This type of storm is called a supercell thunderstorm. The spinning of these supercell thunderstorms is visible via Doppler radar. A supercell is an organized thunderstorm that contains a very strong, rotating updraft. This rotation helps to produce severe weather events such as large hail, strong downbursts, and tornadoes. Supercell storms are usually isolated from other thunderstorms because it allows them to have more energy and moisture from miles around.
These storms are rare, but always a threat to life and property. A tornado begins as a rotating, funnel-shaped cloud extending from a thunderstorm cloud base. A funnel cloud is made visible by cloud droplets, however, in some cases it can appear to be invisible due to lack of moisture. When the funnel cloud is half-way between the cloud base and the ground, it is called a tornado.
What is the path length of tornadoes? How long do they last? How fast do they move? Tornado paths range from yards to one mile wide and are rarely more than 15 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 no state is immune.
Peak months of tornado activity in the U. 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.
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 humid 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. A necessary ingredient for tornado formation. The change in wind speed and direction with height is known as wind shear.
This wind 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.
During the spring and summer months southerly winds prevail across the plains. Among the most severe storms, supercells can bring strong winds, hail, and even tornadoes. See more extreme weather pictures. When weather conditions are conducive for tornado formation, the National Weather Service issues a tornado watch. When a tornado has been sighted or indicated on radar, a tornado warning is issued. Some scientists, meteorology buffs, and adrenaline junkies hit the road during tornado season to chase storms.
Researchers race to place sensors in tornadoes' paths. The sensors measure data such as wind speed, barometric pressure, humidity, and temperature. The challenge for researchers is being in the right place at the right time. Every morning they study weather conditions and head for the area that seems most likely to spawn a twister. They drive through severe storms, dodge lightning, face flash floods, and get pounded by hail—sometimes for years—before ever spotting a tornado.
All at considerable risk. In , National Geographic Explorer Tim Samaras and his team were killed while trying to study a tornado in Oklahoma. See photos of Samaras's work. All rights reserved. What is a tornado? Lightning Strikes A supercell thunderstorm strikes in South Dakota. Share Tweet Email. Why it's so hard to treat pain in infants.
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Animals This frog mysteriously re-evolved a full set of teeth. Tornadoes can form at any time of year, but most occur in the spring and summer months along with thunderstorms. May and June are usually the peak months for tornadoes. Texas and Florida. Oklahoma and Indiana. Oklahoma and Texas.
March is also the month when the worst tornado in U. The South then typically sees its greatest threat of tornadoes as we head into March and into the spring season.
With jet stream winds still strong and ample moisture returning north periodically, the threat of tornadoes spreads farther north. By April, surface dew points in the 60s, or even 70s, penetrate farther north as actual temperatures sometimes climb into the 80s and 90s, supplying fuel for severe thunderstorms.
The wintertime jet stream continues to be powerful especially over the southern United States, but it wanders in latitude at times giving quick flicks of atmospheric energy and wind shear every few days or so. May is typically the peak in tornado activity nationally due to the best setup of warm air, jet-stream disturbances swinging out of the Rockies and plentiful moisture east of the Rockies.
Parts of the Midwest and Plains also see increased tornado activity due to that region's proximity to stronger jet-stream winds that are typically located closer to the Canadian border in summer. Parts of the Mid-Atlantic and Northeast also see increased tornado activity. Tornadoes can occur pretty much anywhere nationwide during the warmest months.
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