Looking at the previous thread has prompted me to ask something I've been
wondering about for a while. Why doesn't thickness appear on any of the
forecast charts until T +36 hrs and later? (I'm looking at the UKMO
charts on Wetterzentrale).

It doesn't appear on any of the archived charts either. Is that because
it's a forecasting tool and isn't used in real time (or marked on archived
charts) or am I just looking at the wrong charts?

Can't see anything on the ng FAQ (apologies if it's there and I've missed
it)

- Tom.

"Tom Bennett" wrote in message
...
Looking at the previous thread has prompted me to ask something I've been
wondering about for a while. Why doesn't thickness appear on any of the
forecast charts until T +36 hrs and later? (I'm looking at the UKMO
charts on Wetterzentrale).

It doesn't appear on any of the archived charts either. Is that because
it's a forecasting tool and isn't used in real time (or marked on archived
charts) or am I just looking at the wrong charts?

Can't see anything on the ng FAQ (apologies if it's there and I've missed
it)

- Tom.

I've pondered this in the past and (somewhat embarrassingly) don't know the
answer; Martin ? I would hazard a guess that in the past when the analysis
and T+24 had tracking on most of the pressure centres an additional
thickness overlay would have often resulted in the charts looking quite
cluttered. One other thought is that forecasters tended to use a collection
of 4-up NWP chart to T+36 (MOLFAX ?) as routine which included the
1000/500mb thickness field, thus the fields were always close at hand. I
don't see any reason why the T+24 at least doesn't have thickness lines
now - I might ask a few questions in the 'house'.

Jon.

"Jon O'Rourke" wrote in message
...

"Tom Bennett" wrote in message

don't see any reason why the T+24 at least doesn't have thickness
lines
now - I might ask a few questions in the 'house'.

Thanks Tom and Jon. I have wondered about this myself. Looking forward
to any further posts in this thread. I hope it isn't lost in the snow
hopers threads which are bound to drift in soon!

Best wishes,

--
Ken Cook, Copley (5miles north of Barnard Castle), County Durham.
830ft
http://mysite.wanadoo-members.co.uk/copley
(MO climat. site updated before 10Z and 19Z daily)
kencookATcopleydurham.freeserve.co.uk
(All times GMT)

"Ken Cook" . Looking forward
to any further posts in this thread. I hope it isn't lost in the snow
hopers threads which are bound to drift in soon!

And a very peaceful and prosperous New Year to you too, Ken. I know what
you mean. I could continue by reminiscing about REAL winters past (up
North!) but we've been down that road lots of times before. I'm sure
we'll judge whatever (if any) white stuff we do get by our own memories,
however selective they're becoming now - I know I always do.

(..............and remember that fall in Weardale - was it 1978? By god,
there was drifts as big as houses. Never seen the like, still there in
June....... And the freezations I measured in December 1981: well, I'll
go to then end of our road if there wasn't pack-ice in the Tyne and
icebergs off Roker too ....................)

:-)

- Tom.

"Tom Bennett" wrote in message
...
Looking at the previous thread has prompted me to ask something I've
been
wondering about for a while. Why doesn't thickness appear on any of
the
forecast charts until T +36 hrs and later? (I'm looking at the UKMO
charts on Wetterzentrale).

I'll answer this question from the information that I know, but
emphasise that there are others who look in to this newsgroup who could
add more detail and perhaps correct some of the below .. though I think
the broad thrust of the answer is correct:-....................

The question should be:.... "why *do* the charts beyond T+24 have
thickness isopleths on them?"

In days long ago, there were only the Baratic (T+0) and the Prebaratic
(T+24). (before my time I hasten to add).

In association with these, upper air charts were issued, both analysis
and forecast (Contour / Prontour), in coded and chart format - the
latter more widely as facsimile was developed.

There was _no need_ to add thickness lines to the Baratic/Prebar surface
charts - forecasters would have separate charts for same - indeed many
outfield forecasters would independently both analyse and 'prog' such
and draw their own conclusions to add to (or deviate from) the guidance
from Dunstable/Bracknell, using the work of Sutcliffe & Forsdyke.

When the T+48/T+72 came along (can't remember when ... certainly in use
by the late 1960's as I was heading up FAX charts for them every night)
then the only way to indicate broad-scale thermal distribution was by
adding the isopleths of thickness. This practice was continued when
T+96/120 were introduced (again, memory hazy ... could be late 1970's?).

In this time, there was no Internet, no ODS, no Horace, no Nimbus etc.,
etc. and production of upper air forecasts in chart format beyond T+24
would have clogged up the land-line FAX circuits too much (remembering
that hourly/3-hourly charts had to be broadcast, along with plotted
tephigrams, upper wind sheets and a whole host of other output - all
taking up sizeable slabs of broadcast time.)

It wouldn't have seemed odd to Met Office users NOT to have thickness on
the ASXX/FSXX - it only seems so now because of the changing times. (And
as Jon has noted elsewhere, for Radiofax use, where reception could be
'iffy' at times, they might have clashed with all the labels,
continuity, tracking, 35kn plots etc.)

Whether there will be any move to put thickness on the T+24, I'm not so
sure; there is no good operational reason for doing this as 'mainstream'
users can pull up the associated TTHK and, more importantly, much
*better* air mass tracers like ThetaW fields to use for things like
expected temperatures, snow risk etc.

Martin.