Extreme weather events

What are the 3 tropical storms and how are they determiend?

• Hurricane

• Typhoon

• Cyclone

• Determined by region

What is a tropical cyclone?

• Large scale rotating storms that form over tropical oceans. They spin due to the deflection of moving air by the Coriolis Effect

What is the name of the area where topical cyclones form?

Source area

What is the track in tropical cyclones?

Tropical cyclones move away from the source area following prevailing winds + ocean currents.

What time period do tropical cyclones occur in the Northern Hemisphere?

June to November because oceans are warmest

What time period do tropical cyclones occur in the Southern Hemisphere?

April to November because oceans are warmest.

Attributes of a tropical cyclone?

• Ocean temperatures above 26.5 degrees celcius

• Wind increases in strength at the eye wall because of the big difference in pressure

• Storm surge in cyclone centre is caused by increased sea level due to strong surface winds pulling water up

• Warm moist air rises because it’s less dense, overtime creates eye + pulls more air to the centre

• Winds rotate outwards at the top

• Clear sky + no winds or clouds in the eye

• Dense cirrus cloud (highest cloud -icy ) canopy

• Heavy rain + strong winds in the eye wall

How do tropical cyclone start?

They start with a cluster of towering thunderstorm clouds.

In warm oceans because there’s high energy

Needs light / low crosswinds

Strong vertical currents rotating because of the coriolis effect

What is storm surge?

Bulge of seawater created by low pressure in the eye + high windspeeds in the eyewall, increases death rate

How are tropical cyclones formed?

1. Tropical cyclones form in tropical areas where warm, moist air is found (above 26.5)

2. High temperatures cause moist air to rise away from the ocean surface

3. The moist air creates thunderstorms to form and some group together

4. This grouping causes a strong upward flow of warm air creating extremely low pressure at the centre of converging storms

5. Air with higher pressure moves in to replace it

6. Because the Earth spins, air does not move in to replace it in a straight line but instead whirls into it (coriolis)

7. The upward moving air causes the storm to start spinning leaving a low pressure funnel in the centre

8. Because of trade winds, the storm starts to move sideways

9. This huge storm creates a large area of low pressure below it which can create a storm surge where the level of sea rises upwards

What are the factors affecting intensity of tropical storms?

• Humidity - lots of moisture needed to source the storm clouds

• Rapid cooling- rising air must condense quickly to produce large amounts of energy to power a cyclone

• Low wind sheer (crosswinds) - cyclones cannot form if winds are blowing in all directions

• Low pressure - cyclones usually form when smaller storms group together

Factors affecting dissipation of tropical storms?

• Cold ocean - no rising air

• Land - no water source

• High wind sheer (crosswinds) - no convergence of storms

What is dissipation of tropical storms?

Cyclones loss of energy and decreasing of intensity