As can clearly be seen in the satellite image an upper air trough currently lies to the west and south west of the Western Cape. The upper trough is in the process of forming a cut-off low from the parent system. The cut-off low is clearly visible to the west of Cape Town this morning. (See Eumetsat satellite image) This rapidly intensifying system will initiate the widespread heavy rain, strong wind and possible flash flooding over parts of the Western Cape, Southern Cape and other parts of the country in the above mentioned period.
Image: Eumetsat (Click on image for larger view.)
The cut-off low is projected to move slowly eastwards and deposit significant amounts (>75mm) of rain over parts of the Western Cape and Eastern Cape. 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 and also the Laingburg Flood in 1981. Apart from the rain gale force (65 km/hr) easterly to south easterly winds are also expected along the Cape and Eastern Cape coastal areas with the possibility of thunderstorms in areas and also the interior.
Due to the irregular nature of a cut-off low, the exact characteristics are generally very difficult to predict. Cut-off low pressure systems are common each year, but they tend to occur mostly during spring and autumn.
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 today and throughout the rest of the weekend.
Communities in the Southern Cape and Garden Route area should remain on full alert. Motorists, travelers and members of the public must take note of the high probability of heavy rain, gale force wind (65km/h) and possible flash flooding. Mossel Bay WX will once again bring you the latest updates as the system progresses. It is still to early to say for certain if the system will result in severe weather, however at this stage the system should be observed full time as from tomorrow morning and throughout the rest of the weekend. MSBWX is currently monitoring this system very closely en encourage all it's weather observers to do the same.
MSBWX hereby ask the general public to forward any reports of severe weather conditions and flash flooding to the MSBWX. Use your cellphone, digital camera, email and private weather station etc. in gathering and forwarding information, photos and data to MSBWX. Email observations to MSBWX by clicking HERE.
We also remind our readers that MSBWX also utilize Twitter to keep our readers informed.
https://twitter.com/MosselBayWX2013
Herewith are a few prediction models.
Images: NCEP (Click on images for larger view.)
- MSBWX
