11. Formation of Tropical Storms Flashcards
(34 cards)
What are tropical storms?
Very intense areas of low pressure which creates huge storms with high winds, heavy rain and storm surges.
They are a natural weather phenomenon which can be expected in certain latitudes and at certain times of the year.
What do tropical storms play an important role in?
Redistributing heat from the tropics towards the poles -> without them the global climate would be very different.
What does cloud and rain do?
Extend in a series of waves from the eye wall
Where is the most powerful part of the storm?
The bank of cloud that circles the central eye -> this is where the winds are most devastating
What do fully formed mature tropical storms have?
A central eye around 10-15 kms in diameter -> the descending air creates calm, clear conditions with higher temps
Stage 1
The sun warms the oceans to a critical 27 degrees Celsius
Stage 2
This draws water vapour up from the ocean surface.
The warm air rises quickly under low pressure conditions.
Stage 3
The rising air evaporates and condenses to form thunderstorm clouds. As the air condenses, it releases latent heat which powers the storm and draws up more water.
Stage 4
Several smaller thunderstorms join together to form a giant spinning storm. When surface winds reach 74 mph, the storm officially becomes a tropical storm.
Stage 5
The storm now develops an eye at its centre,
The outer edge of the eye is the eyewall where the most intense weather conditions (strong winds and heavy rain) are felt.
Stage 6
The Coriolis effect causes the air to spin upwards around a central calm eye of the storm.
Cold air sinks in the eye, therefore there is no cloud, so it’s drier and much calmer.
Stage 7
As the storm is carried across the ocean by the prevailing winds, it continues to gather strength.
Stage 8
On reaching land, the storm’s energy supply (evaporated water) is cut off.
Friction with the land slows it down and it begins to weaken.
If the storm reaches warm seas after crossing the land, it may pick up strength again.
What areas do tropical storms form?
Only form in areas between 5-30 degrees north and south of the equator where the high rates of insolation from the sun warm the oceans.
When are tropical storms most common?
in Summer and Autumn when sea temps are highest
What kind of wind do tropical storms need?
Need a low wind shear (wind that remains constant and doesn’t vary with height).
This allows tropical storm clouds to rise to high levels without being ripped apart.
What sea temps do tropical storms form at?
Only form when sea temps are 26/27 degrees celsius and above depth of 70m.
This provides heat and moisture that causes warm air to rise rapidly, creating a deep area of low pressure. Latent heat is then released to power the storm.
Why don’t tropical storms usually form on the equator?
The coriolis effect is too weak to allow storms to start spinning. The coriolis effect increases with distance from the equator.
Where are tropical storms most likely to form?
Where there is atmospheric instability and warm air is forced to rise.
The Inter-Tropical Convergence Zone where 2 limbs of the Hadley Cell meet to form low pressure on the ground is a perfect place for tropical storms to form.
What is used to classify tropical storms?
The Saffir-Simpson Scale
Based on sustained windspeeds and has 5 categories.
What is the NOAA prediction based on?
- sea surface temps
- atmospheric conditions
- climate seasons such as El Nino and La Nina
Can tropical storms be predicted?
To an extent they are predictable as they are restricted to the tropics and occur in Summer and Autumn
Strong winds description
Tropical storms are powerful with average wind speeds in excess of 120km/h
Cause of tropical storms
- A deep area of low pressure and the deeper the low pressure, the stronger the wind as bigger diffs.
- The bigger the pressure difference, the stronger the winds.
