Last warning: Exam 3 Monday, April 9: end of volcanoes, tsunami, and weather through tornadoes;...
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Transcript of Last warning: Exam 3 Monday, April 9: end of volcanoes, tsunami, and weather through tornadoes;...
• Last warning: Exam 3 Monday, April 9: end of volcanoes, tsunami, and weather through tornadoes; review tomorrow, 5.15 PM, UPSTAIRS in Rm 223.
• Exam 4 is on the website (as always, only partially applicable)
ANNOUCEMENTS
homework
•If you have not yet done the homework, you do have until 5 PM; be sure not to have any spaces in the URL (if you copy and paste, you might see %20recent -- the %20 has to go for the website to load). So: http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2007aqbk.php#summary
A couple of clicker review Qs
A cold front means that
1. A cold air mass is moving into a warm air mass
2. A warm air mass is moving into a cold air mass
3. Two air masses are next to each other, but neither is really moving
Which hemisphere…
1. Northern2. Southern
severe weather (the good stuff)
• defined as– thunderstorms– tornadoes– hurricanes– blizzards – heat waves– dust storms
thunderstorms
• we have an average of 40 of them per year; the high is central/southern Florida (>100/year)
• three critical conditions– water (vapor) in the lower atmosphere– change in temperature with altitude so that air
cools rapidly– air moving rapidly upward to take warm, moist air
up into the upper troposphere
1) moist air
need moisture in upper atmosphere, so need it to come from lower atmosphere
2) temperature change
if warm air cools slowly (or if there isn’t enough moisture) the forming cloud will evaporate as fast as it forms
3) updraft
taking the moisture upward has to be a continuing process
so what actually happens?
• rising moisture in warm air condenses
• growing cumulus cloud becomes cumulonimbus
• stage lasts about 10 minutes
• some lightning, little/no rain, but precipitation forming
Stage 1: developing stage (cumulus stage)
so what actually happens?
• mass of frozen precipitation becomes heavier than the cloud
• rising and falling masses of air
Stage 2: mature stage
• stage lasts about 20 minutes (can be much longer)
• black or dark green cloud• thunder/lightning/rain/
tornadoes
approximate altitude ofthe tropopause
so what actually happens?
• downdraft > updraft• rain decreases
Stage 3: dissipating stage
• lightning still a hazard• cloud dissipates
Hail….
• round or irregular pieces of ice• concentric rings
(This is in a person’s hand…)
Hailstone size Size (“) Updraft wind speed
pea 1/4 24 mph
penny 3/4 40 mph
quarter 1 49 mph
walnut 1 1/2 60 mph
golf ball 1 3/4 64 mph
tennis ball 2 1/2 77 mph
baseball 2 3/4 81 mph
tea cup 3 84 mph
grapefruit 4 98 mph
http://www.lightningsafety.noaa.gov/science.htm
If you would like to read more about lightning, go here:
Tornadoes…
• We hold the record here in the US– generally ~1200/yr– avg. 70 fatalities
• How do they form?– the classic answer: "warm moist Gulf [of Mexico] air meets cold
Canadian air and dry air from the Rockies" -