Tropical Revovling Storms Flashcards
Requirements for a TRS
Unstable Atmosphere
Pre existing disturbances
Deep warm ocean +26 degrees
5-25 degrees N/S for Coriolis
Stages of development of TRS
Tropical Disturbance - pressure drops/trough forms
Tropical Depression - Winds 20-33kts
Tropical storm - rotating winds 34-63 knots
Tropical revolving storm - winds greater than 64kt
Structure of a TRS
Eye - No cloud - Warm descending air - 20/50km
Eye wall - most severe winds and rain
Spiral rain bands - walls of cloud with clear bands of descending air
Average diameter of TRS
500km
Typhoons are located/time of year
South Pacific - July To October - 16 on average
Hurricanes - Located/Time of year
Mid Atlantic - Less than 10 on average
June to October
Cyclones - Location/Time of year
Indian Ocean - average of 7 a year
May to November
Bay Of Bengal - Indian Ocean
2 cyclones
Madagascar - cyclones
8 cyclones
E. Australia - Cyclones
5 cyclones
China Sea - Typhoons
16 on average
SW USA - Hurricanes
9 on average
SE USA
7 Hurricanes on average
Where do the most TRS occur
South Pacific - 16 on average
July to October
Most severe winds in TRS NH/SH hemisphere
NH - To the right of its track
SH - To the left of its track
Thermal Depression
Surface heating causes air to rise creating low pressure at surface - localised or large scale
Polar Low
Occurs in winter at high latitudes
Cold air passes over warmer water
Cold air gains energy from warmer sees triggering instability
Also lowers air density and overall pressure
100km long and usually last 48 hours
Orographic Low
Low pressure develops on lee side of mountain
Calm weather conditions
Cold front can cause severe TS to develop
What is the main energy source of a tropical revolving storm?
Latent heat from condensing water vapour
SW Indian Ocean
5 Cyclones on average
TRS Occur in NH between
June - October
Where is Orographic depression to be anticipated
On the lee side of the mountain range
Lee Low is
Air flow meets a mountain barrier as as it flows down the lee side warms and compresses and then produces convergence at surface forcing air to rise
Most intense if the wind flow is perpendicular to the mountain range and winds have a high velocity
West African Tornado (WAT)
Example of an easterly wave - disturbances close to the ITCZ which take the form of a line of thunderstorms moving east to west
March and November
The eye
Found at the centre
30-50km
Lowest surface pressure
Calmest conditions
Descending air warming at the DALR which causes eye to be warmer than the air in the eye wall
East of Darwin average cyclones
9
West of Darwin cyclones
5
Number of cyclones in India a year
12 per year
