================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

Don't normally say too much in between my weekly forecasts but in light of the
developing very cold and prolonged scenario I thought I'd say a few things.
Looking at the last few runs of all the models I would say that the ingredients
are coming into place for a possible major very cold spell. Confidence in this
is now 40% at Haytor (rising from 10% last Friday). Very cold air pushing down
from the Arctic (sub 492 DAM) to the east of the Russian anticyclone will help
persistence as will the continued feed of low potential vorticity tropical air
from the south to the west. Not quite a classic omega pattern yet but could well
end up as one. Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures of -5
to -10 deg C are easily attainable. Operational GFS is showing outbreaks of
light snow over the UK in the developing easterly this is consistent and to be
expected in a slightly unstable situation despite high pressure. Of course the
orientation and resting place of the anticyclone is key as always as to
locations that get snow, all of southern Britain is at risk of at least some
light snow. A wind either due east or south of east could give Devon and
Cornwall some persistent and heavier snowfall, but that detail is elusive at
present. Clearly one has to go for a lot of dry cold weather too in western
areas and I think eventually we will see fronts pushing in from the west, but
these are likely to struggle more against a more intense block than last time
due to:

1. Radiation balanace
2. Cold air advection from the north to the east of the high
3. Orientation and lack of a strong westerly flow coming out if the States
unlike last time

This one should be watched because we could be facing (40% chance) a month of
very cold weather albeit on the dry side of normal.

Will.
--

" Ah yet another day to enjoy "
-------------------------------------------------------------------------------
A COL BH site in East Dartmoor at Haytor, Devon 310m asl (1017 feet).

mailto:
www: http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm

DISCLAIMER - All views and opinions expressed by myself are personal
and do not necessarily represent those of my employer.
-------------------------------------------------------------------------------

On Tue, 3 Jan 2006 10:07:10 -0000, "Will Hand"
wrote:


================================================= ===================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================= ===================

Don't normally say too much in between my weekly forecasts but in light of the
developing very cold and prolonged scenario I thought I'd say a few things.
Looking at the last few runs of all the models I would say that the ingredients
are coming into place for a possible major very cold spell. Confidence in this
is now 40% at Haytor (rising from 10% last Friday). Very cold air pushing down
from the Arctic (sub 492 DAM) to the east of the Russian anticyclone will help
persistence as will the continued feed of low potential vorticity tropical air
from the south to the west. Not quite a classic omega pattern yet but could well
end up as one. Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures of -5
to -10 deg C are easily attainable. Operational GFS is showing outbreaks of
light snow over the UK in the developing easterly this is consistent and to be
expected in a slightly unstable situation despite high pressure. Of course the
orientation and resting place of the anticyclone is key as always as to
locations that get snow, all of southern Britain is at risk of at least some
light snow. A wind either due east or south of east could give Devon and
Cornwall some persistent and heavier snowfall, but that detail is elusive at
present. Clearly one has to go for a lot of dry cold weather too in western
areas and I think eventually we will see fronts pushing in from the west, but
these are likely to struggle more against a more intense block than last time
due to:

1. Radiation balanace
2. Cold air advection from the north to the east of the high
3. Orientation and lack of a strong westerly flow coming out if the States
unlike last time

This one should be watched because we could be facing (40% chance) a month of
very cold weather albeit on the dry side of normal.

Will.

Will,

Would you see the influence of this possibly huge developing
anticyclone to stretch beyond the European Alps - any drier than
normal spell would have severe consequences on the ski industry.

While the north, east and western resorts had good early season
snowfalls due to the prevailing wind, resorts around to the south have
been struggling with the absence of any meaningful snow since the
beginning of December.

Obviously the temeratures have been at times very cold and
sufficiently low enough for snowmaking - but this has only been enough
to keep skiiers who stick to the pistes happy enough.

Thanks,

Scott

Thanks for the update - I was thinking the winds were to much from a
southerley direction at first, fingers crossed then

Paul

--

_______________________________
Paul Crabtree
Brampton, Cumbria
117m A.S.L
www.bramptonweather.co.uk
"Will Hand" wrote in message
...

