Severe Weather 101 – Tornadoes and tornado safety
Tuesday, April 21st, 2009 9:30am MDT
Last year's Windsor Tornado highlights the very real danger twisters present in Colorado. Do you know when to do when one strikes?
One fact that may surprise those new to Colorado is that we are actually on the western edge of the infamous Tornado Alley. This large swath of land comprises much of the nation’s midsection and is a unique place as the United States sees more tornadoes than any other place on earth. In fact, tornadoes have been recorded in all 50 states including Alaska and Hawaii.
Closer to home, Colorado sees our share of these storms. In fact, one metro area county – Weld County – holds the distinction of being the “tornado capital of the world”. With 220 tornados from 1950 – 2006, no single county in the nation has had more tornadoes! Adams County is number two in the state and isn’t far behind with 148 over that same period. Granted these numbers are skewed a bit simply due to the sheer size of those counties, but it does serve to highlight the real danger that tornadoes present.
One common myth is that tornadoes don't strike metropolitan areas. This has been disproved many times including here in Colorado in 1981 when an F2 tornado struck Thornton. Image courtesy the City of Thornton archives.
Even here in the metro area tornadoes are a real danger. The Thornton area was struck in 1982, four miles from my childhood home – a pretty scary experience let me tell you! At 2:30 p.m. this tornado touched down. By 2:45 p.m., the tornado had hit Thornton City Hall. The tornado’s destruction sent 53 injured people to hospitals, 25 homes were destroyed and 239 structures were damaged.
The most well known tornado outbreak in the metro area occurred on June 15, 1988. Five tornadoes resulted in seven injuries and damage in excess of $15 million.
The greatest threat for tornadoes occurs during late spring and early summer when you have a combination of heat and moisture in the lower atmosphere. Here in Colorado, tornadoes are frequent from May through August with June being the most active month. However, there is no hard and fast rule for when tornadoes strike, as Colorado witnessed on March 29, 2007 when Holly, Colorado was struck by an EF-3 tornado with winds of 165 mph. Two women lost their lives as a result of that event and 160 homes were damaged.
Colorado ranks 10th in terms of the number of tornadoes with 1,113 events from 1950 – 1994. One good thing is that our high altitude and drier air do make it harder for the monster supercells that spawn the biggest tornadoes to form. Most of our tornadoes are small and short lived. Further, thanks to the wide open spaces of the eastern half of our state, many strike sparsely populated areas. This is reflected in the fact that we rank 38th for tornado related deaths.
Most tornadoes are not powerful enough to cause widespread damage – most are weak and according to the National Weather Service, 89 percent have a life span of less than 10 minutes and result in less than 5 percent of tornado fatalities. These weaker tornadoes typically have wind speeds less than 110mph which will damage a wood frame construction home but may completely destroy a mobile home or outbuilding.
Of the 10 percent of tornadoes that are considered strong, some may last 20 minutes or more and cover distances in excess of 20 miles. These major tornadoes can have speeds to 165mph, account for 30 percent of tornado deaths and will cause considerable damage to almost any type of structure.
The remaining 1 percent of tornadoes are considered violent in nature and result in 70 percent of tornado fatalities. They simply destroy everything in their paths, can last more than an hour and travel more than 50 miles. The only chance for survival in a violent tornado is inside a safe roof or underground shelter.
Tornado Safety
Holly, Colorado was devastated by a tornado in 2007. Do you know what to do when a twister is coming? (AP Photo)
With the severe weather season upon us, it is wise to have a plan of action should a tornado threat arise. Think about what you will do whether at school, at home, at work or outdoors. Get in, get down and cover up. That is the quick and easy rule to remember. Get inside a sturdy structure, get to the lowest floor or an interior room, and cover your head.
A well-built structure with a basement or underground storm shelter is the safest place to be. If a basement isn’t available, move to a small interior room like a closet or bathroom. More people are injured by flying debris from tornadoes than anything so that is why you need to cover up with a blanket or get under a piece of heavy furniture.
Modular homes, no matter how well anchored, provide little or no shelter from a tornado. Most tornado fatalities occur in mobile / modular homes. If you find yourself in one of these when the threat is announced, immediately seek shelter in a more sturdy building or storm shelter.
Tornadoes can even strike in mountain areas. Last year on August 23rd, this rope tornado struck Park County near Eleven Mile Reservoir. Image courtesy Jerry Bivens.
When driving in open country and you see a tornado, simply drive away from the path of the tornado – usually at a 90 degree angle to the path is best. While we all have seen video of people doing it, do not seek shelter beneath a highway underpass as these act like wind tunnels and actually serve to increase the wind speed and collect flying debris. In the extreme situation that you simply cannot get away from a tornado, abandon your vehicle immediately. Lie down in a ditch or culvert and cover your head. This isn’t a particularly good option, but it is safer than remaining in a vehicle.
Two old and outdated pieces of advice still seem to linger although they have been disproved. One states to open all the windows in your home so as to “equalize the pressure.” This in fact does nothing to protect your property and studies show it may actually cause more damage. The second bad piece of advice says to hide in the southwest corner of a basement with the theory being tornadoes move from the southwest to the northeast thus you will minimize your exposure. This erroneously assumes all tornadoes move in the same direction and that simply isn’t the case.
In the end, you simply need to be aware of what is going on around you. If the skies look threatening, it is better to be safe than sorry.
This is part two of a  five part series on Colorado’s severe weather.
Tags: Severe Weather, tornado
July 23rd, 2009 at 12:19 PM
There are still occurrences that cannot be halted by advanced technology. Just like weather disturbances such as thunderstorms, hail, tsunami, and even the destructive tornadoes. Awareness is the best practice to save lives when these disasters occur. Establishing sturdy tornado shelters could be an effective way to safety.