"Chris Handscomb" wrote in message
...
| Was just wondering if anyone could tell me how you could gauge how much rain
| was likely to fall from a frontal system as it passes over the UK. Like this
| cold front that will clear overnight tonight. I notice that the BBC are
| forecasting very little rain from it except in the far north-west. But how
| do they know? Is it purely from the results of all the
| quasi-semi-cross-frontal-geostrophic thing equations in the computer models?
| Is there a way of telling by hand by looking at satellite images, synoptic
| charts etc?
|
| Please help - I'm very curious!
| My amateur weather prediction status is on the line!
|
| Jeremy

Hi Jeremy/Chris ?!

Fronts are areas of large-scale ascent. The intensity of precipitation can be
gauged by the depth of the cloud, however precipitation intensity in polar
air masses is likely to be enhanced due to ice processes even in quite shallow
clouds.

The development of cloud within a front is dependant on many factors including
frontal waves, local orographic effects, pressure tendencies and upper-air
developments. From what I can see from the data available online, there will be
significant upper forcing behind the cold front in the N. The upper trough and
associated vorticity, at 55N 19W at 06z, will further aid ascent, but not fuly engage
the front until it is over the N.Sea.

http://makeashorterlink.com/?E2FF15DD5
(AVN 300mb for 18z)
http://makeashorterlink.com/?Y20042ED5
(MetO 500mb for 18z)
http://www.sat.dundee.ac.uk/pdus/BW/...10600BW1_g.jpg
(55N19W upper trough)

Looking at satellite pictures and synoptic charts can also help in the short-term.
Isobaric troughing at the surface is sometimes something to look for, as shown
on the latest ASXX.

http://129.13.102.67/wz/pics/bracka.gif

Colder cloud tops, indicating greater depth, seen in the IR imagery also.

HTH Joe

"Joe Hunt" wrote in message
...

Snip

http://makeashorterlink.com/?Y20042ED5
(MetO 500mb for 18z)

Interesting red 'blob' around 42N68W... which ends up here :-
http://tinyurl.com/n0xu
http://met.psu.edu/trop-cgi/ukmettc2...y &hour=144hr

Jon.

"Jon O'Rourke" wrote in message
...

"Joe Hunt" wrote in message
...

Snip

http://makeashorterlink.com/?Y20042ED5
(MetO 500mb for 18z)

Interesting red 'blob' around 42N68W...

Or even 22N55W ish looking at it the right way up with my glasses on ;-)

Jon.

Thanks Jon, spent a few minutes trying to work out where the red blob was,
though the chart had changed

Chris
Kempston, Bedford

--

"Jon O'Rourke" wrote in message
...

"Jon O'Rourke" wrote in message
...

"Joe Hunt" wrote in message
...

Snip

http://makeashorterlink.com/?Y20042ED5
(MetO 500mb for 18z)

Interesting red 'blob' around 42N68W...

Or even 22N55W ish looking at it the right way up with my glasses on ;-)

Jon.

"Chris Mantle" wrote in message
...
Thanks Jon, spent a few minutes trying to work out where the red blob
was,
though the chart had changed

Chris
Kempston, Bedford

--


Hi Chris, hope you've enjoyed the rain

managed nearly 7mm in last 2 days. wow.

Joe. Bedford (just 2mm in whole of August)

www.weatherwise.org.uk

Hi Joe,

I never thought it was never going to fall from the sky again as it seems to
have gone east , west, north and south over the past couple of weeks. Maybe
we will be lucky with some snow this winter to make up

Chris

--

"Joe" wrote in message
...

"Chris Mantle" wrote in message
...
Thanks Jon, spent a few minutes trying to work out where the red blob
was,
though the chart had changed

Chris
Kempston, Bedford

--


Hi Chris, hope you've enjoyed the rain

managed nearly 7mm in last 2 days. wow.

Joe. Bedford (just 2mm in whole of August)

www.weatherwise.org.uk