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

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/stages/td.rxml

Tropical depression: disorganized group of thunderstorms

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