On Friday, April 5, 2013 10:40:41 AM UTC+1, George Booth wrote:

It's

not a case of your being in a rain shadow it's simply that under these

strong north-easterlies convergence lines become established along the

NE-SW trending part of the Essex-Suffolk coast and/or along the E-W axis

of the Thames Estuary. These become conveyor belts of heavy showers and

if they do not shift then places along them experience high snowfall

totals e.g. south-east Essex January 1987. I should add they are not

unique to the South-East. These lines can be relatively narrow and

nearby areas experience little precipitation-all well shown on the radar

yesterday. Epping's short lived heavy snow was the result of one of the

convergence lines (the more northerly one) extending inland although we

are very much on the limits whereas south-east Essex and north Kent can

be seriously affected.

As an aside, I mentioned the other day all the local annual rainfall

data I have been collecting covering the last 150 years. Some impressive

differences in rainfall figures between weather stations in the same

area for the same year.

Are convergence lines impossible to pinpoint in forecasts? I appreciate that forecasters, in these situations, can warn people of a high chance of showery activity but are we any further than 1987 in saying exactly where it will snow? Obviously there will always be the usual suspects that seem to catch the snow better than others - but it is clear that this isn't always the case

On 05/04/2013 13:35, Scott W wrote:


On Friday, April 5, 2013 10:40:41 AM UTC+1, George Booth wrote:

It's

not a case of your being in a rain shadow it's simply that under these

strong north-easterlies convergence lines become established along the

NE-SW trending part of the Essex-Suffolk coast and/or along the E-W axis

of the Thames Estuary. These become conveyor belts of heavy showers and

if they do not shift then places along them experience high snowfall

totals e.g. south-east Essex January 1987. I should add they are not

unique to the South-East. These lines can be relatively narrow and

nearby areas experience little precipitation-all well shown on the radar

yesterday. Epping's short lived heavy snow was the result of one of the

convergence lines (the more northerly one) extending inland although we

are very much on the limits whereas south-east Essex and north Kent can

be seriously affected.

As an aside, I mentioned the other day all the local annual rainfall

data I have been collecting covering the last 150 years. Some impressive

differences in rainfall figures between weather stations in the same

area for the same year.

Are convergence lines impossible to pinpoint in forecasts? I appreciate that forecasters, in these situations, can warn people of a high chance of showery activity but are we any further than 1987 in saying exactly where it will snow? Obviously there will always be the usual suspects that seem to catch the snow better than others - but it is clear that this isn't always the case


One for the experts perhaps. From a personal point of view convergence
lines were, for many years, of great interest to me from a gliding point
of view, with associated strong lift-as long as you kept away from the
showers of course. Weatherwise I do believe they can be forecast with
reasonable accuracy and they regularly appear on UKMO forecast charts.
From a more local view I have interest in those which appear in the
Essex area and in south Edinburgh/Midlothian - areas I know well - and
yes given the same parameters the convergence lines will appear in the
same locations.
Mind you as far as forecasting what will happen in somebody's back
garden or wherever, well that's another matter. Some time ago I worked
with Jack Harrison (Weatherjack) on soaring forecasts and quickly
learned to take care in what I actually said.

So, over to anyone who actually puts those 'Christmas Trees' on the charts

--
George in Epping, west Essex, 350'asl
www.eppingweather.co.uk
www.winter1947.co.uk

"Scott W" wrote in message
...


On Friday, April 5, 2013 10:40:41 AM UTC+1, George Booth wrote:

It's

not a case of your being in a rain shadow it's simply that under these

strong north-easterlies convergence lines become established along the

NE-SW trending part of the Essex-Suffolk coast and/or along the E-W axis

of the Thames Estuary. These become conveyor belts of heavy showers and

if they do not shift then places along them experience high snowfall

totals e.g. south-east Essex January 1987. I should add they are not

unique to the South-East. These lines can be relatively narrow and

nearby areas experience little precipitation-all well shown on the radar

yesterday. Epping's short lived heavy snow was the result of one of the

convergence lines (the more northerly one) extending inland although we

are very much on the limits whereas south-east Essex and north Kent can

be seriously affected.

As an aside, I mentioned the other day all the local annual rainfall

data I have been collecting covering the last 150 years. Some impressive

differences in rainfall figures between weather stations in the same

area for the same year.

