On 22/04/2018 00:32, Dave Ludlow wrote:
On Sat, 21 Apr 2018 23:23:38 +0100, N_Cook wrote:

So about 28mm in 55 minutes with a peak rate of 200mm/hr

A PWS in Bitterne reports 68mm - peaking 223 mm/h and almost all
during that late evening thunderstorm, with one at Midanbury 53mm and
both are supported by the rainfal radar accumulated precipitation
estimates.

Only 7 mm here in W Fareham but boy was that a spectacular horizon to
horizon lightning spectacular, lasting about 45 minutes with mostly
c-c flashes every second or two at times. It may only be April but I
haven't observed a 'summer' thunderstorm like that for donkeys years -
brilliant!


I don't know what the peak lightning strike rate was but that IoW site
gave 76 strikes per minute at 22:51, with 31 mile range setting.
Now to retrospectively work out what the likely rise in the deep-level
sewer system probably was, using previous data obtained in daylight
hours. A few thousand old-stock homes that discharge roof rain into the
sewer system. The deep system interconnects with the local sewer system,
and , which it should not do, couples to the storm drain system that is
open to the nearby tidal river due to failed outlet flap valves, due to
dilapidations in the pipe-runs.