Useful Notes:Tornadoes
a useful notes page explaining tornadoes and tornado related subjects, including the common myths


(permanent link) added: 2012-04-26 13:10:19 sponsor: datubaman (last reply: 2012-05-03 17:09:16)

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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.


The Basics
  • 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.
Safety
  • Tornado Watch, Warning, Emergency
    • Tornado Watch: A Tornado Watch is issued when conditions are ripe for a tornado to form.
    • 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.
  • 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 are:
      • Designate a shelter area and equip it with what you need to survive.
      • Make a plan so that you are able to get to that shelter in a moments notice.
      • 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.
    • 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.
    • 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, like so.
      • IF YOU ARE IN A MOBILE HOME, GET OUT IMMEDIATELY!!! Then, head to the nearest fixed structure and get inside, or head into the closest ditch if there isn't one nearby. Mobile homes are VERY dangerous places to be in a tornado, and can be destroyed by even the smallest ones.
    • 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 as to avoid it.
      • If the tornado is headed towards you, pull over to the side of the road, find a ditch as far away from the road as possible, and then get in the ditch. DO NOT try to outrun it.
      • If the tornado is headed towards you and you do not think you have time to do the above, buckle your seatbelt (as it should be already), roll up your windows, put your head between your knees, and pray to God Almighty that you survive.
    • 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 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.
      • 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 there 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:
    • AT HOME:
      • DO NOT LEAVE YOUR HOUSE! Unless you are in a mobile home, your best bet is to stay put. Leaving will only increase the chances of you getting killed. 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 NOTrun 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, I REPEAT, DO NOT TRY AND HIDE UNDER AN OVERPASS!!! AN UNDERPASS WILL NOT PROTECT YOU FROM A TORNADO! The details will be explained below.

Ratings
  • 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. (Except in Canada, where it is still used.)
  • 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 65mph to 85 mph, an EF1 ranges from 86mph to 110mph, an EF2 ranges from 111mph to 135mph, an EF3 ranges from 136mph 165mph, an EF4 ranges from 166 to 200 mph, and an EF5 is any tornado with winds above 200mph.

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.

Myths
  • General Misconceptions
    • The winds of a tornado are exclusively located within the funnel cloud. Do Not Touch the Funnel Cloud.
      • 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.
  • Safety
    • 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.
  • Behavior
    • Skipping Houses
      • 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.
  • Geography
    • Trailer Parks Attract Tornadoes
      • FalseMobile 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.
    • Tornadoes cannot strike downtown areas.
    • Tornadoes cannot cross rivers/hills/valleys/mountains.
      • 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, just like these goggles.

Tornado Extremes
  • Largest Tornado Outbreak
    • The Late April 2011 Outbreak. April 25-28, 2011. This outbreak consisted of 127 EF 0's, 147 EF 1's, 50 EF 2's, 22 EF 3's, 11 EF 4's, and 4 EF 5's, for a grand total of 358 tornadoes. Tornadoes we reported as from Texas all the way north through to Michigan, New York, and even into Ontario.
  • Deadliest Tornado
    • USA
      • The Tri-State Tornado March 18, 1925. 747 people were killed by this tornado.
    • World
      • The Daulatpur-Saturia, Bangladesh Tornado April 26, 1989. ~1,300 people were killed by this tornado.
  • Costliest 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.
  • Widest
    • Wilber-Hallam, Nebraska Tornado May 22, 2004. This tornado peaked at 2.5 miles wide.
  • Fastest Forward Speed
    • The Tri-State Tornado March 18, 1925. This tornado was not only long-lived but fast at 73 mph.
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