Ch 10 Flashcards
(33 cards)
Thunderstom
A storm with lightning and thunder, produced by a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail.
Thunderstorms form when
warm, humid air rises in an unstable environment
Types of Thunderstorms
Air-mass thunderstorm
severe thunderstorm
super-cell thunderstorm
Air mass thunderstorm
not associated with a front or other type of synoptic-scale forcing mechanism;; typically are associated with warm, humid air in summer months;; develop during the afternoon in response to insolation
Air mass thunderstorms usually occur
in mT
Stages of Development of Thunderstorm
- cumulus stage
- mature stage
- dissipating stage
Severe Thunderstorm
strong thunderstorm with wind gusts in excess of 58 mph and or hail with a diameter of .75 inches or more
Why do some thunderstorms persist over many hours?
the existence of strong vertical wind shear;; the change in wind with height
Wind speeds
increase with altitude cause the updraft to tilt
when downdrafts reach the surface
the denser cool air spreads out along the ground. The leading edge of this out flowing downdrafts acts like a wedge, forcing warm, moist surface air into the thunderstorm. The down drafts act to maintain the updrafts
Gust Front
outflow boundary
roll cloud
may form as warm air is lifted along the leading edge of the gust front
Supercell thunderstorm
often-dangerous thunderstorm with a very organized internal structure including a rotating updraft that allows it to keep going for up to several hours;; capable of producing severe weather including high winds, large hail, and strong tornadoes
Supercell
consists of a single, very powerful cell that at ties can extend to heights of 20 km persist for many hours
Squall lines
relatively narrow band of thunderstorms, some of which may be severe, that develops in the warm sector of a middle-latitude cyclone;; frequently develop along a dryline
Microbursts
strong localized downdraft from a thunderstorm with peak gusts lasting 2 to 5 minutes
Ligthning
any form of visible electrical discharge produced by thunderstorms
Thunder
the sound caused by a lightning stroke as it heats the air and cause it to rapidly expand
What causes lightning
the origin of charge separation in clouds must hinge on rapid vertical movements within clouds
Step-leaders
ionize the air, forming a narrow conductive path
Dart leader
re-ionizes the conductive path
Tornadoes
violent rotating column of air, from a cumulonimbus cloud;; typical width of tens to hundreds of meters and a lifespan of minutes to hours
Tornado Alley
are of the US in which tornadoes are most frequent
Tornado Familly
series of tornadoes produced by a single supercell, resulting in damage path segments along the same general line
