Large and Small scale atmospheric disturbances

Question 1

Hurricane formation necessities

Answer 1

1.* warm oceans with surface temperatures in excess of 27°c, and a deep layer of water to 60m
2.* A location between 5°c N and S of the equator (without this, the Coriolis force is not sufficient to create the spinning motion characteristics of hurricanes)
3. *relatively stable and uniform atmospheric conditions of temperature, humidity and pressure - in the upper troposphere, air drawn in at lower altitudes must be able to escape
4. relative humidity over 60% to provide sufficient energy to power the hurricane
5. little change of horizontal wind with height
6. existing cyclonic spinning of winds in the lower troposphere

• most important

Question 2

hurricane formation broken down

Answer 2

• As this weather system moves westward across the tropics, warm ocean air rises into the storm, forming an area of low-pressure underneath
• This causes more air to rush in
• The air then rises and cools, forming clouds and thunderstorms
• Up in the clouds, water condenses and forms droplets, releasing even more heat to power the storm
• When wind speeds within such a storm reach 74 mph, it’s classified as a hurricane

Question 3

hurricane facts + terminology

Answer 3

• The eye (middle of the storm) is between 5-50km high
• The main throat of the storm can be between 10-20km wide
• The main cyclonic circulation (swirling motion of winds) of the storm is between 3-7km
• Hurricanes can cause storm surges (secondary hazard)

Question 4

How can hurricanes be classified?

Answer 4

• Wind speed
• Height of storm surge
• Pressure
• Damage

Question 5

How is hurricane intensity measured?

Answer 5

saffir-Simpson scale which goes from category 1-5 based upon sustained wind speed

Question 6

what are the Hazards associated with hurricanes?

Answer 6

Storm Surges:
- Tropical storms and hurricanes generate storm surges from the drag of wind over the water.
- The height of storm surges relates to the storm size, strength and forward speed.
- Storm surges account for 90% of deaths resulting from tropical cyclones, and extensive damage to agricultural land by salt contamination from sea water.
- Short term impacts include death and injury from drowning or building collapses, destruction of infrastructure, homes and businesses destroyed

Wind Speed:
- destruction of buildings and flying debris

Associated rainfall:
- risk of further flooding
- mass movement
-

Question 7

Tornado formation

Answer 7

1. The sun heats the ground and air near the surface is warmed and rises. This forms shallow cumulus clouds.
2. If the atmosphere is unstable, this warm air rises higher creating tall cumulonimbus clouds.
3. At altitude, wind shear can occur creating an upper air inversion, and the faster moving air can begin to spin and roll over the slower air below. Creating an invisible horizontal wind, rolling and spinning cylinder.
4. Powerful warm air updraughts tilt the cylinder vertically, creating a column of spinning winds.
5. Falling downdraughts of cold air within the supercell help bring the column downwards.
6. If this reaches the ground, a tornado is formed