Below is a quick summary of the storms over Somerset as seen by the
Cobbacombe radar: the assessment is based upon the 2x2km radar product (5
minute scans). Note that the radar it not 'truth' - but is useful is these
instances to look at the spatial pattern of rainfall.

Units are in mm (or mm/hr) and time is GMT.



Timeline:

0900Z: Showery rain 2mm/hr approaches Portland, with heavier cells ~8mm/hr
around 1000Z

1200Z: band of rain progresses northwestwards, up to ~16mm/hr, stretching
from south Devon across to Dorchester: one cell (~8mm/hr) tracks up the Exe
estuary. This band clears to the north west, although further cells track up
the Exe.

1500Z: first echoes of significant rain develop in the east of the region
over Shaftesbury: these develop in a matter of ~10 minutes, producing rain
rates 32mm/hr, and move very slowly WNW.

1600Z: quite extensive area of heavy rain (10mm/hr) established over
Yeovil/Frome/Shaftesbury area. Another cell(s) develops to the SW over
Crewkrene.

1700Z: Large expanse of rainfall over much of eastern Somerset (8mm/hr). A
very heavy cell develops over Crewkerne (32mm/hr).

1800Z: Whole system moves WNW, with most of the heavy cells declining in
intensity through until 2000Z, when mostly 4mm/hr regions left.

2200Z: band of moderate/heavy rain from Brixham to Clovelly.





Total rainfall (midnight 28/29th through midnight 29/30th May 2008):



Total weight of water that fell within 100km radius of the Cobbacombe radar
was in excess of 251 million tonnes!



Highest total for the day was at Batcombe (north of Bruton/east of
Evercreech) with a total of 70.1mm. Surrounding areas also had high totals
(e.g. 67.9 and 60.1mm) which suggests that this total is plausible -
although strong gradients were present: 6km to the west of Batcombe, the
Bath and West showground had only about 20mm (being between a 22.3 and
18.9mm estimate).



Around Crewkrene, scene of flooding at Vinney Bridge, the highest local
total was 58.1mm at South Perrott, near the source of the River Parrett.



80 square kilometres had 50mm or more rainfall:

One 4sqkm near Dunkeswell (59.3mm); 16sqkm to the south and east of
Crewkerne (up to 58.1mm); 32sqkm to the southwest of Gillingham (up to
67.3mm); 28sqkm to the East and North of Bruton (up to 70.1mm)



1460 square kilometres had 25mm or more rainfall:

Obviously the 25mm+ region(s) were far more extensive than above. Main areas
were the eastern 'foothills' of Dartmoor, along the Exe estuary (and to the
southwest of Exeter); north of Honiton towards Wellington and Wiveliscombe;
to the south and east of Chard and Crewkerne; south and east of Yeovil;
Sedgemoor and Bridgewater. The largest area was stretched northwards from
Sturminster Newton/Shaftsbury to Midsomer Norton and west to Cheddar.



9192 square kilometres had 10mm or more rainfall:

Needless to say, a large area: take an area bounded by Brixham-Clovelly in
the SW, Torrington-Lynton to the NW, Ottery St Mary - Blandford Forum in the
south and the Bristol Channel coast to the North: almost all areas within
the box had 10mm+.

"CHRIS KIDD" wrote...
Below is a quick summary of the storms over Somerset as seen by the
Cobbacombe radar: the assessment is based upon the 2x2km radar
product (5 minute scans). Note that the radar it not 'truth' - but
is useful is these instances to look at the spatial pattern of
rainfall.

snip

Highest total for the day was at Batcombe (north of Bruton/east of
Evercreech) with a total of 70.1mm. Surrounding areas also had high
totals (e.g. 67.9 and 60.1mm) which suggests that this total is
plausible -

.... many thanks for posting that comprehensive summary. Is it possible
to determine from the radar output over what period of time those
totals were produced?

Martin.



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

Martin,

Some of the maximum time/accumulations a

5 minutes: 13.9mm near Crewkrene & Dunkeswell

30 minutes: 46.6mm near Crewkrene (Bruton, Sherborne & Dunkeswell 25mm)

60 minutes: 56.8mm near Crewkrene (Bruton 40mm)

Chris


"Martin Rowley" wrote in message
...
"CHRIS KIDD" wrote...
Below is a quick summary of the storms over Somerset as seen by the
Cobbacombe radar: the assessment is based upon the 2x2km radar product (5
minute scans). Note that the radar it not 'truth' - but is useful is
these instances to look at the spatial pattern of rainfall.

snip

Highest total for the day was at Batcombe (north of Bruton/east of
Evercreech) with a total of 70.1mm. Surrounding areas also had high
totals (e.g. 67.9 and 60.1mm) which suggests that this total is
plausible -

... many thanks for posting that comprehensive summary. Is it possible to
determine from the radar output over what period of time those totals were
produced?

Martin.



