An Amateur’s Guide to Surviving a Tornado

How a Tornado forms

A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone. ~Wikipedia

That is a great description of a tornado. What is it exactly? It is the violent updraft of a thunderstorm, usually a Supercell thunderstorm.

Even though we cannot properly distinguish tornado generating storms from not, there are specific Tornadogenesis patterns. The cycle begins when a strong thunderstorm develops a rotating mesocyclone a few miles up in the atmosphere. As rainfall in the storm increases, it drags with it an area of quickly descending air known as the Rear Flank Downdraft. This powerful downdraft drags down the mesocyclone to near surface areas. As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of the storm. This convergence of warm air in the updraft, and this cool air, causes a rotating wall cloud to form in the already rotating airmass.

The Rear Flank Downdraft slowly chokes the mesocyclone, causing it to take in smaller and smaller area of air. A funnel cloud forms within minutes of the mesocyclone descending.

A tornado will grow as long as there is warm moist air feeding the updraft, but as the RFD slowly wraps around the mesocyclone, it weakens and slowly dissipates. A tornado is still dangerous in this stage, whether its touching the ground or not.

The visible parts of a tornado is formed by condensation of moisture within the funnel and flying debris from the ground below. The violently twisting columns of air is not visible. Thus a tornado that have yet to visibly touch down can still deal tremendous damage to objects below

How to spot a tornado

All that knowledge is useless unless you know what to look for.

Sign #1: Severe Thunderstorm Tornadoes form from severe thunderstorms. It is usually accompanied with heavy rain, hail and lightning.

Sign #2: Rotating wall clouds or funnel clouds Rotating wall clouds and funnel clouds originate from the lowering down of the mesocyclone, almost a certain sign of a tornado developing or approaching.

Sign #3: Green skies. When, in the middle of a thunderstorm, you see that the dark sky is turning green, it could be a sign of tornado formation. Green tinted storm clouds are the result of dense moisture in the atmosphere reflecting/refracting green light. My theory is that the RFD contains enough moisture to cause such reflection, and the green is a sign of the downdraft touching down.

Sign #4: Tornado watch. A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch

Sign #5: Flying debris in the air. A tornado may pick up debris on its way to your house.

Sign #6: Calm period after heavy rain and/or hail This signals the passing of the RFD and the beginning of the mesocyclone updraft area. It is often referred to as a rain free base a portion of the lower storm base that is, well, precipitation free.

These are numerous signs, and you don’t need all of them, and you may not see any of them, but the best bet is that you will encounter a few of these signs before coming in contact with a tornado.

Tornado Safety Rules

Do’s, don’ts and never’s of tornado survival- this is what you need to know.

Do:

• Go to the basement or take shelter in a small interior ground floor room such as a bathroom, closet or hallway.
• Stay away from windows, outside walls and doors.
• If possible, find shelter in another building if you are in a gymnasium, church or auditorium. If you are in one of these buildings and cannot leave, take cover under a sturdy structure such as a table or desk.
• Get as close to the ground as possible, protect your head and watch for flying debris

Don’t:

• Take shelter under a bridge or overpass.
• Remain in a vehicle or mobile home.
• Attempt to ‘stablize pressure’ by opening windows.
• Dive for the southwest corner of your basement, just find some good shelter.

NEVER:

• Attempt to outrun a tornado in a motor or other vehicle.
• Keep on walking or driving because ‘what are the chances’.
• Take open shelter close to a hill or lake because ‘tornadoes don’t hit lakes’.
• Attempt to photograph an oncoming tornado.
• Chase tornadoes.