It has been shown a few times already but for anyone who hasn't seen it
I can recommend the documentary on BBC4 at 10:30 this evening.

Norman.
(delete "thisbit" twice to e-mail)
--
Norman Lynagh Weather Consultancy
Chalfont St Giles
England

Yes Norman ,I hadn't seen it before ,and yes it was very good .
Obviously though it raised some questions , like the arrogance of Helen
Young to say the British public don't understand what the JetStream means
so therefore she won't let us see it in our forecasts, and ,the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

RonB
"Norman Lynagh" wrote in
message ...
It has been shown a few times already but for anyone who hasn't seen it
I can recommend the documentary on BBC4 at 10:30 this evening.

Norman.
(delete "thisbit" twice to e-mail)
--
Norman Lynagh Weather Consultancy
Chalfont St Giles
England

..........the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?
this is consistent with with the tendency to +ve values of the NAO index in the latter half of the
C20,though in recent years this seems to declined .However,I'm not sure the conventional NAO indices
reflect properly current storm track regimes.It's hard to find an uptodate blocking climatology,most
concentrate on cyclones.(tho I haven't looked exhaustively)
This recent paper may be of interest-

Trigo,R.M., I. F. Trigo, C. C. DaCamara, and T. J. Osborn, 2004: Climate impact of the European
winter blocking episodes from the NCEP/NCAR Reanalyses. Clim. Dyn ., 23 (1), 17-28.
online at-
http://www.nersc.no/MACESIZ/Papers/tri04.pdf

Also it's discussion of cloudiness and max/min temperatures may be of relevance to the perceived
decline in fog mentioned elsewhere,

--
regards,
david
(add 17 to waghorne to reply)

In article ,
Ron Button writes:
Yes Norman ,I hadn't seen it before ,and yes it was very good .
Obviously though it raised some questions , like the arrogance of Helen
Young to say the British public don't understand what the JetStream means
so therefore she won't let us see it in our forecasts,

Of course they never _will_ understand it if they are never exposed to
it. US forecasters use it, and I can't believe that the American
audience is any more intelligent than ours.

and ,the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

Blocking highs and the position of the Jetstream are clearly linked, but
isn't it over-simplifying to imply that they are cause and effect?
--
John Hall
"I look upon it, that he who does not mind his belly,
will hardly mind anything else."
Dr Samuel Johnson (1709-84)

"Ron Button" wrote in message
...
Yes Norman ,I hadn't seen it before ,and yes it was very good .
Obviously though it raised some questions , like the arrogance of Helen
Young to say the British public don't understand what the JetStream means
so therefore she won't let us see it in our forecasts, and ,the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

RonB

Yes, it was interesting but, as with all programmes of this type, lacking
much real science. I wouldn't say Helen Young was arrogant. I think it's a
fact that most of the British public understand very little about
'jetstreams'. A bit like the chicken and the egg.... a). Should
forecasters; given the time; refer to the science behind their forecasts and
thereby encourage the public to increase their knowledge OR b) Should the
media provide some good, in depth science programmes so the public can
understand the science behind the forecasts? I'm afraid in the present
'climate' of audience ratings and cost effectiveness neither will happen -
though a little of the first should be possibe.
John
--
York,
North Yorkshire.
(Norman Virus Protected)

"Ron Button" wrote in message ...
the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

RonB



Does the course of the Jet Stream influence the positioning of areas
of LP and HP? Or is the positioning of pressure systems dependant on
completely different criteria, and indeed, do HP areas themselves
steer the course of the Jet Stream?

"N-le-W" wrote in message
m...
"Ron Button" wrote in message
...
the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

RonB

Does the course of the Jet Stream influence the positioning of areas
of LP and HP?

Putting it simply....??
Yes..basically the Polar Front Jet, which effects our part of the world,
lies along a boundry of strong horizontal temperature contrasts. The wind
blowing parallel to the mean isotherms. This jet is usually associated with
frontal zones. Areas of the jet in which the flow is accellerating or
deccellerating result in ageostrophic flow 'across' the jet, which in turn
results in vertical motion. Typically the left (cold) exit and the right
(warm) entrance to the jet are areas of cyclonic development ...and vice
versa for anticyclonic development.

Do HP areas themselves steer the course of the Jet Stream?

Generally yes for large semi-permanent highs ( Azores High, Asiatic High).
Large highs are areas of small horizontal thermal variation - at least to
any depth. Small horizontal temperature gradient = no jet stream. Smaller
transient highs, often in polar air, may be a result of and influenced by
the Jet Stream.
Cheers
John
--
York,
North Yorkshire.
(Norman Virus Protected)

"John Whitby" wrote in message ...
"N-le-W" wrote in message
m...
"Ron Button" wrote in message
...
the statement
made by the commentator that 'There has been reduction of blocking Highs
across the U.K. thereby allowing the JetStream a freer access to Western
Europe' . Is that true ?

RonB

Does the course of the Jet Stream influence the positioning of areas
of LP and HP?

Putting it simply....??
Yes..basically the Polar Front Jet, which effects our part of the world,
lies along a boundry of strong horizontal temperature contrasts. The wind
blowing parallel to the mean isotherms. This jet is usually associated with
frontal zones. Areas of the jet in which the flow is accellerating or
deccellerating result in ageostrophic flow 'across' the jet, which in turn
results in vertical motion. Typically the left (cold) exit and the right
(warm) entrance to the jet are areas of cyclonic development ...and vice
versa for anticyclonic development.

Do HP areas themselves steer the course of the Jet Stream?

Generally yes for large semi-permanent highs ( Azores High, Asiatic High).
Large highs are areas of small horizontal thermal variation - at least to
any depth. Small horizontal temperature gradient = no jet stream. Smaller
transient highs, often in polar air, may be a result of and influenced by
the Jet Stream.
Cheers
John


Thanks for that.

I think I know what you're saying