Those in the south of Britain who woke to steady (and notable) rainfall
this morning might have been surprised to look at the Exeter analysis

http://www.weather.org.uk/charts/UKCpf000.png

and find no fronts in association with this rain .... however,
inspecting the upper air charts, particularly:-

http://www2.wetter3.de/Animation_00_UTC/06_1.gif

shows the culprit: a broad 'pool' of cold air aloft (slightly 'bluer'
colours on this output) and if you follow it through the sequence, the
feature actually intensifies. This indicates potential for
instability-based vertical motion and if the atmosphere is moist enough
(which it obviously is), then thick cloud and rain can result. These
things can result in surprisingly significant icing for aircraft
operations, which are not what the surface/mslp pattern might indicate.

Surface charts don't always show the whole story, particularly with
blocked anticyclonic features.

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

On Fri, 28 Jan 2005 08:40:59 -0000, Martin Rowley wrote in

huge snip of interesting stuff

Surface charts don't always show the whole story, particularly with
blocked anticyclonic features.

It's interesting to look at the 06Z ASXX, as that now has a "trough" pasted
into the northerly flow, just to the north of that band of rain. The
inclusion of such a feature is often done to illustrate the effects of an
upper feature on surface conditions.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 28/01/2005 08:58:28 UTC

"Martin Rowley" wrote
Those in the south of Britain who woke to steady (and notable) rainfall
this morning might have been surprised to look at the Exeter analysis

Uni Basel hadn't missed the rain. I have become a great fan on account of
their reliability:
http://pages.unibas.ch/geo/mcr/3d/meteo/index.htm

Jack

Thanks, Martin, I was indeed wondering just that as I looked at the fairly
heavy rain outside. Another weather mystery solved - only 2,199 to go.

Dave
"Martin Rowley" wrote in message
...
Those in the south of Britain who woke to steady (and notable) rainfall
this morning might have been surprised to look at the Exeter analysis

http://www.weather.org.uk/charts/UKCpf000.png

and find no fronts in association with this rain .... however,
inspecting the upper air charts, particularly:-

http://www2.wetter3.de/Animation_00_UTC/06_1.gif

shows the culprit: a broad 'pool' of cold air aloft (slightly 'bluer'
colours on this output) and if you follow it through the sequence, the
feature actually intensifies. This indicates potential for
instability-based vertical motion and if the atmosphere is moist enough
(which it obviously is), then thick cloud and rain can result. These
things can result in surprisingly significant icing for aircraft
operations, which are not what the surface/mslp pattern might indicate.

Surface charts don't always show the whole story, particularly with
blocked anticyclonic features.

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

The forecasts I heard stressed the drizzle or LIGHT rain expected. Only
'nuisance value' was mentioned which is not too easy to interpret though I
took it to be small amounts!



6 miles to East of Bury St. Edmunds I recorded 7.5mm 24hrs to 0900 Z and
note that Brooms Barn Research Station (Bury St. Edmunds) reports 9.5mm same
period. This would be their most rain for 09 to 09 24hr period since 8
November.
It's disappointing that the forecasts (other than Basel?) miss a
significant event after such a long dry spell although of course the hind
casts well document the reasons for it .

NickS, Woolpit. Suffolk.


"Martin Rowley" wrote in message
...
Those in the south of Britain who woke to steady (and notable) rainfall
this morning might have been surprised to look at the Exeter analysis

http://www.weather.org.uk/charts/UKCpf000.png

and find no fronts in association with this rain .... however, inspecting
the upper air charts, particularly:-

http://www2.wetter3.de/Animation_00_UTC/06_1.gif

shows the culprit: a broad 'pool' of cold air aloft (slightly 'bluer'
colours on this output) and if you follow it through the sequence, the
feature actually intensifies. This indicates potential for
instability-based vertical motion and if the atmosphere is moist enough
(which it obviously is), then thick cloud and rain can result. These
things can result in surprisingly significant icing for aircraft
operations, which are not what the surface/mslp pattern might indicate.

Surface charts don't always show the whole story, particularly with
blocked anticyclonic features.

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

"Jennikhbm (Suffolk)" wrote in message
...
The forecasts I heard stressed the drizzle or LIGHT rain expected.
Only 'nuisance value' was mentioned which is not too easy to interpret
though I took it to be small amounts!

.... indeed, I was screaming at the telly yesterday when the presenter
(can't remember who) was waffling about 'not a lot of rain with a high'
nonsense; can't comment further 'cos I don't know what they were basing
that on, but you can't *ever* relax with a slow-moving high pressure,
particularly one parked with it's c-o-g well to the west as this one.

Martin.

"Martin Rowley" wrote in message
...

"Jennikhbm (Suffolk)" wrote in message
...
The forecasts I heard stressed the drizzle or LIGHT rain expected. Only
'nuisance value' was mentioned which is not too easy to interpret though
I took it to be small amounts!

... indeed, I was screaming at the telly yesterday when the presenter
(can't remember who) was waffling about 'not a lot of rain with a high'
nonsense; can't comment further 'cos I don't know what they were basing
that on, but you can't *ever* relax with a slow-moving high pressure,
particularly one parked with it's c-o-g well to the west as this one.

Martin.

For most of yesterday the nusiance value staement was correct but in the
evening there were some very short heavy bursts of rain. Total fore
yesterday was 2.5mm most of which fell over a relatively short period. I did
wonder what was the reason and it was good to see the explanation this
morning.

Alan

Martin Rowley wrote:

snip

Surface charts don't always show the whole story, particularly with
blocked anticyclonic features.


Or even, as in a notable event in the mid-seventies, in an apparently
typical boring warm sector. Steady SW wind, 200ft cloud base, 1500M
visibility, steady barometer, then 5 minutes later the barometer had fallen
7mb, the cloud was on the deck, visibility 500M, and the wind had increased
about 10kts. After another five minutes the pressure was about a millibar
shy of where it had been before the fall and everything else was back to
normal.

Graham

Alan Gardiner wrote:

snip

For most of yesterday the nusiance value staement was correct but in the
evening there were some very short heavy bursts of rain. Total fore
yesterday was 2.5mm most of which fell over a relatively short period. I
did wonder what was the reason and it was good to see the explanation this
morning.

I heard Luke Harvey on Radio 5 mention this morning that one racecourse had
11mm overnight. Unfortunately, I didn't catch which one it was.

Graham

Alan Gardiner wrote:

For most of yesterday the nusiance value staement was correct but in
the evening there were some very short heavy bursts of rain. Total
fore yesterday was 2.5mm most of which fell over a relatively short
period. I did wonder what was the reason and it was good to see the
explanation this morning.

Alan

Its been utterly gorgeous up here on the West Coast -- enough cloud to keep
the frosts away and make the mountains and vistas astonishingly beautiful
with shafts of light bouncing off the contours.
Enough sun to cheer us all up and make it warm enough to work easily -- we
almost have no surface water where it should not be for the first time since
last May.
It would be wonderful if this could carry on for as long as it likes.

If anyone is comtemplating a walking / photographic break around here --- go
for it -- its stunning just now

--

regards
Jill Bowis [Oban]

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