Transcript today • Hurricanes • Beginning of a video

today
• Hurricanes
• Beginning of a video
– the video will be at the library (“Hurricane
Katrina: the storm that drowned a city”) on
reserve in media services
READ for Wednesday
• first two pages of ch. 8
• sec. 8.2: Tropical cyclones
• p. 246 (Hurricanes)
• go on-line and watch
http://learners.gsfc.nasa.gov/mediaviewer
/birth_hurr/
Clickers, of course (you’re
here and so you get credit)
Hurricanes (“tropical
cyclones”)
• A hurricane is a type of tropical cyclone:
low-pressure system that forms in the
tropics
• Accompanied by thunderstorms
• Hurricane is used in the northern Pacific
and Atlantic Oceans
• Names of Atlantic hurricanes are rotated
on 6-yr basis
A joke when I was a kid…
• Why don’t hurricanes ever have boy’s
names?
A joke when I was a kid…
• Why don’t hurricanes ever have boy’s
names?
• Have you ever heard of a himicane?
(Boys and girls names used since 1979)
• Other ocean basins have names
generally more applicable to the
cultures of people who live there
Some 2005 statistics
• 28 named storms (21 in 1933)
• 15 hurricanes (12 in 1969)
• 4 major hurricanes hit the US (3 in 2004
and other years)
• 7 tropical storms before Aug. 1 (5 in
1977)
And some hurricane facts
• Generally ~ 300 miles (500 km) wide
• The eye at the center is generally 20-40
miles across (30-65 km)
• Hurricane-force winds stretch outwards
from the center of the storm anywhere
from 25 to 150 miles (40 - 240 km)
• The right side of the storm is more
dangerous
How do hurricanes form?
• Need
– warm seawater
– warm air
– weak winds
– Coriolis effect
stages
•
•
•
•
Tropical disturbance
Tropical depression
Tropical storm
Hurricane
Tropical depression: disorganized group of thunderstorms
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/stages/td.rxml
If your last name starts with H - P, please put
your name on a piece of paper, together with
the name of the person next to you, and answer
this:
What happens to the warm rising air in the
center of a growing tropical storm (and
why) ?
Tropical storm (Katrina, Aug. 30, 2005)
http://www.nnvl.noaa.gov/hurseas2005/Katrina1315z-050830-1kg12.jpg
Eye and eyewall of the hurricane
• Winds can’t get in to the core
• Air sinks in the core
• Strongest winds
in the system in
the eyewall
NASA photo
How do hurricanes die?
• need warm water to replenish system
– need warmth
– need water
• need weak wind
Why is damage greater on the
“right” side of a hurricane?
20 mph
100 mph