Bit late in the day-but rapidly evolving line convection with Line
Echo Wave Pattern suggests tornado risk for southern coastal
counties.
Maybe alert AWS users could turn logging to every 1 minute.
Please report any wind damage/obs here,
thanks,
David

On 3 Nov, 12:10, Waghorn  wrote:
> Bit late in the day-but rapidly evolving line convection with Line
> Echo Wave Pattern suggests tornado risk for southern coastal
> counties.
> Maybe alert AWS users could turn logging to every 1 minute.
> Please report any wind damage/obs here,
> thanks,
> David

Post was too late, but reviewing radar imagery this morning suggests
presence of a 'Broken-S' LEWP feature just south of the apex of the
wave feature crossing southern England.
I would be very interested to hear of any reports of wind damage
across Wiltshire/Hampshire 1130-1230Z ,
thanks,
David

On Nov 3, 1:05 pm, Waghorn  wrote:
> On 3 Nov, 12:10, Waghorn  wrote:
>
> > Bit late in the day-but rapidly evolving line convection with Line
> > Echo Wave Pattern suggests tornado risk for southern coastal
> > counties.
> > Maybe alert AWS users could turn logging to every 1 minute.
> > Please report any wind damage/obs here,
> > thanks,
> > David
>
> Post was too late, but reviewing radar imagery this morning suggests
> presence of a 'Broken-S' LEWP feature just south of the apex of the
> wave feature crossing southern England.
> I would be very interested to hear of any reports of wind damage
> across Wiltshire/Hampshire 1130-1230Z ,
> thanks,
> David

I was out of view of the sky between 1000 - 1200, but around 1200
there seemed to be a light shower.
I thought wave features normally generated continuous frontal rain,
yet this one seemed to produce showers - how come?

Nick

On Nov 3, 1:56 pm, Nick  wrote:
> On Nov 3, 1:05 pm, Waghorn  wrote:
>
>
>
> > On 3 Nov, 12:10, Waghorn  wrote:
>
> > > Bit late in the day-but rapidly evolving line convection with Line
> > > Echo Wave Pattern suggests tornado risk for southern coastal
> > > counties.
> > > Maybe alert AWS users could turn logging to every 1 minute.
> > > Please report any wind damage/obs here,
> > > thanks,
> > > David
>
> > Post was too late, but reviewing radar imagery this morning suggests
> > presence of a 'Broken-S' LEWP feature just south of the apex of the
> > wave feature crossing southern England.
> > I would be very interested to hear of any reports of wind damage
> > across Wiltshire/Hampshire 1130-1230Z ,
> > thanks,
> > David
>
> I was out of view of the sky between 1000 - 1200, but around 1200
> there seemed to be a light shower.
> I thought wave features normally generated continuous frontal rain,
> yet this one seemed to produce showers - how come?
>
> Nick

Sorry this was Southampton I was referring to. There were cb clouds
around too, mostly to the south.

Nick

> On Nov 3, 1:05 pm, Waghorn wrote ...
> > Post was too late, but reviewing radar imagery this morning 
> > suggests
> > presence of a 'Broken-S' LEWP feature just south of the apex of 
> > the
> > wave feature crossing southern England.
> > I would be very interested to hear of any reports of wind damage
> > across Wiltshire/Hampshire 1130-1230Z ,
> > thanks,
> > David


... we were in the Castlepoint (NNE of central Bournemouth / SW of 
Hurn) shopping area as the trough (drawn attached to the shallow wave 
on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then 
a short period of heavy rain ~1145/1150Z, before abrupt clearance to 
dry/well-broken cloud 1205Z.

Wind was 'gusty' without being anything out of the ordinary -  nothing 
noted within the cloud structure that was out of the ordinary.

From the SYNOPs for Hurn, the top gust was 36 kn (reported on the 
1150Z & 1250Z issue, but I fancy that it actually occurred ON the 
1150Z data capture, so it was credited to both hours).

