Educational - Tornados
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A tornado is a violently rotating column of air which descends from a thunderstorm cloud system. The destructive forces generated by tornadoes are unbelievable. Large buildings are reduced to rubble. Railroad cars are lifted off their tracks...and straws of grass are driven into trees and telephone poles.
These small...severe storms...form thousands of feet above the earth's surface...usually during warm...humid...unsettled weather...and usually in conjunction with a severe thunderstorm. Sometimes a series of two or more tornadoes are associated with a parent thunderstorm.the funnel-shaped cloud of the tornado is made visible by cloud droplets...dust and debris sucked into its circulation and contains very high-speed winds rotating about a small...relatively calm center.scientists have estimated that wind speeds vary from 150 miles per hour in weaker tornadoes to over 300 miles per hour in the strongest.
On the average...tornado paths are only a quarter of a mile wide and seldom more than 15 miles long. However...there have been spectacular instances in which tornadoes have had paths of more than mile wide and 300 miles long. Most tornadoes travel from the southwest to northeast with an average speed of 30 MPH. But the speed has been observed to range from almost no motion to 70 MPH.
Most tornadoes occur in the deep south and in the broad,relatively flat basin between the Rockies and the Appalachians...but notate is immune. Peak months of tornado activity for Michigan are April,May, and June. However...tornadoes have occurred in every month and at all times of the day or night. A typical time of occurrence is on an unseasonably warm and sultry spring afternoon between 3 p.m. And 9 p.m.
Continued vigilance and quick response to tornado watches and warnings are critical...since tornadoes can strike virtually anywhere at any time. Most tornadoes are abrupt at onset...short-lived and often obscured by rain or darkness. The best way to deal with the mispreparedness. Every individual and business should have a tornado emergency plan for their homes and places of work...and should learn how to protect themselves in cars...open country...and other situations that may arise.
Remember if a tornado warning is issued for your area...a tornado is imminent. Know what to do...have an emergency plan to protect yourself and those for whom you are responsible. Quick response when a tornado approaches can save many lives. There may be only seconds in which to take action.
Remember...tornadoes can occur at any time. The time for planning is now.
There are five basic steps in the National Weather Service warning system. Every part of the system has to work for the greatest number of people to get the warning in time.
Step 1. The watch
Meteorologists using the latest in computers...radar and satellite data are always monitoring the weather elements. When a high probability of severe weather exists...a tornado or severe thunderstorm watch is issued. Watches may be issued hours before any severe storm hits the area. The forecasters at the national severe storms forecast center in Kansas City Missouri use every tool available including satellite pictures...radar reports...and numerous weather charts...to predict the areas where severe thunderstorms and tornadoes are likely to occur.
Step 2. Spotters
Severe weather spotters are constantly being trained under the Sky warn training program. Spotting severe weather is serious business and requires specific training. However...once an observer is trained in severe weather spotting procedures...they are one of the most reliable tools of the National Weather Service meteorologist. Spotters serve as the National Weather Service's eyes in the field.
Step 3. Civil defense and the state police
Any information that the National Weather Service issues is relayed to individual cities and towns through state and local civil defense and the State Police.
Step 4. The media
The vast majority of people are reached through the cooperation of the media. A direct line between the National Weather Service and local media offices insures that severe weather information is relayed quickly and broadcast within the shortest time possible.
Step 5. The users
Users include everyone within the severe thunderstorm or tornado warning area. We want to reach the greatest number of people possible and provide a concise...yet persuasive...message of necessary action.even if every other step in the warning system works...it does little good unless the users know what to do...and act.
Tornado safety rules
- We can do little to prevent a tornado from occurring...but by knowing the safety rules...we can minimize the number of deaths and injuries.
- A tornado watch means that tornado development is possible.keep a watchful eye on the sky for threatening weather and stay tuned to radio and television and listen for weather bulletins.
- A tornado warning means that a tornado has been sighted or indicated by radar. Persons in the path of the storm should seek shelter immediately...preferably in a storm cellar...underground excavation...or in a steel-framed or concrete reinforced building.
- In homes...the basement offers the greatest safety. Seek shelter under sturdy furniture...if possible. In homes without basements...takeover in the center part of the house...on the lowest floor...in a small room such as a closet or bathroom...or under sturdy furniture.stay away from windows.
- In schools...hospitals...and shopping centers...move to pre-designated shelter areas. Interior hallways on lowest floors are best. If the building is not of reinforced construction...go to a nearby one that is...or take cover outside on low...protected ground.stay out of auditoriums...gymnasiums...and other structures with wide free-span roofs.
- In open country...move away from the tornado's path at right angles. If there is not time to escape...lie flat in the nearest ditch or ravine.
- In your car...do not try to outrun a tornado. If available take shelter in a sturdy structure. Otherwise...get in the nearest ditch or depression until the tornado passes.
- Mobile homes are particularly vulnerable to overturning during strong winds and should be evacuated when strong winds or tornadoes are forecast. Damage can be minimized by securing trailers with cables anchored in concrete footing. Trailer parks should have community storm shelters. If there is no shelter nearby...leave the trailer park and take cover on low-protected ground.
What causes tornadoes
Tornadoes form under a certain set of weather conditions in which three very different types of air come together in a certain way. Near the ground lies a layer of warm and muggy air along with strong south winds. Colder air and strong west or southwest winds lie in the upper atmosphere. Temperature and moisture differences between the surface and the upper levels create what we call instability...while the change in wind with height is known as wind shear. This shear is linked to the eventual development of rotation from which a tornado may form.
A third layer of hot dry air becomes established between the warm moist air at low levels and the cool dry air aloft. This hot layer acts as a cap and allows the warm air underneath to warm further...making the air even more unstable. Things start to happen when a storm system aloft moves east and begins to lift the various layers. Through this lifting process the cap is removed...thereby setting the stage for explosive thunderstorm development as strong updrafts develop, complex interactions between the updraft and the surrounding winds may cause the updraft to begin rotating...and a tornado is born.
The plains of the central United States are uniquely suited to bring all of these ingredients together...and so have become known as tornado alley. The main factors are the Rocky Mountains to the west...the Gulf of Mexico to the south...and a terrain that slopes downward from west to east.
During the spring and summer months southerly winds prevail across the plains. At the origin of those south winds lie the warm waters of the Gulf of Mexico...which provide the moisture at low levels. Hot dry air forms over the higher elevations to the west...and becomes the cap as it spreads eastward over the moist Gulf air. Where the dry air and the Gulf air meet near the ground...a boundary known as a dry line forms to the west of Oklahoma. A storm system moving out of the southern Rockies may push the dry line eastward...with severe thunderstorms and tornadoes forming along the dry line or in the moist air just ahead of it.