Hi there,

Yesterday's band of snow was pretty unusual for a weather front, what with
the sudden temp drop, heavy snow, thunder & lightning and all. What would
you say it was we experienced? The closest thing I can think of is a squall
line. That's the great thing about the weather - just when you think you've
got it sussed nature throws something unexpected at you.

Regards.

David


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In article ,
David Gartrell writes:
Yesterday's band of snow was pretty unusual for a weather front, what with
the sudden temp drop, heavy snow, thunder & lightning and all. What would
you say it was we experienced? The closest thing I can think of is a squall
line.

I'd call it an active cold front (but a "squall line" may just be
another way of saying the same thing0.

That's the great thing about the weather - just when you think you've
got it sussed nature throws something unexpected at you.

Yep.
--
John Hall
"Three o'clock is always too late or too early
for anything you want to do."
Jean-Paul Sartre (1905-1980)

"David Gartrell" wrote in
:

Yesterday's band of snow was pretty unusual for a weather front, what
with the sudden temp drop, heavy snow, thunder & lightning and all.
What would you say it was we experienced? The closest thing I can
think of is a squall line. That's the great thing about the weather -
just when you think you've got it sussed nature throws something
unexpected at you.

It looked as though we had some sort of hybrid squall line/line convection
event - it reminded me, in sort, of a squall line type event described by
Browning and Reynolds in the Quarterly Journal of the Royal Met Soc in 1993.

Diagnostic study of a narrow cold-frontal rainband and severe winds
associated with a stratospheric intrusion
235 - 257
KA BROWNING; R REYNOLDS

Cheers
Richard

As a new poster to this group have found the last two days exiting and
informative. To be able to take my partner out in the road with the first
rain falling from the leading edge of the front saying "Watch this!" and
then the rain / snow hitting accompanied by the temperature fall monitored
on a temp probe borrowed from our Australian Bearded Dragon's reptarium was
a splendid climax to the tracking of the front down the country.
I've been called a geek a few times this past few days... but it sure paid
off. Even my partner was running from probe position calling out the temp
readings and back again as we both marvelled at the drama unfolding.
Thanks all for the hints, tips, obs, photos and humour. It's been a
memorabe few days.

Les



Richard Dixon wrote:
"David Gartrell" wrote in
:

Yesterday's band of snow was pretty unusual for a weather front,
what with the sudden temp drop, heavy snow, thunder & lightning and
all. What would you say it was we experienced? The closest thing I
can think of is a squall line. That's the great thing about the
weather - just when you think you've got it sussed nature throws
something unexpected at you.

It looked as though we had some sort of hybrid squall line/line
convection event - it reminded me, in sort, of a squall line type
event described by Browning and Reynolds in the Quarterly Journal of
the Royal Met Soc in 1993.

Diagnostic study of a narrow cold-frontal rainband and severe winds
associated with a stratospheric intrusion
235 - 257
KA BROWNING; R REYNOLDS

Cheers
Richard

Ooops.. sorry, "Thanks All" should have been a new post. Interesting
thread.. distracted me.

Les

"Pharmanaut" wrote in message


To be able to take my partner out in the road with the first
rain falling from the leading edge of the front saying "Watch this!" and
then the rain / snow hitting accompanied by the temperature fall monitored
on a temp probe borrowed from our Australian Bearded Dragon's reptarium was
a splendid climax to the tracking of the front down the country.
I've been called a geek a few times this past few days... but it sure paid
off. Even my partner was running from probe position calling out the temp
readings and back again as we both marvelled at the drama unfolding.

Here's a good one if you make home brew. Watch out for increased
activity in the water trap when there is thunder about. Works for cheese
making too.

A very unsettled set of phases a. 6th Feb 08:47 which will tend
toward thunder but be a little too breezy for it I think. 13th Feb 13:40
which will most likely bring cols. The weather forecasters will be
sweating this lot out, I imagine.

20th Feb 09:18* thunderyish, unsettled with bouts of troughs (or ridges
or cols - not sure (but at least I won't be alone.))

28th Feb 03:24* this is similar to the preceding.

6th Mar 23:14. Wet and windy.

From the 13th Mar the time of the lunar phase is 21:01 which will bring
thunder but not too much breeze, unless there is a singularity* in here
that I have not seen. (From the 6th of March it will be stormy so...)


