THUNDERSTORMS &TORNADOES

QUESTION OF THE DAYWhere would you expect to find the greatest proportion of Tstorms and why?

CYCLONECirculation around ANY low-pressure centerIntensity and size do not matter

Tornadoes and Hurricanes are smaller than mid-latitude cyclones and more violent

THUNDERSTORMS Storm that produces lightning and thunder Characterized based upon the up/down draft

of air NOT circular motion of air Forms when warm, humid air rises in an

unstable environmentUnequal heating of earth’s surface (Air-

Mass Tstorms)Unequal heating along with frontal

wedging or oorgraphic lift (Severe Tstorms)

AIR-MASS THUNDERSTORMS Occur in mT air that moves Northward from

Gulf. Most frequent during Spring and Summer Frequently around midafternoon

Thunderstorm Project produced a model of the life cycle of a Tstorm Cumuls Stage Mature Stage Dissipating Stage

CUMULUS STAGE Formation of cumulus clouds allow for

moisture to be at greater heights Clouds grow vertically

Cumulonimbus clouds form Dominated by updraft

Downdraft forms and failing precipitation causes dragEntrainment intensifies downdraft

MATURE STAGE Officially starts when precipitation leaves the

cloud Updraft and downdraft exists side by side

and grow the cloud Anvil top forms when cloud reaches base of the

stratosphere Most active stage: Gusty winds, ligthning,

hail/heavy precipitation

DISSIPATING STAGEDominated by the downdraft

Cooler air aloft and falling precipitation causes cloud to evaporate

SEVERE THUNDERSTORMS Characterized by heavy downpours, flash

flooding, strong/gusty winds, hail, lightning, and maybe tornadoes.Must have winds over 58mph or hailstones

.75 in diameter or produce a tornado

SUPERCELL TSTORMS Single, powerful cell up to 65,000’ and 12-30

miles in diameter 2000-3000/year in the US

Can form mesocyclones when updraft rotates

THUNDER & LIGHTNING Thunder is: Expanding air

Heat Lightning Lightning is created due to separation of

charges in a cumulonimbus cloud Sheet Lightning

Within the cloud or between clouds 80% of all lightning

Cloud to Ground Lightning 20% of lightning strokes Most damaging and dangerous

Flash is made up of individual strokes Leader, step leader, return stroke, and dart leader

TORNADOES AKA: twisters, cyclones Violent windstorms that are a vortex Contains lower pressure inside the vortex

than the surrounding areas

TORNADO FORMATION Form in association with severe thunderstorms

Located wherever severe weather is: cold fronts, squall lines, hurricanes, supercells

Only tornado if funnel cloud touches surface

F-SCALE Fujita Intensity Scale

Determined based upon damage produced

TORNADO FORECASTING

Alters public to POSSIBLITY of tornadoes over a specific area for a certain time period. 65,000sq.km for 4-6

hours

Issued by local NWS ACTUAL sighted

tornado in an area or indicated by radar Smaller areas and

for shorter periods of time

Watches Warnings