Thunderstorm and Severe Weather Quiz Flashcards
What are the types of hazards result from severe weather
- Flooding
- Lightning
- Winds (and microbursts)
- Hail
- Tornadoes
Definition
Thunderstorm
A storm that generates lightning and thunder
Definition
Air-Mass Thunderstorm
Forms in a warm, moist, unstable air mass
- Most frequent in the afternoon in spring and summer
Definition
Organized Thunderstorms
Form by frontal activity, upper level support (jet stream), steep lapse rates, etc
- Produce majority of severe weather
What stages do thunderstorms go through in their life cycle
- Cumulus stage
- Mature stage
- Dissipation stage
Definition
Entrainment
Pull of cool, dry air into the cloud - intersifies the downdraft by aiding evaporation and cooling
Definition
Most Active Period
Gusty winds, lightning, heavy precipitation, small hail, etc.
Influencing Factors of Flooding
- Rainfall intensity and duration
- Surface conditions
- Topography
Cumulus Stage
Clouds continute to grow vertically and form a cumulus tower
- Dominated by updrafts
How does Cumulus Stage form
Require moist air and the release of latent heat
Mature Stage
Falling precipitaiton causes drag on air and initiates downdrafts
Dissipating Stage
- Downdrafts and entrainment being to dominate
- Updrafts weaken and supply of moisture is cutoff
- Cloud beings to evaporate
Thunderstorm Occurrence and Growth
Air mass thunderstorms formed in high surface temps and unequal heating
- Mountainous regions have the most air-mass thunderstorms
What can triggered thunderstorms
- Convergence from sea to land airflow
- Convergence and frontal wedging associated with mid-latitude cyclones
- Convergence along the ITCZ
Severe Thunderstorm
A thunderstorm containing one or more of the following (NOAA)
- Winds > 58mph
- Hail > .75 in
- Tornado
Gust Front
Boundary separating cold downdraft and relatively warm, moist surface air (“mini cold front”)
Shelf/Roll Cloud
May often form on leading edge of gust front
Supercell
Thunderstorm consisting of a single very powerful cell that can extend to heights of 65000 ft and have a diameter of 12-30 miles
Mesocyclone
Vertical cylinder of cyclonically rotating air that develops in updraft of a supercell, often precedes damaging hail and tornadoes
- Caused by increase in wind speed and change in direction with height
Squall Line
Narrow band of thunderstorms
- Usually develops 60 - 80 miles in advance of cold front
Where can a Squall Line form
Along a dryline
Mesoscale Convective Complex (MCC)
Many individual thunderstorms organized into a large oval to circular cluster
Where does MCC most frequently occur
In the Great Plains
Lightning
A sudden flash of light generated by the flow electrons between areas of opposite charge
Lightning Process
Stepped Leader
A narrow negatively charged channel that emerges from cloud base
St. Elmo’s Fire
A bright electric discharge that’s projected from pointed objects when they are in a strong electric field during a thunderstorm
Ball Lightning
A rare form of lightning that may consist of a reddish, luminous ball of electricity or charged air
Dirty Tunderstorm
Lightning within ash clouds from volcanic eruptions
How does Hail form?
Forms by adding layers of ice each time are cycled through thunderstorms
Downburst
A strong localized downdraft with straight-line concentrated bursts of wind
When does downburst winds produce?
When there’s a great deal of evaporative cooling
Microbursts
Downburst with a diameter < 4 km
- Usually only last 2 - 5 minutes
Macrobursts
Downburst with a diameter > 4 km
Tornado
A violently rotating column of air that extends downward from a cumulonimbus cloud to the surface
Most intense tornadoes are associated with what?
Supercells
Wall Cloud
an area of rotating clouds that extends downward beneath the updraft area of mesocyclone
Enhanced Fujita Intensity Scale (EF-Scale)
Intensity of a tornado by the damage caused and a proxy for estimating wind speeds
