Tornadoes are the most fearsome and destructive of all meteorological phenomena. Thus it is quite popular for them to show up in fiction. However, there are a great many misconceptions surrounding them and a great many myths surrounding them, and thus another case of Do Not Touch the Funnel Cloud ensues. Hopefully, this should clear things up for you.
What is a tornado?
A tornado is a rapidly rotating column of air that forms underneath a supercell thunderstorm. More specifically, to be considered a tornado, it must:
contact the ground
have a rotating wind speed of at least 65 mph
originate from a supercell thunderstorm
How do tornadoes form?
Generally speaking, warm, moist air meets cold dry air, but as to exactly how, nobody knows. No, seriously, ask any meteorologist and they will give you the same answer.
What do they look like?
It varies a lot really, but as for their shape, there are three common categories: Rope◊, Stovepipe◊, and Wedge◊. A tornado will often change shape during its existence, and most will eventually end up as a rope tornado near the end (this is called "Roping Out"). Their color depends on two factors, the color of whatever the tornado picks up, and the direction it is viewed from. Or, it can be invisible by not having a funnel cloud.
What do they sound like?
Although it depends on a variety of factors, the most commonly associated sound is a low and steady rumbling sound, like a passing freight train.
Tornado Watch, Warning, Emergency
Tornado Watch: A Tornado Watch is issued when conditions are ripe for a tornado to form.
Particularly Dangerous Situation (PDS) Tornado Watch: Conditions that are capable of producing many tornadic storms (an outbreak) and/or supercells capable of producing very strong tornadoes (EF 3 or above) are present.
Tornado Warning: A Tornado Warning is issued when there is considerable evidence that a tornado has formed or is in the process of doing so.
Tornado Emergency: A Tornado Emergency is an unofficial statement that is quickly rising in popularity. It is issued when a tornado has formed and is headed towards a populated area.
What to look or listen for
Strong and persistent rotation in the cloud base.
A whirling cloud of dust and debris on the ground under said cloud base. May or may not be at the base of a funnel cloud.
Hail or heavy rain followed by either a dead calm or sudden wind shift. BEWARE OF RAIN-WRAPPED TORNADOES.
A loud, continuous roar or rumble that does not dissipate.
Small, bright blue-green or white flashes at ground level.
Persistent lowering of the cloud base, or a portion of it.
A sudden power outage (e.g. the power was fine one minute, flickering and/or instantly out the next) if storms are around is also a possibly serious warning sign. If this happens in combination with any of the above, run for the best cover in your house because it means the tornado is right on top of you.
What to do
NOTICE: FOLLOWING THESE INSTRUCTIONS WILL NOT COMPLETELY GUARANTEE YOUR SAFETY! HOWEVER, DISREGARDING THEM WILL PRACTICALLY GUARANTEE YOUR DEATH! REMEMBER, THERE IS NO SAFE PLACE IN A TORNADO, ONLY LESS DANGEROUS ONES.
In general, the first and best way of ensuring your survival is to prepare. The best ways to do this, well before any tornado watches or warnings are issued, are:
Designate a shelter area and equip it with what you need to survive. This should either be underground (ideally, such as a basement or storm cellar) or an interior room with no windows and no exterior walls. If you live in a mobile home know where your park's community shelter is, or where the nearest solid structure is.
Make a plan so that you are able to get to that shelter in a moment's notice.
For those who live in mobilehomes and cannot evacuate quickly via vehicle - or who fear an unwarned-for tornado that can't be escaped - a very good idea is to have an underground shelter built UNDER the mobilehome with an entrance to the shelter through the floor of the mobilehome or immediately outside one of the doors.
You should also have digging tools (at least a strong shovel and thick work gloves) in your shelter space in case you need to dig yourself out, and a whistle or air horn or other loud alarm device to get attention for others to help you dig out. If you can't fit digging tools (you're in a bathtub under a mattress, for example) make sure to have that whistle or air horn in your space next to you, and in a way where you will not have to move to use it if you are trapped.
GET A WEATHER RADIO WITH BATTERY BACKUP so you can be alerted to warnings even if you are sleeping or have the TV off or the power is out. If you have a smartphone, it also is a good idea to invest in a quality weather warning/storm conditions app.
