In the local record maximum rain rate as 530mm/hour (sic 0.53m/hr) 00:15
27 Dec 2020 for a short duration. The owner , an ex metman , cannot
confirm it as genuine or not, but looks iffy. Later a short burst of
340mm/hr, overall 23mm in 6 hours. Could they be genuine extreme
rain-rate records?
If genuine it would explain why the local storm drain flap valve into
the local tidal river has been fully open , unnoticed, for a few months.
Flap nearly vertical, self weight holding it 20 degrees off vertical ,
backwards beyond vertical, against the hinge joint.
It was realised there was a problem because the lowest road drain water
traps had the level going up and down exactly with the highest tides.

--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

On 10/03/2021 18:09, N_Cook wrote:
In the local record maximum rain rate as 530mm/hour (sic 0.53m/hr) 00:15
27 Dec 2020 for a short duration. The owner , an ex metman , cannot
confirm it as genuine or not, but looks iffy. Later a short burst of
340mm/hr, overall 23mm in 6 hours. Could they be genuine extreme
rain-rate records?

That would obviously be an extreme value and represents consecutive tips
in about one second. While not impossible, I'd be quite sceptical that
it was genuine. But difficult to be sure without seeing a log of the
data (eg a wlk file), preferably with a short archive interval. If it
was just an isolated pair of tips I've be very sceptical, but it
obviously depends what was happening in general to the rainfall record
at the time.

An issue like this certainly can be artefactual. If it's an old gauge
then there could be contact bounce in the reed switch. Or if the front
cover to the ISS is not making a good seal then water can get in and on
to the contacts in the plug/socket from the rain gauge, giving
spuriously high rain rates.

On 10/03/2021 18:09, N_Cook wrote:
In the local record maximum rain rate as 530mm/hour (sic 0.53m/hr) 00:15
27 Dec 2020 for a short duration. The owner , an ex metman , cannot
confirm it as genuine or not, but looks iffy. Later a short burst of
340mm/hr, overall 23mm in 6 hours. Could they be genuine extreme
rain-rate records?
If genuine it would explain why the local storm drain flap valve into
the local tidal river has been fully open , unnoticed, for a few months.
Flap nearly vertical, self weight holding it 20 degrees off vertical ,
backwards beyond vertical, against the hinge joint.
It was realised there was a problem because the lowest road drain water
traps had the level going up and down exactly with the highest tides.

The first question is, how were they measured? We had a number of
different recording rain gauges when I worked at Kew Observatory in the
late 60s. We measured over 150mm per hour on a few occasions. But then
that was a Jardi rate of rain recorder which had a 6 foot radius
collector. I don't think any amateur AWS is likely to be able to cope
with that sort of intensity. I think it an unlikely event. Can you find
out what the rainfall radar was showing at that time?

On 10/03/2021 19:11, JGD wrote:
On 10/03/2021 18:09, N_Cook wrote:
In the local record maximum rain rate as 530mm/hour (sic 0.53m/hr)
00:15 27 Dec 2020 for a short duration. The owner , an ex metman ,
cannot confirm it as genuine or not, but looks iffy. Later a short
burst of 340mm/hr, overall 23mm in 6 hours. Could they be genuine
extreme rain-rate records?

That would obviously be an extreme value and represents consecutive tips
in about one second. While not impossible, I'd be quite sceptical that
it was genuine. But difficult to be sure without seeing a log of the
data (eg a wlk file), preferably with a short archive interval. If it
was just an isolated pair of tips I've be very sceptical, but it
obviously depends what was happening in general to the rainfall record
at the time.

An issue like this certainly can be artefactual. If it's an old gauge
then there could be contact bounce in the reed switch. Or if the front
cover to the ISS is not making a good seal then water can get in and on
to the contacts in the plug/socket from the rain gauge, giving
spuriously high rain rates.

The only extra info I have , as of the moment, is he looked into his log
, rather than the www feed I copied, the maximum record was 523.6mm/hour .
Otherwise at some point, the noise on my roof woke me up, but I did not
check the time, just downloaded the www image the next morning, perhaps
200m from his met station.
Model is Davis Vantage Pro 2 , no idea of age

--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

On 10/03/2021 19:23, Metman2012 wrote:
On 10/03/2021 18:09, N_Cook wrote:
In the local record maximum rain rate as 530mm/hour (sic 0.53m/hr)
00:15 27 Dec 2020 for a short duration. The owner , an ex metman ,
cannot confirm it as genuine or not, but looks iffy. Later a short
burst of 340mm/hr, overall 23mm in 6 hours. Could they be genuine
extreme rain-rate records?
If genuine it would explain why the local storm drain flap valve into
the local tidal river has been fully open , unnoticed, for a few
months. Flap nearly vertical, self weight holding it 20 degrees off
vertical , backwards beyond vertical, against the hinge joint.
It was realised there was a problem because the lowest road drain
water traps had the level going up and down exactly with the highest
tides.

The first question is, how were they measured? We had a number of
different recording rain gauges when I worked at Kew Observatory in the
late 60s. We measured over 150mm per hour on a few occasions. But then
that was a Jardi rate of rain recorder which had a 6 foot radius
collector. I don't think any amateur AWS is likely to be able to cope
with that sort of intensity. I think it an unlikely event. Can you find
out what the rainfall radar was showing at that time?

From previous experience of definite heavy rainfall locally, the radar
image showed nothing abnormal, apperently because we have some high
ground between us and the Chilbolton radar station, in radar shadow.


--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm