Folowing on from Martins comments of fronts in Highs... an interesting Low
in the High for Saturday
http://129.13.102.67/wz/pics/brack1.gif
Phil
--

http://homepage.ntlworld.com/phil.layton/meteo.htm

"Phil Layton" wrote in message
...
Folowing on from Martins comments of fronts in Highs... an interesting Low
in the High for Saturday

Saw that on TV this evening.
As one not akin to these things. How do you get a low in a high?

Is this high a floppy one? Looks solid to me on the ECMWF.

JT

On Thu, 12 Feb 2004 22:12:03 -0000, John Taverner wrote in


"Phil Layton" wrote in message
...
Folowing on from Martins comments of fronts in Highs... an interesting Low
in the High for Saturday

Saw that on TV this evening.
As one not akin to these things. How do you get a low in a high?

Is this high a floppy one? Looks solid to me on the ECMWF.

John - I did post about this odd feature earlier today. Here is what I
wrote:

"I bet this will confound some opinions on anticyclonic weather, with a
band of rain moving in from the west on Friday across Ireland and then into
other northern areas on Saturday. Six hour rainfall figures of up to 5mm
seem to be forecast

http://www.wetterzentrale.de/pics/Rtavn364.html

It seems to be associated with a short wave upper vortex moving through the
high.

http://www.wetterzentrale.de/pics/Rtavn361.html

The MO FAX charts have this marked as a cold front.

http://www.wetterzentrale.de/pics/brack0a.html"

The charts have changed a little since then, but the same features are
present - an upper low moving through the high.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 12/02/2004 22:42:14 UTC

A few thoughts:.......

Meteorological analysis and forecasting has always been about the
atmosphere in three (indeed four) dimensions; it is just that in the
early days of organised synoptic meteorology (late 19th / much of first
third of 20th centuries), only *surface* observations were available.
But even then, a lot was suspected regarding what we call the 'upper
air', and great attempts were made to understand the links between
surface patterns and aloft (hence Kite-borne instrumentation,
Meteorographs, Nephoscopes, visual pilot balloon ascents etc. of the
first third of the last century).

Even Bjerknes and co-workers, when developing the 'Norwegian theory'
recognised that the classic frontal structure with fixed slopes,
standard cloud types etc., was not the full answer; it is just that they
didn't have the information to determine differently, at least in a
'real-time' sense.

The Exeter analyses and prognoses (that are being discussed here) only
tell the msl story if you like; routinely in any forecast office, the
fields aloft will be displayed/overlain on cloud and radar imagery (and
the mslp output). We (the Internet community) also have the ability to
view the upper pattern in concert with the surface: see -

http://www.wetterzentrale.de/pics/Rtavn301.gif
where 500 and mslp patterns are combined.

This (if you view in the next couple of days .. this link will show
different time-steps every 6 hours) will show the situation developing.
Note that the colours describe the contour height field at 500 hPa
(roughly mid-troposphere); compare with the colour-bar at the right-hand
side, and you can see that an area of lower contour heights (relative to
surrounding) is running through the pattern, right over the area of high
pressure - this is a trough or upper low - looks well formed for a time
(yellow as against surrounding oranges).

The Chief Forecaster at Exeter will choose some standard symbology
(trough/front) to show on the *surface* chart to represent this
important featu upper troughs are associated with colder air aloft
(on this field, the temperatures at 500 hPa are indicated and you can
see this).

Each analyst will have their own particular ideas of showing & following
the feature (on what is, after all a surface chart - some will use
midlevel humidity, or surface precipitation, or axis of ThetaW or
whatever). Whichever parameter is used, it is important to be consistent
so that the feature can be followed through the forecast sequence.

Remember that the mslp output is only drawn to *4* hPa intervals. If you
were to draw to 1 hPa (or even 0.5 hPa), then in this situation, a
surface trough would be found (perhaps even a surface low. Indeed, on
many of the mslp charts, you can see a 'weakness' in the pattern 'around
the edges' which betrays what is being forced above.

To keep up to date with the situation, use:-

http://www.wetterzentrale.de/topkarten/fsavneur.html

and click between the '500hPa,Bodendruck', the 'Mittl.Wolken' and
'Niederschlag' (500/mslp, mid-level cloud & precipitation respectively),
and you can see the way the situation is developing.