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"Michael McNeil" wrote in message
news:839b03a4e9e27fba99881f2e04fc23be.45219@mygate .mailgate.org...

Here's a good one if you make home brew. Watch out for increased
activity in the water trap when there is thunder about. Works for cheese
making too.

A very unsettled set of phases a. 6th Feb 08:47 which will tend
toward thunder but be a little too breezy for it I think. 13th Feb 13:40
which will most likely bring cols. The weather forecasters will be
sweating this lot out, I imagine.

Thunder in winter I would imagine would be associated with windy
weather as it is usually linked to the passage of a cold front or the
gusty NW airflow behind one.

20th Feb 09:18* thunderyish, unsettled with bouts of troughs (or ridges
or cols - not sure (but at least I won't be alone.))

Troughs, ridges or cols eh?
You will probably be right with such a vague forecast as that.

Here's my forecast for 20th Feb:
It will be cold, mild or something in between.

Col - Not a trough or a ridge!
--
Bolton, Lancashire.
160m asl.
http://www.reddwarfer.btinternet.co.uk

It looked as though we had some sort of hybrid squall line/line convection
event - it reminded me, in sort, of a squall line type event described by
Browning and Reynolds in the Quarterly Journal of the Royal Met Soc in 1993.

Diagnostic study of a narrow cold-frontal rainband and severe winds
associated with a stratospheric intrusion
235 - 257
KA BROWNING; R REYNOLDS

Cheers
Richard
Hi Rich,
my view on this is that this was a squall line event forced by a low level cold front propagating as
a gravity current.Frictional effects,as the cold air headed south,wld've sharpened the frontal
boundary.I'm not sure about the role of the upper air,though mode of propagation of the GC is
sensitive to enviromental shear,and p'haps some tropopause folding occured as well.It's possible the
Chilbolton image I pointed out shows this GC head.
Classic papers on this are-
Carbone, RE, 1982: A severe frontal rainband.Part I: Stormwide hydrodynamic structure. J. Atmos.
Sci., 39, 258-279
Shapiro, M.A., T. Hampel, D. Rotzoll, and F. Mosher, 1984: The frontal hydraulic head: A micro-alpha
triggering mechanism for mesoconvective weather systems. Mon. Wea. Rev., 113, 1166-1183.
Anyone not familiar with GCs see-
http://www.damtp.cam.ac.uk/user/fdl/...14/jeshome.htm
'cleft and lobe' instabilty at the head forces convergence and updrafts which form Cbs.(cf the sea
breeze or US dry line),

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

"Waghorn" wrote in
:

Hi Rich,
my view on this is that this was a squall line event forced by a low
level cold front propagating as a gravity current.Frictional effects,as
the cold air headed south,wld've sharpened the frontal boundary.I'm not
sure about the role of the upper air,though mode of propagation of the
GC is sensitive to enviromental shear,and p'haps some tropopause
folding occured as well.It's possible the Chilbolton image I pointed
out shows this GC head.

Hi Dave

I imagine the colder denser air behind the cold front could well have acted
as a density current, especially when augmented by sublimation of the snow
falling from the cloud above - I think the mechanism for this sort of front
was still in question when I left it, one author tried to rubbish the
density current idea, others still held on to it.

Plenty of upper level support for this one, look how the dry slot
dramatically appears in the imagery between 1130 and 1730. It may be that
the dry air overran the surface front as well as dug in behind, causing some
convective instability that led to the storms? Plenty of food for thought.

http://meteosat.e-technik.uni-ulm.de...V/E2/20040128-
1130-WV-E2.gif
http://meteosat.e-technik.uni-ulm.de...V/E2/20040128-
1730-WV-E2.gif

Cheers
Rich

Plenty of upper level support for this one, look how the dry slot
dramatically appears in the imagery between 1130 and 1730. It may be that
the dry air overran the surface front as well as dug in behind, causing some
convective instability that led to the storms? Plenty of food for thought.
Yes,there does seem to be a dry area in WV that moves SW then SE.A few signs of overrunning in this
image-
http://www.sat.dundee.ac.uk/abin/pro...roject.ch4.jpg

The kinematics of gravity current are fairly simple,at least in theory.I wonder if wld be possible
to figure the rate of motion of the cold front and compare it with GC theory,allowing for frictional
effects,

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