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The United States averages 1200 tornadoes a year.  Over the past week we've seen one of the most deadly outbreaks of April storms since 2008.  This severe weather spanned over 15 states in a three day period, and while the number of tornado sightings being investigated is 267, they estimate the final count will be somewhere in the neighborhood of 140 separate tornadoes.  That's a lot of angry, swirling wind.

In reading the comments to the outstanding diaries during this last week by our own dedicated weather watcher, weatherdude, and by watching video online captured by storm chasers and hapless fools, it became clear to me that many people have no idea what to do when severe storms or tornadoes break out, or when they should do it.  After consultation with weatherdude I've decided now would be a good time to offer some handy advice in the hope that it might save some lives.  So follow me over the curly thing for some understanding of the kind of monster you might find yourself confronted by and some tips of what to do and NOT do before, during and after a severe storm or tornado should one visit you or your neighbors.

What Creates Severe Thunderstorms and/or Tornadoes?

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Severe thunderstorms and tornadoes are a product of two different air masses colliding.  
From NOAA:

Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.

Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.

Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.

As an example, let's look at what caused yesterday's severe weather to form using a forecast image from weather.com.

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As you can see, there was a cold front from the north and dry air from the west colliding with moist air from the south.  As the cold front and the dry air pushed eastward, it caused severe weather to break out along the line of collision.  To the north of the jetstream there were strong winds, rain, hail and wet snow.  Below the jetstream severe thunderstorms formed and produced a series of tornadoes.  All of this advanced eastward as the cold front and the southwest winds pushed into the warm, moist air, producing severe thunderstorms and tornadoes along the dryline throughout the midwest from Oklahoma to Indiana.

The most active months for tornadoes are generally May and June, but tornadoes can happen at any time of the year.  And while the majority of tornadoes are produced in "Tornado Alley," in the plains states and midwest running from Texas through the Dakotas, there is no place that is immune from this kind of weather activity.

So There's a Severe Thunderstorm/Tornado Watch/Warning Near Me.  What's the Big Deal?

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The big deal is that both severe thunderstorms and tornadoes can be deadly.  Severe thunderstorms can produce hurricane force winds along with large hail, deadly lightening and torrential rain.  They can be every bit as damaging as a tornado.

Tornadoes came to be measured according to the Fujita Scale, created by Dr. T. Theodore Fujita.  He wanted to measure the severity of tornadoes according to where they were located and what damage they did. His scale had them ranging from F0 through F5 of strength according to wind speed.  This is a good starting point, so let's examine what each F level is, again borrowing from NOAA.  Please click on the F-numbered link to see characteristic damage of each number on the scale:

  • F0

    Wind speed: 40-73mph

    Typical damage: Light.  Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.

  • F1

    Wind speed:  73-112mph (Note that this is now within hurricane force wind territory.)

    Typical damage:  Moderate. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.

  • F2

    Wind speed:  113-157mph

    Typical damage:  Considerable. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

  • F3

    Wind speed:  158-206mph

    Typical damage:  Severe. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.

  • F4

    Wind speed:  207-260mph

    Typical damage:  Devastating. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.

  • F5

    Wind speed:  261-318mph

    Typical damage:  Incredible. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Over the course of time it became clear that estimating the strength of tornadoes was not as black and white as could be hoped for. It became apparent that one tornado could vary in strength from place to place and produce different amounts of damage depending on what was in its path.  So the EF (Enhanced Fujita) Scale was implemented in 2007.  This is based on several factors, such as the type of structure hit, the building materials used, wind speed, the speed with which a tornado is moving, etc.  For example, a trailer will fold like a cheap deck of cards at relatively low wind speeds of short duration, while a concrete structure under the same pressure may stand up to extreme, sustained winds and suffer damage only to its weak areas (doors and windows, roof.)  While tornadoes can move at ground speeds of 30-70mph, they can also get caught in something of a holding pattern and hover over one spot for quite some time, grinding into the earth as they rotate.  The EF scale tries to take all of these considerations into account.  To provide some context, here is a video of a train that drove into a tornado and was derailed all caught on tape by the engine's black box.  Notice the graphic towards the end.  This tornado lasted for 18 minutes, and in that time the F scale ranged from F0 to F3, changing intensity many times over the course of its time on the ground.  These determinations are made after the fact, and if you're caught in a tornado you'll not be pondering the intricacies of the ratings system. you'll be fighting for your life.

