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You are in: Weather > SA regional > Ecucation  BERGWIND Bergwind is the South African name for fohn wind or mountain wind. It is a hot, dry wind that blows from the interior of South Africa to the coast and usually is blustery. Most people find it rather unpleasant. It can be mild at times blowing at about 10km/h, but sometimes it can be really strong and may gust up to 100km/h causing some structural damage to buildings and uprooting trees. FORMATION Bergwinds usually occur when a strong high pressure exists south or south-east of the country and when a high pressure is also situated over the country. These conditions usually only occur in winter, but sometimes in summer too, hence bergwinds are mainly a autumn-winter-spring phenomemon. Since air rotates anti-clockwise around a high pressure in the southern hemisphere the wind direction to the north of the high pressure will be easterly or north-easterly, especially along the west coast of southern Africa. The bergwinds will usually start blowing along the Namibian coast and the first indication of bergwinds is a rise in temperature, sometimes this rise can be rapid. In winter of 1985 in CT, the temperature rose from 3°C at 07:00 in the morning to 27°C by 07:35 that SAME morning. This is not a common occurrence, but rather an extreme case. Since air in a high pressure descends and warms up as it descends it stands to reason that the off-shore winds will be warm to hot and the temperature will usually rise about 10 degrees Centigrade from the interior of SA to the coast. So the temperate at Upington may be 20°C, while at Alexander Bay it may be over 30°C. At the same time a coastal low will develop along the coast. Off-shore flow ahead of the coastal low is usually easterly to north-easterly in direction along the west coast and north-westerly along the east coast. Humidities are usually very low, sometimes as low as 5%, usually between 10-40%. The temperatures vary from 25°C to 35°C in winter and over 40°C in summer. Behind the coastal low the wind is on-shore and usually north-westerly to south-westerly in direction. It is cool and moist and usually associated with fog. The coastal low moves down the west coast and around the Cape Point and then up the east coast of South Africa until it fills up near Maputo in Mozambique. The bergwinds obviously follow the same pattern. The highest official temperatures recorded in South Africa (51.5° C) was recorded one summer during a bergwind occurring along the Eastern Cape coastline. The bergwinds are usually followed by a cold front in winter. Click on the minimized diagram below to view an enlarged image of the typical coastal low and bergwinds.
 Click to view a larger image. [ 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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