Don't be surprised if this situation produces quite a bit of rain
locally (as Mike has already indicated). These features always need
watching. The broadscale situation (large upper ridge in our longitude,
with deep/cold anchoring lows SE Europe [ hence the snow in Athens ] and
west of the Azores), will quite frequently throw these patterns up. They
are a real problem, not only for 'general' forecasting, but for aviation
as well: the icing and turbulence (particularly the former), can be
quite marked on these small-scale features.

Martin.


"Mike Tullett" wrote in message
...
On Thu, 12 Feb 2004 22:12:03 -0000, John Taverner wrote in


"Phil Layton" wrote in message
...
Folowing on from Martins comments of fronts in Highs... an
interesting Low
in the High for Saturday

Saw that on TV this evening.
As one not akin to these things. How do you get a low in a high?

Is this high a floppy one? Looks solid to me on the ECMWF.

John - I did post about this odd feature earlier today. Here is what
I
wrote:

"I bet this will confound some opinions on anticyclonic weather, with
a
band of rain moving in from the west on Friday across Ireland and then
into
other northern areas on Saturday. Six hour rainfall figures of up to
5mm
seem to be forecast

http://www.wetterzentrale.de/pics/Rtavn364.html

It seems to be associated with a short wave upper vortex moving
through the
high.

http://www.wetterzentrale.de/pics/Rtavn361.html

The MO FAX charts have this marked as a cold front.

http://www.wetterzentrale.de/pics/brack0a.html"

The charts have changed a little since then, but the same features are
present - an upper low moving through the high.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 12/02/2004
22:42:14 UTC

Martin,

Many thanks for an informative post - another to keep.

Phil

--

http://homepage.ntlworld.com/phil.layton/meteo.htm
"Martin Rowley" wrote in message
...
A few thoughts:.......

.... turning into a very tasty feature now: the 500hPa is forecast to be
(by midday Sunday) down to MS30, associated with a sub-552dam upper low
/ sub 530dam Thickness. The model rainfall totals don't look too great
(somewhere around 1 to 2 mm per 6hr period), but the rain might linger
in any one point and make a mess of the day for some.

Martin.

,... turning into a very tasty feature now:
V prominent feature in WV and two vortices south of the UK-
http://www.sat.dundee.ac.uk/pdus/BW/...31800BW1_g.jpg

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

"Waghorn" wrote in message
news:c0jc72
snip
It strikes me that the MSLP analyses are now somewhat old
fashioned.Tools are now available PV
analysis,WV imagery,Objective analysis,visualisation techniques to
give a truly 3D/4D picture (and
condense it onto a single page 'chart')

.... internally within the Met Office, all these techniques are used: the
output you see as ASXX/FSXX charts are just the 'public-facing' stuff.
On closed networks, user-modified fields utilising all above are
routinely available. Whether these would ever make it into the 'public
domain' is a politico-economic decision rather than a scientific one.

Martin.

A few thoughts:.......

Meteorological analysis and forecasting has always been about the
atmosphere in three (indeed four) dimensions; it is just that in the
early days of organised synoptic meteorology ....
It strikes me that the MSLP analyses are now somewhat old fashioned.Tools are now available PV
analysis,WV imagery,Objective analysis,visualisation techniques to give a truly 3D/4D picture (and
condense it onto a single page 'chart')
On the lines of this see 'SATREP' (can't find link ATM ) and ANASYG/PRESYG eg
http://ams.confex.com/ams/pdfview.cgi?username=25491

Weather forecasting seems somewhat conservative in respect of adopting state of the art research
(perhaps for good reason).AIUI it took quite a while for the Norwegian model to be fully accepted in
the UK,

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

"Waghorn" wrote in message
...

Snip to the bit I want to argue about!

Weather forecasting seems somewhat conservative in respect of adopting state
of the art research
(perhaps for good reason).AIUI it took quite a while for the Norwegian model
to be fully accepted in
the UK,

As Martin said, that is untrue. The Norwegian model may not have been
acepted in Britain quicky. However, that was nearly 100 years ago. I don't
think there are many meteorologists from that time who have moved to Exeter!

Where they are being conservative is in not admitting global warming is a
serious problem. You are one of the worst. I have given you evidence that
there will be a rapid climate change event within the next ten years, and yet
you have dismissed it, on the grounds that "The sky is not falling in!"

Where is your evidence?

Cheers, Alastair.