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Sat, 04 Feb 2012 | |
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You are in: Weather > SA regional > Ecucation  COASTAL LOWS A coastal low is a shallow low pressure system limited to the lower layers of the atmosphere and is formed when the wind blows from the land TO the sea, usually during bergwinds. These coastal low pressure systems usually form off the Namibian or West Coast of SA. They then slowly move doen the coast and round the SW Cape and then move up the East Coast of SA where they finally fill up along the Mozambique coast where the plateau ceases to exist. Click on the minimised image below to view a larger diagram showing how the coastal low is formed.
 Click to view a larger image. Air moves off the coast at a height of approximately 1500m. This creates a relative "vacuum" at the surface as air rises to replace the air that is moving away from the coast. In a low pressure system, air rises clockwise in the southern hemisphere and the resultant circulation around the low pressure is the same. Hence, prior to the presence of a coastal low, the winds are usually offshore and in Cape Town they are usually in the form of hot, dry NE bergwinds. Once the coastal low moves through the area, the hot, dry winds are replaced by cool, moist NW-SW winds and usually fog. Coastal lows usually precede cold fronts in winter.
 Click to view a larger image. Click on the minimised image above to view a larger image showing the various synoptic features associated with a coastal low. [ back ]
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ALEXANDER BAY 24/16 ALLDAYS 34/22 BEAUFORT WEST 27/14 BELA-BELA 31/20 BETHLEHEM 24/14 BISHO 19/16 BLOEMFONTEIN 25/16 CALVINIA 31/17 CAPE ST LUCIA 27/24 CAPE TOWN 34/20 CLANWILLIAM 42/24 DE AAR 25/19 DURBAN 31/22 EAST LONDON 22/20 ERMELO 26/12 FAURESMITH 25/17 FICKSBURG 25/18 GEORGE 24/17 GRAAF-REINETT 21/12 GRAHAMSTOWN 25/13 HERMANUS 28/17 JOHANNESBURG 28/16 JOUBERTINA 19/16 KIMBERLEY 24/19 KLERKSDORP 32/19 KOMATIPOORT 26/20 KROONSTAD 29/17 LADYSMITH 29/19 LANGEBAAN 26/21 LEPHALALE 34/20 LYDENBURG 26/14 MAFIKENG 29/16 MUSINA 31/21 NELSPRUIT 27/19 NEWCASTLE 32/19 OUDTSHOORN 29/17 PAARL 36/21 PHALABORWA 30/22 PIETERMARITZBURG 30/17 PLETTENBERG BAY 21/16 POLOKWANE 30/14 PORT ALFRED 21/17 PORT ELIZABETH 19/16 PORT ST JOHNS 27/21 POTCHEFSTROOM 33/18 PRETORIA 29/17 QUEENSTOWN 22/16 RICHARDS BAY 33/23 ROBERTSON 34/15 RUSTENBURG 32/19 SASOLBURG 32/16 SKUKUZA 32/20 SOWETO 28/17 SPRINGBOK 31/20 STILBAAI 23/16 SUTHERLAND 25/12 TZANEEN 29/19 ULUNDI 33/19 UMTATA 22/19 UPINGTON 27/20 VEREENIGING 30/16 VREDENDAL 25/20 VRYBURG 26/19 WELKOM 28/17 WITBANK 26/12 WORCESTER 35/17 |
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