"Tudor Hughes" wrote in message
...
On Oct 30, 6:04 pm, " wrote:
On Oct 30, 5:57 pm, Bonos Ego wrote:

What a day!

For those of us in the SW, the pictures on Spotlight are going to be
interesting!

For those not living in the South West, but have SKY TV, and would
like to watch spotlight, try Sky TV Channel 987.

There's some video footage here
toohttp://news.bbc.co.uk/1/hi/england/devon/7700167.stm

From those incredible pictures people could be forgiven for
calling it snow because that's what it looks like. The hail must have
been very small but there's a huge volume of it which makes one think
it must be of low density. But hail is clear ice so that cannot be
the case. Does anyone have any explanation of these characteristics?
The storm cannot have had a supercell structure or the hail would
probably have gone up and down a few times before finally falling out
as large hail.

Tudor Hughes, Warlingham, Surrey.

============================
============================

Tudor, I think a lot of it was soft hail or graupel which blows around
easily in the wind and drifts. Also mixed in were small hail (looking at the
picture showing footprints). Possibly also a bit of wet snow too as the
wet-bulb freezing level lowered in the very heavy precipitation. Actually I
don't think it looks like snow at all, sure it is white but it is laying
"funny", doesn't have that light puffy look to it. But yes to the layman and
to people who are not used to seeing much snow I can see why they might
think it was snow.

Will
--

On 31 Oct, 16:05, Tudor Hughes wrote:
On Oct 30, 6:04*pm, " wrote:

On Oct 30, 5:57 pm, Bonos Ego wrote:

What a day!

For those of us in the SW, the pictures on Spotlight are going to be
interesting!

For those not living in the South West, but have SKY TV, and would
like to watch spotlight, try Sky TV Channel 987.

There's some video footage here toohttp://news.bbc.co.uk/1/hi/england/devon/7700167.stm

* * * From those incredible pictures people could be forgiven for
calling it snow because that's what it looks like. *The hail must have
been very small but there's a huge volume of it which makes one think
it must be of low density. *But hail is clear ice so that cannot be
the case. *Does anyone have any explanation of these characteristics?
The storm cannot have had a supercell structure or the hail would
probably have gone up and down a few times before finally falling out
as large hail.

Tudor Hughes, Warlingham, Surrey.

I think the hail was carried along in 'rafts' similar to logs. It then
accumulated in a few small areas, hence the very localised large
thicknesses, and amount of muck mixed up in it.

A very similar, though much less severe, event happened in Padstow (I
posted a link to a video earlier in this thread.) I know that in that
case rafts of hail floating on the water were carried to the bottom of
the town and piled up 2 - 3 feet deep in places, whilst 100 yards away
there was virtually none.

Graham
Penzance

Looking at the 1km radar data it would appear that the heaviest rainfall was
alligned with the eastern side of the Otter valley - with the western-side
of the valley being virtually free of heavy rain - the steering effects of
the surface are often overlooked.

Chris


"Will Hand" wrote in message
...
Hi Nick,

Awesome stuff indeed.
Here are some links to pictures
http://www.thisisexeter.co.uk/galler...l/gallery.html
http://www.bbc.co.uk/devon/content/i..._gallery.shtml

It's estimated that circa 120mm rain fell in storm centre allowing for
hail.

First I was aware of it was listening to Radio Devon on way to work at
0730 this morning, when they were going on about snow drifts and flooding.
Snow was, of course, hail. Apparently the hail floated on the water and
when it subsided huge chunks of ice 2 feet high were left in car parks
hemming in cars and there is still hail around.

What was the cause?

Occlusion slow moving oriented N-S across E. Devon with normal amounts of
rain associated with it. Low centre nearby. Potential vorticity filament
associated with jet streak to west of low in upper air tracked east and
helped de-stabilise the warm air part of the occlusion. Deep instability
released as air north of low was of Arctic origin and thunderstorms
spawned. But that was not all ... once the storms got going they became
trapped in the almost-calm centre of the low and could not go anywhere,
hence a local deluge with huge amounts of hail. Very localised and
unpredictable, even in hindsight. Exeter had circa 6mm rain, Ottery St
Mary 100mm. High resolution 1km radar imagery available at work showed
torrential rain and a widespread hail signal. Evidence of rotation and a
comma-like structure too. The investigation continues ...

What a day!

For those of us in the SW, the pictures on Spotlight are going to be
interesting!

Will (from a serenely quiet but very cold Haytor)
--

"Nick Gardner" wrote in message
...
Last night has got to be one of the most memorable 'weather' nights ever.
A thunderstorm of the intensity I have not witnessed since those summer
'biggies' from what now seems like a long time ago.

