Summer is not over! (well, there's a 75-80% chance that it is not
over!)

On Tuesday, 19th August, much of the UK will be dominated by high
pressure. The weather will be settled, with plenty of sunshine and
warmer than average daytime temperatures. The majority of the UK will
be dry and most of us will have breathed a big sigh of relief to get
rid of the low pressures, cood temperatures and wet conditions that
will have plagued us in the preceeding week.

The coming week looks dreadful, but I think the weather will improve
towards the 19th. Right in the middle of my holiday in Cornwall too!
No guearantees that it will stay to the bank holiday, but this
increases the chances that it will.

Paul

On Aug 10, 12:39*am, Dawlish wrote:
Summer is not over! (well, there's a 75-80% chance that it is not
over!)

On Tuesday, 19th August, much of the UK will be dominated by high
pressure. The weather will be settled, with plenty of sunshine and
warmer than average daytime temperatures. The majority of the UK will
be dry and most of us will have breathed a big sigh of relief to get
rid of the low pressures, cood temperatures and wet conditions that
will have plagued us in the preceeding week.

The coming week looks dreadful, but I think the weather will improve
towards the 19th. Right in the middle of my holiday in Cornwall too!
No guearantees that it will stay to the bank holiday, but this
increases the chances that it will.

Paul

It just looks so wet this week - especially tomorrow and especially in
the West. No weather warnings out yet, but expect some. It looks like
Autumn in the SW and the tourists are not going to go home like
lobsters this week! The model output for this has been incredibly
consistent, since my forecast of low pressure dominance for the 12th.
By tomorrow, we will have had 12 days of consistency about tomorrow's
(and this week's) autumnal weather. The models have done very well.

Quite a model wobble on this forecast yesterday, but the higher
pressure is back today on the gfs. My confidence in it has presenttly
dropped below 75%, but I still feel that higher pressure on the 19th
is more likely than the low pressure in this Met Office forecast from
yesterday:

"After a cool and showery day on Friday, the weather should generally
improve over the coming weekend, with more in the way of warm sunshine
and less showers around. However, more wet and windy weather is
expected to arrive from the Atlantic to affect southwest England,
Wales and Northern Ireland later on Sunday. From Monday to Wednesday,
the weather looks distinctly unsettled and often quite windy across
the United Kingdom, with a mix of sunshine and showers. The showers
heavy in places and merging to give more prolonged spells of rain at
times, while also turning disappointingly cool again. Towards the end
of next week and into the following weekend, there is a hint of a
change to more settled, warmer weather, especially in the south and
east.

Updated: 1238 on Sun 10 Aug 2008"

It's an interesting situation. Here's a case where the model output
actually is variable, at less than 10 days. I'm hoping the gfs has a
better handle on the situation next week, but after the output over
the last 24 hours, I'm not as confident as I was early yesterday
morning.

Paul

On Mon, 11 Aug 2008 00:50:20 -0700 (PDT), Dawlish
wrote:


Towards the end
of next week and into the following weekend, there is a hint of a
change to more settled, warmer weather, especially in the south and
east.

Updated: 1238 on Sun 10 Aug 2008"


Hi Paul

All I would say is that I have seen this 'hint of high pressure' quite
a few times so far in the last month!

My feeling is that we are 'bound' to get some very pleasant weather in
September and October. I seem to recall that we have had a run of
quite quiet autumns recently.

R

On Aug 11, 9:07*am, Robin Nicholson
wrote:
On Mon, 11 Aug 2008 00:50:20 -0700 (PDT), Dawlish
wrote:

*Towards the end

of next week and into the following weekend, there is a hint of a
change to more settled, warmer weather, especially in the south and
east.

Updated: 1238 on Sun 10 Aug 2008"

Hi Paul

All I would say is that I have seen this 'hint of high pressure' quite
a few times so far in the last month!

My feeling is that we are 'bound' to get some very pleasant weather in
September and October. I seem to recall that we have had a run of
quite quiet autumns recently.

