Unless otherwise noted below, the discussion is based on products
available via:-
http://www.wetterzentrale.de/topkarten/
http://www.westwind.ch
and http://www.wetter.com/home/

Verifying: 2004 June 08 up to ~midday

2004 Jun 04: D-04: all available models
Synoptic: ( I won't detail individual runs now as they have converged on
a broadly agreed scenario):-
1. Low slow-moving in the NE Atlantic, well to the west or southwest of
Ireland.
2. Low (some complex) over Baltic or Finland with frontal trough coming
south across southern Norway/Sweden (varying intensity/activity).
3. Troughing (but high variability) in the Biscay/FitzRoy/SW Approaches
area.
4. High pressure in belt from Iceland - Faeroes - 'NW Europe', but with
variability.

Of the available runs:- the following keep high pressure dominant over
the bulk of British Isles ... EC, NGP, UKMO, GME

Of the available runs:- the following allow the trough from Biscay to
make progress northwards to varying degrees ... GFS, JMA, GEM
(NB .. EC & JMA based on 12Z yesterday).


Run-to-run evolution: The JMA has now joined the GFS in the latters
pessimistic line - the GFS consistency charts (via the Wetterzentrale
website) show its agreement run-to-run well. Looking at the spaghetti
plots though, for 08/00Z, the change from anticyclonic flow to neutral
then cyclonic (500hPa) flow at that time is still well to the SW of
Brest on the majority of members, and although the trend *will* be to
increasing development, I suggest that that the deterministic (i.e.
operational) run may be a little fast.

Inference:

I don't think I have much to change to yesterday's ideas ... the highest
risk of extensive and persistent cloud cover lies with the NW of France
and SW Britain, though no doubt with some variations. If the UKMO (and
others) are right regarding the trough/front over southern Scandinavia
being a weak affair then cloud cover here, though large at times, should
break up with the flow from the NW. If the EC and UKMO (unmodified) turn
out to be right, then although there will be areas of medium level cloud
about, the inference may be much better than that indicated. The trend
to a 'plumey' breakdown looks good ... will it hold off for long enough
is the question.





WARNING: THIS IS *NOT* A NAKED-EYE EVENT! TAKE APPROPRIATE PRECAUTIONS.

For more details see:-
http://www.transitofvenus2004.org.uk/
and more generally:-
http://www.britastro.org/main/



--
FAQ & Glossary for uk.sci.weather at:-
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Forecast discussion: Venus transit 2004 Jun 08

Unless otherwise noted below, the discussion is based on products
available via:-
http://www.wetterzentrale.de/topkarten/
http://www.westwind.ch
and http://www.wetter.com/home/
(which latter have just changed the appearance of the site ... afaik,
there are more products there!)

Verifying: 2004 June 08 up to ~midday


2004 Jun 05: D-03: all available
Synoptic:
All showing the same broad/synoptic approach but there are important
differences, particularly the GME and GFS keep and enhance a frontal
link from southern Scotland - central North Sea - northern Germany at
08/00Z, this moving steadily north over Scotland, but quasi-stationary
in the east. This feature has appeared previously, but the models are
very keen to keep a lot of moisture associated with this link, hence
more pessimism cloud with this feature. It may be that in the west,
this is linked with the faster northward progression of the troughs
swinging around the mid-Atlantic low running into and enhancing a
pre-existing frontal boundary - see below.

The plume coming up from the Biscay area is firmly there, and by 08/06Z,
the GFS has falling contours (albeit irregularly) over the top of a
northward propagating plume of high thetaE/thetaW (i.e. warm/humid air)
with it's origin back over western Iberia. This too must imply large
areas medium/unstable cloud.

Run-to-run evolution: Still some variation regarding how quickly
developments from the Biscay/Iberia region take place - the EC (12Z) run
in particular has developed more of a trough from central Ireland to
northern France. Some models make much less of the frontal link over
southern Scandinavia (e.g. EC - much faster/less defined), but others
maintain the activity, and in any case, as noted above, there is the
complication of re-activating an old linkage across the North European
Plain / central North Sea (the cold front *currently* to the NW of
Ireland on the ASXX 06Z).

Inference: (% chance of seeing at least half of event)
- far N.Scotland, N.Isles, N. Jutland, Danish main islands: well broken
cloud, at least initially, with reasonable chance thin/well-broken
throughout ... cloud increasing from the south in west: 70%
- SW Norway: areas stratocumulus, with weak frontal cloud over top at
some time: 50%
- much of Scotland (away from far N.), northern-most Germany /
Netherlands & remainder of Jutland: large areas of cloud for lengthy
periods - some staying overcast throughout - tendency (on most hopeful
scenario) for breaks from south (but N.Sea coasts large areas low cloud
/ mist): 10%
- NW France (principally regions bordering Biscay): large areas medium &
high cloud, with clusters convective/thundery CB - within area though
high variability both in time and space with ocnl thinning/breaking: 30%
- Ireland: large areas cloud at all levels, but with less humid air than
elsewhere, good chance of breaks: 40%
- East / NE England (principally on/near N.Sea coastline): humid air
over relatively cold sea, implies potential low cloud/mist and/or fog:
20%
- SW Wales / Bristol Channel / SW England: large areas upper cloud, with
increasing amounts medium cloud from south (or developing): 40%
- N & NE France, Belgium, much of Netherlands & much of Rhineland.
Morning mist/fog or stratus - should clear readily this time of year,
but may spoil the first-contact, otherwise small amounts or nil: 70%
- Remainder of England & Wales: irregular fog/stratus -
thinning/breaking (but spoiling first hour or so for some) ...
increasing cirrus and/or altocumulus from southwest: 70%






WARNING: THIS IS *NOT* A NAKED-EYE EVENT! TAKE APPROPRIATE PRECAUTIONS.

For more details see:-
http://www.transitofvenus2004.org.uk/
and more generally:-
http://www.britastro.org/main/


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

Unless otherwise noted below, the discussion is based on products
available via:-
http://www.wetterzentrale.de/topkarten/
http://www.westwind.ch
and http://www.wetter.com/home/

Verifying: 2004 June 08 up to ~midday

2004 Jun 06: D-02: all available 'course-scale', plus some Mesoscale
models & Meteograms.

Synoptic:
Latest deterministic runs have now backed off the broader / stronger
belt of high pressure from the Norwegian Sea to central/southern Europe
in favour of more cyclonic-looking pattern for the entire NE Atlantic
seaboard (including most of the British Isles). The developments over
southern Scandinavia / Baltic are similar. The 500 hPa ridge on the
latest GFS is much further east on the 00Z run, allowing developments
from the SW to propagate strongly from that direction. In my reading of
things, from the broadscale, we've switched to a much more pessimistic
reading - and the GFS *has* been consistent in this respect, so it's
indications must carry some weight.

Run-to-run evolution:
see comments above. Another worrying factor lies in the large amount of
cloud that we've picked up currently. It is difficult to see a mechanism
to get rid of this: no major 'clean' air-mass change; if anything, more
humid air coming up from the south, though by the same token, some
over-turning of the air should lead to better breaks in cloud-cover (as
is happening today/Sunday here in SE England). Now that we are only a
couple of days away, we have available mesoscale models with explicit
cloud output.

Inference:
I don't think any useful tinkering with the % probs. from yesterday can
be done, but I've looked at the GFS Meteograms where available which
come out like this:

Bergen: cloudy - low cloud - tending to break, but probably half cover
Oslo: cloudy - possibly thinning/breaking towards midday, but probably
75% cover.
Copenhagen: - cloudy, but thinning / breaking well as NW'ly sets in.
Hamburg: irregular cover - some high cloud, but indications of
persistent low cloud as well.
De Bilt: thin/high cloud, otherwise not bad.
Brussels: similar to De Bilt.
Strasbourg: clear.
Paris: clear, apart from early fog/stratus indicated.
Toulouse: thin or clear.
Brest: Cloudy, with extensive medium and upper layers.
London: well-broken cloud, possibly temporarily clear - thin/high
initially, but cloudier by midday.
Manchester: cloud increasing/thickening, thick overcast by midday.
Dublin: Cloudy - becoming thicker/lower base.
Aberdeen: Cloudy all levels.

The NMM meso model is more pessimistic, implying almost complete cloud
cover (from whatever level), for much of our area - only Shetland,
northern Jutland, southeastern Norway and parts of inland NW France are
shown with small/nil amounts of cloud.







WARNING: THIS IS *NOT* A NAKED-EYE EVENT! TAKE APPROPRIATE PRECAUTIONS.