The lightning started around 23:45 but the rain did not really get going
until just after midnight, though it was a mixture of torrential rain and
hail. The road outside soon resembled a mini-glacier with hail floes
running everywhere.

The lightning was regular, frequent and overhead with amazing cloud-cloud
flickering and the occasional ground strike; the thunder was the house
foundation shaking type and at times truly deafening. The brightness of
the lightning was awe inspiring.

I have just checked the rain gauge and it was blocked by hailstones that
still had not melted but there was 63 mm of rain in there. The Davis AWS
recorded a total of 70 mm since midnight with 40 mm falling between 0:00
and 3:00. These rainfall figures are probably much lower than what
actually fell.

With reports that Ottery St Mary and many villages around here are
flooded and cut off, the A30 and part of the motorway at Junction 29
closed due to multiple accidents. There have been 'hail drifts' (not snow
as reported by some people) so deep that cars have been buried in them,
it certainly has been one of those nights to remember.
________________
Nick.
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk

On Oct 31, 10:06*pm, "CHRIS KIDD" wrote:
Looking at the 1km radar data it would appear that the heaviest rainfall was
alligned with the eastern side of the Otter valley - with the western-side
of the valley being virtually free of heavy rain - the steering effects of
the surface are often overlooked.

Chris


The western side of the valley certainly saw some very heavy rainfall/
hail.

Finnimore Industrial Estate and the hospital (picture 26 and 7 here
http://www.bbc.co.uk/devon/content/i...llery.shtml?26)
are both on the western side of the river and there was hail from
there to the A30. The flash flooding to the west in Rockbeare (see
images and video on my website) was caused by a local stream whose
catchment is along and west of the western Otter Valley ridge between
Rockbeare Hill and Aylesbeare Hill. Our rain rate peaked at 108mm/hour
(although we only saw about 11mm in total in a 20 min period) before
ceasing before midnight. We only managed 0.8mm from midnight to 03Z
when much of the action was happening just a mile or two to the east
of us.

Steve.
Highest/lowest of 2008 so far: 28.0C/-4.3C.
No. of Air frosts 36...
www.rockbeareweather.co.uk

On Oct 31, 6:42*pm, "Will Hand" wrote:
"Tudor Hughes" wrote in message

...
On Oct 30, 6:04 pm, " wrote:

On Oct 30, 5:57 pm, Bonos Ego wrote:

What a day!

For those of us in the SW, the pictures on Spotlight are going to be
interesting!

For those not living in the South West, but have SKY TV, and would
like to watch spotlight, try Sky TV Channel 987.

There's some video footage here
toohttp://news.bbc.co.uk/1/hi/england/devon/7700167.stm

* * * From those incredible pictures people could be forgiven for
calling it snow because that's what it looks like. *The hail must have
been very small but there's a huge volume of it which makes one think
it must be of low density. *But hail is clear ice so that cannot be
the case. *Does anyone have any explanation of these characteristics?
The storm cannot have had a supercell structure or the hail would
probably have gone up and down a few times before finally falling out
as large hail.

Tudor Hughes, Warlingham, Surrey.

============================
============================

Tudor, I think a lot of it was soft hail or graupel which blows around
easily in the wind and drifts. Also mixed in were small hail (looking at the
picture showing footprints). Possibly also a bit of wet snow too as the
wet-bulb freezing level lowered in the very heavy precipitation. Actually I
don't think it looks like snow at all, sure it is white but it is laying
"funny", doesn't have that light puffy look to it. But yes to the layman and
to people who are not used to seeing much snow I can see why they might
think it was snow.

Will
--

Thanks, Will. You're right that it doesn't look like snow on
closer inspection.

Tudor Hughes, Warlingham, Surrey.

Tudor, I think a lot of it was soft hail or graupel which blows around
easily in the wind and drifts. Also mixed in were small hail (looking at
the picture showing footprints).

From what I can make out now, the 'drifts' were formed by water carrying the
hail along. This explains why the hail has collected in places that it has,
likes dips and drains.

The fields around here still have piles of hail in the hedgerows where the
rainwater running off the fields carried the hail but it got 'filtered out'
by the hedgerows. Other examples of this are everywhere.

There was very little wind and the hail and rain was coming down vertically.

The hail was white/opaque and consistently around 5 mm in diameter. There
was definitely no snow falling at any time. The DPs were around 5°C for most
of the event itself which was from 00:00 to 02:00.
________________
Nick.
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk