A tornado slides across Oklahoma. Prototype courtesy NSSL/NOAA.

Continued vigilance and quick response to tornado watches and warnings are critical, since tornadoes can strike most anywhere at any time. Nigh tornadoes are abrupt at onset, short-lived and frequently obscured past pelting or darkness. That'southward why it'due south so important to programme ahead. Every individual, family, and business organization should accept a tornado emergency plan for their homes or places of work, and should learn how to protect themselves in cars, open state, and other situations that may arise.

The most important footstep yous can take to prepare for a tornado is to have a shelter program in identify. Where volition you lot go when a tornado alert has been issued for your canton or city? Is it a basement or a storm cellar? Is there an interior room on the footing floor that you tin use equally a storm shelter? Have a plan, and make sure everyone in your family or workplace knows it.

Having a NOAA Conditions Radio can relieve your life. Weather Radios are sold at many retailers and websites, including electronics, department, sporting appurtenances and boating accompaniment stores. Or you lot can heed online.

Know the difference between a picket  and a warning

Tornado Watch

Weather condition are right for tornadoes, and tornadoes are possible. Remain alert: watch the sky and tune in to NOAA Weather Radio, commercial radio, or a local idiot box station in case a alert is issued.

Tornado Warning

A tornado has been spotted by man eye or radar, and is moving toward you in the alert surface area. Have shelter immediately.

What to do before a tornado

Be alert to conditions conditions. Listen to NOAA Weather Radio or tune in to a local television station for the latest information.

Expect for the following danger signs:

  • Dark, greenish sky
  • Large hail
  • A large, dark, depression-lying cloud (particularly if rotating)
  • A loud roar, like to a freight railroad train

What to do during a tornado

When a tornado warning has been issued for your county or city, seek shelter immediately!

If you are in: Take this activity:
A construction (residence, edifice, school, hospital, etc.) Caput to your pre-designated shelter expanse. This could be a basement, storm cellar, or the everyman building level. If you are home and you lot don't have a basement, go to the nigh interior room of the ground flooring. Frequently a bathroom or laundry room makes a suitable shelter area because the water pipes reenforce the walls, providing a more sturdy structure. Stay abroad from corners, windows, doors, and exterior walls. Put equally many walls as possible between you lot and the outside. Become downwards on your knees and utilize your easily to protect your head and neck. Practice not open windows.
A vehicle If you can drive away from the tornado, do and then. If you don't have time or non certain if yous take fourth dimension, or you're not certain which way the tornado is moving, become out of the vehicle. Caput to the lowest floor of a nearby edifice or tempest shelter. If there's no edifice or shelter nearby, follow the instructions for what to do if you're outside with no shelter.
A mobile domicile or trailer Get out immediately and go to the lowest floor of a nearby building or storm shelter. Mobile homes provide little to no protection against tornadoes.
The outside with no nearby shelter Prevarication apartment in a nearby ditch or depression and embrace your head and neck with your easily. Exist aware of the potential for flooding in the ditch you are occupying. Practise not become under and overpass or bridge.  You are safer in a depression, flat location. If yous are in an urban or congested expanse, do not try and outrun the tornado in your vehicle. Instead, leave the vehicle immediately and seek shelter. Be aware of flight debris. Tornadoes can pick upwards large objects and turn them into missiles. Flying droppings crusade the most tornado deaths.

What to do after a tornado

Afterward a tornado passes, it is important to take some precautions. Be conscientious as your leave your tornado shelter, since there might be unseen damage waiting for you on the other side of doors. If your home has been damaged, walk advisedly around the outside and cheque for things like loose power lines, gas leaks, and general structural damage. Leave the premises if yous olfactory property gas or if floodwaters exist around the building. Call your insurance agent and have pictures of the damage to your abode or vehicle. If the destruction is all-encompassing, don't panic. The American Blood-red Cross and other volunteer agencies will arrive with nutrient and h2o, and temporary housing will be designated by FEMA.