R

Yes, I agree, Robin. The previous MetO 6-15 days forecast had exactly
that for next week (not the week after, as in yeasterday's update)!
I've not felt that those hints have generated enough confidence for a
forecast - hence no forecast of settled weather from me, until this
one.

Paul

On Aug 11, 9:28*am, Dawlish wrote:
On Aug 11, 9:07*am, Robin Nicholson



wrote:
On Mon, 11 Aug 2008 00:50:20 -0700 (PDT), Dawlish
wrote:

*Towards the end

of next week and into the following weekend, there is a hint of a
change to more settled, warmer weather, especially in the south and
east.

Updated: 1238 on Sun 10 Aug 2008"

Hi Paul

All I would say is that I have seen this 'hint of high pressure' quite
a few times so far in the last month!

My feeling is that we are 'bound' to get some very pleasant weather in
September and October. I seem to recall that we have had a run of
quite quiet autumns recently.

R

Yes, I agree, Robin. The previous MetO 6-15 days forecast had exactly
that for next week (not the week after, as in yeasterday's update)!
I've not felt that those hints have generated enough confidence for a
forecast - hence no forecast of settled weather from me, until this
one.

Paul

It must be born in mind that the MetO forecasts will be generated
using a lot of additional data so it will not be surprising that it
may be at odds with GFS - GFS Operational runs and ensembles will be a
part of the mix (often small) that will vary given the situation.

Steve.
www.rockbeareweather.co.uk

On Aug 11, 9:39*am, Steve Willington
wrote:
On Aug 11, 9:28*am, Dawlish wrote:





On Aug 11, 9:07*am, Robin Nicholson

wrote:
On Mon, 11 Aug 2008 00:50:20 -0700 (PDT), Dawlish
wrote:

*Towards the end

of next week and into the following weekend, there is a hint of a
change to more settled, warmer weather, especially in the south and
east.

Updated: 1238 on Sun 10 Aug 2008"

Hi Paul

All I would say is that I have seen this 'hint of high pressure' quite
a few times so far in the last month!

My feeling is that we are 'bound' to get some very pleasant weather in
September and October. I seem to recall that we have had a run of
quite quiet autumns recently.

R

Yes, I agree, Robin. The previous MetO 6-15 days forecast had exactly
that for next week (not the week after, as in yeasterday's update)!
I've not felt that those hints have generated enough confidence for a
forecast - hence no forecast of settled weather from me, until this
one.

Paul

It must be born in mind that the MetO forecasts will be generated
using a lot of additional data so it will not be surprising that it
may be at odds with GFS - GFS Operational runs and ensembles will be a
part of the mix (often small) that will vary given the situation.

Steve.www.rockbeareweather.co.uk- Hide quoted text -

- Show quoted text -

This forecast is still in the balance for next tuesday - but there's
something that we haven't seen on any chart, even at T264+, for weeks.
A North African plume!!

http://www.wetterzentrale.de/pics/Rtavn2642.png

I'll believe it if it stays for another day's runs!

Paul

"Dawlish" wrote in message
news:fb2bc050-2556-457f-b28e-

This forecast is still in the balance for next tuesday -
Paul

Not Tuesday, Wednesday - it keeps gettin put back each day.
Which is what I expect anyway so your not much hope anyway

Dave R

On Mon, 11 Aug 2008 at 09:55:06, Dawlish wrote in
uk.sci.weather :

This forecast is still in the balance for next tuesday - but there's
something that we haven't seen on any chart, even at T264+, for weeks.
A North African plume!!

How is that different from a Spanish one?
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

On Aug 12, 8:18*am, Paul Hyett wrote:
On Mon, 11 Aug 2008 at 09:55:06, Dawlish wrote in
uk.sci.weather :



This forecast is still in the balance for next tuesday - but there's
something that we haven't seen on any chart, even at T264+, for weeks.
A North African plume!!

