Engineering Geology and Geohazards Lecture 4: Tropical Cyclones

Question 1

Define a tropical cyclone

Answer 1

generic term for a
non-frontal low-pressure system over tropical
or sub-tropical waters with organized
convection.

Question 2

List the requirements of a tropical storm/cyclone

Answer 2

• A warm sea temperature in excess of 26 degrees Celsius to at least 50m in depth.
• High relative atmospheric humidity
• Atmospheric instability & light wind
• A location of at least 4 - 5 latitude degrees from the Equator or 500 km N-S
  (Coriolis force)

Question 3

How are tropical storms classified?

Answer 3

classified by the maximum
sustained surface winds velocity*
that they hold.

Question 4

Lists the wind speed of different tropical storm classifications

Answer 4

Wind Speed
(Km/h)

Tropical Depression 36- 63

Tropical Storm 64- 117

Hurricane >118

Question 5

List the saffir simpson wind speeds(W/S= Wind speed) for hurricane category classification

Answer 5

W/S (Km/h) Pressure(Mbars)
Cat 1 - 118- 152 >980 mb
Cat 2 - 153-176 965-979 mb
Cat 3 - 177- 208 945-964 mb
Cat 4 - 209- 247 920-944 mb
Cat 5 - >248 < 919 mb

Question 6

What are the main hazards associated with tropicals storms

Answer 6

Strong winds – Causing
1. Widespread damage
2. Storm surges

Heavy rainfall – Causing
1. Flooding
2. Landslides
3. Land erosion