How Do I Know a Tornado is Coming at Me?

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If last week's tornado outbreak proved anything, it's that you cannot depend on local weather outlets alone to accurately predict when or where a tornado will go.  While states and localities in Tornado Alley have a much better system in place to alert you, other states that have seldom seen this kind of acute weather activity do not.  Knowing that there is a warning in your area will not tell you with any accuracy whether a tornado is going to directly hit you.  Some larger towns and cities sometimes have tornado sirens while others do not.  Local stations, especially in Tornado Alley, will give you a general idea of a storm approaching and that's better than nothing, but if you live in a small town or in a rural area, you're pretty much on your own.

Furthermore, looking outside to see if there's a funnel cloud bearing down on you is a poor indicator of a tornado's presence.  Sometimes there is no visible presence of a tornado on the ground, particularly in the early stages, before the swirling winds have sucked up enough dust and debris to be seen.  Seeing a tornado also depends on which side of the storm is visible to you.  If there is heavy rain and hail in advance of the storm then all you will see is a wall of clouds and water.

Certainly, if you see a funnel or wedge-shaped cloud then you are in the presence of a tornado and should take cover immediately.  But any of the storm fronts in the image above can also conceal a tornado.  Let's let look to this list put together for NOAA by Roger Edwards of the Storm Prediction Center in Norman, Oklahoma for some sound advice.

Know the signs of a tornado: Weather forecasting science is not perfect and some tornadoes do occur without a tornado warning. There is no substitute for staying alert to the sky. Besides an obviously visible tornado, here are some things to look and listen for:

   1. Strong, persistent rotation in the cloud base.
   2. Whirling dust or debris on the ground under a cloud base -- tornadoes sometimes have no funnel!
   3. Hail or heavy rain followed by either dead calm or a fast, intense wind shift. Many tornadoes are wrapped in heavy precipitation and can't be seen.
   4. Day or night - Loud, continuous roar or rumble, which doesn't fade in a few seconds like thunder.
   5. Night - Small, bright, blue-green to white flashes at ground level near a thunderstorm (as opposed to silvery lightning up in the clouds). These mean power lines are being snapped by very strong wind, maybe a tornado.
   6. Night - Persistent lowering from the cloud base, illuminated or silhouetted by lightning -- especially if it is on the ground or there is a blue-green-white power flash underneath.

Old farmers and seasoned storm chasers will tell you that an approaching storm front that has a distinctive greenish tint or where the cloud colors range from navy to black, or both, is trouble.  Paying attention to the cloud formation and color as well as the signs listed above can save your life if you react appropriately.

What Should I Have on Hand if a Severe Storm/Tornado is Coming?

You should have a kit put together and have it handy should you need to take cover.  Here's a list of things that you should include in such a kit.

  • A weather radio:  There are many different types of weather radios, and some are going to be better than others.  Do a bit of research and find out which kind would be best.  Any weather radio should have the capability to run on batteries since a storm may knock out power, leaving you with no power source.
  • Flashlights:  Flashlights also come in varying degrees of goodness.  You want solid, durable, dependable flashlights for any emergency kit.
  • Batteries:  If your flashlights and radios work on batteries, then you'll want to have a supply with them in your kit.  You should stock fresh batteries periodically to make sure they'll work when you need them.
  • A first-aid kit:  Your typical first-aid kit will do.
  • Medications:  You should have an emergency supply of all the medications that your family must use daily.  Store them in a water-tight container.
  • A credit card:  Keep a credit card in your first-aid kit, just in case.
  • A change of dry clothes for everyone in your home:  Nothing fancy, just something warm and dry in case you need it.
  • Blankets or sleeping bags:  You may need to wrap yourselves in these for both warmth or protection.  You want them stored tightly and to be as handy as possible.

This is a good, basic emergency kit to have on-hand no matter where your safety location is.  If your safety location is a basement or cellar, please include these items:

  • Food:  Keep a supply of non-perishable food in a water and animal proof container.
  • Water:  Like with any disaster, you may need water, especially if the power is disrupted.  Often storms will disrupt power for days or even weeks at a time.  It's always a good idea to store some water away for any emergency.  You can live for a while without food, but you'll need water.

