1. Atmospheric Disturbances
Tropical Storms & Cyclones

2. Intro to Tropical Storms
Storms are regional atmospheric disturbances.
Storms have high winds and most have precipitation.
2 major categories of storms:
Tropical cyclones occur in tropical regions (within Hadley cells)
Extratropical cyclones occur in Ferrel cells and are winter weather disturbances.
Both types of storms are cyclones which are rotating masses of low-pressure air.

3. Tropical Storms Around the Globe Atlantic - hurricanes
Named from Caribbean god Huracan
Western Pacific – typhoons – most common
Named from the Chinese word for “great wind”
Indian Ocean and Australia – cyclones
South Atlantic - almost none

4. Tropical cyclone genesis areas and related storm tracks

5. Hurricane Formation Steps in the formation of hurricanes
Tropical disturbance  Tropical depression
Tropical storm -- winds greater than 37 mph
Hurricane, Typhoon, Cyclone -- winds greater than 74 mph
5 categories from the Saffir-Simpson scale based on the hurricane wind speed

6. Classification of Tropical Cyclones
V. Storms
Classification of Tropical Cyclones

7. Tropical Cyclones form in one air mass
Air mass-A large mass of air with nearly the same temperature, humidity, and density
Tropical Cyclones form from the Trade Winds because they need a warm climate
Latent heat-the heat required to convert something into a different state of matter (Ex. solid  liquid or vapor, liquid  vapor) without change of temperature.

8. How a Tropical Cyclone Forms
Warm, humid air forms in great quantity only over a warm ocean.
When hot, humid tropical air rises and expands, it cools and is unable to contain the moisture it held when warm.
Rainfall begins.
Tremendous energy is released as this moisture changes from water vapor  liquid.

9. V. Storms
The dynamics of a tropical cyclone, showing the influence of the Coriolis effect. Note that the storm turns the “wrong” way (that is, counterclockwise) in the Northern Hemisphere, but for the “right” reasons.

10. Tropical cyclone structure
Hurricane characteristics
Sustained winds greater than 120 km/hr (74 mph)
Average diameter = 600 km (350 mi)
Central pressure = ~ 950 mb to 870 mb

11. V. Storms
(b) How precipitation develops in an extra-tropical cyclone. These relationships between two contrasting air masses are responsible for nearly all the storms generated in the polar frontal zone and thus responsible for the high rainfall within these belts and the decreased salinities of surface waters below.

14. Vertical temperature profile across a hurricane
Hurricane eye
-- average diameter = 25 km (15 miles)
-- area of descending air
-- strongest winds in eye wall (clouds just outside eye)
Hurricane eye

15. The double eye wall of Hurricane Emily
Hurricane with a double eye wall (occurs near maximum strength)
eye walls

16. Hot tower in Hurricane Rita
A hot tower is a part of the eye wall that rises to great height (up to 36 km); it can indicate hurricane strengthening

17. Erratic hurricane path examples
Hurricane paths are controlled by trade winds, upper air flow, air pressure systems and ocean temperatures; they can be quite erratic.

19. V. Storms
The warmest waters (shown in orange) are the breeding grounds of tropical cyclones are shown as orange-shaded areas. The storms follow curving paths: First they move westward with the trade winds. Then they either die over land or turn eastward until they lose power over the cooler ocean of mid-latitudes.

20. Predominant Atlantic hurricane paths

23. How a Tropical Cyclone Dies
Can lose power over cooler land
Can lose power over cooler ocean mid-latitudes (in Ferrel Cells) curving farther north or farther south

24. V. Storms
The Atlantic Hurricane Season of 2005 Was the Most Destructive Ever Recorded
A record 28 tropical cyclones formed, and 15 of these became hurricanes.
Three hurricanes reached category 5 strength.
One of these was Hurricane Katrina, the most costly natural disaster to befall the United States.
Another was Wilma, the most intense Atlantic hurricane ever seen.

25. V. Storms
The Atlantic Hurricane Season of 2005 Was the Most Destructive Ever Recorded (cont’d.)
The 2005 season was extraordinarily costly in lives and property:
Total damage estimates exceed US$100 billion, and at least 1,777 dead.
More than 1.5 million people were displaced, the greatest number since the Great Depression of the 1930s.

26. Hurricane Destruction and Fatalities are caused by several factors:
Wind
Heavy rain
Tornadoes
Storm surge-Rise in water level associated with pressure drop

27. Blown sand from Hurricane Katrina

28. Extratropical Cyclones Form between Two Air Masses
V. Storms
Extratropical Cyclones Form between Two Air Masses
(a) The genesis and early development of an extratropical cyclone in the Northern Hemisphere

29. Extratropical Cyclones
Don’t become hurricanes or typhoons, but they cause weather patterns
Cause strong winds, huge waves, and rain/snow
Can form nor’easters: big, cold, storms in the north causing heating bills to rise, less fishing & shipping, and destruction

30. Heat transfer of cyclones
Tropical cyclones-are necessary to move large amount of heat from tropics to higher latitudes quickly (faster than convection)
Extratropical cyclones-mix warmth from tropics with polar air to redistribute heat important to life on earth!

31. Review Video Severe Tropical Storms
What are hurricanes, typhoons, and tropical cyclones?

32. Video Questions Indian Ocean storms are called what?
Western Pacific storms are called what?
Atlantic Ocean storms are called what?
From where do hurricanes draw their energy?
What 2 elements do hurricanes need to form around?
What speed must air be spinning to be a category 1 hurricane?
What is the most destructive category of hurricane?
What is the clear zone in the center of the hurricane?
What is a wall of seawater hitting land called?