For more details see:-
http://www.transitofvenus2004.org.uk/
and more generally:-
http://www.britastro.org/main/


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

Forecast discussion: Venus transit 2004 Jun 08

Unless otherwise noted below, the discussion is based on products
available via:-
http://www.wetterzentrale.de/topkarten/
http://www.westwind.ch
http://www.wetter.com/home/
http://www.unibas.ch/geo/mcr/3d/meteo/
(this latter for high-res meso output)

Forecast discussion: 2004 transit of Venus
Verifying: 2004 June 08 up to ~midday


2004 Jun 07: D-01: GFS EC GME JMA UKMO NGP
Synoptic:
Picture for 06Z:
Low ... slow-moving/occluded well out in the NE Atlantic.
High ... slow-moving Norwegian Sea with weak ridge southwards to
Shetland.
High ... Slovenia/Austria with large extension of same across NW Germany
and the central North Sea.
Trough ... (thundery plume) north-south from west Spain through the Bay
of Biscay.
Warm-front ... moving slowly north east/west just north of the central
Belt of Scotland, expected Buchan peninsula to Tiree by 12Z.
Cold-front ... Heligoland Bight to Berlin, moving slowly (very) south or
quasi-stationary initially, but moving NE'wards by midday area Fisher
towards Jutland.
Cold-front ... (frontogenetic west of the northward advecting warm
plume) Isles of Scilly/far SW Cornwall - Belfast, expected Exeter,
Manchester, Glasgow by midday, with discrete low forming somewhere over
the southern Pennines.
Occlusion ... Oslo - Bergen, moving south and fragmenting: not
particularly noteworthy as a baroclinic feature.

Run-to-run evolution:
Broad/synoptic-scale similar - last 48-60hr, the GFS and most other
models have confirmed the less intense high to north, allowing advance
northwards of the very warm/hot plume - still run-to-run problems with
the cold front over the North European Plain, but the situation above
looks set. The cloud frames from the various models are consistent over
the past 48 hr as well.

Inference:

In broad terms, I haven't seen anything to change the ideas of a couple
of days ago: here a repeat, but some of the % have changed and I've
noted in CAPITALS where I've made the change.

(% chance of seeing at least half of event)

- far N.Scotland (E.G. SUTHERLAND, CAITHNESS & LEWIS), N.Isles, NORTH
AND CENTRAL Jutland, Danish main islands: well broken cloud, at least
initially, with reasonable chance thin/well-broken throughout ... cloud
increasing from the south in west: 70% FOR MOST, BUT 60% NORTH MAINLAND
SCOTLAND/ORKNEY AND 80% SHETLAND, NORTHERN TIP OF JUTLAND.

- SW Norway: areas stratocumulus, with weak frontal cloud over top at
some time, BUT GOOD PROSPECT OF SMALL/NIL AMOUNTS OF CLOUD AREAS
BORDERING THE SKAGGERAK: 50%, BUT 80% TO LEEWARD OF SOUTHERN MOUNTAINS.

- much of Scotland (away from far N.), northern-most Germany (E.G.
WILHELMSHAVEN-HAMBURG-BREMEN) / FAR-NORTHERN Netherlands
(LEEUWARDEN/GRONINGEN) & remainder of Jutland: large areas of cloud for
lengthy periods - some staying overcast throughout - tendency (on most
hopeful scenario) for breaks from south (but N.Sea coasts large areas
low cloud / mist): 10% (BUT 20% PARTS OF SOUTHERN SCOTLAND AWAY FROM
N.SEA COASTS AND ALSO OVER NETHERLANDS/N.GERMANY)

- NW France (principally regions bordering Biscay): large areas medium &
high cloud, with clusters convective/thundery CB DEVELOPING - within
area though high variability both in time and space with ocnl
thinning/breaking: 40% (HAVE UPPED THE % FROM 30 ... AM SLIGHTLY MORE
OPTIMISTIC HERE FOR THIS PERIOD).

- Ireland: large areas cloud at all levels, but with less humid air than
elsewhere, good chance of breaks FROM WEST: 40%, BUT PERHAPS 50% ACROSS
SOUTHWESTERN 'HALF' OF ISLAND AND ALL WEST-COASTAL AS MARINE SC BREAKS
SOMEWHAT.

- East / NE England (principally on/near N.Sea coastline): humid air
over relatively cold sea, implies potential low cloud/mist and/or fog:
20%

- SW Wales / Bristol Channel / SW England: large areas upper cloud, with
increasing amounts medium cloud from south (or developing); ALSO,
VARIABLE SEA MIST/FOG/LOW CLOUD: 50% OVERALL, BUT VARYING FROM 25% ISLES
OF SCILLY - FISHGUARD (AND COASTS FACING THE WIND WHERE FOG LIES
OFFSHORE, NOT SURE THIS IS GOING TO BE A WIDESPREAD PROBLEM THOUGH) TO
60% SWANSEA, EXETER ETC.