Are convergence lines impossible to pinpoint in forecasts? I appreciate that
forecasters, in these situations, can warn people of a high chance of
showery activity but are we any further than 1987 in saying exactly where it
will snow? Obviously there will always be the usual suspects that seem to
catch the snow better than others - but it is clear that this isn't always
the case

========================

The Met Office 1.5 km model does a reasonable (not perfect though) job of
these. But that detail is rarely put out for public consumption as the MetO
see it as a money earner for paying customers. If it was going to be really
heavy leading to widespread disruption then more detail would have been
attempted in any warnings.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

"Scott W" wrote in message
...
On Friday, April 5, 2013 11:20:28 AM UTC+1, George Booth wrote:
On 05/04/2013 10:58, Scott W wrote:

On Friday, April 5, 2013 10:40:41 AM UTC+1, George Booth wrote:

On 04/04/2013 20:15, Keith (Southend)G wrote:



Maximum temperature for me here at Southend-on-Sea was +2.9�C, which
beat my previous lowest April maximum of 3.4� of 6th APril 2008.







Bob Prichards records I have show 2.8�C on the 3rd April 1964,
3.3�C 14th April 1966, 4.4�C 1970.







How we forget it's nothing new.







Keith (Southend)



http://www.southendweather.net



"Weather Home & Abroad"











09-09 maximum of 2.9 here (daytime max 2.1 yesterday) so the coldest



April 09-09 day in my record but only by a squeak. Light snow showers



earlier gave way to brighter conditions and there's a lot of daylight



now before 0900 GMT and the temperature crept up.



Early days I know but the monthly anomaly is running at -7.1 deg of the



1981-2010 mean. The landscape has a barren look.



09-09 maximum here was 3.2C at 0850z this morning. The minimum: 1.4C at
1208z yesterday. Despite snow grains pretty much all day yesterday I
only recorded 0.6mm in the snowdon. It looks like the snow was heavier
and more intense further east and south of here



..........and to the north of you as well Scott. Heavy wet snow driven

by 30mph gusts. Poor visibility in those showers as well. It's all about

those energy lines we spoke about yesterday. Radar showed these nicely.



--

George in Epping, west Essex, 350'asl

www.eppingweather.co.uk

www.winter1947.co.uk

Interesting, what was your 09-09 rainfall, George? I must be in a rain
shadow here? Both my gauges are roughly in agreement - and I was laying
concrete slabs yesterday - it was only towards around 3pm that the soil was
even starting to become sodden with precipitation - so I'm fairly confident
no rainfall was missed here...

Move to Woodford ...1.7mm of melted snow between 1000 and 1700 bst max temp
2.4c at 1730z !

RonB

On 05/04/2013 15:55, Eskimo Will wrote:

"Scott W" wrote in message
...


On Friday, April 5, 2013 10:40:41 AM UTC+1, George Booth wrote:

It's

not a case of your being in a rain shadow it's simply that under these

strong north-easterlies convergence lines become established along the

NE-SW trending part of the Essex-Suffolk coast and/or along the E-W axis

of the Thames Estuary. These become conveyor belts of heavy showers and

if they do not shift then places along them experience high snowfall

totals e.g. south-east Essex January 1987. I should add they are not

unique to the South-East. These lines can be relatively narrow and

nearby areas experience little precipitation-all well shown on the radar

yesterday. Epping's short lived heavy snow was the result of one of the

convergence lines (the more northerly one) extending inland although we

are very much on the limits whereas south-east Essex and north Kent can

be seriously affected.

As an aside, I mentioned the other day all the local annual rainfall

data I have been collecting covering the last 150 years. Some impressive

differences in rainfall figures between weather stations in the same

area for the same year.

Are convergence lines impossible to pinpoint in forecasts? I appreciate
that forecasters, in these situations, can warn people of a high chance
of showery activity but are we any further than 1987 in saying exactly
where it will snow? Obviously there will always be the usual suspects
that seem to catch the snow better than others - but it is clear that
this isn't always the case

========================

The Met Office 1.5 km model does a reasonable (not perfect though) job
of these. But that detail is rarely put out for public consumption as
the MetO see it as a money earner for paying customers. If it was going
to be really heavy leading to widespread disruption then more detail
would have been attempted in any warnings.

Will

http://rasp.inn.leedsmet.ac.uk/
I've found that this is good, including forecasting zones of streeting
in summer. Never really looked at it from a winter perspective but the
BL Max Up/Down (Convergence) is the one to check.
A very interesting site.
You may need to adjust the transparency.

