcasts any time, and some will sound an alarm any time the NWS issues a severe weather statement, followed by that statement.

The newer WX radios have something called S.A.M.E. or Specific Area Message Encoding. This allows you to customize what counties you will get the alarm for. So instead of being waked for a storm that is 100 miles away, you only get the alarm for counties you programmed. It is highly recommend spending the extra money and getting the S.A.M.E. radio.

An additional note, many local Emergency Management Agencies will also use the NOAA radio as one of the ways to send out disaster information, such as a chemical spill in your area that they are evacuating for. They are also being used to send out the new Amber Alerts for missing children.

These radios are well worth the money! Contact your local NWS office for details on NOAA WX radio, or better yet, visit your local Radio Shack and they will be glad to demonstrate one for you. No one should be without a weather radio. Think of it as your smoke detector for severe weather.

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17) What does WX mean anyway?

Quite simply, it's an abbreviation for Weather.

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18) Why do you people put your lives in danger and chase storms?

The first thing you need to understand is that most experienced chasers are not really willfully putting themselves in great danger. They have educated themselves to a point where they understand what the storm is doing. In addition, they also have many sources available to them for information on the storm at any given time, and are probably in contact via radio with other chasers in different viewing positions. Combining all of this gives them a very good idea of exactly what is going on with the storm, so they can make a best effort to stay out of danger. That said, mother nature still likes to remind us who is boss once in a while.

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19) What states have the most tornadoes?

Texas has the most number of tornadoes. Florida has the most per square mile. Oklahoma has the most number of devastating tornados that level houses to the ground.

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20) How fast do tornadoes travel?

Tornadoes can rotate at speeds over 200 mph, but their forward motion is much slower. They average 30 mph, but can range from near stationary to nearly 70 mph.

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21) Can I hide under an overpass like they did in that video?

No! Please don't. This was a very popular video that was shown any times over the years on various TV programs. Even though that video was heavily hyped, they were only skirted by the outer winds of a very weak tornado. The truth is, in the recent Oklahoma tornadoes on May 3, 1999; many people died or were seriously injured by trying to take shelter under an overpass. You have a great chance of death or serious injury from wind blown debris under an overpass. Find a nearby concrete culvert that is below the average surrounding ground level instead! The idea is to get out of the way of the debris.

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22) How much do you get paid to chase storms?

Most chasers get paid nothing. To them it is a hobby, and they like to have the privilege of witnessing spectacular weather. Storm chasing can be quite expensive. A few other chasers have been able to recover a small amount of their expenses by selling some of their photos or video to individuals and media outlets.

Other storm chasers might work for television stations and provide reports from the field during severe events. Most of these chasers do get paid, but it is seasonal and spotty work. Some storm chasers are part of educational groups that are doing research. Also, there are a few storm chasers that offer tours that take people out to tornado alley to witness nature. These allow for persons that are interested in storms and chasing to get a taste of what it’s about, and be able to go along with experienced storm chasers.

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23) I want to be a storm chaser for a career. How do I do that?

The first thing you should realize, as there is really no such thing as a "career" in storm chasing. Read the answer to question 22 for information on what storm chasers get paid. That being said, the best way to get into storm chasing is to connect with an existing storm chaser to learn the ropes. Also, read, read, read, and read some more. Read everything you can get your hands on about severe weather. There is a ton of information on the web about severe weather. A web search from Google.com will turn up lots of results. You can also find out a lot of information at on this website.

Knowing the basics of severe storms is a must. You can do that online right here.

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This page will be added to as good questions come in. If you have one, feel free to e-mail me, I will answer it via e-mail, and if it's good, add it to this page.

Last Updated on Wednesday, 15 April 2009 00:15
 
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