Coming back here (travelling NE), no sign of any debris etc., but 
looking at the radar, we were too far south perhaps. However, the 
low-level shear associated with the trough was obviously notable, as a 
light aircraft doing 'circuits and bumps' from EGHH was slipping 
sideways and the pilot was obviously having difficulty correcting for 
changing wind direction & speed at his/her altitude ~ 1500ft.

Martin.


-- 
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N   Long: 01.88W
NGR: SU 082 023

On 3 Nov, 14:25, "Martin Rowley"
 wrote:
> > On Nov 3, 1:05 pm, Waghorn wrote ...
> > > Post was too late, but reviewing radar imagery this morning
> > > suggests
> > > presence of a 'Broken-S' LEWP feature just south of the apex of
> > > the
> > > wave feature crossing southern England.
> > > I would be very interested to hear of any reports of wind damage
> > > across Wiltshire/Hampshire 1130-1230Z ,
> > > thanks,
> > > David
>
> ... we were in the Castlepoint (NNE of central Bournemouth / SW of
> Hurn) shopping area as the trough (drawn attached to the shallow wave
> on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then
> a short period of heavy rain ~1145/1150Z, before abrupt clearance to
> dry/well-broken cloud 1205Z.
>
> Wind was 'gusty' without being anything out of the ordinary -  nothing
> noted within the cloud structure that was out of the ordinary.
>
> From the SYNOPs for Hurn, the top gust was 36 kn (reported on the
> 1150Z & 1250Z issue, but I fancy that it actually occurred ON the
> 1150Z data capture, so it was credited to both hours).
>
> Coming back here (travelling NE), no sign of any debris etc., but
> looking at the radar, we were too far south perhaps. However, the
> low-level shear associated with the trough was obviously notable, as a
> light aircraft doing 'circuits and bumps' from EGHH was slipping
> sideways and the pilot was obviously having difficulty correcting for
> changing wind direction & speed at his/her altitude ~ 1500ft.
>
> Martin.
>
> --
> Martin Rowley
> West Moors, East Dorset (UK): 17m (56ft) amsl
> Lat: 50.82N   Long: 01.88W
> NGR: SU 082 023

Reports of damage coming in from the Romsey-Petersfield, Hampshire,
area- trees down etc.
Any body with an AWS in this area?
David

Looks great on the Weatheronline radar, like a purple snake


Waghorn wrote:
> Bit late in the day-but rapidly evolving line convection with Line
> Echo Wave Pattern suggests tornado risk for southern coastal
> counties.
> Maybe alert AWS users could turn logging to every 1 minute.
> Please report any wind damage/obs here,
> thanks,
> David


-- 
I am using the free version of SPAMfighter.
We are a community of 6 million users fighting spam.
SPAMfighter has removed 1467 of my spam emails to date.
Get the free SPAMfighter here: http://www.spamfighter.com/len

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"Waghorn"  wrote in message 
news:2b98b550-ed3d-4b9f-b149-fa180a817075@m16g2000yqc.googlegroups.com...

> Reports of damage coming in from the Romsey-Petersfield, Hampshire,
>area- trees down etc.

David, I'm reliably informed there was tornado activity reported in the 
Hampshire area. Building damage was also reported over west Sussex.

HTH.

Jon.

In message 
, 
Waghorn  writes
>On 3 Nov, 14:25, "Martin Rowley"
> wrote:
>> > On Nov 3, 1:05 pm, Waghorn wrote ...
>> > > Post was too late, but reviewing radar imagery this morning
>> > > suggests
>> > > presence of a 'Broken-S' LEWP feature just south of the apex of
>> > > the
>> > > wave feature crossing southern England.
>> > > I would be very interested to hear of any reports of wind damage
>> > > across Wiltshire/Hampshire 1130-1230Z ,
>> > > thanks,
>> > > David
>>
>> ... we were in the Castlepoint (NNE of central Bournemouth / SW of
>> Hurn) shopping area as the trough (drawn attached to the shallow wave
>> on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then
>> a short period of heavy rain ~1145/1150Z, before abrupt clearance to
>> dry/well-broken cloud 1205Z.
>>
>> Wind was 'gusty' without being anything out of the ordinary -  nothing
>> noted within the cloud structure that was out of the ordinary.
>>
>> From the SYNOPs for Hurn, the top gust was 36 kn (reported on the
>> 1150Z & 1250Z issue, but I fancy that it actually occurred ON the
>> 1150Z data capture, so it was credited to both hours).
>>
>> Coming back here (travelling NE), no sign of any debris etc., but
>> looking at the radar, we were too far south perhaps. However, the
>> low-level shear associated with the trough was obviously notable, as a
>> light aircraft doing 'circuits and bumps' from EGHH was slipping
>> sideways and the pilot was obviously having difficulty correcting for
>> changing wind direction & speed at his/her altitude ~ 1500ft.
>>
>> Martin.
>>
>> --
>> Martin Rowley
>> West Moors, East Dorset (UK): 17m (56ft) amsl
>> Lat: 50.82N   Long: 01.88W
>> NGR: SU 082 023
>
>Reports of damage coming in from the Romsey-Petersfield, Hampshire,
>area- trees down etc.
>Any body with an AWS in this area?
>David


You might be able to get some details from:

<www.winchesterweather.org.uk/index.html>

I'm not sufficiently knowledgeable to understand more than the basics.

There are some local newspaper reports:

<www.hampshirechronicle.co.uk/news/4717793.Storm_hits_Twyford_near_Winche
ster/>
<www.hampshirechronicle.co.uk/news/4717489.Freak_weather_brings_chaos_to_
Winchester_area/>


-- 
Elizabeth

On Nov 3, 5:19 pm, Elizabeth  wrote:
> In message
> ,
> Waghorn  writes
>
>
>
> >On 3 Nov, 14:25, "Martin Rowley"
> > wrote:
> >> > On Nov 3, 1:05 pm, Waghorn wrote ...
> >> > > Post was too late, but reviewing radar imagery this morning
> >> > > suggests
> >> > > presence of a 'Broken-S' LEWP feature just south of the apex of
> >> > > the
> >> > > wave feature crossing southern England.
> >> > > I would be very interested to hear of any reports of wind damage
> >> > > across Wiltshire/Hampshire 1130-1230Z ,
> >> > > thanks,
> >> > > David
>
> >> ... we were in the Castlepoint (NNE of central Bournemouth / SW of
> >> Hurn) shopping area as the trough (drawn attached to the shallow wave
> >> on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then
> >> a short period of heavy rain ~1145/1150Z, before abrupt clearance to
> >> dry/well-broken cloud 1205Z.
>
> >> Wind was 'gusty' without being anything out of the ordinary -  nothing
> >> noted within the cloud structure that was out of the ordinary.
>
> >> From the SYNOPs for Hurn, the top gust was 36 kn (reported on the
> >> 1150Z & 1250Z issue, but I fancy that it actually occurred ON the
> >> 1150Z data capture, so it was credited to both hours).
>
> >> Coming back here (travelling NE), no sign of any debris etc., but
> >> looking at the radar, we were too far south perhaps. However, the
> >> low-level shear associated with the trough was obviously notable, as a
> >> light aircraft doing 'circuits and bumps' from EGHH was slipping
> >> sideways and the pilot was obviously having difficulty correcting for
> >> changing wind direction & speed at his/her altitude ~ 1500ft.
>
> >> Martin.
>
> >> --
> >> Martin Rowley
> >> West Moors, East Dorset (UK): 17m (56ft) amsl
> >> Lat: 50.82N   Long: 01.88W
> >> NGR: SU 082 023
>
> >Reports of damage coming in from the Romsey-Petersfield, Hampshire,
> >area- trees down etc.
> >Any body with an AWS in this area?
> >David
>
> You might be able to get some details from:
>
> <www.winchesterweather.org.uk/index.html>
>
> I'm not sufficiently knowledgeable to understand more than the basics.
>
> There are some local newspaper reports:
>
> <www.hampshirechronicle.co.uk/news/4717793.Storm_hits_Twyford_near_Winche
> ster/>
> <www.hampshirechronicle.co.uk/news/4717489.Freak_weather_brings_chaos_to_
> Winchester_area/>
>
> --
> Elizabeth

What time did this lot come through? If it was 1145 in West Moors I'd
guess after 1200 in this area (Southampton/Winchester), didn't notice
anything out of the ordinary here (Southampton) though. Just a fairly
light shower.

Nick

"Waghorn"  wrote in message 
news:642e7c7d-72a8-48f2-a884-ba682d9f68fe@d21g2000yqn.googlegroups.com...
> Bit late in the day-but rapidly evolving line convection with Line
> Echo Wave Pattern suggests tornado risk for southern coastal
> counties.
> Maybe alert AWS users could turn logging to every 1 minute.
> Please report any wind damage/obs here,
> thanks,
> David

Hi David, long time no speak!

Interestingly I have developed some tornado diagnostics at work running off 
a 4km model (Jon knows about them!). The diagnostics are based on 0-1km 
helicity, deep vertical wind shear, CAPE and cloud base height. The 
forecasts were indicating a high tornado risk in the English Channel and 
right on the coast from IOW westwards at 12Z with the area moving east and 
weakening early afternoon. It looked quite impressive, so I am heartened to 
hear of a possible tornado. Unfortunately they are not available publicly.

Thanks.

Will
--

In message 
, 
Nick  writes
>On Nov 3, 5:19 pm, Elizabeth  wrote:
>> In message
>> ,
>> Waghorn  writes
>>
>>
>>
>> >On 3 Nov, 14:25, "Martin Rowley"
>> > wrote:
>> >> > On Nov 3, 1:05 pm, Waghorn wrote ...
>> >> > > Post was too late, but reviewing radar imagery this morning
>> >> > > suggests
>> >> > > presence of a 'Broken-S' LEWP feature just south of the apex of
>> >> > > the
>> >> > > wave feature crossing southern England.
>> >> > > I would be very interested to hear of any reports of wind damage
>> >> > > across Wiltshire/Hampshire 1130-1230Z ,
>> >> > > thanks,
>> >> > > David
>>
>> >> ... we were in the Castlepoint (NNE of central Bournemouth / SW of
>> >> Hurn) shopping area as the trough (drawn attached to the shallow wave
>> >> on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then
>> >> a short period of heavy rain ~1145/1150Z, before abrupt clearance to
>> >> dry/well-broken cloud 1205Z.
>>
>> >> Wind was 'gusty' without being anything out of the ordinary -  nothing
>> >> noted within the cloud structure that was out of the ordinary.
>>
>> >> From the SYNOPs for Hurn, the top gust was 36 kn (reported on the
>> >> 1150Z & 1250Z issue, but I fancy that it actually occurred ON the
>> >> 1150Z data capture, so it was credited to both hours).
>>
>> >> Coming back here (travelling NE), no sign of any debris etc., but
>> >> looking at the radar, we were too far south perhaps. However, the
>> >> low-level shear associated with the trough was obviously notable, as a
>> >> light aircraft doing 'circuits and bumps' from EGHH was slipping
>> >> sideways and the pilot was obviously having difficulty correcting for
>> >> changing wind direction & speed at his/her altitude ~ 1500ft.
>>
>> >> Martin.
>>
>> >> --
>> >> Martin Rowley
>> >> West Moors, East Dorset (UK): 17m (56ft) amsl
>> >> Lat: 50.82N   Long: 01.88W
>> >> NGR: SU 082 023
>>
>> >Reports of damage coming in from the Romsey-Petersfield, Hampshire,
>> >area- trees down etc.
>> >Any body with an AWS in this area?
>> >David
>>
>> You might be able to get some details from:
>>
>> <www.winchesterweather.org.uk/index.html>
>>
>> I'm not sufficiently knowledgeable to understand more than the basics.
>>
>> There are some local newspaper reports:
>>
>> <www.hampshirechronicle.co.uk/news/4717793.Storm_hits_Twyford_near_Winche
>> ster/>
>> <www.hampshirechronicle.co.uk/news/4717489.Freak_weather_brings_chaos_to_
>> Winchester_area/>
>>
>> --
>> Elizabeth
>
>What time did this lot come through? If it was 1145 in West Moors I'd
>guess after 1200 in this area (Southampton/Winchester), didn't notice
>anything out of the ordinary here (Southampton) though. Just a fairly
>light shower.
>
>Nick

Unfortunately, neither my husband nor I made a note of the time, but my 
husband reckons it was just before lunch, roughly 11:30. Where we are, 
in Winchester, there was a lot of rain and high winds, such that the 
rain was blown around so much it looked like mist. It was severe enough 
and lasted long enough to drag me away from the computer and look out 
other windows (the window next to my desk looks out onto the brick wall 
of the house next door, so not very good for the limited weather obs I'm 
capable of). When the system passed over, it cleared very quickly, so I 
assume it was fairly localised. The rainful was sufficiently heavy that 
for quite some time after there was a significant amount of water 
running down the road which I think had as much to do with the volume 
versus drains blocked by leaves.

There was a beautiful and strong double rainbow to the east, which I 
completely failed to photograph. I'm not very good at this weather 
reporting, am I. ;)
-- 
Elizabeth

In article <Oe+PtYP3DI8KFwTV@chelonium.plus.com>,
 Elizabeth  writes:
>In message <a1433447-d3bb-4769-bed0-92054c84c83d@j19g2000yqk.googlegrou
>ps.com>, Nick  writes
>>On Nov 3, 5:19 pm, Elizabeth  wrote:
>>> In message
>>> ,
>>> Waghorn  writes
>>>
>>>
>>>
>>> >On 3 Nov, 14:25, "Martin Rowley"
>>> > wrote:
>>> >> > On Nov 3, 1:05 pm, Waghorn wrote ...
>>> >> > > Post was too late, but reviewing radar imagery this morning
>>> >> > > suggests
>>> >> > > presence of a 'Broken-S' LEWP feature just south of the apex of
>>> >> > > the
>>> >> > > wave feature crossing southern England.
>>> >> > > I would be very interested to hear of any reports of wind damage
>>> >> > > across Wiltshire/Hampshire 1130-1230Z ,
>>> >> > > thanks,
>>> >> > > David
>>>
>>> >> ... we were in the Castlepoint (NNE of central Bournemouth / SW of
>>> >> Hurn) shopping area as the trough (drawn attached to the shallow wave
>>> >> on 12Z ASXX) passed overhead; rain steadily/moderate from 1030Z, then
>>> >> a short period of heavy rain ~1145/1150Z, before abrupt clearance to
>>> >> dry/well-broken cloud 1205Z.
>>>
>>> >> Wind was 'gusty' without being anything out of the ordinary -  nothing
>>> >> noted within the cloud structure that was out of the ordinary.
>>>
>>> >> From the SYNOPs for Hurn, the top gust was 36 kn (reported on the
>>> >> 1150Z & 1250Z issue, but I fancy that it actually occurred ON the
>>> >> 1150Z data capture, so it was credited to both hours).
>>>
>>> >> Coming back here (travelling NE), no sign of any debris etc., but
>>> >> looking at the radar, we were too far south perhaps. However, the
>>> >> low-level shear associated with the trough was obviously notable, as a
>>> >> light aircraft doing 'circuits and bumps' from EGHH was slipping
>>> >> sideways and the pilot was obviously having difficulty correcting for
>>> >> changing wind direction & speed at his/her altitude ~ 1500ft.
>>>
>>> >> Martin.
>>>
>>> >> --
>>> >> Martin Rowley
>>> >> West Moors, East Dorset (UK): 17m (56ft) amsl
>>> >> Lat: 50.82N   Long: 01.88W
>>> >> NGR: SU 082 023
>>>
>>> >Reports of damage coming in from the Romsey-Petersfield, Hampshire,
>>> >area- trees down etc.
>>> >Any body with an AWS in this area?
>>> >David
>>>
>>> You might be able to get some details from:
>>>
>>> <www.winchesterweather.org.uk/index.html>
>>>
>>> I'm not sufficiently knowledgeable to understand more than the basics.
>>>
>>> There are some local newspaper reports:
>>>
>>> <www.hampshirechronicle.co.uk/news/4717793.Storm_hits_Twyford_near_Winche
>>> ster/>
>>> <www.hampshirechronicle.co.uk/news/4717489.Freak_weather_brings_chaos_to_
>>> Winchester_area/>
>>>
>>> --
>>> Elizabeth
>>
>>What time did this lot come through? If it was 1145 in West Moors I'd
>>guess after 1200 in this area (Southampton/Winchester), didn't notice
>>anything out of the ordinary here (Southampton) though. Just a fairly
>>light shower.
>>
>>Nick
>
>Unfortunately, neither my husband nor I made a note of the time, but my
>husband reckons it was just before lunch, roughly 11:30. Where we are,
>in Winchester, there was a lot of rain and high winds, such that the
>rain was blown around so much it looked like mist. It was severe enough
>and lasted long enough to drag me away from the computer and look out
>other windows (the window next to my desk looks out onto the brick wall
>of the house next door, so not very good for the limited weather obs
>I'm capable of). When the system passed over, it cleared very quickly,
>so I assume it was fairly localised. The rainful was sufficiently heavy
>that for quite some time after there was a significant amount of water
>running down the road which I think had as much to do with the volume
>versus drains blocked by leaves.
>
>There was a beautiful and strong double rainbow to the east, which I
>completely failed to photograph. I'm not very good at this weather
>reporting, am I. ;)

