On 30/07/2017 16:41, Dave Ludlow wrote:
Last night here in west Fareham we had two non-thundery torrential
downpours as the rain area crossed between 00:30 and 02:00 BST. The
first lasted 40 minutes and peaked at ~45mm/hour at 00:45 then tailed
off to stop briefly before resuming at 01:30.

The second downpour ended about 02:10 BST and peaked for a minute or
two at 100 mm/hour at 01:40 BST, roof gutters overflowed and it
looked and sounded as torrential as a thunderstorm would produce (no
hail though).

The above is from my VP2 bucket tips but I did empty the rain gauge
at 3 am and 21mm fell in those two 40 minute periods, just over half
in the second burst. However...

None of this was apparent on the (Netweather) 5 minute 500m rainfall
radar before, during or after the rain. The maximum rate shown for
here was (is still) ~8 mm/hour and the radar 24 hour total currently
for my location and nearby stands at ~10 mm (true total is ~24mm).

I assume that the heaviest part of the downpours were too brief to
register on radar - can anyone tell me if this is a common problem, as
I haven't noticed it occurring to this extent previously. Or is it
likely to be a rainfall radar calibration issue?


24 hour rainfall ending 30/0900 Z in Romsey was also 24mm, and some
of the rain was most certainly torrential.

Five significant rainfall events of 19mm or more have occurred this
July, (only one accompanied by thunder), leading to 132mm for the
month, the wettest July by some margin (20mm) in my 43 year record.

Nigel (Romsey, Hampshire)
40m amsl