On Sat, 10 Jan 2004 08:58:11 -0000, PJB wrote in


Thanks Paul, I'm OK on the low level baroclinic zone. Could you just
amplify
the last sentence. What is a 'shortwave Upper Trough' is this just a
'trough' of low pressure, but at altitude and not necessarily at the
surface?

Yes Phil a shortwave is a trough of low pressure at a certain height (say
300mb) it is called a shortwave becuase it is much smaller than a typical
"long wave" upper trough which stretch for thousands of miles (such as when
we are in an omega block - that is the longwave pattern) a shortwave is a
much smaller feature, but it can provide the required forcing to deepen a
low very quickly.

It's also worth noting these "short waves" typically move faster [1] than
the long waves in which they are embedded. The latter can almost be
thought of as quasi-stationary in many situations, with the shorter ones
moving through them. There is a slight analogy with ocean waves [2] where
the long waves move at greater speed than the short waves.

[1] The speed of wave movement "c" is given by the Rossby Equation:

c = U - Lβ²/4π²

Where U is wind speed within the wave, β is ∂f/∂y a measure of how fast the
coriolis effect (parameter) is changing with latitude and L is latitude.
This formula shows the importance of wavelength. When it exceeds a certain
figure, c goes negative and the wave retrogresses - goes back to the west.

[2] The major difference between the two types of wave is that motion
within an atmospheric wave is largely horizontal, whilst that of an ocean
wave is vertical.

Apoligies if the symbols don't show up correctly. This is my first attempt
at using the Windows Character Map.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 10/01/2004 09:43:26 UTC
My aurora images here http://www.mtullett.plus.com/29a-oct and
http://www.mtullett.plus.com/20-nov/

Yes Phil a shortwave is a trough of low pressure at a certain height (say
300mb) it is called a shortwave becuase it is much smaller than a typical
"long wave" upper trough which stretch for thousands of miles (such as when
we are in an omega block - that is the longwave pattern) a shortwave is a
much smaller feature, but it can provide the required forcing to deepen a
low very quickly.
Another way to think about this is in terms of PV.The short wave trough is a PV anomaly -a
tropopause depression-which induces ascent ahead of itself depending on it's structure.As it
approaches the surface baroclinic zone development can take place-depending on timing and diabatic
factors.If this PV anomaly 'phase locks' with the surface low ie develops an optimal westerly tilt
structure then explosive development can take place.
Let's not forget Browning's 'Sting-in the tail' of the back bent occlusion and the strong jet.

BTW how popular is PV thinking currently with you operational forecasters ?

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

Your on a high speed train and want to visit the buffet. It's on a
100+mph stretch of the East Coast mainline

Much more turbulence on thhe west coast line ;-).
For the state of the art on jet streak dynamics see-
http://www.atmos.albany.edu/student/...et_streak.html
http://www.iac.ethz.ch/~sdirren/my_h...iences/Rossby/
http://www.atmos.washington.edu/~hakim/pubs.html
on PV dynamics-
http://www.met.reading.ac.uk/~sws98slg/midlatdyn.html

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

"Waghorn" wrote in message
...
Your on a high speed train and want to visit the buffet. It's on a
100+mph stretch of the East Coast mainline

Much more turbulence on thhe west coast line ;-).

.... no doubt! Strange how railways (like the weather itself) forms the
backdrop to the psychology of these islands ;-)

For the state of the art on jet streak dynamics see-
http://www.atmos.albany.edu/student/...et_streak.html
http://www.iac.ethz.ch/~sdirren/my_h...iences/Rossby/
http://www.atmos.washington.edu/~hakim/pubs.html
on PV dynamics-
http://www.met.reading.ac.uk/~sws98slg/midlatdyn.html


.... thanks for those links: I'm certainly not an expert and will read
them up - however, at the end of the day, some poor sod at 0200 in the
morning has got to decide whether to issue a warning or not and hope
he/she has read the signs aright. I'm glad it's not me anymore!!

Martin.

In article ,
Mike Tullett writes:
Apoligies if the symbols don't show up correctly. This is my first attempt
at using the Windows Character Map.

They didn't here, but that may be the fault of a news server en route
not being able to cope.
--
John Hall

"The covers of this book are too far apart."
Ambrose Bierce (1842-1914)

Thanks All,
Fascinating stuff and I'll keep the emails. I know there are books on the
issues, but I understand much more by asking questions and receiving
answers. So thanks very much for that.

Phil

Thanks everyone on this thread.. Most informative, and a few more
mysteries uncovered...

I know strange things happen off Newfoundland, but it has always been
a black box with contrasting airmasses involved. The details in this
thread were very interesting

Richard Webb

"RJ Webb" wrote in message
...
| Thanks everyone on this thread.. Most informative, and a few more
| mysteries uncovered...
|
| I know strange things happen off Newfoundland, but it has always been
| a black box with contrasting airmasses involved. The details in this
| thread were very interesting
|
| Richard Webb

The culprit is just off Florida as we speak -

http://www.wetterzentrale.de/pics/nws1.html

Joe

On Sat, 10 Jan 2004 10:55:45 +0000, John Hall wrote in


In article ,
Mike Tullett writes:
Apoligies if the symbols don't show up correctly. This is my first attempt
at using the Windows Character Map.

They didn't here, but that may be the fault of a news server en route
not being able to cope.

John - I did see it fine in both Dialog and OE. Here is a URL to an htm
page I've uploaded which should show all the characters correctly.

http://www.mikett.plus.com/post_to_uksciweather.htm

You are far more of an expert on Usenet then I, so could I ask what is the
general policy regarding such posts as mine that contain none ASCII
characters? Would they be classed as binary, as they must have the 8th bit
set?

I'd hate to fall foul of Usenet protocol:-)

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 10/01/2004 12:36:05 UTC

In article ,
Mike Tullett writes:
On Sat, 10 Jan 2004 10:55:45 +0000, John Hall wrote in


In article ,
Mike Tullett writes:
Apoligies if the symbols don't show up correctly. This is my first attempt
at using the Windows Character Map.

They didn't here, but that may be the fault of a news server en route
not being able to cope.

John - I did see it fine in both Dialog and OE. Here is a URL to an htm
page I've uploaded which should show all the characters correctly.

http://www.mikett.plus.com/post_to_uksciweather.htm

Thanks. That displays correctly for me in IE6.

You are far more of an expert on Usenet then I,

I wouldn't regard myself as an expert.

so could I ask what is the
general policy regarding such posts as mine that contain none ASCII
characters? Would they be classed as binary, as they must have the 8th bit
set?

I'd hate to fall foul of Usenet protocol:-)


Don't worry, I don't think that they'd be classed as binary.

My understanding is that news these days generally copes with 8-bit
characters (is "8 bit clean" in the jargon), but that this is not
guaranteed, and it's possible that a news server en route has "lost" the
8th bit. It could instead be a deficiency in my newsreader, Turnpike. Or
maybe I just don't have a suitable character set installed. Your headers
for the post in question included:

Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 8bit

which look plausible to me.
--
John Hall
"Men occasionally stumble over the truth, but most of them pick
themselves up and hurry off as if nothing ever happened."
Winston Churchill (1874-1965)