- N & NE France, Belgium, much of Netherlands & much of Rhineland.
Morning mist/fog or LOW/GROUND-BASED stratus - should clear readily this
time of year, but may spoil the first-contact, otherwise small amounts
or nil: 80%, BUT 90% FURTHER INTO METROPOLITAN FRANCE, GERMANY ETC.

- Remainder of England & Wales: irregular fog/stratus -
thinning/breaking; CLOUD ACROSS NORTHERN ENGLAND (AWAY FROM EAST COAST)
SLOWLY BREAKING UP (but spoiling first hour or so for some) ...
increasing cirrus and/or altocumulus from SOUTH OR southwest: 70%
(IF IT IS ANYTHING LIKE THIS MORNING HERE IN EAST BERKSHIRE, THEN EVEN
WITH A LOT OF CIRRUS AND SOME IRREGULAR MEDIUM CLOUD, THE PROSPECTS ARE
FINE.)

Latest mesoscale models available .... e.g. NMM ... ETA ... all broadly
confirm above ideas ... though the NMM is again very pessimistic with
cloud cover away from the baroclinic (i.e. frontal / pseudo-frontal)
areas in the west and north: however, it did rather overdo the cloud
cover yesterday.)

Latest Meteograms ... changes noted in brackets:
Bergen: cloudy - low cloud - tending to thin/break, but probably half
cover (similar to yesterday's ideas).
Oslo: cloudy - possibly thinning/breaking towards midday, but probably
75% cover. (similar)
Copenhagen: - cloudy, but thinning / breaking well as NW'ly sets in.
(similar)
Hamburg: thick high cloud, rather persistent; some low cloud, but
non-persistent. (more high cloud, less low cloud .. a 'better' viewing
prospect).
De Bilt: thin/high cloud or clear. (similar)
Brussels: similar to De Bilt. (similar)
Strasbourg: clear (or occasional high/thin cloud). (similar)
Paris: clear (or thin/high cloud), apart from early fog. (similar).
Toulouse: medium/upper cloud, thick at first becoming thin/well-broken
or clear (more pessimistic as to upper cloud, but overall not too bad).
Brest: Cloudy, with extensive medium and upper layers, but reasonable
start, with thin/high cloud only. (more optimistic for first few hours).

London: well-broken cloud, possibly temporarily clear - thin/high
initially, but cloudier by midday. (similar - the increase in cloud
probably high-levels only).
Manchester: cloud increasing/thickening, near-overcast by midday. (some
suggestion of the cloud not so thick late morning - a more optimistic
picture).
Dublin: Cloudy - becoming thicker/lower base. (similar).
Aberdeen: Cloudy all levels. (similar - note southeasterly off the North
Sea).


That's the lot! I'll have another look at things early this evening, and
perhaps post an update, but if nothing by 2000 UTC, then assume that
figures/description above hold good.

Have a good time everyone ...

Martin.






WARNING: THIS IS *NOT* A NAKED-EYE EVENT! TAKE APPROPRIATE PRECAUTIONS.

For more details see:-
http://www.transitofvenus2004.org.uk/
and more generally:-
http://www.britastro.org/main/


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

Martin Rowley wrote:
Forecast discussion: Venus transit 2004 Jun 08

snippity snip

Thank you for all your hard work over the last couple of weeks it has
been fascinating reading the developing situation and I have made use of
your predictions in discussions with my astronomy society colleagues as
we make our plans for transit day.

It's now looking very good that we will see the transit tomorrow
(Oxon/Berks) so very pleased. I refuse to believe that with the current
weather situation and a full six hours to play with that we will see
nothing at all. I hope I haven't spoken too soon!!

John
Reading Astronomical Society

"jochta" wrote in message
...
Martin Rowley wrote:
Forecast discussion: Venus transit 2004 Jun 08

snippity snip


It's now looking very good that we will see the transit tomorrow
(Oxon/Berks) so very pleased. I refuse to believe that with the
current
weather situation and a full six hours to play with that we will see
nothing at all. I hope I haven't spoken too soon!!


.... I'm not that far away from you and I certainly expect to see a good
deal. My rig (bino's strapped to a projection plate), is all ready in
the garage to go: had a dummy run this morning and got a superb image of
the early sun.

Good luck tomorrow!

Martin.


--
Martin Rowley: data via -
http://homepage.ntlworld.com/booty.weather/metindex.htm
Bracknell (Wooden Hill/Tawfield), Berkshire
NGR: SU 854 667 Elev: 80m
Lat: 51DEG23MIN30SEC(N): Long: 00DEG46MIN28SEC(W)