================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

Don't normally say too much in between my weekly forecasts but in light of
the
developing very cold and prolonged scenario I thought I'd say a few
things.
Looking at the last few runs of all the models I would say that the
ingredients
are coming into place for a possible major very cold spell. Confidence in
this
is now 40% at Haytor (rising from 10% last Friday). Very cold air pushing
down
from the Arctic (sub 492 DAM) to the east of the Russian anticyclone will
help
persistence as will the continued feed of low potential vorticity tropical
air
from the south to the west. Not quite a classic omega pattern yet but
could well
end up as one. Air close to the surface will become very cold as it
stagnates
due to radiation balance at this time of year so 850 hPa temperatures
of -5
to -10 deg C are easily attainable. Operational GFS is showing outbreaks
of
light snow over the UK in the developing easterly this is consistent and
to be
expected in a slightly unstable situation despite high pressure. Of course
the
orientation and resting place of the anticyclone is key as always as to
locations that get snow, all of southern Britain is at risk of at least
some
light snow. A wind either due east or south of east could give Devon and
Cornwall some persistent and heavier snowfall, but that detail is elusive
at
present. Clearly one has to go for a lot of dry cold weather too in
western
areas and I think eventually we will see fronts pushing in from the west,
but
these are likely to struggle more against a more intense block than last
time
due to:

1. Radiation balanace
2. Cold air advection from the north to the east of the high
3. Orientation and lack of a strong westerly flow coming out if the States
unlike last time

This one should be watched because we could be facing (40% chance) a month
of
very cold weather albeit on the dry side of normal.

Will.
--

" Ah yet another day to enjoy "
-------------------------------------------------------------------------------
A COL BH site in East Dartmoor at Haytor, Devon 310m asl (1017 feet).

mailto:
www:
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm

DISCLAIMER - All views and opinions expressed by myself are personal
and do not necessarily represent those of my employer.
-------------------------------------------------------------------------------

"Will Hand" wrote in
:

but these are likely to struggle more
against a more intense block than last time due to:

1. Radiation balanace
2. Cold air advection from the north to the east of the high
3. Orientation and lack of a strong westerly flow coming out if the
States unlike last time

Will - you missed the most important factor:

4. Richard being out of the country.

Cheers
Richard

Will Hand wrote:

================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures of -5
to -10 deg C are easily attainable.

A technical query - I thought 850 hPa is a useful level as it is free
from immediate boundary layer effects, such as radiative cooling, and a
lot of the relatively high 850 hPa temps shown on the models are due to
adiabatic warming through anticyclonic subsidence. Typically how long
does it take for radiative cooling effects to transfer to 850 hPa in
light wind clear-sky situations at our latitude in mid-winter, and how
much is indirectly due to land surface radiation and how much directly
due to radiation from the atmosphere itself?

Martin

On Tue, 3 Jan 2006 10:07:10 -0000, "Will Hand"
wrote:


Thanks for your forecast Will - interesting as always. :-)

I'll confess right now that I am no more than an amateur model
watcher, but going on the model output alone (plus 'gut feeling') I
think that we're in for nothing more than a not particularly cold
'snap' followed by about average temps.

This is mainly based on watching the model output over the past few
days (mainly UKMO, ECM and GFS) - on Sunday the GFS was ramping up the
potential for a pretty major cold spell with dollops of snow. It
stayed that way for a few runs then slowly started to come into line
with ECM and UKMO which were predicting something much less severe,
namely winds swinging around to the south and bringing in less cold
air.

Now we all know that the model output is unreliable, especially when
forecasting beyond 3 or 4 days and particularly so this winter. Things
may well change again, but I'm becoming increasingly convinced that
any snow amounts will be very slight (and confined to the south east
for a day or two) and any cold will not be severe.

I'm still hoping for a major cold and snowy spell this winter as
things look most promising, but sad to say I don't think that this
forthcoming cold 'snap' is "the one".

Just my two cents' worth - please carry on with your forecasts which
are, let's admit it, usually very informative. :-)

"JPG" wrote in message
ups.com...
Will Hand wrote:

================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures of -5
to -10 deg C are easily attainable.

