Physical Geography Lecture Outline 28 Localized Severe Weather
Physical Geography: A Landscape Appreciation 10e 2
Thunderstorms Violent convective storms with thunder and
lightning Causes: Unstable Air and Convection Clashing Air Masses
and Cold Fronts Convergence 3
Where would you expect the most thunderstorms? Physical
Geography: A Landscape Appreciation 10e 4 18% 0% 0% 82% 1.
Mid-latitudes 2. Polar Regions 3. Equatorial Regions 4. At the
Sub-Tropical High
Thunderstorms by Latitude 5 2011 Pearson Education, Inc.
Causes of Thunderstorms Convection of Unstable Air Convergence
Clashing of Air Masses 2011 Pearson Education, Inc. 6
Which state would you expect to have the most T-storms?
Physical Geography: A Landscape Appreciation 10e 7 9% 9% 0% 9% 0%
73% 1. Florida 2. Missouri 3. Colorado 4. Vermont 5. Oregon 6. New
York
8 2011 Pearson Education, Inc.
Stages in Formation 9 Physical Geography: A Landscape
Appreciation 10e
10 Figure 7-29 Lightning Electric discharge Separation of
charges due to friction with ice particles Release of electrons
Lightning types Cloud to ground Cloud to cloud Within cloud
Thunder
Physical Geography: A Landscape Appreciation 10e 16
Thunderstorm Safety Take cover, stay there! Building is best.
Car is 2nd (dont touch metal) Dont BE or be UNDER the highest point
Crouch on toes if out in open 5 second difference in lightning +
thunder arrival = 1 mile away Physical Geography: A Landscape
Appreciation 10e 17
Tornadoes Physical Geography: A Landscape Appreciation 10e
18
Is a tornado a low or high pressure system? Physical Geography:
A Landscape Appreciation 10e 19 18% 9% 73% 1. Low 2. High 3.
Depends upon the individual storm
Physical Geography: A Landscape Appreciation 10e 21
Tornado formation Vertical wind shear creates horizontal
rotation Tilted into vertical by thunderstorm updraft Mesocyclone
and tornado development 22
Causes: Unstable air from clashing air masses Unstable air from
convection or convergence Physical Geography: A Landscape
Appreciation 10e 23
If cP air meets mT air, which will rise? Physical Geography: A
Landscape Appreciation 10e 24 0% 0% 1. cP 2. mT
If mT air meets cT air, which will rise? Physical Geography: A
Landscape Appreciation 10e 25 0% 0% 1. mT 2. cT
Which type of front will most likely have a tornado? Physical
Geography: A Landscape Appreciation 10e 26 0% 0% 0% 1. Warm front
2. Cold front 3. Stationary front
27 2011 Pearson Education, Inc.
Physical Geography: A Landscape Appreciation 10e 28
Locations in US Tornado Alley clash between cP and mT Dry Line
cT meets mT Florida Convergence, Hurricanes, Convection Other
Locations Convection, Cold Fronts Physical Geography: A Landscape
Appreciation 10e 29
Tornado Wind Patterns
Dangers Winds!!!!! Flying debris
Flying Debris
Watch vs. Warning Watch - Conditions are conducive to the
development of tornadoes in and close to the watch area. Warning -
tornado has been sighted by spotters or indicated on radar and is
occurring or imminent in the warning area.
Danger signs Strong, continuous rotation in clouds Whirling
dust and/or debris on ground beneath cloud layer Hail or heavy rain
followed by extreme shifts in wind Loud, continuous rumble which
doesn't fade over time Bright, blue-green flashes near the ground
of power lines breaking Lowering of the clouds in a spiraling
fashion Funnel cloud not moving toward left or right
Tornado Safety Mobile home or vehicle GET OUT and AWAY!!
Basement is best Orunder a stairwell or in windowless room or
bathtub Cover yourself
Tornado classification 36
37 2011 Pearson Education, Inc.
Greensburg, Kansas 2007 Physical Geography: A Landscape
Appreciation 10e 38
Joplin, Missouri- Spring, 2011 Physical Geography: A Landscape
Appreciation 10e 40
Topeka, Kansas, Spring 2011 Physical Geography: A Landscape
Appreciation 10e 41
Tuscaloosa, AL 4/27/2011 1 minute raw footage Tuscaloosa
Joplin, MO 5/22/2011 http://www.youtube.com/watch?
feature=endscreen&v=VQDkmziz1n8&NR =1 Physical Geography: A
Landscape Appreciation 10e 42
Why so many tornadoes reported recently? More reporting and
pictures captured! Many reported twice More people = more people
impacted More people living in urban areas when they are hit, many
are impacted 2011 was A particularly violent year favorable
atmospheric conditions Climate change? Physical Geography: A
Landscape Appreciation 10e 43
