Uncategorized

TORNADO DRILL – Severe Weather Awareness Week 2015

| by Henry Luker

A tornado is a rapidly rotating column of air in contact with the ground. A visible cloud is not needed for a tornado to be in progress. Some tornadoes may not appear to extend to the ground but are causing considerable damage. Tornadoes take on various shapes and sizes, and most produce winds less than 120 MPH. However, a few are capable of producing winds over 200 MPH. Some tornadoes are very small and last for only a minute or so, while others can be a mile wide or larger and stay on the ground for over an hour.

Tornado Drill 2015

The Iowa and Nebraska tornado drill will be held this morning from 10:00 AM to 11:00 AM and will allow you to practice your readiness plans.

Tornado Watch vs Warning

733Iowa Tornado History

734

Tornadoes have occurred during any time of the day across Iowa and in each month of the year. However, they are most likely to form in the late afternoon and early evening hours during the months of April, May, and June.

 

EF Scale

732

 

The severity of a tornado is expressed through the use of the Enhanced Fujita Scale (“EF Scale”). The EF Scale became operational on February 1, 2007 and is used to assign a ‘rating’ to a tornado based on estimated wind speeds and related damage. It is important to note that the EF Scale is a set of wind estimates, not wind measurements. The estimates are derived based on the damage done by a tornado to homes, crops, trees, etc. An EF SCale rating is determined based on the highest wind speed which occurred within a damage path.

The EF Scale was revised from the original Fujita Scale (“F Scale”) to align wind speeds more closely with associated storm damage. The Fujita Scale is named after Dr. T. Theordore Fujita who first introduced the scale in 1971. The new EF Scale is now used in place of the F scale. The main difference between the F and EF scale is that the EF Scale takes into account the construction of structures damaged by a tornado.

Tornado Safety

735

 

Before the Storm:

  • Know the county in which you live and the names of nearby cities.
  • Have a NOAA Weather Radio with a warning alarm tone and battery backup.
  • Make sure your family and people in your workplace are familiar with these safety precautions. Review the procedures and practice them.

In a Home or Building:

  • Move underneath a table, workbench, or staircase.
  • Stay away from the corners of the room because debris is usually displaced into those areas.
  • Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned.
  • If an underground shelter is not available, move to the lowest, most interior room available.
  • Stay away from windows.

In an Office Building, Shopping Mall, or School:

  • Go into an interior hallway and crouch on the ground floor against a wall.
  • Cover your head with your hands.
  • Leave wide-open rooms like gyms, auditoriums, or the common areas of shopping malls.

If you are Caught out in the Open or in a Vehicle:

  • Never try to outrun a tornado especially if it is nearby. Tornadoes can move at speeds of over 50 MPH and change directions quickly.
  • Highway overpasses are not safe shelters for tornadoes and should be avoided.

Many people mistakenly think that highway overpasses provide safety from a tornado. In reality, an overpass may be on of the worst places to seek shelter from a tornado. Seeking shelter under an overpass puts you at a greater risk of being killed or injured by flying debris.

Tornadic winds can make the most benign item a dangerous missile. In addition to the debris that can injure you, the winds under an overpass are channeled and could easily blow you or carry you out from under the overpass.

Some information from this post was taken from National Weather Service Des Moines preparedness documents