What a weather-related week we have had, starting on Sunday with forecasts and warnings for disruptive rain and all that materialised was 100mm of liquid sunshine as they say in the classics.
Then at 8am on Monday morning the rain arrived with a vengeance.
Roads and houses were flooded, damage was caused to infrastructure and there were four reported deaths.
Naturally, the armchair critics had a field day criticising the metro for not clearing drains and maintaining infrastructure.
The question must then be asked; what do the statistics say about the event?
Was it just a heavy downpour or an extreme event?
Firstly, the return value rates it a one-in-10-year event, which does not sound that extreme.
However, the 128.4mm measured on Tuesday morning at the airport was the sixth highest 24-hour figure in the last almost 90 years (since records started at the airport area in 1937).
It is also a record for October, surpassing the previous record of 91mm set in October 1953.
This is only the 12th time that more than 100mm of rain was measured in a 24-hour period in the Bay.
Though it was far from the September 1968 and March 1981, and the complete anomaly of January 1951 (unusual to occur in summer), it was just pipped by the others, and most especially the August 2006 event.
It was the duration of the rain that differed that made the most difference.
In 1968, the bulk of the 429mm fell in just four hours, in 1981, the 224mm fell in just over an hour, and in 2006, the 128mm in just over four hours.
This event started on Monday morning and continued at a steady pace until Tuesday at about 11am. That is more than 24 hours later.
During this period, I measured just shy of 200mm in the Newton Park area, and have numerous reports of figures in excess of 200mm in the Rowallan Park and Greenbushes areas.
Had that same rainfall (128.4mm measured at the airport) fallen in four hours, it would then become a one-in-200-year event.
If this occurred, this would have been just as disastrous as 2006, when a similar figure was measured.
Incidentally, August 2006 was the last time we received this amount of rain in 24 hours.
Naturally, we had some clever people circulating a fake weather warning about an approaching storm at 3pm in the afternoon so that they could go home early.
However, any boss having a good command of the English language would quickly pick up that the grammar matched that used in spam emails.
Though there was some rainfall in the catchment, and we should see a rise in the dam levels shortly, unfortunately, they did not get the same figures as recorded in the Bay.
If they did, it would have topped most dams in the catchment.
Though it is still early days, this rainfall is surely a sign that the Seasonal Forecast is credible as it forecast favourable falls for the summer season.
The question always posed to me after we have had good rains is: how much fell in the catchment area?
As regular readers know, I have stated that by all measures, the drought has been broken, yet we are still being charged drought tariff rates and are still under severe restrictions.
According to the ex-mayor, this means the metro collects an extra R24m per month at these steeped rates.
Debating this on social media, apparently the speaker of council does not want to put this matter on the agenda for discussion. One can only contemplate why.
This week in history:
1823:
“Settler’s homes were flooded after a prolonged drought.” — the first weather record in the Bay.
Dam levels:
Down from 76.02% to 75.31%
Weather safety tips:
If caught in the middle of a field during a lightning storm, curl up in a ball. Under no circumstances should you seek shelter under a tree.
Now on Facebook, Instagram, and Twitter: WEATHER GURU
E-mail garthsampson59@gmail.com with feedback or requests
HeraldLIVE
WEATHER GURU | Floods a one-in-10-year event
Image: SUPPLIED
What a weather-related week we have had, starting on Sunday with forecasts and warnings for disruptive rain and all that materialised was 100mm of liquid sunshine as they say in the classics.
Then at 8am on Monday morning the rain arrived with a vengeance.
Roads and houses were flooded, damage was caused to infrastructure and there were four reported deaths.
Naturally, the armchair critics had a field day criticising the metro for not clearing drains and maintaining infrastructure.
The question must then be asked; what do the statistics say about the event?
Was it just a heavy downpour or an extreme event?
Firstly, the return value rates it a one-in-10-year event, which does not sound that extreme.
However, the 128.4mm measured on Tuesday morning at the airport was the sixth highest 24-hour figure in the last almost 90 years (since records started at the airport area in 1937).
It is also a record for October, surpassing the previous record of 91mm set in October 1953.
This is only the 12th time that more than 100mm of rain was measured in a 24-hour period in the Bay.
Though it was far from the September 1968 and March 1981, and the complete anomaly of January 1951 (unusual to occur in summer), it was just pipped by the others, and most especially the August 2006 event.
It was the duration of the rain that differed that made the most difference.
In 1968, the bulk of the 429mm fell in just four hours, in 1981, the 224mm fell in just over an hour, and in 2006, the 128mm in just over four hours.
This event started on Monday morning and continued at a steady pace until Tuesday at about 11am. That is more than 24 hours later.
During this period, I measured just shy of 200mm in the Newton Park area, and have numerous reports of figures in excess of 200mm in the Rowallan Park and Greenbushes areas.
Had that same rainfall (128.4mm measured at the airport) fallen in four hours, it would then become a one-in-200-year event.
If this occurred, this would have been just as disastrous as 2006, when a similar figure was measured.
Incidentally, August 2006 was the last time we received this amount of rain in 24 hours.
Naturally, we had some clever people circulating a fake weather warning about an approaching storm at 3pm in the afternoon so that they could go home early.
However, any boss having a good command of the English language would quickly pick up that the grammar matched that used in spam emails.
Though there was some rainfall in the catchment, and we should see a rise in the dam levels shortly, unfortunately, they did not get the same figures as recorded in the Bay.
If they did, it would have topped most dams in the catchment.
Though it is still early days, this rainfall is surely a sign that the Seasonal Forecast is credible as it forecast favourable falls for the summer season.
The question always posed to me after we have had good rains is: how much fell in the catchment area?
As regular readers know, I have stated that by all measures, the drought has been broken, yet we are still being charged drought tariff rates and are still under severe restrictions.
According to the ex-mayor, this means the metro collects an extra R24m per month at these steeped rates.
Debating this on social media, apparently the speaker of council does not want to put this matter on the agenda for discussion. One can only contemplate why.
This week in history:
1823:
“Settler’s homes were flooded after a prolonged drought.” — the first weather record in the Bay.
Dam levels:
Down from 76.02% to 75.31%
Weather safety tips:
If caught in the middle of a field during a lightning storm, curl up in a ball. Under no circumstances should you seek shelter under a tree.
Now on Facebook, Instagram, and Twitter: WEATHER GURU
E-mail garthsampson59@gmail.com with feedback or requests
HeraldLIVE
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