South African Weather Flashcards
The cold Benguela currents affect the -
West coast
The warm Agulha currents effect the -
East coast
South African Winter Patterns:
- The _____ and ______ high pressure systems move _________, bringing ________ winds to the south and south western coastal regions.
- With the absence of the heat lows to the interior the _______ and ____ highs are linked across the land. Generally cool to cold conditions prevail.
- A separate cell of ___ pressure usually forms over the _____ to _______ interior. This subsiding air results in clear skies and calm conditions over large parts of the interior.
- During the South African winter the ITCZ moves well ____ of the equator (between _ degrees N and __ degrees N). This results in the disappearance of the ____ ____ monsoon. The south east trade winds still blow, move across the equator and re-curve north eastwards to become part of the great summer monsoon of India.
- The _____ ___ monsoon moves further ____, crossing the coast well ____ of _____. This results in the Congo Air Boundary moving much further ____.
- With the northwards movement of the Indian and Atlantic high pressure systems, mid Atlantic depressions linked with cold fronts invade the ________ regions of South Africa. On occasions these cold fronts have influenced regions as far north as Zambia under unusual conditions where a strong high pressure systems follows closely behind the cold front.
- Cloudy conditions associated with rain influence the southern, south western and south eastern coasts. Uplift is mainly due to cyclonic or frontal actions, but orographic uplift does occur over the escarpment where where snowfall may occur. Interior snowfall usually occur with the presence of a strong high following closely behind the cold front, thus pushing the cold air into the interior. A strong upper air low aids with the uplift and enables condensation and cloud formation to take place.
South African Winter Patterns:
- The Indian and Atlantic high pressure systems move northwards, bringing westerly winds to the south and south western coastal regions.
- With the absence of the heat lows to the interior the Atlantic and Indian highs are linked across the land. Generally cool to cold conditions prevail.
- A separate cell of high pressure usually forms over the central to northern interior. This subsiding air results in clear skies and calm conditions over large parts of the interior.
- During the South African winter the ITCZ moves well north of the equator (between 5 degrees N and 20 degrees N). This results in the disappearance of the north east monsoon. The south east trade winds still blow, move across the equator and re-curve north eastwards to become part of the great summer monsoon of India.
- The South West monsoon moves further north, crossing the coast well north of Angola. This results in the Congo Air Boundary moving much further north.
- With the northwards movement of the Indian and Atlantic high pressure systems, mid Atlantic depressions linked with cold fronts invade the southern regions of South Africa. On occasions these cold fronts have influenced regions as far north as Zambia under unusual conditions where a strong high pressure systems follows closely behind the cold front.
- Cloudy conditions associated with rain influence the southern, south western and south eastern coasts. Uplift is mainly due to cyclonic or frontal actions, but orographic uplift does occur over the escarpment where where snowfall may occur. Interior snowfall usually occur with the presence of a strong high following closely behind the cold front, thus pushing the cold air into the interior. A strong upper air low aids with the uplift and enables condensation and cloud formation to take place.
South African summer weather patterns:
- The _____ and _____ high pressure systems move further southwards, causing _______ winds to blow well ____ of the continent
- When the _____ high pressure system develops well out to ___, the influx of _______ laden air from over the warm Indian ocean influences the _______ parts of Southern Africa, often bringing rainy conditions along the _________ and _______ areas.
- ______ laden _____ ____ trade winds invade the ________ parts of the region, sometimes re-curving ________ influencing the northern and central provinces of South Africa and, on occasions, they move _________ to influence Zim and Zam.
- Uplift from the _______ high and _____ ___ Trades will cause condensation, cloud formation and rainfall when moist air is in circulation.
- The _______ high pressure system is a source of ____ subsiding air, having its centre fairly near the ____ coast of South Africa. It has a short “sea track” and therefore carries little _______.
- When the air from the ______ high meets the _____ high, uplift occurs due to undercutting effect of the cold _______ high and forms a moisture boundary, often affecting the rainfall distribution over the entire region. When this zone of lifting action occurs north drought conditions prevail, while widespread rains occur when this interaction is found __________.
South African summer weather patterns:
- The Indian and Atlantic high pressure systems move further southwards, causing westerly winds to blow well south of the continent
- When the Indian high pressure system develops well out to sea, the influx of moisture laden air from over the warm Indian ocean influences the eastern parts os Southern Africa, often bringing rainy conditions along the escarpment and Lowveld areas.
- Moisture laden South East trade winds invade the eastern parts of the region, sometimes re-curving southwards influencing the northern and central provinces of South Africa and, on occasions, they move northwards to influence Zim and Zam.
- Uplift from the Indian high and South East Trades will cause condensation, cloud formation and rainfall when moist air is in circulation.
- The Atlantic high pressure system is a source of dry subsiding air, having its centre fairly near the west coast of South Africa. It has a short “sea track” and therefore carries little moisture.
- When the air from the Atlantic high meets the Indian high, uplift occurs due to undercutting effect of the cold Atlantic high and forms a moisture boundary, often affecting the rainfall distribution over the entire region. When this zone of lifting action occurs north drought conditions prevail, while widespread rains occur when this interaction is found southwards.
Coastal low:
Areas affected -
Coastal lows at the western coast move -
And at the east coast move -
Weather conditions associated -
Eastern and western coasts.
Southwards
Northwards
Light drizzle or showers and overcast conditions
The South Westerly Buster:
The cause, and area of origin?
Type of weather and time of the year?
Area affected?
When the anti-cyclonic flow of air from a high pressure system to the south west ridges in behind a coastal low.
Strong south westerly winds, stratocumulus and stratus cloud.
KZN south coast. Follows the wake of the coastal low northwards along the east coast. Winter
The cape doctor:
The cause, time of year and area of origin?
Type of weather?
Area affected
Summer months. Caused by a high pressure system west of cape town.
South easterly winds and clear skies.
The western Cape.
The black south easter:
The cause, and area of origin?
Type of weather?
Area affected?
Same as the The Cape Doctor, but this time provides more moist laden air due to a long sea track.
Strong winds(South Eastern) and overcast conditions with rain and showers. Strong temperature drop.
Western Cape
Easterly Weather - Guti:
The cause, and area of origin?
Type of weather?
Area affected?
Moist cool air from a high pressure system over the Indian ocean moves inland on the eastern side, causing orographic cloud.
Low stratus cloud, appear as fog.
The eastern winds move the cloud farther inland and affects Johannesburg.
Tropical Cyclones:
The cause, and area of origin?
Type of weather?
The area with contain clear and calm skies?
Direction of movement?
Form over warm waters that area at least 26 degrees, tends to form during the summer and early autumn months. Coriolis force plays a big role in the circulatory motion, explains why they do not form within 3 degrees latitude of the equator.
Overcast conditions, strong winds up to 300kph and heavy rainstorms.
The eye of the storm
Westwards from the place of birth.
