CLIMATE: JAMAICA
Climate is the average state of the weather. And weather is concerned with daily changes
in temperature, wind, cloud and rain. When we examine the climate of Jamaica we look
at:
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Temperature (degree of heat and cold)
Winds (their movement and direction)
Rainfall (its causes and its seasons).
TEMPERATURE
How hot or cold a place is depends mainly on how far it is north or south of the equator.
The higher the latitude the colder the climate.
What is the latitude of Jamaica? If you look at the globe you will see that Jamaica is in the
tropical zone south of the Tropic of Cancer. However, its distance north of the equator
has a moderating effect on its temperature, and hence Jamaica is said to have a semitropical climate.
Apart from latitude, the greatest factor in determining the temperature of a country is
altitude.
Most of the effective heat we enjoy is radiated from the earth’s surface, which has been
warmed by the sun. In reaching the surface of the earth the sun’s rays have to pass
through layers of atmosphere, a process that causes it to lose some of its heat.
If we imagine these layers of atmosphere as blankets retaining the heat radiated by the
earth’s surface we will see that by climbing above these layers it will become colder.
Temperature decreases by 1.7 degrees Celsius for every 100 metres of ascent.
Because Jamaica is a very mountainous country, temperatures vary widely in different
parts of the island. For example, the temperature might drop to about 10 degrees C in
Mandeville, (626 m), while in Kingston the mean temperature is 26 degrees C.
On the whole, Jamaica’s climate has no extremes, especially since the surrounding sea
has a moderating effect on the weather, and the variety of climate is considered healthy
and beneficial.
CLIMATE: JAMAICA (2)
WINDS
Local winds, from the sea by day and from the land at night, are very noticeable in
Jamaica because it is an island. The prevailing winds in the West Indies are from the
north-east.
RAINFALL
The heat of the sun, like the fire under a kettle, turns water into water vapour. This
process is called evaporation. If the temperature of air is lowered, the water vapour it
contains in the form of clouds will fall as rain. This process is called condensation.
Jamaica has two rainy seasons, the first in May and the other in October and November.
As a rule, rain follows the sun. It appears to pass over all places between the Tropics of
Cancer and Capricorn twice a year. In Jamaica the sun is directly overhead about the
second week in May and in early August.
The periods of heavy rainfall reach their maximum shortly after the sun has been directly
overhead.
HURRICANES
A hurricane is a storm revolving around a centre of low pressure that contains almost no
wind.
As a hurricane develops, the winds from the area of high pressure rush towards the lowpressure centre. Powerful gales of up to 200 kilometres (120 miles) per hour are built up.
The calm vortex in the centre, the 'eye' of the hurricane, varies in diameter from thirty to a
few hundred miles, and usually moves westwards. Hurricanes are invariably
accompanied by driving rains.
Nowadays weather stations discover hurricanes as soon as they develop and give
warning to those places towards which a hurricane may be heading. On the approach of
a hurricane the barometer falls and the thermometer usually rises.
The hurricane season is between July and October, though a hurricane may occasionally
arise in June or November. On September 12, 1988, Jamaica suffered the worst
hurricane in living memory when Hurricane Gilbert devastated the island.