WHEN A WATCH IS ISSUED'
If you do not have them on already and are able to get to them, put on a pair of thick-soled shoes when a tornado watch is issued and have a sturdy rain jacket within reach. In the aftermath of a tornado, you will need them. Having a motorcycle helmet with visor (or a bicycle helmet and goggles) nearby is also a good idea - most fatal injuries are head injuries, and there's going to be a lot of sand/mud/grit/glass you do not want in your eyes.
Put dogs on leashes and small dogs or cats in carriers. Pet birds and small animals should be put in their cages. If there is room, carriers, cages, and leashed pets should be moved to the shelter area. If there is not room, they should be placed in the most interior room or the basement in general. As for horses and similar large animals there are two schools of thought: one says freeing them to allow to run to safety on instinct is best, the other says keeping them contained is better. As most barns and stables are flimsy structures, it's likely better to allow free running if particularly severe storms are possible or likely, and you can track/identify the horses or livestock.
Make sure your phone is charged (or on charger) and easy to grab fast. Make sure your wallet/purse is in reach - it probably should be kept on you.
If you live in a mobilehome and have chosen to flee in a vehicle to stronger shelter/away from the storm, make sure the vehicle has a full or at least half full tank of gas, the tires are properly inflated, and it will start. In fact, if you can do it, the watch is probably the best time to go ahead and evacuate your mobilehome for a sturdier building if you can stay at a friend's or family member's or similar.
If there is a watch and/or severe storms are around during sleeping hours, if it is at all possible, sleep in your shelter area (e.g. if you have a basement or underground shelter or safe room capable of sleeping in).
REMEMBER, JUST BECAUSE YOU DON'T SEE A TORNADO, DOESN'T MEAN IT ISN'T THERE. OFTEN, A TORNADO CAN BECOME RAIN-WRAPPED, MEANING THAT THE TORNADO BECOMES OBSCURED BY RAIN. ANOTHER THING THAT OFTEN HAPPENS IS THAT A TORNADO FORMS, BUT NO FUNNEL CLOUD IS VISIBLE.
WHEN A TORNADO WARNING IS ISSUED OR YOU SEE TORNADO CONDITIONS
IF YOU ARE AT HOME:
Head to an interior closet or bathroom on the lowest floor. If you have a basement, go there. Try to get under something sturdy like a table or a mattress. Do not go under an area where there is a heavy object like a piano or a refrigerator on the floor above, as these would be the places most likely to give way.
Avoid windows. If it shatters, it will send shards flying everywhere.
When you get to your shelter, get on your knees, crouch down and cover your head, put on your motorcycle helmet and/or bike helmet and goggles, and cover your head like so.◊
IF YOU ARE IN A MOBILE HOME, GET OUT IMMEDIATELY!!! Put on your helmet as you are doing so. Then, head to the nearest underground space or fixed structure and get inside, or head into the closest ditch if there isn't anything else nearby. If you have more lead time (20-30 minutes of warning) driving out of the storm's path is a better idea than a ditch. Mobile homes are VERY dangerous places to be in a tornado, and can be destroyed by even the smallest ones. Despite previous advice to the contrary, you even have a better chance of surviving driving away from the tornado in a vehicle or outside in a ditch than you do in a mobile home. GET. OUT. Unless, of course, you have an underground shelter built under or next to the mobilehome, in which case get down into it.
IF YOU ARE OUTDOORS:
If there is a fixed structure nearby, like a house or a gas station, head inside and get into an inside room.
If there is not a fixed structure nearby, or there is and you don't think you could get to it in time, try and find a low spot, like a ditch, dive into it, lie flat on your belly, and put your hands over your head.
ON THE ROAD:
If the tornado is off in the distance, and there is not much traffic, try and vary your speed and angle and direction as to avoid it.
If the tornado is headed towards you (if it looks like it is steady and not moving, IT IS MOVING TOWARD YOU), find an underground space or a fixed, solid structure and get inside as soon as possible. If there are no such options, pull over to the side of the road, and get into a ditch as far away from the road as possible. DO NOT try to outrun it unless you are experienced enough with weather and sure enough of your surroundings (and the tornado is moving slowly enough) that you are certain of escape.
