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?