Tornado……………………………………………………………………………………..?
Jul 29, 2010
in
Tornado
please answer: why does tornadoes form in the middle of the U.S than any other places and explain how air comes together meets ad oiginates???THANK UU it’s for a test
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5 comments
Freight_Train on July 29, 2010 at 10:48 pm
Happy Thanksgiving to you and your family.
There is an excellent link regarding this question. and the answer that would be required is a little to long to answer here in this forum.
SEE THIS LINK
http://www.srh.noaa.gov/jetstream/tstorms/ingredient.htm
Tornadoes are formed by Supercell Thunderstorms, Thunderstorms require three ingredients for their formation:
* Moisture,
* Instability, and
* a lifting mechanism.
Sources of moisture
The central and southeastern U.S. has access to two moisture sources the Atlantic ocean and the Gulf of Mexico which helps explain why there are so much rain in that region.
Sources of moisture
Typical sources of moisture are large bodies of water such as the Atlantic and Pacific oceans as well as the Gulf of Mexico.
Water temperature plays a large role in how much moisture is in the atmosphere. Recall from the Ocean Section that warm ocean currents occur along east coasts of continents and cool ocean currents occur along west coasts. The amount of ocean water evaporation into the atmosphere is higher in warm ocean currents and therefore put more moisture into the atmosphere than with cold ocean currents at the same latitude.
The southeastern U.S. has access to two moisture sources in the Atlantic ocean and the Gulf of Mexico which helps explain why there are so much rain in that region.
Instability
Instability: Air is considered unstable if it continues to rise when given a nudge upward (or continues to sink if given a nudge downward). An unstable air mass is characterized by warm moist air near the surface and cold dry air aloft. In these situations, if a bubble or parcel of air is forced upward it will continue to rise on its own. As it rises it cools and some of the water vapor will condense, forming the familiar tall cumulonimbus cloud that is the thunderstorm.
Characteristics of an unstable air mass with warm moist air near the surface with colder and drier air aloft. Air that is forced upward will continue to rise, and air that is forced downward will continue to sink.
Sources of Lift (upward)
Typically, for a thunderstorm to develop, there needs to be a mechanism which initiates the upward motion, something that will give the air a nudge upward. This is done by several methods.
Differential Heating
This heating of the ground and lower atmosphere is not uniform. For example, a grassy field will heat at a slower rate than a paved street. The warmest air, called thermals, tends to rise. In the image (right) a wildfire provided the differential heating for a cumulus cloud to form over the smoke plum.
Fronts, Drylines and Outflow Boundaries
Clouds covering mountain peak as air is forced up due to terrainFronts are the boundary between two air masses of different temperatures. Fronts lift warm moist air. Cold fronts lift air the most abruptly. If the air is moist and unstable thunderstorms will form along the cold front.
Drylines are the boundary between two air masses of different moisture content and separate warm moist air from hot dry air. While the temperature may be different across the dryline, the main difference is the rapid decrease in moisture behind the dryline. It is the lack of moisture which allows the temperatures to occasionally be higher than ahead of the dryline. However, the result is the same as the warm moist air is lifted along the dryline forming thunderstorms. This is common over the plains in the spring and early summer.
Outflow boundaries are a result of the rush of cold air as a thunderstorm moves overhead. The rain-cooled air acts as a "mini cold front", called an outflow boundary. Like fronts, this boundary lifts warm moist air and can cause new thunderstorms to form.
Most tornadoes are spawned from supercell thunderstorms. Supercell thunderstorms are characterized by a persistent rotating updraft and form in environments of strong vertical wind shear.
Wind shear is the change in wind speed and/or direction with height.
The updraft lifts the rotating column of air created by the speed shear. This provides two different rotations to the supercell; cyclonic or counter clockwise rotation and an anti-cyclonic of clockwise rotation.
The updraft lifts the rotating columnThe directional shear amplifies the cyclonic rotation and diminishes the anti-cyclonic rotation (the rotation on the right side of the of the updraft in the illustration at left). All that remains is the cyclonic rotation called a mesocyclone. By definition a supercell is a rotating thunderstorm.
K babeā„ on July 29, 2010 at 10:48 pm
because of where the fronts are located & the humidity in the air.
Chase on July 29, 2010 at 10:48 pm
Cold air from the east and hot air from the west and cold ari from the north and hot air from the south meet in the middle causing extreme amounts of pressure which causes tornadoes
Wolfman on July 29, 2010 at 10:48 pm
You know, you should really be doing your test yourself but anyway…………
Tornadoes need three ingredients to form :
#1. Warm, moist air from the Gulf of Mexico.
#2. Warm, dry air from Mexico.
#3. Cool, dry air from the Rocky mountains or Canada.
The warm, moist air is at the bottom, near the ground. The warm, dry air is situated right on top of the warm, moist air. And the cool, dry air is at the top.
In the area of the warm, moist air, clouds develop. They grow by the energy released by condensation : latent heat. They grow until they reach the warm, dry air (also called a cap). The cap prevents the growth of any more clouds. The clouds move in two separate directions at the top. It will eventually make the shape of an anvil. If the warm, moist air is stong enough, it will burst through the cap to reach the cool, dry air. When the warm ,moist air mixes with the cool, dry air, then there will be instability. This instability causes wind shear (wind moving at different speeds, heights, and directions. When this instable air collides, it starts rolling like a barrel. This barrel of air is called a mesocyclone. An updraft tips the mesocyclone into the storm. The mesocyclone has an area of rotation 2-6 miles in length. Scientists don’t know how a mesocyclone reaches the ground as a tornado, but they think a downdraft pushes it down to the ground. Once the tornado is formed, it needs warm, moist air to keep going. If it runs out, then it will dissipate.
nickname on July 29, 2010 at 10:48 pm
They form in the middle for a number of reasons but it is mostly from the cPc (continental polar canadian) air masses colliding with the mTg (maritime tropical gulf) air masses, which makes the air circulate.
The air DOES NOT come from the mountains. The mountains act as barriers from the wind coming from the oceans and do not let it effect the cPc and mTg air masses.
Basically, the mountains are like perfect sides for the Tornado alley. The cold air coming from canada and warm air coming from the gulf makes the unstable air.