Form 4 option lesson

1. Weather and Climate
A Revision of Topics
Mr. T. Tonna

2. Index
 Topic One: Depressions
 Topic Two: Anticyclones
 Topic Three: Tropical Storms
– Case Study: Hurricane Katrina, 2005
 Topic Four: Micro-Climate of an Urban Area
 Topic Five: Climate of The Maltese Islands
 Class Quiz- Who Wants to be a Millionaire?
Mr. T. Tonna

3. Depressions
 Depressions are low pressure systems that
form in the mid-latitude region (30 -60 N/S)
when warm air meets cold air.
 When this occurs the warm air is forced
above the colder air. It then cools and
clouds form which produce rain.
Mr. T. Tonna

4. Mr. T. Tonna
Warm Front Cold Front Occluded
Front
The Beginning
of the
depression
The End of
the
Depression
When the
warm and cold
fronts join.

5. Mr. T. Tonna

6. Anticyclones
 Anticyclones are formed from an area of high
pressure.
 They tend to bring clear, settled weather.
 In an anticyclone, air descends and pressure
increases. This brings very light winds (which blow
outwards from the centre in a clockwise motion),
clear skies and dry conditions (because the air is
descending and warming up, there are no clouds
and no rain).
Mr. T. Tonna

7. Mr. T. Tonna
Winter
Anticyclones
Summer
Anticyclones
Dry and bright with very little
cloud.
Very little cloud
Sun low in the sky, so cold
conditions.
Dry with light winds
Clear evening skies mean that
nights can be very cold.
Sun high in the sky, so hot and
sunny
Early morning frost and fog
may last all day.
Cloudless skies at night allow
heat to escape, so nights can
be cool.
Extensive low cloud or fog may
produce overcast or ‘gloomy’
conditions.
Risk of thunderstorms at end of
‘heat wave’ conditions
Early morning dew and mist.

8. Tropical Storms
 Tropical storms are areas of extremely low
pressure, they produce violent weather with high
winds, thick cloud and torrential rain.
 There are three main criteria needed for a tropical
storm to develop:
 Warm Tropical Oceans (Temperature of 24 C or more)
 Late Summer early Autumn where sea temperature is
optimum.
 In Certain Latitudes: 5 -20 North and South.
Mr. T. Tonna

9. Mr. T. Tonna

10. Hurricane Katrina (2005)
 Hurricane Katrina formed as Tropical Depression over the
south-eastern Bahamas on August 23, 2005. It grew into a
Category 5 Hurricane.
 New Orleans had: Winds over 175miles per hour (over
280km/h); An estimated 80 percent of New Orleans was
under water, up to 20 feet deep in places; The centre eye
had a low pressure of 920 mbar.
 1 million people homes destroyed $81 billion in damages.
 Oil facilities were damaged and as a result petrol prices
rose in the UK and USA.
 Total Estimated Damages exceeded $150 billion in
Louisiana and Mississippi alone.
Mr. T. Tonna

11. Micro-Climate of an Urban Area
 A Micro-climate is a local atmospheric zone where the
climate differs from the surrounding area.
 Human activity has a big influence on the climate of an
urban area.
 Climate in Urban Areas are affected by human factors
such as pollution, the colour of buildings, people
themselves and factories etc.
 An urban heat island (UHI) is a metropolitan area that
is significantly warmer than its surrounding rural
areas due to human activities.
Mr. T. Tonna

12. Mr. T. Tonna

13. Climate of the Maltese Islands
 The climate is typically Mediterranean, with hot, dry summers,
warm and sporadically wet autumns, and short, cool winters with
adequate rainfall. Nearly three-fourths of the total annual rainfall
of about 600 millimetres (24 inches) falls between October and
March; June, July, and August are normally quite dry.
 The Rainfall and Temperature are highest in July and lowest in
December.
 Malta is extremely windy with only 7.7 % days considered as
calm. Most common wind is the north-westerly ‘il-Majjistral’
(19% of the days in a year).
Mr. T. Tonna

14. Mr. T. Tonna

15. Quiz Time
Mr. T. Tonna