WEATHER SYSTEMS

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WEATHER SYSTEMS

• WEATHER AND CLIMATE

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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.

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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?

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What is your weather like today?

• Which picture describes your weather today?

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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.

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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.

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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

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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.

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I.T.C.Z
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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.

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Conditions associated with the I.T.C.Z

• Heavy rainfall
• Overcast skies with cumulus clouds
• Light and calm winds
• High temperatures

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ITCZ
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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.

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Tropical Waves
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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
  dont have a low pressure centre and strong winds.

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Tropical Waves
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Hurricanes
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Hurricanes

• Hurricanes are strong , low- pressure systems
  with strong winds of gt 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.

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Hurricanes

• Warm ocean water gt26 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.

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Hurricanes
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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.

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Hurricanes
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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.

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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.

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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.

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Anticyclones
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Weather associated with anticyclones

• Dry and sunny
• Clear skies
• Moderate winds
• Moderate temperatures