A technical query - I thought 850 hPa is a useful level as it is free
from immediate boundary layer effects, such as radiative cooling, and a
lot of the relatively high 850 hPa temps shown on the models are due to
adiabatic warming through anticyclonic subsidence. Typically how long
does it take for radiative cooling effects to transfer to 850 hPa in
light wind clear-sky situations at our latitude in mid-winter, and how
much is indirectly due to land surface radiation and how much directly
due to radiation from the atmosphere itself?

Martin


Martin, no straight answers as it part depends on moisture, but in a typical
profile it is of the order of days. Land surface radiation I think dominates,
especially from snow covered surfaces, but again moisture and cloud complicate
the issue. However, at this time of year the short wave input is low or nil
depending on latitude and this is what is important.

Will.
--

"Scott Whitehead" wrote in message
...
On Tue, 3 Jan 2006 10:07:10 -0000, "Will Hand"
wrote:


================================================= ===================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================= ===================

Don't normally say too much in between my weekly forecasts but in light of
the
developing very cold and prolonged scenario I thought I'd say a few things.
Looking at the last few runs of all the models I would say that the
ingredients
are coming into place for a possible major very cold spell. Confidence in
this
is now 40% at Haytor (rising from 10% last Friday). Very cold air pushing
down
from the Arctic (sub 492 DAM) to the east of the Russian anticyclone will
help
persistence as will the continued feed of low potential vorticity tropical
air
from the south to the west. Not quite a classic omega pattern yet but could
well
end up as one. Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures of -5
to -10 deg C are easily attainable. Operational GFS is showing outbreaks of
light snow over the UK in the developing easterly this is consistent and to
be
expected in a slightly unstable situation despite high pressure. Of course
the
orientation and resting place of the anticyclone is key as always as to
locations that get snow, all of southern Britain is at risk of at least some
light snow. A wind either due east or south of east could give Devon and
Cornwall some persistent and heavier snowfall, but that detail is elusive at
present. Clearly one has to go for a lot of dry cold weather too in western
areas and I think eventually we will see fronts pushing in from the west, but
these are likely to struggle more against a more intense block than last time
due to:

1. Radiation balanace
2. Cold air advection from the north to the east of the high
3. Orientation and lack of a strong westerly flow coming out if the States
unlike last time

This one should be watched because we could be facing (40% chance) a month of
very cold weather albeit on the dry side of normal.

Will.

Will,

Would you see the influence of this possibly huge developing
anticyclone to stretch beyond the European Alps - any drier than
normal spell would have severe consequences on the ski industry.

While the north, east and western resorts had good early season
snowfalls due to the prevailing wind, resorts around to the south have
been struggling with the absence of any meaningful snow since the
beginning of December.

Obviously the temeratures have been at times very cold and
sufficiently low enough for snowmaking - but this has only been enough
to keep skiiers who stick to the pistes happy enough.

Thanks,

Scott


Scott, depends where the block finally ends up. ATM it doesn't look too good for
the Alps as regards fresh snowfall.

Will.
--

"Will Hand" wrote in message
...

"JPG" wrote in message
ups.com...
Will Hand wrote:

================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

Air close to the surface will become very cold as it stagnates
due to radiation balance at this time of year so 850 hPa temperatures
of -5
to -10 deg C are easily attainable.

A technical query - I thought 850 hPa is a useful level as it is free
from immediate boundary layer effects, such as radiative cooling, and a
lot of the relatively high 850 hPa temps shown on the models are due to
adiabatic warming through anticyclonic subsidence. Typically how long
does it take for radiative cooling effects to transfer to 850 hPa in
light wind clear-sky situations at our latitude in mid-winter, and how
much is indirectly due to land surface radiation and how much directly
due to radiation from the atmosphere itself?

Martin


Martin, no straight answers as it part depends on moisture, but in a
typical
profile it is of the order of days. Land surface radiation I think
dominates,
especially from snow covered surfaces, but again moisture and cloud
complicate
the issue. However, at this time of year the short wave input is low or
nil
depending on latitude and this is what is important.

Will.
'No straight answers' now that just about sums up wx fx in the UK, Mind the
rest of the world suffers much the same. Who was who said 'Wx Fx is not an
exact science '
Jo North Devon.

Your confidence (albeit 40 per cent) in this doesn't appear to be
shared by Paul Bartlett who seems confident that southwesterlies will
return by the 12th.

Curious. And we shall see I s'pose.