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WEATHER SYSTEMS
WEATHER AND CLIMATE
Weather
 Weather describes the conditions of the
atmosphere at a particular time.
 Climate describes the long term
atmospheric characteristics. It deals with
average figures of each element over a
period of time, (e.g. average monthly
temperatures) etc.
What is Weather
 Weather describes whatever is happening
outdoors in a given place at a given time. Weather
is what happens from minute to minute.
 The weather can change a lot within a very short
time. For example, it may rain for an hour and then
become sunny and clear.
 Weather includes daily changes in precipitation,
barometric pressure, temperature, and wind
conditions in a given location. What is your
weather like today?
What is your weather like today?
 Which picture describes your weather
today?
What is Climate
 Climate describes the total of all weather
occurring over a period of years in a given
place. This includes average weather
conditions, regular weather sequences (like
winter, spring, summer, and fall), and
special weather events (like tornadoes and
floods). Climate tells us what it's usually like
in the place where you live.
DIFFERENCES BETWEEN THE
TWO
 Weather is the actual conditions in the
atmosphere at a particular place and time
over a twenty four hour period.
 Climate is the average atmospheric
conditions a place gets based on a period of
over thirty years.
 The climate of a place is described as its
average weather conditions.
Caribbean weather systems
 A weather system is a large area of the
atmosphere that has special temperature
and moisture conditions.
 INTER TROPICAL CONVERGENCE ZONE
 TROPICAL WAVES
 HURRICANES
 COLD FRONTS
 ANTICYCLONES
I.T.C.Z
 The ITCZ is an area of low pressure lying
east to west across the equatorial region.
 The hot air from the north east trade winds
meet the hot air from the south east trade
winds in this region.
 The hot moist air is forced to rise, resulting
in rainfall.
 This belt of low pressure moves north and
south of the equator with the seasons.
I.T.C.Z
I.T.C.Z
 In June it drifts northwards and may affect
Trinidad and Tobago and the rest of the
southern Caribbean.
 In December it drifts south and affects
Guyana. It is also active in March and
September when the hottest place is the
equator.
Conditions associated with the
I.T.C.Z
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Heavy rainfall
Overcast skies with cumulus clouds
Light and calm winds
High temperatures
ITCZ
Tropical Waves
 They are weak, low pressure systems that
lack a closed centre.
 They form near Africa over the warm waters
of the Atlantic Ocean and move westwards
into the Caribbean.
 They affect most of the islands of the
Caribbean during the months of June to
December.
Tropical Waves
Conditions associated with
Tropical Waves
 Moderate winds
 Heavy and continuous rainfall
 Overcast skies
 High temperatures.
Tropical waves can eventually develop into
hurricanes. They are not hurricanes since
they don’t have a low pressure centre and
strong winds.
Tropical Waves
Hurricanes
Hurricanes
 Hurricanes are strong , low- pressure
systems with strong winds of > 120 km per
hour.
 Winds blow into them in an anti-clockwise
direction with heavy rainfall.
 They start off as tropical waves near Africa
and move into the Caribbean during June to
December.
Hurricanes
 Warm ocean water >26 degrees celsius.
 Coriolis effect north and south of latitudes
10 degrees north and south, this causes the
spiral motion of the hurricane and influences
its path.
 Divergent upper level winds allowing
updraughts of air.
 Most Caribbean islands are affected by
hurricanes.
Hurricanes
Hurricanes
 Wind speeds above 120 km/ hour.
 Wind direction varying between north east and
south east.
 Torrential rain
 Overcast skies with towering cumulonimbus
clouds.
 Thunderstorms with lightning.
 Temperatures remain high averaging 27 degrees
celsius.
Hurricanes
Cold Fronts
 A front is an area where two air masses of
different temperatures meet.
 Cold dry air moves south from the North
American continent and pushes under the
warm, moist Caribbean air.
 The rising warm air cools and condenses
resulting in heavy rainfall.
Weather Associated with Cold
Fronts
 Cooler temperatures,
18 – 21 degrees
celcius.
 Moderate rainfall that
lasts for days
depending on the
movement of the
frontal system.
 Moderate cloud cover
 Winds from the north.
Anticyclones
 Anticyclones are high pressure systems.
 Winds blow out of them in an anti- clockwise
direction.
 They form around mid- latitudes and may
drift into the Caribbean. They are stable with
sinking air blowing out of the centre.
 They affect most of the Caribbean north of
Trinidad and Tobago.
Anticyclones
Weather associated with
anticyclones
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Dry and sunny
Clear skies
Moderate winds
Moderate temperatures