This is your basic emergency kit.  Store it in a waterproof bag or container and have it handy so you can grab it if you need to seek shelter immediately.  Don't put it off, you never know when you might need it.  Every home should have such an emergency kit, along with a fire extinguisher and working smoke/heat detector.  If a storm is approaching, throw your cellphone in there and beat feet to a safer place.

The Storm is HERE!  Where Should I and My Emergency Kit Go to Be Safe?

Back when I was a kid, we had periodic drills for everything from tornadoes to atomic fallout.  Schools in many locales, particularly in Tornado Alley, still have tornado and severe storm drills.  My sister's company also has routine tornado drills that are coordinated by the weather service around Chicagoland.

You, too, should have a plan in place in case a tornado is coming toward you, just as you should have a plan for a fire or other disaster, and you should practice so that you can do what needs to be done in as short a time as possible.

Any time a severe thunderstorm or tornado watch is issued, you should be prepared.  If the watch is elevated to a warning, don't mess around.  You should have a plan in place of where you will go and your safety kit handy to grab to take with you.  Go to the safest place available to you.  

If you have a mattress that you can store close at hand, then do so or use your sleeping bags as cover.  Pull your protective covering over top of you and your loved ones.  Get down as low as you can, become a ball, head to knees with your head on the ground.  Think tiny.  If you have kids and/or pets then have them ball up and you ball up around them.  Cover your head with your hands and arms.  Someone suggested in comments the other day to use bicycle helmets if you have them and I think that's a fine idea, but you still need to cover your head and neck with your arms and hands.  

Where you should be taking cover depends on what options are available to you and the time you have to get there.  Let's look at some of the options.

  • The Local Storm Shelter:  If there is time to get to a local shelter then do so, but don't mess around about it.  Judging the time and safety of leaving your home to seek shelter elsewhere is a tricky business.  Many places don't have storm shelters, or they're located in area schools which may or may not be open at the time of the storm.  You should take the time to find out what is available in your area and plan accordingly.
  • Your Basement:  If you have a basement, go there.  You should get away from all windows if there are any.  Be aware of where heavy furniture is on the floors above, and avoid being under them.  Under the stairs is really your best option for safety, or under a large table stored there.  Once there take the actions listed above.
  • A Storm Cellar:  Very few places have a storm cellar anymore.  But those in farm country may still have this option available.  All of the procedures for taking cover listed above should be implemented in the cellar.  If you have a cellar, then having an old mattress and your emergency kit there will save you time, and time is precious.
  • An interior bathtub, closet or stairs on the lowest floor of your house:  If you live in a house with no basement then one of these may be your only refuge.  This will afford you some protection by virtue of having more framing around them and, in the case of the bathtub, will be anchored down by pipes.  You want to make sure that whichever you choose is an interior structure.  You do not want to be near the outside walls. Follow the same duck and cover instructions above.
  • In a highrise building: The stairwell or other interior structure on the lowest floor available.  You want to be on the lowest available floor in the interior of the building.  Stay away from windows.  Do NOT take the elevator, as you may end up trapped there.  The stairs are better.
  • If you live in a trailer or modular home, GET OUT!  These things are deathtraps, you and everything you own will become projectiles.  If there is a storm shelter available and there is time, go there with all haste and speed.  If there is a solid secure building near at hand, run there and take cover.  If it's your neighbor's house, don't wait to knock on the door, get inside and take the appropriate actions above.  You can sort out the whole trespassing thing later.  If there are none of these options available, then run as far away from your home as possible, and away from trees if you can, find the lowest point you can, then drop flat and cover your head with your hands and arms.

As you can see, depending on what kind of structure you find yourself in, your options range from "scary" to "I'm gonna die!"  This is why it's crucial to make a plan and practice.  You want everyone who lives in your home to know that plan and be able to implement it on a moment's notice.

Let's Talk About Cars

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Let's assume for a moment that you find yourself out in your car when you are suddenly in danger from a severe storm or tornado.  As you can see from the pictures above, cars are not a safe place to be in such circumstances.  The choices you make can mean the difference between life and death.