If the tornado is headed towards you and you do not think you have time to do any of the above, buckle your seatbelt (as it should be already), roll up your windows, put your head between your knees, put on any helmet and goggles you might have (from a motorcycle helmet to a hard hat), and leave the vehicle running so the air bags will activate if there is a collision. This should be your very last resort, because your odds of surviving with it are very, very low.
After the Tornado:
REMAIN CALM! Freaking out will make things worse, and will get in the way of your ability to make decisions.
If you are trapped in debris, calculate your situation before you move. Are there downed power lines or open electrical wiring in your way or on you? If so, DO NOT MOVE. Will moving collapse the structure or debris further on you or on others? If the answer to that is no and you can get out of the debris under your own power, do so. Otherwise, scream, use your phone if it still works to call 911, make use of your air horn or whistle - make as much noise with as little movement as possible.
In the same way, be absolutely careful when lifting debris off of others. Yes, you may want to just get your little brother out NOW. But being aware of electric shock hazards and worse collapses will save both your lives.
If you are with family members or any other group, STAY TOGETHER and wait for emergency personnel.
Watch your step! After a tornado, there will be debris everywhere. You need to be aware of where you are putting your feet so you don't accidentally step on an exposed nail. This is why when watches are issued, you should wear thick work boots or combat boots.
FOR THE LOVE OF GOD, STAY AWAY FROM DOWNED POWER LINES!!! They don't flash and spark like in the movies.
DO NOT LIGHT A MATCH OR A LIGHTER. There will be a significant chance that the tornado caused a gas line to rupture.
Follow any instructions given to you by emergency personnel. It is their job to make sure that you stay alive, so following their orders is in your best interests.
If the medics say that you are OK, then go out and help. After a tornado, especially a big one, emergency services will be stretched to their limits, they will need all the help they can get.
Stay out of heavily damaged houses, they could collapse at any time.
WHAT NOT TO DO:
DO NOT LEAVE YOUR HOUSE! Unless you are in a mobile home OR the tornado is already wiping fixed structures from their foundations elsewhere, your best bet is to stay put. Leaving a fixed structure will only increase the chances of you getting killed in anything below an EF 5. A storm capable of spawning a tornado will also be capable of producing rain in mass quantities, high winds, and hail. Flash floods are also possible.
DO NOT run around and try to open every door and window. It will rob you of valuable time you need to take shelter.
ON THE ROAD:
DO NOT TRY AND HIDE UNDER AN OVERPASS. AN OVERPASS WILL NOT PROTECT YOU FROM A TORNADO. The details will be explained below.
The Fujita Scale or F-Scale was developed by Dr. Ted Fujita as a way to equate certain amounts of damage with a tornado's wind speed. Implemented in 1971, it ranked tornadoes on a six point scale from 0 to 5. It was a good idea, but it had some major problems. It did not take into account how different structures handle being struck by a tornado, and many other factors. Also, the evaluation of the damage itself was very subjective. On February 1, 2007, the F-scale was abandoned for the Enhanced Fujita Scale, but only in the US. Canada didn't switch over until April 1, 2013.
The Enhanced Fujita Scale or EF-Scale is the successor and improved version of the Fujita Scale. Unlike the F-Scale, the EF-Scale is much more specific about what sorts of damage results in where a tornado is ranked. It also takes into further account how different factors effect how much damage a structure suffers, such as the kind of structure, how it was built, how well it was built, effects of debris, etc. Like the F-Scale it was based on, the EF-Scale ranks tornadoes on a 6-point scale from 0 to 5. An EF0◊ has wind speeds ranging from 65 to 85 mph, an EF1◊ ranges from 86 to 110 mph, an EF2◊ ranges from 111 to 135 mph, an EF3◊ ranges from 136 to 165 mph, an EF4◊ ranges from 166 to 200 mph, and an EF5◊ is any tornado with winds above 200 mph.
Other Terms and Terminology
Supercell: The type of thunderstorm that tornadoes spawn from. They contain a large rotating core called a mesocyclone.
Tornado Family: Tornadoes that spawn from the same supercell are referred to as this.
Tornado Outbreak: An event where a single storm system spawns multiple tornadoes.
False: The funnel cloud is only the center of the tornado, the winds themselves extend well outside the funnel cloud. Actually the funnel cloud is just the part of the tornado where the pressure drops low enough for water vapor to condense.
