On 12 Aug, 11:19, Steve Willington wrote:
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

Sorry for any typos found in the above comments - a quick brain dump
with no proof reading!

Steve.
www.rockbeareweather.co.uk

On Aug 12, 11:32*am, Steve Willington
wrote:
On 12 Aug, 11:19, Steve Willington wrote:





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

Sorry for any typos found in the above comments - a quick brain dump
with no proof reading!

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

- Show quoted text -

You are forgiven. Thanks Steve.

On Aug 12, 11:32*am, Steve Willington
wrote:
On 12 Aug, 11:19, Steve Willington wrote:





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

Sorry for any typos found in the above comments - a quick brain dump
with no proof reading!

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

- Show quoted text -

No typos found, and my first job in Bracknell was as a sub-
editor, a job that gives one a hawk eye but also encourages pedantry.
More importantly, a nice clarification of the mechanisms associated
with Spanish plumes. Thanks, Steve.

Tudor Hughes, Warlingham, Surrey.

On Aug 11, 9:40*pm, "Dave R." wrote:
"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

This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........

On Aug 12, 5:41 pm, Dawlish wrote:
On Aug 11, 9:40 pm, "Dave R." wrote:

"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

This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........

What the runs do seem to agree on is that it will be *most* settled
period since the end of July, which will be something of a relief even
if we don't get a high as such. Latest GFS suggests something very hot
around the 26th perhaps.

Nick

On Tue, 12 Aug 2008 at 10:42:11, wrote in
uk.sci.weather :

This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........

What the runs do seem to agree on is that it will be *most* settled
period since the end of July, which will be something of a relief even
if we don't get a high as such. Latest GFS suggests something very hot
around the 26th perhaps.

A forecast *two weeks* ahead? About as reliable as a politicians
promise...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

On Aug 13, 9:32*am, Paul Hyett wrote:
On Tue, 12 Aug 2008 at 10:42:11, wrote in
uk.sci.weather :



This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........

What the runs do seem to agree on is that it will be *most* settled
period since the end of July, which will be something of a relief even
if we don't get a high as such. Latest GFS suggests something very hot
around the 26th perhaps.

A forecast *two weeks* ahead? About as reliable as a politicians
promise...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

I don't think Nick's comments were a forecast! However, mine, at the
top of this thread certainly was and at the moment, it looks likely
that next Tuesday will be anything like calm and settled!

Paul

On Aug 13, 10:14 am, Dawlish wrote:
On Aug 13, 9:32 am, Paul Hyett wrote:



On Tue, 12 Aug 2008 at 10:42:11, wrote in
uk.sci.weather :

This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........

What the runs do seem to agree on is that it will be *most* settled
period since the end of July, which will be something of a relief even
if we don't get a high as such. Latest GFS suggests something very hot
around the 26th perhaps.

A forecast *two weeks* ahead? About as reliable as a politicians
promise...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

I don't think Nick's comments were a forecast! However, mine, at the
top of this thread certainly was and at the moment, it looks likely
that next Tuesday will be anything like calm and settled!

Paul

Well it could be down in the southwest according to the GFS 0600!
Seems to still be very variable even as soon as the weekend.

Nick

Yes, another utterly uselsess forecast by Dawlish.
Youre wasting your time. No ones interested.


Dawlish wrote:
On Aug 13, 9:32 am, Paul Hyett wrote:
On Tue, 12 Aug 2008 at 10:42:11, wrote in
uk.sci.weather :



This possible high pressure and settled weather is such a tease! Still
in the balance on both the gfs and the ECM. Neither model has shown
consistency since the gfs flagged up high pressure with 5 consecutive
runs. Looking at when I forecast that I've actually got the date wrong
at T240 (blushes). well it was late at night! I still thought it was
Tuesday! The 10 day forecast is actually for Wednesday. I'll get my
coat..........
What the runs do seem to agree on is that it will be *most* settled
period since the end of July, which will be something of a relief even
if we don't get a high as such. Latest GFS suggests something very hot
around the 26th perhaps.
A forecast *two weeks* ahead? About as reliable as a politicians
promise...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

I don't think Nick's comments were a forecast! However, mine, at the
top of this thread certainly was and at the moment, it looks likely
that next Tuesday will be anything like calm and settled!

Paul

In article ,
Pressure In Berne writes:
Yes, another utterly uselsess forecast by Dawlish.
Youre wasting your time. No ones interested.

Wrong. And you needn't think that having changed your Usenet identity
means that we can't guess who you are.
--
John Hall "George the Third
Ought never to have occurred.
One can only wonder
At so grotesque a blunder." E.C.Bentley (1875-1956)