Name: _____________________________________
Notes: Thunderstorms
Date: _____________________
Atmospheric Science
DIRECTIONS: Go to the website: http://www.srh.noaa.gov/jetstream/
Select “Thunderstorms” in list of JetStream Topics to fill in your notes that follow.
A. Introduction
 It is estimated that as many as ____________ thunderstorms occur worldwide each day.
 The most frequent occurrence of thunderstorms in the U.S. is in the _____________________
states.
B. Ingredients for a Thunderstorm
1. Sources of Moisture – examples include _________________________________________
2. Instability – when a bubble or parcel of air is forced _______________, forming the familiar
tall ___________________________ clouds
3. Sources of Lift – a mechanism that nudges air upward by creating a difference in air
_________________ (examples – differential heating, fronts, and terrain)
C. Life Cycle of Thunderstorms
1. The Towering Cumulus Stage – air within the cloud is dominated by an ________________
2. The Mature Stage – strong _____________ and _____________ coexist
3. The Dissipating Stage – a downdraft dominates, or cuts off the updraft of warm moist air
D. Types of Thunderstorms
1. Ordinary Cell
 Also called a ________________ thunderstorm
 Consists of one updraft and one downdraft
 Typically _______–lived and not _____________.
2. Multi-cell Cluster
 Occurs when an individual thunderstorm cell matures, moves downstream, and
another cell forms in its place.
 Known as “training thunderstorms”\
 Often these storms will appear on the radar to be _____________________
 Produce tremendous ____________ over relatively small areas leading to
___________ ________________.
3. Multi-cell Squall Line
 Form in a line which can extend laterally for hundreds of miles
 Can persists for many hours and produce damaging ________ and ________
 More likely to produce “___________-________” wind damage rather than
tornadoes (result of a powerful downdraft)
 Long-lived squall lines are called ____________________
4. Supercell Thunderstorm
 Special kind of single-cell thunderstorm
that may persist for hours
 Responsible for nearly all of the significant
______________ in the U.S. and for most
of the _________________ larger than golf
ball size
 The most ideal conditions for supercells
occur when the winds are ___________, or
turning clockwise with height.
 Tornadoes usually form in the ______ cloud, which are isolated lower clouds below
the rain-free base and below the main storm tower
E. Thunderstorm Hazards – Hail
 Hail is precipitation that is formed when
____________ in thunderstorms carry
raindrops upward into extreme cold areas of
the atmosphere. This often happens
repeatedly, which causes a layered
appearance of hailstones.
 The states that have the most hail storms are:
_______________, ____________________
and __________________
F. Thunderstorm Hazards – Damaging Winds
 _________________ are defined as strong winds produced by a downdraft over a horizontal
area of up to 6 miles. There are two types:
1. Microburst – small downburst that lasts __-__ minutes that may create hazardous
conditions for ___________. Can produce destructive winds up to _____ mph.
2. Macroburst – last __-___ minutes and may produce winds as high as _____mph.
G. Thunderstorm Hazards – Tornadoes
 A tornado is a violently rotating ___________ of air descending from a thunderstorm and in
contact with the ground
 In a typical year, about ________ tornadoes will strike the United States.
 Most tornadoes are spawned by ________________ thunderstorms that form in
environments of strong vertical ______ __________, which is the change in wind speed
and/or direction with height.
 Rotating supercell thunderstorms that may contain tornadoes appear
on Doppler Radar with a classic “_______” shape
 _______________ ________________ (EF) Scale – a scale from 0-5
that estimates tornado wind speeds by assessing the damage left
behind by a tornado
H. Thunderstorm Hazards – Flash Floods
 Nearly half of all flash flood fatalities are ______________-related
 Most flash floods are caused by ______-____________ thunderstorms
 Two safety rules that you should follow in the event of a flash flood watch or warning are:
1. ____________________________________________________________________
2. ____________________________________________________________________