The latest model runs are giving more clearer detail of the severe weather system predicted for parts of the Western/Northern/Southern and Eastern Cape this weekend.
The latest synoptic chart clearly show a high-pressure cell in the South Atlantic and in the South Indian Ocean. In the centre and currently moving along the coastline we have two low pressure systems with a coastal low over the coast of Kwazulu Natal. We also have eastward movement. Sometimes the South Atlantic high is driven further south than usual and it moves in behind the trough squeezing it against the South Indian high. This is not yet visible. This pincer-like action leads to the development of a cut-off low.
If the air pressure is low enough it can drop heavy amounts of rain of long periods which normally result in flash flooding. Cut-off lows caused the destructive floods and loss of life in September 1968 in Port Elizabeth. The current models indicate that Port Elizabeth and surrounding areas might again experience flash flooding this weekend. Heavy rain (75 - 100mm) as from Friday the 13th to Saturday the 14th of July 2012 is predicted for Port Elizabeth and surrounding coastal areas. The system is expected to move eastwards along the coast also effecting East London and other areas along the eastern seaboard up to the 16 July 2012.
Apart from possible heavy rain snow is also expected in parts of the Western/Southern/Northern and Eastern Cape provinces and Lesotho as of Friday, 13 July 2012. Heavy snowfall over parts of the Eastern Cape can be expected on Saturday, 14 July 2012. Temperatures are expected to plummet below zero with very cold conditions setting in. As per usual several mountain passes and roads will be closed to traffic in the event of heavy rain, snowfall or icy and waterlogged road conditions.
South Africans should prepare themselves for a significant weather system that is expected to bring a wet and cold weekend with widespread, unseasonal rainfall that is likely to be heavy in some places. While snowfalls are expected on the mountains, at present the main feature of this weather system is the risk of heavy rainfall in some areas.Due to the irregular nature of a cut-off low, the exact characteristics are generally very difficult to predict. The SAWDOS is of the opinion that should this weather system develop it would be unusual. Cut-off low pressure systems are common each year, but they tend to occur mostly during spring and autumn. They are less common in winter.
It is still to early to say for certain if the system will result in severe weather, however at this stage it appears that this is a significant system that should be observed full time as from tomorrow morning and throughout the rest of the weekend. The SAWDOS is currently monitoring this system very closely.
All SAWDOS Weather Observers and even non SAWDOS weather observers are hereby requested to report heavy continues rain and other abnormal weather phenomena in their area of observation. The SAWDOS is not sure where and if this heavy rain will occur. Be alert and send observations to the SAWDOS as we will in turn publish the observations to the benefit of the general public.
Send information to:
SAWDOS Email
SMS Information to: 076 251 3482
Twitter Messages: Click HERE or @SAWDOS1
Images courtesy: U.S. National Center for Environmental Prediction (NCEP)+ NOAA and Snow-forecast.com
No comments:
Post a Comment