--
George in Epping, west Essex, 350'asl
www.eppingweather.co.uk
www.winter1947.co.uk

In article ,
George Booth writes:
snip
It's not a case of your being in a rain shadow it's simply that under
these strong north-easterlies convergence lines become
established along the NE-SW trending part of the Essex-Suffolk
coast and/or along the E-W axis of the Thames Estuary. These
become conveyor belts of heavy showers and if they do not shift
then places along them experience high snowfall totals e.g. south-
east Essex January 1987.

The current issue of "Weather" has an interesting article about the
climate of SE England and East Anglia which includes a map showing
snowfall amounts in the heavy snow of early February 2009, illustrating
these "streaks" (which in that case affected parts of Surrey
particularly badly).
--
John Hall
"Madam, you have between your legs an instrument capable
of giving pleasure to thousands and all you can do is scratch it."
Sir Thomas Beecham (1879-1961) to a lady cellist

On 05/04/2013 19:26, John Hall wrote:
In article ,
George Booth writes:
snip
It's not a case of your being in a rain shadow it's simply that under
these strong north-easterlies convergence lines become
established along the NE-SW trending part of the Essex-Suffolk
coast and/or along the E-W axis of the Thames Estuary. These
become conveyor belts of heavy showers and if they do not shift
then places along them experience high snowfall totals e.g. south-
east Essex January 1987.

The current issue of "Weather" has an interesting article about the
climate of SE England and East Anglia which includes a map showing
snowfall amounts in the heavy snow of early February 2009, illustrating
these "streaks" (which in that case affected parts of Surrey
particularly badly).


Another article by W.S Pike, is in Weather Vol 59, Issue 2, February 2004

'A radar study of the snowfalls over
south-eastern England during
daylight hours on 8 January 2003'

south Essex and north Kent were the areas most affected with between 15
and 20cm of snow

Another Bill Pike article, which I think Richard mentioned is Pike, W.
S. (1991)
'Persistent coastal
convergence in a heavy snowfall event on
the south-east coast of England'. Meteorol.
Mag., 119, pp. 21–32

--
George in Epping, west Essex, 350'asl
www.eppingweather.co.uk
www.winter1947.co.uk

On 05/04/13 19:26, John Hall wrote:
In ,
George writes:
snip
It's not a case of your being in a rain shadow it's simply that under
these strong north-easterlies convergence lines become
established along the NE-SW trending part of the Essex-Suffolk
coast and/or along the E-W axis of the Thames Estuary. These
become conveyor belts of heavy showers and if they do not shift
then places along them experience high snowfall totals e.g. south-
east Essex January 1987.

The current issue of "Weather" has an interesting article about the
climate of SE England and East Anglia which includes a map showing
snowfall amounts in the heavy snow of early February 2009, illustrating
these "streaks" (which in that case affected parts of Surrey
particularly badly).

My boss said there was about 10 inches of snow in Guildford from that
event yet at work which is about 10 miles SE and up in the Surrey hills
there was no more than about 4 inches.

"Adam Lea" wrote in message
...
On 05/04/13 19:26, John Hall wrote:
In ,
George writes:
snip
It's not a case of your being in a rain shadow it's simply that under
these strong north-easterlies convergence lines become
established along the NE-SW trending part of the Essex-Suffolk
coast and/or along the E-W axis of the Thames Estuary. These
become conveyor belts of heavy showers and if they do not shift
then places along them experience high snowfall totals e.g. south-
east Essex January 1987.

The current issue of "Weather" has an interesting article about the
climate of SE England and East Anglia which includes a map showing
snowfall amounts in the heavy snow of early February 2009, illustrating
these "streaks" (which in that case affected parts of Surrey
particularly badly).

My boss said there was about 10 inches of snow in Guildford from that
event yet at work which is about 10 miles SE and up in the Surrey hills
there was no more than about 4 inches.

I had 4 inches in Crowthorne Berkshire.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

In article ,
Adam Lea writes:
On 05/04/13 19:26, John Hall wrote:

The current issue of "Weather" has an interesting article about the
climate of SE England and East Anglia which includes a map showing
snowfall amounts in the heavy snow of early February 2009, illustrating
these "streaks" (which in that case affected parts of Surrey
particularly badly).

My boss said there was about 10 inches of snow in Guildford from
that event yet at work which is about 10 miles SE and up in the
Surrey hills there was no more than about 4 inches.

I can well believe that. Here in Cranleigh there was only 2-3 inches.
I'd heard that there had been 10 inches in Guildford.
--
John Hall
"Madam, you have between your legs an instrument capable
of giving pleasure to thousands and all you can do is scratch it."
Sir Thomas Beecham (1879-1961) to a lady cellist