For many years, the recommendation was to get out of your car and lay flat in the ditch.  Over time it's become apparent that this may not be a good idea, as your car or someone else's can flip and crush you and flying debris tends to collect there.  But that means you have limited options.  What to do, what to do?  Let's look to our handy NOAA list once again for advice.

In a car or truck: Vehicles are extremely dangerous in a tornado. If the tornado is visible, far away, and the traffic is light, you may be able to drive out of its path by moving at right angles to the tornado. Otherwise, park the car as quickly and safely as possible -- out of the traffic lanes. [It is safer to get the car out of mud later if necessary than to cause a crash.] Get out and seek shelter in a sturdy building. If in the open country, run to low ground away from any cars (which may roll over on you). Lie flat and face-down, protecting the back of your head with your arms. Avoid seeking shelter under bridges, which can create deadly traffic hazards while offering little protection against flying debris.

The one thing you shouldn't do is assume you can drive through that severe storm or tornado!  Let's go back and review this previously linked video again.  I want you to replay it a few times, ignoring the tornado and instead focusing on the cars.  You'll notice that on the road to the right of the overpass there is a van that makes a wise choice by pulling a u-turn and heading away from the tornado.  Then if you look under the overpass you'll see there is a truck and three cars that had to know the tornado was there yet continued to drive into it.  The truck and two cars make it out, but one does not.  I have no idea what happened to whoever was in the now missing car, but I have the feeling it wasn't good.  Also notice that there is a vehicle stopped under the overpass waiting for the tornado to pass.  This could have been a disaster for the driver as well as the three vehicles that made it out of the tornado.  Had the tornado made the slightest turn, they would all become projectiles.

Take a close look at those cars in the pictures above.  Don't let that happen to you.

The Storm is Over, What Do I Do Now?

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Greensburg, Kansas F5 tornado damage.  Image courtesy of FEMA

I've read several scenarios on what to do after you've been hit by a tornado or deadly storm.  Some of them recommend you go around shutting off the gas and electricity but, to my way of thinking, simplest is best.  Get your family together and keep them together, then carefully make your way out of the damage and wait for the emergency people to come.  Pick your way carefully out of the mess, watching out for broken glass, nails and especially downed power lines or standing water with exposed wires in it.  You don't want to stay in a damaged house as it may collapse or catch fire.  Get well away from your house before using your phone or even turning on a flashlight, as these can spark any gas that may be leaking.  Don't spark up a smoke for the same reason.  If someone is injured, use what supplies you have to tend to them.  Try to keep yourself and others dry and warm.  Resist the temptation to play hero by charging into a neighbor's damaged home.  Leave it to the professionals.

Are You an Experienced Storm Chaser?  No?

Even experienced storm chasers can get too excited and get too close, putting themselves in mortal peril.  If you're not all that experienced at storm chasing or you're just hanging out with your buddies drinking beer and you decide it's a good idea to film that monster tornado in your backyard from your porch you are wrong.  Don't be a fool.  Just put that video cam down and back away, swiftly!

______________________________

For those who would like to have good information on hand in making a plan, consider printing out the NOAA safety sheet that I've used liberally throughout this diary.  

If you're interested in the science of tornadoes, I recommend this paper for the fascinating data it contains.

For a look at a rare tornado experience that happened last week, I direct you to this video of the Atoka/Tushka, Oklahoma tornado, where there were multiple vortexes.  While that in and of itself isn't so unusual, what was unusual was that one of them was spinning clockwise.  Nearly all tornadoes spin counter-clockwise, but because of wind sheer splitting the vortex, it produced two separate tornadoes spinning in different directions.  Some of the aftermath of this unusual occurance can be seen here.

For other information on how to be safe during other forms of weather disasters and an expanded list of what to include in your safety kit and disaster preparations I recommend this PDF from NOAA.

I hope the information in this diary will help those who have little experience with this kind of weather.  Pack an emergency kit, make a plan and stay safe, everyone.

Originally posted to Got a Grip on Wed Apr 20, 2011 at 05:59 PM PDT.

Also republished by Severe Weather Liveblog, Three Star Kossacks, Living Simply, and State of the Skies.

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