Rain and storm for Cpt

[genetic]

I see Windguru has added WRF 1km resolution for Cape Town;

The Weather Research and Forecasting (WRF) Model is a next-generation mesocale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs.

Forecast based on WRF model with 1 km resolution. Updates 4 times per day and offers forecast for 42 hours.

https://www.windguru.cz/help.php?sec=models

 

[Segg]

This mornings Satellite & Radar overlay

Looks moist down there

 

[Gordon_R]

This mornings Satellite & Radar overlay

Looks moist down there

Most of the precipitation is just offshore. Cutoff-lows are like that, potentially very heavy rainfall, but hard to predict where they will go. Just like tropical cyclones, see:



Edit: Source: https://www.cpc.ncep.noaa.gov/products/international/cpci/data/00/gfs_precip_24h_safrica.html

 

[WAslayer]

Most of the precipitation is just offshore. Cutoff-lows are like that, potentially very heavy rainfall, but hard to predict where they will go. Just like tropical cyclones, see:

View attachment 631548

Why is this chart so hard to find on that site..?

Edit: still looking for it..

 

[Geoff.D]

Ja they don't make it easy to find. I have a link on my PC but not on my tablet.
PS: I don't use google to synch across devices! I prefer to stuff up only one device with google at a time.
It is a very strange way in which that low is moving. Moved south west yesterday. Then turned back east wards and moved south east off shore. So we I'll have to see if the next line of cold fronts will push it back northwards or not.

 

[Segg]

Here's the Radar showing where the rain is concentrated, it doesn't seem to be that heavy either - time in UTC so add 2 hours for SAST

 

[Gordon_R]

Ja they don't make it easy to find. I have a link on my PC but not on my tablet.
PS: I don't use google to synch across devices! I prefer to stuff up only one device with google at a time.
Is siege way in which that low is moving. Moved south west yesterday. Then turned back east wards and moved south east off shore. So we I'll have to see if the next line of cold fronts will push it back northwards or not.

Sorry, forgot to post link. Multiple charts here: https://www.cpc.ncep.noaa.gov/products/international/cpci/data/00/fcsts_safrica.shtml

Here's the Radar showing where the rain is concentrated, it doesn't seem to be that heavy either - time in UTC so add 2 hours for SAST

Bone dry here, just some fog around...

 

[Gordon_R]

Quick bit of meteorology trivia. One of the most significant differences between a cutoff-low and and a tropical cyclone is a 'cold' and broad upper trough outside the tropics, and a compact 'warm' core in the tropics.

This can be seen very clearly on this morning's charts (Tues 12th), with a low over Cape Town, and a cyclone in the Mozambique Channel. In this case the temperature difference in the mid-level atmosphere at the 500hPa level (roughly 5-6km elevation) is over 20C!



Source: https://www.cpc.ncep.noaa.gov/products/international/cpci/data/00/gfs_500mb_tmp_safrica.html

 

[Gordon_R]

Widespread moderate to heavy rain over parts of the Western Cape up to 8am on Mon 11th:
http://www.weathersa.co.za/media/data/climate/nr_daily_rai.pdf

Highest include Tygerhoek 145mm(??), Riversdale 48mm, Franschhoek 43mm, Swellendam 39mm, Grabouw 35mm, Malmesbury 34mm, Porterville 33mm, Robertson 25mm, Stilbaai 25mm, Worcester 25mm, Ceres 24mm, Villiersdorp 23mm, Ladismith 22mm, Langebaan 21mm, Prince Albert (Little Karoo) 20mm, Cape Agulhas 19mm, Mossel Bay 19mm, Cape Point 18mm, Kirstenbosch 17mm, etc. Heavy rain also fell in several other provinces.

More rainfall figures for the 24 hours to 8am on Tues 12th: http://www.weathersa.co.za/media/data/climate/nr_daily_rai.pdf

Highest include Tygerhoek 118mm(??), Robertson 34mm, Kirstenbosch 32mm, Ashton 29mm, Cape Agulhas 29mm, Struisbaai 25mm, etc. Heavy rain also fell in several other provinces.

