hanna mcphee and Ml dixon- red

What is a Hurricane?

  • Severe tropical storms that rotate in a counter-clockwise direction around an "eye."
  • Wind speeds range from 74 mph. to more than 155 mph.
  • The most dangerous parts of hurricanes are storm surges (large waves created by hurricane winds)
  • Hurricanes are categorized by the saffir-simpson and beaufort scale hurricane scale.


Tropical Cyclone Classifications (all winds are 10-minute averages)
Beaufort scale
10-minute sustained winds (knots)
N Indian Ocean
IMD
SW Indian Ocean
MF
Australia
BOM
SW Pacific
FMS
NW Pacific
JMA
NW Pacific
JTWC
NE Pacific &
N Atlantic
NHC & CPHC
0–6
<28
Depression
Trop. Disturbance
Tropical Low
Tropical Depression
Tropical Depression
Tropical Depression
Tropical Depression
7
28-29
Deep Depression
Depression
30-33
Tropical Storm
Tropical Storm
8–9
34–47
Cyclonic Storm
Moderate Tropical Storm
Trop. Cyclone (1)
Tropical Cyclone
Tropical Storm
10
48–55
Severe Cyclonic Storm
Severe Tropical Storm
Tropical Cyclone (2)
Severe Tropical Storm
11
56–63
Typhoon
Hurricane (1)
12
64–72
Very Severe Cyclonic Storm
Tropical Cyclone
Severe Tropical Cyclone (3)
Typhoon
73–85
Hurricane (2)
86–89
Severe Tropical Cyclone (4)
Major Hurricane (3)
90–99
Intense Tropical Cyclone
100–106
Major Hurricane (4)
107-114
Severe Tropical Cyclone (5)
115–119
Very Intense Tropical Cyclone
Super Typhoon
>120
Super Cyclonic Storm
Major Hurricane (5)

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How Hurricanes Form

They need these conditions:
  • Low air pressure
The low pressure rising makes it possible for new, high pressure to replace it. This causes the formation of the eye and circulation. This is also the start of a hurricanes violent winds that create storm surges.
The low Pressure
  • Warm temperatures
The water emperatures for a hurricane must be at least 80 degrees farenheit to a depth of 50 meters. This and warm temperatures from the sun cause the water to evaporate and to make an unstable atmosphere which creates the actually thunderstorm and convection to kickstart and sustain a hurricane.

external image hurricane_formation.jpg
  • Moist/cool ocean air
The cool ocean air makes it possible for the warm water vapor to cool quickly. It is necissary for the water vapor to cool at a fast rate becasue this releases the energy, or latent heat of the hurricane. The moist air also helps create an unstable atmosphere to heighten the chances of a more violent disturbance/thunderstorm to start or create more energy for the hurricane.

external image Hurricane_Formation.gif
  • Tropical winds (near the equator)
The coriolis effect deflects the winds, such as the tradewinds, moving twords the low pressure points. These two winds counteracting eachother creates circulation and movement.

external image hurricane_structure_new.jpg



Hurricane Steps to Formation
  1. The warm temperatures create water vapor that rises
  2. The water vapor cools as it goes higher into the atmosphere and starts to condense
  3. This water vapor and condensation makes the air lighter and it continues to rise
  4. Meanwhile, warm moist air is moving over the ocean taking the place of the water vapor that has just risen
  5. This creates a wind and repeats itself until a cyclonic pattern formsexternal image image004.jpg

Also Review...

  • Hurricane Lab
  • Hurricane Test
  • Chapter 30/page 556 in Textbook