Ch 19 - Tropical Revloving Storms Flashcards
Factors that a TRS needs to form
Coriolis - Gives us the rotation
Moisture - A lot of moisture to fuel the TRS
Warm seas - Over 26.5C (and deep)
The role of the Equatorial Low Pressure Belt
Has the maximum heating as it is the Heat equator ITCZ
Low pressure than means air is rising leaving low pressure on the surface
Depends on the land/sea masses and the season
TRS originate on the ITCZ
Easterly Waves (July)
When the equatorial low pressure belt is mixing with the Azores high in the south Atlantic
Storms develop and develop into a TRS if conditions are right (account for 80% of the storms that hit the US)
The ITCZ = low pressure which rotates anticlockwise which is why there is easterly airflow
Azores high (clockwise) mixes with ITCZ which forms; troughs of low pressure, convective activity which leads to storms/TS developing which impact N. America. Can develop on mainland Africa where there are lots of TS which then feed this system.
Hurricane Season in the US
Fed from the easterly waves in July/ August/ September
Can be as many as a couple of waves a week
~1 in a 100 turn into a TRS
Hence the uk gets the tail end of storms
Mesoscale Convective Systems/Areas (MCAs)
Groups or clusters of Cu/Cb which form on equatorial lows
Can be 100-1000km long and can last for 1-2 days
Can form multi-cell TS
Regions Affected by TRS
N America
China
NE Pacific
N India
Madagascar
W Australia
N Australia
Northern Hemisphere TRS Season
June to October
Southern Hemisphere TRS Season
January to march
N. Atlantic
Hurricanes
10-12 a year
N.E Australia
Cyclones
9 Per season
S. China Sea
Typhoons
25
N. E. Pacific
Hurricanes
16/17
N India
Cyclones
5/6
Madagascar
Cyclones
10/11
W. Australia
Cyclones
7
N Australia
Cyclones
2
TRS Stages of Development
Tropical Disturbance - Pressure drop/trough/ trigger of some sort
Tropical Depression - TS, Winds 20-30kts
Tropical Storm - TS with rotating winds 34-63kts and is now named
*Severe Tropical Storm (CTB)
Tropical revolving Storm - Wind >64kts rotating around a defined core
Development of a TRS
Convection - rising air - cools - condenses - latent heat released - warming - capacity for moisture increases
Source - deep warm seas
Will have an eye - with the walls being the most violent part of the storm in terms of wind speed and turbulence
Can reach the tropopause
Calm in the eye of the storm
Size of Cyclone
Average size 500km < 2000km (whole storm)
Storm Eye; 20-50km
the storm eye is an area of descending air and therefor high pressure
Average heigh - 12km
Usually 8-12 degrees n/s of the EQ
Shown by TCAC
Also on WMO advisory reports
