Cornish rainfall from radar...
 

Looking at the 1km radar:

Main band of rain encroaches upon the western tip of Cornwall ~18:00 on the
16th, reaching St Austell Bay at ~20:00. Most of the rain rates are 5mm/hr,
but a few heavier regions ~10mm/hr.

After 21:00 a stronger line of rainfall (10m/hr) appears aligned NNW-SSE
through Penzance, moving eastwards through Falmouth ~22:00. Although this
line dissipated somewhat as it moved over St Austell, there was orographic
enhancement over Bodmin Moor over the next 2-3 hours. Meanwhile out to the
west a thin line (5km E-W) of very heavy rain (50mm/hr) developed. This
line first appears fragmented, but started to form a continuous line from
northern Cornwall, southwards across the Lizard and out into the channel at
~03:00 on the 17th. This line then develops slightly to the east of the
Lizard, so that by 04:00 it stretches from St Austell, south-westwards just
to the East of the Lizard. On the southeast side of this line (about 50km
out over the channel) there appears to a much drier region being dragged
northwards. The thin line of heavy rain then wriggles north-eastwards,
decaying over the next 3-4 hours.



Given the thinness of the heavy rainfall area I suspect it would have missed
many of the gauge locations: maximum rainfall accumulations based upon the
radar suggest in excess of 50mm in a band no more than 4-5km wide; 35 sq
kilometres with 75mm total over Bodmin Moor, and ~ 13 sq kilometres with
75mm on the St Austell area.

Cornish rainfall from radar...
 

"Chris" wrote ...
Looking at the 1km radar:

Main band of rain encroaches upon the western tip of Cornwall ~18:00
on the 16th, reaching St Austell Bay at ~20:00. Most of the rain
rates are 5mm/hr, but a few heavier regions ~10mm/hr.

After 21:00 a stronger line of rainfall (10m/hr) appears aligned
NNW-SSE through Penzance, moving eastwards through Falmouth ~22:00.
Although this line dissipated somewhat as it moved over St Austell,
there was orographic enhancement over Bodmin Moor over the next 2-3
hours. Meanwhile out to the west a thin line (5km E-W) of very
heavy rain (50mm/hr) developed. This line first appears fragmented,
but started to form a continuous line from northern Cornwall,
southwards across the Lizard and out into the channel at ~03:00 on
the 17th. This line then develops slightly to the east of the
Lizard, so that by 04:00 it stretches from St Austell,
south-westwards just to the East of the Lizard. On the southeast
side of this line (about 50km out over the channel) there appears to
a much drier region being dragged northwards. The thin line of heavy
rain then wriggles north-eastwards, decaying over the next 3-4
hours.

Given the thinness of the heavy rainfall area I suspect it would
have missed many of the gauge locations: maximum rainfall
accumulations based upon the radar suggest in excess of 50mm in a
band no more than 4-5km wide; 35 sq kilometres with 75mm total over
Bodmin Moor, and ~ 13 sq kilometres with
75mm on the St Austell area.



.... Thanks very much for all that information Chris; interesting to
see the output from Restormel EA river monitoring gauge (R. Fowey)
he-

http://www.environment-agency.gov.uk...stationId=3152

a sharp increase in the short period after 17/0600 NOV, which suggests
that an awful lot of rain had fallen in the hours preceding upstream
of this point - threatening the 'highest recorded' value since the
station opened in 1961. There will no doubt be EA gauges co-located
with the sensing point, so we'll get a better idea of spatial rain
totals in due course - however, as you point out, getting a 'true'
total rainfall is always problematical.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

Cornish rainfall from radar...
 

On Nov 17, 9:37*pm, "Chris" wrote:
Looking at the 1km radar:

Main band of rain encroaches upon the western tip of Cornwall ~18:00 on the
16th, reaching St Austell Bay at ~20:00. Most of the rain rates are 5mm/hr,
but a few heavier regions ~10mm/hr.

After 21:00 a stronger line of rainfall (10m/hr) appears aligned NNW-SSE
through Penzance, moving eastwards through Falmouth ~22:00. Although this
line dissipated somewhat as it moved over St Austell, there was orographic
enhancement over Bodmin Moor over the next 2-3 hours. Meanwhile out to the
west a thin line (5km E-W) of very heavy rain (50mm/hr) developed. This
line first appears fragmented, but started to form a continuous line from
northern Cornwall, southwards across the Lizard and out into the channel at
~03:00 on the 17th. This line then develops slightly to the east of the
Lizard, so that by 04:00 it stretches from St Austell, south-westwards just
to the East of the Lizard. On the southeast side of this line (about 50km
out over the channel) there appears to a much drier region being dragged
northwards. The thin line of heavy rain then wriggles north-eastwards,
decaying over the next 3-4 hours.

Given the thinness of the heavy rainfall area I suspect it would have missed
many of the gauge locations: maximum rainfall accumulations based upon the
radar suggest in excess of 50mm in a band no more than 4-5km wide; 35 sq
kilometres with 75mm total over Bodmin Moor, and ~ 13 sq kilometres with
*75mm on the St Austell area.

Thanks Chris (I seem to remember you with providing me with some
useful info after the St Ives flood, I was going on amounts recorded
in a couple of buckets - on a farm run by relations near Zennor - and
couldn't quite believe the 8" until your radar analysis supported it)

The flood areas affected fit in perfectly with it being a very narrow
NNE/SSW band. I believe around 80mm was recorded somewhere (near
Colliford I think), but not sure of the length of period covered,
probably 24 hours.

Graham
Penzance