Jun 9, 2009 7:31 pm US/Mountain
Severe Colo. Thunderstorms Produce Funnel Clouds
AURORA, Colo. (CBS4) ―
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Dennis Harris sent in this photo of a funnel cloud over his house near Broomfield at about 4:30 p.m on Tuesday."
Dennis Harris/YouReport
Funnel clouds were spotted north of Denver and in Weld County on Tuesday as severe thunderstorms moved through the area.
The National Weather Service said one briefly touched down near Firestone in Weld County.
Heavy rain and hail also fell in some areas but there were no reports of damage.
The warnings came two days after at least five tornadoes touched down in Colorado, including one that damaged a mall in Aurora.
The National Weather Service said Tuesday that the Aurora twister had wind speeds of around 100 mph and that one car was flipped by the wind.
A construction trailer near the Southlands Mall was torn apart. The windows and roofs of houses and apartment buildings were damaged by the wind and some garage doors were also broken.
The following tornado facts are from Dave Aguilera's Weather 4 Kids section.
Know when to take cover: the difference between a tornado watch and a tornado warning
Tornado Watch: Is issued when conditions are just right for tornadoes to develop. It does not mean tornadoes are imminent, just that you should be aware that the possibility is there. When you hear or see that a watch is in effect, you should keep an eye and ear tuned to television or radio so you know what is going on with the weather.
Tornado Warning: Is issued when a tornado has been spotted, or indicated on Doppler radar. When a tornado warning is issued for your town or county you should take immediate safety precautions.
What is a Tornado?
A tornado is a rapidly rotating column of air dropping from a strong thunderstorm to the ground. That thunderstorm cloud is known as a cumulonimbus cloud.
What causes a Tornado?
Inside a cumulonimbus cloud or thunderstorm, you have updrafts and downdrafts. Warm rises up into the thunderstorm and cold air sinks down in the thunderstorm.
Now all air masses have a certain amount of spin, but, the updrafts and downdrafts in a thunderstorm increase that spin inside the storm. This motion creates a horizontal rotating column of air. The rising and dropping air tilt that column vertically and if that column of air extends to touch the ground, Bingo, you have a tornado!
The technical term for this process is called "Conservation of Angular Momentum." Have you ever seen an ice skater doing spins on the ice? When the skater pulls their arms in close to their body, they can spin faster and faster.
With a thunderstorm, the tighter the spinning air goes, the stronger the rotating column of air gets.
How long can a tornado last?
Some twisters may last only for a couple of minutes and are on the ground for a few feet to a few miles. While some can last several minutes to several hours and travel from a few miles to more than a hundred miles. A few of these huge tornadoes may have paths of destruction that are a mile wide.
When do tornadoes occur?
In Colorado, primetime for tornadoes is from mid May through mid August. Colorado twisters have been reported in 9 out of 12 months of the year.
The big month for tornadoes is June. Through the years most of the recorded tornadoes in our state have popped up in the month of June.
Most of our tornadoes happen between 1pm and 9 pm. In fact, 88 percent of them occur during this time period. And over half of all twisters threaten between 3pm and 6 pm.
If you break it down by county, Weld County in Northeast Colorado is the big winner or loser (depending on how you look at it) in number of tornadoes. In fact, Weld County on average has one of the biggest numbers of tornadoes across the country! The reason for that is primarily due to Weld counties size. It is 2 to 3 times larger than most counties in the United States.
Where are Tornadoes most likely to form?
Tornadoes can occur anywhere in the state of Colorado, but, most of them develop in Eastern Colorado. Most of those occur east of Interstate 25.
Twisters have been reported in every state in the United States. But, if we look at the nation as a whole, the bulk of tornado producing thunderstorms hit an area that meteorologist call "Tornado Alley." This is an area of land in the nation's midsection that is clobbered by more tornadoes than anyplace else in the world!
This area runs from North Texas through Oklahoma, Kansas, Missouri, and Ohio. That's not to say all tornadoes occur in this area. But, a large number of them do. Other areas that pick up a lot of tornadoes include many southern states like Mississippi, Alabama, Georgia and Florida.
How is the Strength of a Tornado measured?
Meteorologists use a scale called the "Enhanced F-scale" to measure the power of a tornado. It is a scale that is based upon how much damage any given tornado produces.
*** Important note about F-scale winds: These precise wind speed numbers are actually guesses and have never been scientifically verified. Different wind speeds may cause similar looking damage from place to place. Even from building to building. A new
"Enhanced F-scale" will be implemented in February 2007.
The Enhanced F-scale replaced the old Fujita scale, (F-scale), which is named after Professor T. Theodore Fujita, a pioneer in the study fo tornadoes. The new Enhanced F-scale gives more detailed information about damage and winds.
Click here to see the Fujita Scale.
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