The wind of a tornado are exclusively vertical.
False: See the definition of a tornado.
Tornadoes destroy mostly by dropping the atmospheric pressure, causing houses to explode.
False: Tornadoes destroy mostly by their intense winds. If you watch any footage of a tornado destroying something, you will notice that the structures tend to be blown away rather than blown up.
There are no tornadoes in _____.
FALSE. In the US alone, every single state has recorded a tornado at some point or another. While this is a half-truth in that generally, tornadoes, say, in California are rare and generally under EF 2 if that, they can and do happen there, and weaker tornadoes aren't nothing to ignore especially in areas unprepared for them, because said areas often have more glass in more places, weaker building codes for wind, and the like. An EF 0 or EF 1 that becomes a whirlwind of glass in a populated open area with no one sheltering can be as if not more deadly than an EF 3 with everyone in proper shelters or that only hits unpopulated land.
Overpasses are great to use as shelter.
FALSE! VERY! VERY! FALSE!: Never seek shelter under an overpass during a tornado! It will probably get you killed! It is a very bad idea to hide under an overpass for several reasons.
The winds can still get underneath the overpass, and will actually accelerate when they do so because of the wind tunnel effect.
Because the winds can still get underneath, the debris it is carrying can still get to you and impale you.
Even if you hold to the girders as tight as you can, you will be blown loose, not to mention the fact that most highway overpasses don't have girders.
Even if the tornado doesn't hit, parking in a traffic lane is illegal and dangerous both to you and to others. Someone may plow right into you because they may not see you in time to stop. You could also trap people in the storms path against their will. Even worse, you could even prevent emergency response vehicles from getting to where they are needed, preventing them from saving lives.
If a tornado is about to strike your house, opening all the windows will reduce the damage.
False: This myth depends on the myth that tornadoes destroy by dropping the atmospheric pressure, which is false, as stated above.
The northeastern most corner of a house is the safest.
False: The rationale behind this myth is the myth that tornadoes only move northeast, which we will get to later, but this one is false because it forgets that the winds of a tornado are circulating and not moving in a straight line.
The southwestern most corner of a house is the safest.
False: This one, which may be heard more often than the "northeastern most corner" version above, is based on the idea that debris will be blown away from the southwestern part of a house. Again, however, this ignores the circulation of a tornado's winds.
If there's no sirens going off there is no danger.
FALSE: Some places (e.g. in the West and Northeast and South US outside of Tornado Alley, for example in Colorado or Montana or New York or North Carolina etcetera) often do not have sirens or other outdoor warning systems, or immediately usable ones to be sounded for a weather threat. Even in places with sirens, winds and rain can drown out their effective range (as in, you can't hear the siren going off or can only faintly hear it), as can city noise in an urban area. Or sirens are run on main electric power, which means if the power goes out they do too. Or someone doesn't trigger them or they don't work for some reason or other. While any civil defense siren going off definitely means you should take shelter and check to see what is happening while you do (don't assume it's a test!), you should also not assume that sirens will warn you of tornadoes - again, get a weather radio, and if you have a smartphone, a weather warning/storm conditions app and/or enable emergency alerts, and if there is severe weather around, pay attention and keep an eye out, because sometimes, although less common than in the past, a dangerous storm can escape notice entirely until someone spots it.
Tornado warnings happen all the time/the sirens go off every storm, there's no need to take shelter unless things look dangerous.
FALSE: A tornado warning or siren activation is only issued under two circumstances: Doppler radar has determined a storm contains a rotating mesocyclone which may form a tornado at any minute (if it hasn't already done so) or someone has reported funnel clouds or a tornado touchdown. It isn't a watch, nor is it even a severe thunderstorm warning, which imply lesser hazards. If it's a tornado warning, there is reason to believe there is an actual tornado. Also, while warnings used to be issued for entire counties (which did make this misconception slightly true, in that most tornadoes aren't big enough to flatten an entire county so a tornado could "miss," say, the northern part of a county, which led people to be far more cavalier about warnings in tornado prone areas), this is no longer the case: warnings are targeted toward a tornado's actual path as of The New Tens. Also, especially at night or in heavy rain/fog/hail conditions, sighting a tornado even at close range may be near impossible. (As an example, people thought the Tri-State Tornado was a fog bank). The only thing still even slightly true about the idea that tornado warnings can be ignored is that most tornadoes are relatively localized with fairly small in comparison damage zones (which is why tornado recovery is often faster than, say, hurricane or earthquake recovery, because resources aren't themselves destroyed within a 50-100 mile radius), that said, are the odds you won't get hit worth what happens if you do get hit unprepared and unsheltered? Especially when the worst thing that can happen from heeding the warnings and taking shelter being some inconvenience or wasted time (which dying in a tornado tends to be a lot more of)?
