Tropical Weather Systems
PHYSICAL GEOGRAPHY 101

Tropical and Equatorial Weather Systems

Tropical and Equatorial Weather differs from Mid-latitude and High Latitude weather in the following ways:
1)
2)
3)
4)

Easterly Wave

Trough of low pressure.
Moves westward due to easterly Trade Winds.
Form between 2-30° Lat.
Showers form on the eastern side of the trough where converging winds are forced to rise.

Equatorial Lows

Occur along the Intertropical Convergence Zone.
Shifts with the seasons.
Small weak storms are often associated with these low pressure centers.

Tropical Cyclones

Hurricanes
Typhoons
Cyclones

Stages of Hurricane Development

1) Tropical Disturbance - wind speeds <20 knots (23 mph)
2) Tropical Depression - wind speeds 20-34 knots
3) Tropical Storm - wind speeds 35-64 knots
4) Hurricane - wind speeds >64 knots (74 mph)

Hurricanes

Circular storms which always begin forming over warm, equatorial waters.
Evaporation and latent heat release drive the storm system by increasing precipitation and more evaporation.
No coriolis effect at the equator, weak coriolis effect where most hurricanes begin development.
As the storm system moves poleward, coriolis effect becomes stronger - faster rate of spin develops.
Characteristics include: very low pressure center, central eye - a calm area in the center of the storm, intense precipitation, and high winds.

Saffir-Simpson Hurricane Damage Potential Scale

Scale Number	Central Pressure (mb)	Winds (mph)	Storm Surge (ft)	Damage
1	> 980	74-95	4 - 5	damage mainly to trees, shrubbery and unanchored mobile homes
2	965 - 979	96-110	6 - 8	some trees blown down; major damage to exposed mobile homes; some damage to building roofs
3	945 - 964	111-130	9 - 12	foliage removed; large trees blown down; mobile homes destroyed; some structural damage to small buildings
4	920 - 944	131-155	13 - 18	all signs blown down; extensive damage to roofs, window and doors; complete destruction of mobile homes; flooding inland
5	< 920	>155	> 18	severe damage to windows and doors; extensive damage to roofs; small buildings overturned and blown away; major damage to lower floors of all structures less than 15 feet above sea level within 500 meters of shore.

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