How is that different from a Spanish one?
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

It has it's source in North Africa - as most plumes that reach the UK
do. The hot, dry, often Saharan air becomes substantially modified as
it crosses Iberia, on its Northward passage to the UK. "Spanish" plume
is a misnomer, as regards the actual source of the hot air, but would
be accurate if applied to the source of the modification of that air
to produce the potential for thunderstorms in the UK.

Look at the source of this hot air in this possible example at +264 on
the gfs.

http://www.wetterzentrale.de/pics/Rtavn2642.png

It is then shown to cross Spain and if it did get to the UK (which I
think is unlikely) I'm sure the press would call it a "Spanish" plume;
but the source of the hot air would not have been Spain.

http://www.wetterzentrale.de/pics/Rtavn3122.png

Only the modification would be Spanish - and French too! Of course,
pedantically, air has no real "source". It just moves from area to
area, but this air mass lingered far longer over North Africa than it
is likely to linger over over Spain.

Paul

On 12 Aug, 09:26, Dawlish wrote:
On Aug 12, 8:18*am, Paul Hyett wrote:

On Mon, 11 Aug 2008 at 09:55:06, Dawlish wrote in
uk.sci.weather :

This forecast is still in the balance for next tuesday - but there's
something that we haven't seen on any chart, even at T264+, for weeks.
A North African plume!!

How is that different from a Spanish one?
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

It has it's source in North Africa - as most plumes that reach the UK
do. The hot, dry, often Saharan air becomes substantially modified as
it crosses Iberia, on its Northward passage to the UK. "Spanish" plume
is a misnomer, as regards the actual source of the hot air, but would
be accurate if applied to the source of the modification of that air
to produce the potential for thunderstorms in the UK.

Look at the source of this hot air in this possible example at +264 on
the gfs.

http://www.wetterzentrale.de/pics/Rtavn2642.png

It is then shown to cross Spain and if it did get to the UK (which I
think is unlikely) I'm sure the press would call it a "Spanish" plume;
but the source of the hot air would not have been Spain.

http://www.wetterzentrale.de/pics/Rtavn3122.png

Only the modification would be Spanish - and French too! Of course,
pedantically, air has no real "source". It just moves from area to
area, but this air mass lingered far longer over North Africa than it
is likely to linger over over Spain.

Paul

There are a few things here that need clarifying:
Spanish plume is a generic term for an elevated mixed layer (EML)
that, in NW Europe, usually has its origins over hot arid surfaces to
the south, often elevated. In the UK the most common source regions
are Iberia and the Sahara. More often than not they remain separate on
their track to the UK during which time they undergo isentropic up-
gliding conserving their potential temperatures. EMLs of Iberian
origin occur a little more frequently across the UK and France than
those from the Sahara (which, interestingly, are far more commonly
found at mid-level above the Caribbean). On many occasions both EMLs
will be present clearly identifiable in soundings from their
respective potential temperatures which will be closely aligned with
source region temperatures, approx 35 to 38C for Iberian and 42 to 46C
for Saharan (dependent on time of year), the EML of Saharan origin
sitting at a higher level than that sourced from Iberia. EMLs occur in
many regions throughout the world and do not necessarily require
elevated arid regions to form, some forming over regions where there
is a large horizontal gradient in soil moisture.
In themselves EMLs are not that exciting, why they are exciting in NW
Europe during the warmer months of the year is on occasions when they
are advected northwards across France they provide a lid allowing the
BL air below this to take up latent and sensible heat elevating WBPTs.
The longer an EML sits over France for instance the higher the BL WBPT
that can realised and the more energy available for convection if the
lid is weakened, due to increasing baroclinicity ahead of an upper
trough, or if under-running occurs. IOW without the EML you would not
attain the high BL WBPTs seen, this is one way of identifying the
region overlain by an EML.
BTW Ac Cast occurs (normally northern edge) when the EML has been
lifted enough for its upper reaches to attain its LCL – it does not
tell you anything about the airmass and its stability above this
level, it could be capped by a further EML (Saharan overlying Iberian)
or subsidence.

Steve.
www.rockbeareweather.co.uk