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

"CHRIS KIDD" wrote in message
Some of the maximum time/accumulations a
5 minutes: 13.9mm near Crewkrene & Dunkeswell
30 minutes: 46.6mm near Crewkrene (Bruton, Sherborne & Dunkeswell
25mm)
60 minutes: 56.8mm near Crewkrene (Bruton 40mm)

.... thanks again: I just wondered how they compared with the list of
'extreme' rainfall events and none of them at face value are
threatening the various records. The 56.8 mm in 60 mins for example,
set against the published record which I believe is 92 mm in 60 mins
at Maidenhead (Berkshire) in 1901 (July).

Martin.



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

Martin,
of course, remember that the figure I use are 4 square kms -
compared with point gauge location: inevitably the point gauge lcoations
will have higher intensities/totals than area avergaes.

Chris



"Martin Rowley" wrote in message
...
"CHRIS KIDD" wrote in message
Some of the maximum time/accumulations a
5 minutes: 13.9mm near Crewkrene & Dunkeswell
30 minutes: 46.6mm near Crewkrene (Bruton, Sherborne & Dunkeswell 25mm)
60 minutes: 56.8mm near Crewkrene (Bruton 40mm)

... thanks again: I just wondered how they compared with the list of
'extreme' rainfall events and none of them at face value are threatening
the various records. The 56.8 mm in 60 mins for example, set against the
published record which I believe is 92 mm in 60 mins at Maidenhead
(Berkshire) in 1901 (July).

Martin.



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

On 1 Jun, 07:36, "Martin Rowley"
wrote:
"CHRIS KIDD" wrote in message
Some of the maximum time/accumulations a
5 minutes: 13.9mm near Crewkrene & Dunkeswell
30 minutes: 46.6mm near Crewkrene (Bruton, Sherborne & Dunkeswell
25mm)
60 minutes: 56.8mm near Crewkrene (Bruton 40mm)

... thanks again: I just wondered how they compared with the list of
'extreme' rainfall events and none of them at face value are
threatening the various records. The 56.8 mm in 60 mins for example,
set against the published record which I believe is 92 mm in 60 mins
at Maidenhead (Berkshire) in 1901 (July).

Martin.

Hi, Martin and Chris,

The 48mm (I think) in 15 minutes at Carlton in Cleveland, North
Yorkshire - Mike Cinderey's site- on August 10th 2003 is not on the
Met O list for some reason. It was verified by the Met O and Stephen
Burt and, I think, Will Hand did some work on it.
I bring it up occasionally just to remind people. One day the Met O
might give it an airing!

Best wishes,
Ken
Copley, Teesdale

"Chris Kidd" wrote in message
...
Martin,
of course, remember that the figure I use are 4 square
kms - compared with point gauge location: inevitably the point gauge
lcoations will have higher intensities/totals than area avergaes.


.... indeed; I note that Philip has 70.1 mm on his summary for a
location in Somerset, but with no period of accumulation. I've no
doubt that in due course we'll get a detailed summary of this event,
but your figures are a useful starting point. The Met Office NCIC
sometimes prepare a summary of information that they are able to
obtain - they get EA gauge data.

Martin.


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

"Ken Cook" wrote

The 48mm (I think) in 15 minutes at Carlton in Cleveland, North
Yorkshire - Mike Cinderey's site- on August 10th 2003 is not on the
Met O list for some reason. It was verified by the Met O and Stephen
Burt and, I think, Will Hand did some work on it.
I bring it up occasionally just to remind people. One day the Met O
might give it an airing!


.... I *think* the 15 min. record is still the 55.9 mm at Bolton on
18th July, 1964. Anyone confirm? I didn't post that one (or indeed
the Carlton-in-Cleveland figure) as I don't think we are dealing with
that sort of intensity - looking at the radar data on the day, but of
course I could well be proved wrong.

Martin.


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

"Martin Rowley" wrote in message
...
"Ken Cook" wrote

The 48mm (I think) in 15 minutes at Carlton in Cleveland, North
Yorkshire - Mike Cinderey's site- on August 10th 2003 is not on the
Met O list for some reason. It was verified by the Met O and Stephen
Burt and, I think, Will Hand did some work on it.
I bring it up occasionally just to remind people. One day the Met O
might give it an airing!


... I *think* the 15 min. record is still the 55.9 mm at Bolton on 18th
July, 1964. Anyone confirm? I didn't post that one (or indeed the
Carlton-in-Cleveland figure) as I don't think we are dealing with that
sort of intensity - looking at the radar data on the day, but of course I
could well be proved wrong.

Martin.


Martin, without checking, from memory that is correct. I wrote a paper
published in Meteorological Applications on 20th Century Extreme rainfalls
and that was one of the 50 in that paper. I have Carlton-in-Cleveland down
as a 21st Century extreme event, along with Boscastle (16/8/04),
Carlisle(7/1/05) etc.
The criteria for an extreme event is high, basically it is a rainfall depth
as a function of duration, all explained in the paper.

See http://adsabs.harvard.edu/abs/2004MeApp..11...15H (abstract only)

but for a full report based on the paper see,
http://www.metoffice.gov.uk/research...84/FRTR384.pdf

For a more up to date study including "less extreme" events see my full
paper at
http://www.metoffice.gov.uk/research...76/FRTR476.pdf

Cheers,

Will (Haytor, Devon, 1017 feet asl)
--