True and False: Tornadoes have gotten a reputation for seemingly "skipping" over houses. Seemingly lifting off of the ground and then coming down again. However, they truly don't do that. At least, not in that way.
A tornado's intensity can vary greatly during its lifespan. Sometimes a tornado will briefly weaken to where it won't do much damage and then quickly re-intensify and start doing damage again.
Some violent tornadoes can briefly split apart at the base into multiple vortices that will simply pass by one structure and hit the one next to it.
Some violent tornadoes can also cause a "satellite" tornado to form, which also have the same effect.
Tornadoes are capable of "skipping" in the sense that it will briefly lose contact with the ground. However, this tends to be more like skipping neighborhoods than skipping individual houses.
Bigger = Stronger
False: While there is a trend for larger tornadoes to be stronger, that is not always the case.This◊ tornado that struck Elie, Manitoba was an F5 (Canada's first and only F5.)
No funnel cloud = No tornado
False: See above.
All tornadoes travel northeast
False: Most do, but not always. Belief in this is what likely got several storm chasers killed or injured (including the very experienced scientist chaser Tim Samaras, who was killed along with his son and his chase partner, and a Weather Channel crew that got injured) in the 2013 El Reno, Oklahoma tornado - most of the chasers who got killed or hurt or otherwise encountered the tornado too closely for their own good seemed to be traveling in a direction that would indicate they believed the tornado would travel from southeast to northeast. The circulation was simply too wide (with satellite tornadoes and variable wind directions) to have any safety margin in almost any direction - distance and/or shelter, not direction, was the only safeguard.
False: Mobile homes (as stated above) are incapable of surviving even the weakest tornadoes. Those weak tornadoes would probably have never been noticed if it had struck elsewhere. This myth most likely comes from TV news specifically going to Trailer Parks, where the easily-damaged mobile homes provide ample shots of extreme devastation, whereas the same tornado might do almost no damage to standard homes.
Tornadoes cannot strike downtown areas.
False:Yes they can. It's rare since the odds of a tornado hitting any one particular area is a complete game of chance, but it is still possible.
False: Tornadoes are in no way hindered by the terrain. There are several cases of tornadoes crossing rivers, going over hills, crossing valleys, and even climbing mountains. Again, the terrain does nothing.
Largest Tornado Outbreak
The Late April 2011 Outbreak, April 25-28, 2011. This outbreak consisted of 127 EF0s, 147 EF1s, 50 EF2s, 22 EF3s, 11 EF4s, and 4 EF5s, for a grand total of 358 tornadoes. Tornadoes were reported from Texas all the way north through to Michigan, New York, and even into Ontario.
The Tri-State Tornado, March 18, 1925. 695 people were killed by this tornado.
The Daulatpur-Saturia, Bangladesh Tornado, April 26, 1989. ~1,300 people were killed by this tornado.
The Joplin, Missouri Tornado, May 22, 2011. This tornado caused approximately $2.8 billion in damage.
Longest Track and Duration
The Tri-State Tornado, March 18, 1925. This tornado traveled over 219 miles, started in Missouri before crossing the border into Illinois and then passing into Indiana. In all it cut through three states (hence the name) in a time span of 3 and a half hours.
The El Reno, Oklahoma Tornado, May 31, 2013. This tornado peaked at 2.6 miles wide.
Fastest Forward Speed
The Tri-State Tornado, March 18, 1925. This tornado was not only long-lived but fast at 73 mph.
Fastest Wind Speed
The Bridge Creek-Moore, Oklahoma Tornado, May 3, 1999. Wind speeds of up to 318 mph were recorded by mobile Doppler radar units.