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Chapter 9 Meteorology

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Severe Thunderstorms
Intense thunderstorms capable of producing heavy showers, flash floods, hail, strong and gusty surface winds, and tornadoes.
Ordinary Cell thunderstorms
A thunderstorm produced by local convection within conditionally unstable air maass. It often forms in the afternoon and dont not reach the intensity of a severe thunderstorm.
Cumulus Stage
The initial stage in the development of an ordinary cell thunderstorm in which rising, warm, humid air develops into a cumulus cloud.
Mature stage
The second stage in the three-stage cycle of an ordinary thunderstorm. This mature stage is characterized by heavy showers, lightning, thunder, and violent vertial motions inside cumulonimbus clouds.
dissipating stage
The final stage in the development of the ordinary cell thunderstorm when downdrafts exsist throught the cumulonimbus cloud
multi-cell storm
Thunderstorms often in a line each of which may be in different stage of its life cycle
squall line
a line of thunderstorms that form along a cold front or out ahead of it
mesoscale convective complexes
A large organized convective weather dydtem comprised of a numver of individual thunderstorms. The size of an MCC can be 1000 times larger than an individual ordinary thunderstorms
dryline
a boundary that separates warm, dry, air from warm, moist air. it usually represents a zone of instability along which thunderstorms form
gust front
A boundary that seperates a cold downdraft of a thunderstorm from warm, humid surface air. On the surface its passage resembles that of a cold front
shelf cloud
a dense, arch-shaped, omnious-looking cloud that often forms along the leading edge of a thunderstorm's gust front, especially when stable air rises up and over cooler air at the surface. also called an arcus cloud
roll cloud
a dense, cylindrical, elongated cloud that appears to slowly spin about a horizontal axis behind the leading edge of a thunderstorms gust front
outflow boundary
a surface boundary seperating cooler more-dense air from warmer less-dense air. outflow boundaries form by the horizontal spreading of cool air that originated inside a thunderstorm
downburst
A severe localized downdraft that can be experienced beneath a severe thunderstorm
microburst
A strong localized downdraft less than 4km wide that occurs beneth thunderstorms. A strong downburst greater across is called a macroburst.
bow echo
a line of thunderstorms on a radar screen taht appears in the shape of a bow. bow echos are often associated with damaging straight-line winds and small tornadoes
derecho
Strong,damaging, straight line winds assosiated with a cluster of severe thunderstorms that most often form in the evening or at night
heat burst
A sudden increase in surface air temperature often accompanied by extreme drying. a heat burst is associated with the downdraft of a thunderstorm, or a cluster of thunderstorms
lightning
a visivle electrical discharge produced by thunderstorms
thunder
the sound due to rapidley expanding gases along the channel of a lightning discharge
stepped leader
an initial discharge of electrons that proceeds intermittently toward the ground in a series of steps in a cloud-to-gound lightning stroke
dart leader
the discharge of electrons that proceeds intermittently toward the ground along the same ionized channel taken by the initial lightning stroke
dry lightning
lightning that occurs with thunderstorms that produce little, if any, appreciatable precipitation that reaches the surface
heat lightning
distant lightning that illuminates the sky but is too far away for its thunder to be heard
st. elmo's fire
a bright electric discharge that is projected from objects when they are in a strong electric field, such as during a thunderstorm...
return stroke
the luminous lightning stroke that propagates upward from the earth to the base of a cloud
tornado
an intense, rotating column of air that often protrudes from a cumulonimbus cloud in the shape of a funnel or a rope whose circulation is present of the ground.
funnel cloud
a tornado whose circulation has not reached the ground. often appears as a rotating conelike cloud that extends downward from the base of the thunderstorm
tornado outbreak
a series of tornadoes that forms within a perticular region- a region that may include several states. often associtaed with widesread damage and destruction
suction vortices
small, rapidly rotating whirls perhaps 10m in diameter that are found within large tornadoes
tornado watch
a forecast issued to alert the public that tornadoes may develop within a specified area
tornado warning
a warning issued when a tornado has actually been observed either visually or on a radar screen. it is also issued when the formation of tornadoes is imminent
fujita scale
A scale developed by t. theodore fujita for classifying tornadoes according to the damage they cause and their rotational wind speed
supercell tornadoes
tornadoes that occur within supercell thunderstorms that contain well-developed mid level mesocyclones
mesocyclone
a vertical column of cyclonically rotating air within a supercell thunderstorm
hook echo
the shape of an echo on a doppler radar screen that indicates the possible presence of a tornado
wall cloud
an area of rotating clouds that extends beneath a supercall thunderstorm and from which a funnel cloud may appear. also called a collar cloud and pedestal cloud
nonsupercell tornadoes
a tornado that occurs with a cloud that is often in its frowing stage and one that does not contain a mid-level mesocyclone of wall cloud. landspouts and gustanadoes are examples of nonsupercall tornados.
gustnadoes
a relatively weak tornado associated with a thunderstorm's outflow. It most often forms along the gust front.
landspouts
Realatively weak nonsupercall tornado that originates with a cumuliform cloud in its growth stage and with a cloud that does not contain a mid-level mesocyclone. Its spin originates near the surface. Landspouts often look like water spouts over land.
NEXRAD
an acronym for next generation weather radar. the main component of NEXRAD is the wsr 88-d doppler radar
waterspout
a column of rotating wind over water that has characteristics of a dust devil and tornado
sonic boom
a loud explosive-like sound caused by a shock wave emanating from an aircraft traveling at or above the speed of sound
flash floods
A flood that rises and falls quite rapidly with little or no advance warning, usually as the result of intanse rain fall over a relatively small area.
supercell storm
an enormous severe thunderstorm that consists primarily of a single rotating updraft. its organized internal structure allows that storm to maintain itself for several hours. the storm can produce large hail and dangerous tornadoes