Reflectivity of the supercell that produced the Moore, Oklahoma tornado on May iii, 1999. At the time of this radar scan, a tornado was on the ground. Paradigm courtesyNWS.

What is a tornado?

A tornado is a violently rotating column of air which descends from a thunderstorm to the ground. No other weather condition miracle can lucifer the fury and subversive power of tornadoes. Tornadoes can be strong plenty to destroy large buildings or lift 20-ton railroad cars from the tracks. A tornado might not have a visible funnel until information technology picks up debris from the ground. The strength of a tornado is measured by the Enhanced Fujita Scale (go on scrolling for information on the Enhanced Fujita Calibration).

How do tornadoes form?

The truth is that scientists don't fully understand how tornadoes form. A parent supercell thunderstorm is needed. Across that, each storm is different. Some enquiry suggests it has to exercise with how strongly the wind changes management with peak or how much moisture is in the air. Other research suggests information technology forms because of the departure between the temperature of the surrounding air and the temperature of the cold downdrafts coming from the storm.

What is a supercell thunderstorm?

A supercell is an organized thunderstorm that contains a very potent, rotating updraft. This rotation helps to produce astringent weather events such as large hail, strong downbursts and tornadoes. Supercells usually class isolated from other thunderstorms considering information technology allows the tempest more than energy and wet. These storms are relatively rare, but always a threat to life and property.

What is the deviation between a funnel cloud and a tornado?

A tornado begins as a rotating, funnel-shaped deject extending from a thunderstorm cloud base, which meteorologists call a funnel cloud. A funnel cloud is made visible by cloud droplets, still, if the cloud lacks moistrue, it may appear to be invisible. A funnel deject does not affect the ground. If the funnel extends far enough down to brainstorm affecting the ground, then it becomes a tornado.

How far does a tornado travel?

Tornado paths range from 100 yards to ii.6 miles wide and rarely travel more than 15 miles, although some strong tornadoes on record accept crossed through multiple states (e.g. theTri-State Tornado of 1925). They can last from several seconds to more than an hour, but nearly don't exceed 10 minutes. Most tornadoes travel from the southwest to northeast with an average speed of 30 mph. However, observed speeds have been recorded betwixt almost no motion and 70 mph.

What causes tornadoes?

Tornadoes form under a certain set of weather condition atmospheric condition in which 3 very dissimilar types of air come together in a certain way. Near the footing lies a layer of warm and boiling air, along with strong south winds. Colder air and strong w or southwest winds lie in the upper atmosphere. Temperature and wet differences between the surface and the upper levels create what is calledinstability, a necessary ingredient for tornado formation. The alter in wind speed and direction with tiptop is known equally wind shear. This wind shear is linked to the eventual development of rotation from which a tornado may form.

A 3rd layer of hot dry air becomes established between the warm moist air at low levels and the absurd dry air aloft. This hot layer acts equally a cap and allows the warm air underneath to warm further, making the air even more unstable. Things start to happen when a tempest 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 evolution as potent updrafts develop. Complex interactions between the updraft and the surrounding winds may cause the updraft to begin rotating-and a tornado is born.

When and where do tornadoes occur?

Most tornadoes occur east of the Rocky Mountains in a region known every bit "Tornado Aisle." The vast majorities of tornadoes occur in the deep south equally well every bit the broad, relatively flat bowl between the Rockies and the Appalachians, notwithstanding no state is immune. Often, the nigh dangerous tornadoes occur in the deep Due south and Southeast, where low visibility because of copse and hills pb to a imitation sense of security during astringent weather outbreaks. Furthermore, the S and Southeast tends to exist more heavily populated than the Plains states. This region has been given the nickname "Dixie Alley."

Summit months of tornado activeness in the U.S. are April, May, and June, but tornadoes have occurred in every month of the twelvemonth.Although they are possible any time of the 24-hour interval or night, tornadoes tend to occur in the late afternoon and early evening hours, when the atmospheric weather are virtually ripe for supercell thunderstorms. They are nigh common from 4pm to 9pm.

