Rain and storm for Cpt pt 2

Gordon_R said:
I prefer millimeters of rain to percentages, but the outlook is looking encouraging. There are two separate events, the first on Sun/Mon/Tues, the second on Wed/Thurs. The latest model runs show widespread moderate rain (and cold), rather than an intense peak:
View attachment 1936293
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Will be really nice to get some rain. This week's warm weather was getting me worried.
 
Pablo37 said:
Looks like Cape Town could see water restrictions start kicking in as early as from Monday. Dams are now in the third week of the lowest levels for the same period for the last 5 years.

View attachment 1936414View attachment 1936415

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Yes, but if you look at the 10 year figures, we are 50% better than 2016 (just before the drought). The CoCT love to impose restrictions, because most of them are revenue generating. The hydrological year only ends in October, so changes at this stage are premature.

P.S. Next week's rain will make zero difference to the dam levels (soil moisture is too low for runoff), but may provide some relief to farmers (although rather late in the season).
 
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Gordon_R said:
Yes, but if you look at the 10 year figures, we are 50% better than 2016 (just before the drought). The CoCT love to impose restrictions, because most of them are revenue generating. The hydrological year only ends in October, so changes at this stage are premature.

P.S. Next week's rain will make zero difference to the dam levels (soil moisture is too low for runoff), but may provide some relief to farmers (although rather late in the season).
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When soil moisture is extremely low, water actually takes longer to pull into the ground.
That's why flash floods happen when it rains heavily after a drought.

It's probably not going to rain heavily, so you're probably right.
 
Gordon_R said:
Yes, but if you look at the 10 year figures, we are 50% better than 2016 (just before the drought). The CoCT love to impose restrictions, because most of them are revenue generating. The hydrological year only ends in October, so changes at this stage are premature.

P.S. Next week's rain will make zero difference to the dam levels (soil moisture is too low for runoff), but may provide some relief to farmers (although rather late in the season).
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It will be interesting to see if there is a City response. With the El Nino they might want to err on the side of caution. From the officials perspective there will be a requirement to begin activating the 'Drought Response', based on the accepted criteria for such. On the other hand there's elections coming up....
 
WAslayer said:
One is coming, but a cut off low doesn't always mean lots of rain.. the one coming is predicted to have minimal rain over the areas that matter to make a difference to the dam levels, aside from the fact that soil is dry now too, so less run off..
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If you stare at the models long enough, there is always a cutoff-low coming. However forecasts beyond 7 days have less than 30% accuracy, so most scenarios never eventuate. This is the current outlook for the week from 17-24 Sep (it will change!)
totp_week2[20260917-24].gif
 
Gordon_R said:
If you stare at the models long enough, there is always a cutoff-low coming. However forecasts beyond 7 days have less than 30% accuracy, so most scenarios never eventuate. This is the current outlook for the week from 17-24 Sep (it will change!)
View attachment 1936459
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Yep.. the amount of rain and days for that rain has changed every single time I have looked at it..

I fully expect to see little to no rain, as that has been the trend thus far..
 
Gordon_R said:
If you stare at the models long enough, there is always a cutoff-low coming. However forecasts beyond 7 days have less than 30% accuracy, so most scenarios never eventuate. This is the current outlook for the week from 17-24 Sep (it will change!)
View attachment 1936459
Click to expand...

WAslayer said:
Yep.. the amount of rain and days for that rain has changed every single time I have looked at it..

I fully expect to see little to no rain, as that has been the trend thus far..
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If you look at the probability of rainfall exceeding 25mm during the same week (17-24 Sep), the outlook is drastically different. I always look at the 7-14 day outlook, but until the probability and the detailed forecast agree, you can be 90% sure that the forecast is not accurate:
wk2_precip_tot_gt_75mm[20260917-24].gif
 
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WAslayer said:
One is coming, but a cut off low doesn't always mean lots of rain.. the one coming is predicted to have minimal rain over the areas that matter to make a difference to the dam levels, aside from the fact that soil is dry now too, so less run off..
Click to expand...
Yeah, only got 36mm in dbn.
 
wingnut771 said:
Doesnt snow help?
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Snow is a type of precipitation, and contrary to belief, in SA it makes up a tiny fraction of the runoff. Snow is also measured in equivalent mm of water (approximately 10:1 ratio), so there is no difference between rain and snow as far as forecasts are concerned.

FYI, some snow is forecast over Lesotho and the Drakensberg early next week:
southafricasnownext3to6days[20260916_0600].jpg
 
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