F.E. Warren AFB, Wyo. -- It's only June, but this year's unusually powerful tornado season is already the country's deadliest since 1998, killing 110 people from Jan. 1 to May 27. It's also predicted to break the current record for number of tornadoes in a year set in 2004 at 1,817 tornadoes.
Cheyenne and Warren had an unusual tornado scare in late May with relatively long strings of severe weather, some producing tornadoes in northeastern Colorado and southeastern Wyoming.
While tornado touchdowns are infrequent in Cheyenne -- the last occurring in 1979 -- the city and base do lie on the northeastern edge of Tornado Alley. Everyone should understand how tornadoes form, how weather experts predict them, how to prepare, and how to react to tornado watches and warnings.
How they form
Severe weather forms from the clash of cold and warm air. The warm air rises through the cooler air, forming clouds and eventually thunderstorms. This explains why the peak points for tornado season occur in spring and fall when temperature change can be sudden and dramatic. As cold air recedes in the summer or dominates in the winter, the chances of tornadoes and severe weather decrease.
The warm air rotates as it rises through the cooler air, which is normal for any thunderstorm.
"Every thunderstorm has a little rotation in it," said John Robertson, 90th Operations Support Squadron weather shop. "It's a normal characteristic. What makes the system that produces tornadoes more unique is the strength of the updraft. As that gets stronger, it develops a mesocyclone - a closed circulation within a certain level of the thunderstorm."
Thunderstorms are made up of levels of air, and different events can be occurring in these levels.
"A lot of thunderstorms possess [mesocyclones] and never produce tornados," Mr. Robertson added. "Each thunderstorm has a number of levels within it. A thunderstorm can have a mesocyclone on one level, but to have a tornado, there needs to be a mesocyclone on multiple levels - at least three."
Tornadoes typically last less than 15 minutes and have a base between 10 and 400 yards. Larger tornadoes -- like the recent one in Windsor, Colo. -- can have bases more than a mile wide. However, size doesn't matter.
"The strength is based on wind speed, not size of the base," said Maj. Dermot Thiel, 90th OSS weather shop.
Strength is determined using the Enhanced Fujita scale instituted Feb. 1, 2007. This scale is an upgraded version of the more well known Fujita scale. It is important to note that the EF-scale is still a set of wind estimates based on damage using estimated 3-second gusts at the point of damage. Measurement instruments are unreliable since they are often damaged by strong winds.
Even without tornadoes, severe weather is dangerous. High winds, flash flooding and hail are all common hazards in severe thunderstorms.
Typically, tornadoes and severe weather form in the late afternoon and early evening hours when temperatures are highest.
"But that doesn't mean it can't happen during all hours of the day," Mr. Robertson said.
How tornadoes are predicted
Technology has allowed meteorologists to identify possible tornado-producing storm cells several days in advance, but identifying a specific time and place is still nearly impossible.
"If you get 15-20 minutes heads up notice, that's outstanding," Mr. Robertson said.
The 90th OSS on base keeps track of storm systems within a five-mile radius of the office, basically covering all of Warren, and the missile complex. The National Weather Service in Cheyenne oversees a forecast region encompassing southeastern Wyoming, western Nebraska and northeastern Colorado.
Because of this difference in coverage, the National Weather Service downtown and the Warren weather shop may approach storms differently.
"Downtown may send an alarm but we will not; it depends on the proximity of the storm to the base," he said. "Our job is to keep the mission in perspective, not have people hiding under their desks when they don't need to."
The weather office here or downtown can send out a number of notification messages, alerting the populace of possible severe weather. They can be a severe thunderstorm watch, a severe thunderstorm warning, a tornado watch and a tornado warning. A tornado watch is when conditions are favorable for tornadoes to form. A tornado warning means a tornado is imminent.
"We can pay a lot more attention to a single cell; focus on our specific area," said Staff Sgt. Jayson Ott, 90th OSS weather office.
"If you hear base sirens go off then you can be pretty sure something is coming toward the base," Sergeant Ott added.
Good indicators that may point to a possible tornado include dark, often greenish skies, a wall cloud, large hail, or a loud roar that sounds like a moving freight train.
However, people should depend first and foremost on the meteorologists on base or in the local community; if the sirens are going off, people should find cover immediately not attempt to predict the weather.
How to prepare
The first thing anyone can do to prepare for a tornado is have a plan.
"Have a plan before it actually happens. Know where you are going to go and who you are going to call if you get caught up in it," said Mike Watts, 90th Civil Engineer Squadron.
A plan should first identify a workable, sturdy shelter, or a safe place, in a home. Finding decent shelter is vital because according to the National Oceanic and Atmospheric Administration, flying debris from tornadoes causes most deaths and injuries.
"A basement or underground shelter is the best shelter," Mr. Watts said. "Protect your head and eyes from deadly flying debris by hiding under a heavy worktable or under the stairs or covering yourself with old blankets, quilts and unused mattresses.
"If there is no basement go to a small, windowless, first floor, interior room like a closet or bathroom. If there is no downstairs bathroom and the closets are full, a hall may be the best shelter. Put as many walls as you can between yourself and the tornado."
People caught in mobile homes, cars or trucks should leave the vehicle immediately and find a safe shelter. If safe shelter is not available, a ditch or depression offers better protection than mobile homes, cars, trucks or any other vehicle. If hiding in a ditch, watch for flash floods.
If people are at work, school, the lake, ballpark or anywhere else outside their homes, go to a designated shelter and follow in-place procedures.
Do not try to leave in a car or other vehicle.
"Vehicles are notorious as death traps in tornadoes, because they are easily tossed and destroyed," said Roger Edwards, Storm Prediction Center.
Plans need to also include tornado kits to allow for survival and rescue if trapped.
Offices at Warren should already have shelter-in-place kits to be used if a tornado occurs during work hours, but creating tornado kits for individual homes is also important.
"When planning for a tornado and sheltering in a safe room, people also need to think about bringing a means of communication, like a cell phone, TV or radio to listen to announcements, flashlight, water and blankets or quilts," Mr. Watts said.
How to react
The base informs residents of a tornado warning using the sirens and Giant Voice and secondary crash net and will soon also use the computer pop ups on government computers. The local area uses sirens as well and details can be heard on TV and radio broadcasts.
"When people hear the sirens, they need to take shelter and monitor local weather radio and TV broadcasts," Mr. Watts said. "They shouldn't go outside and look. They shouldn't be moving. If it's a tornado warning, take cover."
Even if there is just a tornado watch, people need to be prepared.
"If it's a tornado watch, do not disregard it. Check your checklist. Be ready to go to the shelter in place position," Mr. Watts said.
"If you're in doubt, take care of yourself. Don't blow off an alarm because you don't know what's going on. It's obviously being sounded for a reason," Mr. Robertson said.
As an extra safety precaution, Col. Mike Morgan, 90th Space Wing commander, has directed security forces to close the gates' outbound lanes.