Download Thunderstorms and Tornadoes

Thunderstorms and Tornadoes
Air Mass Thunderstorms
Surface heating! The source for all unstable air
rising!
• As air is forced to rise, it accumulates, creating
lots of rising moist air
• Air that is forced to rise and cool quickly will
try to stabilize – thunderstorm
• Late afternoon thunderstorms in the summer
• Stage A – Rising air from surface heating
• Stage B – Sinking air that has cooled. Cold air
wants to be at the surface
• Stage C – No more rising air means no more
power for the storm, and the storm “dissipates”
Terms
• Gust Front: (aka outflow boundary) the edge
of gusty, cooler surface winds from
thunderstorm downdrafts – we feel this often
from approaching thunderstorms
• Squall Line: line of thunderstorms that can
form along or ahead of a cold front
Severe Thunderstorms
• Associated with frontal zones
• WHY?
TURBLENCE!
• Cold front advances
on a warm front
• Also seen during
Occluded front
• Tornadoes can be
associated with these storms
Tornadoes
http://www.geo.hunter.cuny.edu/~tbw/wc.note
s/10.thunderstorms.tornadoes/animations/nT
winds.html
Tornadoes
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Another response to unstable air
Also called “funnel clouds”
http://www.spc.noaa.gov/faq/tornado/
Mesocyclones form from supercells--which are
rotating thunderstorms with a well-defined
circulation
• Cyclone = low pressure. Tornadoes can be as
low as 100mb
Tornado Paths
• Typically from
SW  NE in the US
• WHY? Where is the
warm moist air
coming from?
• Air moves from H L