If the figures for Tygerhoek are correct, that may explain the flooding on the N2 yesterday!

Outside Riviersonderend in the Overberg: http://www.elsenburg.com/research-farm/tygerhoek-research-farm

 

[Segg]

I see on the satellite loop that the system is now dissipating, Cape Town Intl reporting scattered cloud at +-1km AGL, and radar hardly showing anything

 

[Gordon_R]

More rainfall figures for the 24 hours to 8am on Tues 12th: http://www.weathersa.co.za/media/data/climate/nr_daily_rai.pdf

Highest include Tygerhoek 118mm(??), Robertson 34mm, Kirstenbosch 32mm, Ashton 29mm, Cape Agulhas 29mm, Struisbaai 25mm, etc. Heavy rain also fell in several other provinces.

If the figures for Tygerhoek are correct, that may explain the flooding on the N2 yesterday!

Outside Riviersonderend in the Overberg: http://www.elsenburg.com/research-farm/tygerhoek-research-farm

https://www.news24.com/SouthAfrica/...e-one-farmer-got-275mm-in-nine-hours-20190313

The small town of Riviersonderend got the lion's share of the recent rains where 275mm fell on one farm in just under nine hours – flooding fields, destroying fencing, pumps and killing 75 sheep.

The floodwaters swept through the farmhouse and the family had to evacuate.

Wesseljan van Deventer, whose farm Blydskap is about 2km from the N2 outside Riviersonderend, said the farm had 351mm between Friday last week to Tuesday morning.

Not clear why one location got so much rain, must be close to the mountains.

Bingo: https://www.google.com/maps/place/R...3ebba72667fb2a!8m2!3d-34.1407972!4d19.9199137

 

[Pineapple Smurf]

https://www.news24.com/SouthAfrica/...e-one-farmer-got-275mm-in-nine-hours-20190313

Hectic rain for this farmer

 

[dualmeister]

killing 75 sheep

 

[Pineapple Smurf]

Quite mesmerising, i think this is my new favourite weather app Hope it is accurate
Nice 5 day graphical interface
https://www.windy.com/-27.980/26.740?-34.561,20.336,8

 

[Geoff.D]

Nothing new about it --- and just as reliable as all the others.

The base data is still ECMWF and GFS. The accuracy depends on how often the base data is updated, and how quick the latest runs are incorporated into the Apps analysis. The fact that they keep introducing so-called dumbed down display enhancements means squat in terms of accuracy. The size of that app is now just ridiculous compared to the original version, making it less and less likely to want to run on older devices.
I only use it on my PC, long gone can it run on my mobile devices and tablet.

 

[werny]

Nothing new about it --- and just as reliable as all the others.

The base data is still ECMWF and GFS. The accuracy depends on how often the base data is updated, and how quick the lastest runs are incorporated into the Apps analysis. the fact that they keep introducing so-called dumbed down display enhancements means squat in terms of accuracy. The size of that app is now just ridiculous compared to the original version, making it less and less likely to want to run on older devices.
I only use it on my PC, long gone can it run on my mobile devices and tablet.

Runs like a dream on my S10+, no issues, use it every day. Also just tested it on a P20 Lite and works just as good, not even a powerful phone.

But ya, like you said the accuracy is not 100%, still a cool app though.

 

[EMAM]

Who are the wind gurus here?
What's the wind forecast for False Bay this weekend?

 

[Pineapple Smurf]

Who are the wind gurus here?
What's the wind forecast for False Bay this weekend?

I'm a noob at weather reporting but i reckon a nice weekend everywhere

 

[Pineapple Smurf]

Finally a little bit of rain for tomorrow

 

[Gordon_R]

Finally a little bit of rain for tomorrow

About 5-10mm possible for Thurs 4th, depending on the area, and which forecast you believe.