Tornado Alley is then active with astringent storms because of its unique location.

Tornado Aisle

Tornado Alley is a nickname given to the plains region of the U.Due south. that experiences a high frequency of tornadoes, many of which are violent tornadoes (classified as EF-three or greater). With the Rocky Mountains to the westward, and the warm waters of the Gulf of United mexican states to the south, this region is in a ripe location to produce supercell thunderstorms.

Midlatitude cyclones, like the 1 illustrated above with the red "50" and fronts, are the large-calibration phenomena that spawn storms that create tornadoes. Every bit midlatitude cyclones move due east off the Rockies, they can tap into the warm, boiling air from the Gulf of Mexico. This air surges n at the low levels as cold, dry out air at upper levels is pulled due south by the storm. These are the basic ingredients for instability, which every thunderstorm needs to grow. Warm, moist air is less dense than cold, dry air. In this density game, the surface air will begin to rise, and in an unstable atmosphere, what goes upward will go on going upwards. Air moving upward is what creates our clouds, pelting, and our thunderstorms. If the upper-level jet stream is potent in this storm, the turning of the winds with height, or "wind shear," will help in creating supercell thunderstorms and tornadoes are possible. All tornadoes are spawned from a parent supercell, but not all supercells produce tornadoes.

Impairment from the 1999 F5 tornado that struck Moore, Oklahoma. Photo courtesy NOAA.

Enhanced Fujita Scale

Dr. T. Theodore Fujita developed the Fujita Tornado Impairment Scale (F-Scale) to provide estimates of tornado strength based on impairment surveys. Since it'due south practically incommunicable to make direct measurements of tornado winds, an guess of the winds based on damage is the best way to allocate a tornado. The new Enhanced Fujita Scale (EF-Scale) addresses some of the limitations identified by meteorologists and engineers since the introduction of the Fujita Scale in 1971. The new scale identifies 28 dissimilar gratis standing structures virtually affected by tornadoes taking into account construction quality and maintenance. The range of tornado intensities remains as before, zippo to five, with 'EF-0' being the weakest, associated with very trivial damage and 'EF-5' representing complete destruction, which was the example in Greensburg, Kansas on May iv, 2007, the first tornado classified every bit 'EF-5'. The EF scale was adopted on February ane, 2007.

The Tempest Prediction Eye has a cursory clarification of the Enhanced Fujita Scale.

EF-Scale Old F-Scale Typical Damage Example (Photos courtesy NWS)
EF-0 (65-85 mph) F0 (65-73 mph) Calorie-free impairment. Peels surface off some roofs; some damage to gutters or siding; branches cleaved off copse; shallow-rooted copse pushed over.
EF-one (86-110 mph) F1 (73-112 mph) Moderate damage. Roofs severely stripped; mobile homes overturned or desperately damaged; loss of exterior doors; windows and other glass broken.
EF-ii(111-135 mph) F2 (113-157 mph) Considerable damage. Roofs torn off well-synthetic houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.
EF-iii (136-165 mph) F3 (158-206 mph) Severe damage. Unabridged stories of well-synthetic houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the footing and thrown; structures with weak foundations diddled abroad some distance.
EF-4 (166-200 mph) F4 (207-260 Devastating damage. Whole frame houses Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.
EF-5 (>200 mph) F5 (261-318 mph) Incredible damage. Strong frame houses leveled off foundations and swept away; car-sized missiles fly through the air in backlog of 100 grand (109 yd); high-rise buildings have significant structural deformation; incredible phenomena will occur.
EF No rating F6-F12 (319 mph to speed of audio) Inconceivable damage. Should a tornado with the maximum air current speed in backlog of EF-five occur, the extent and types of harm may not exist conceived. A number of missiles such as iceboxes, water heaters, storage tanks, automobiles, etc.will create serious secondary damage on structures.