I think that's a very good report. It came through Cranleigh, Surrey
about 1pm, I think, and must have lasted for the better part of an hour.
Heavy rain, but I didn't notice that it became particularly windy.
-- 
John Hall  "[It was] so steep that at intervals the street broke into steps,
            like a person breaking into giggles or hiccups, and then resumed
            its sober climb, until it had another fit of steps."
                                      Ursula K Le Guin "The Beginning Place"

Nick wrote:

> What time did this lot come through? If it was 1145 in West Moors I'd
> guess after 1200 in this area (Southampton/Winchester), didn't notice
> anything out of the ordinary here (Southampton) though. Just a fairly
> light shower.

I was at work in Chilworth, just north of Southampton. Biggest gusts of 
wind were at 1200Z - a couple of minutes later a friend reported strong 
gusts at Hursley (5 miles to the north). Gusts were very noticeable, 
especially seeing as the windows don't fit properly! Clearance was very 
rapid and we were soon basking in sunshine (until the blinds were closed!).

Seems to have caused flooding around Romsey - trees were blocking the 
main road north out of the town. Also trees down on the railway at 
Chandlers Ford and at Shawford south of Winchester.

Jonathan

On 3 Nov, 18:33, "Will Hand"  wrote:
> "Waghorn"  wrote in message
>
> news:642e7c7d-72a8-48f2-a884-ba682d9f68fe@d21g2000yqn.googlegroups.com...
>
> > Bit late in the day-but rapidly evolving line convection with Line
> > Echo Wave Pattern suggests tornado risk for southern coastal
> > counties.
> > Maybe alert AWS users could turn logging to every 1 minute.
> > Please report any wind damage/obs here,
> > thanks,
> > David
>
> Hi David, long time no speak!
>
> Interestingly I have developed some tornado diagnostics at work running off
> a 4km model (Jon knows about them!). The diagnostics are based on 0-1km
> helicity, deep vertical wind shear, CAPE and cloud base height. The
> forecasts were indicating a high tornado risk in the English Channel and
> right on the coast from IOW westwards at 12Z with the area moving east and
> weakening early afternoon. It looked quite impressive, so I am heartened to
> hear of a possible tornado. Unfortunately they are not available publicly.
>
> Thanks.
>
> Will
> --

Hi Will

GFS yesterday flagged this up as well, with the primary risk along the
coast and downwind of IoW type event. However, we have seen a number
of cases now of long tracked tornadoes occuring along triple points/
wave features with LEWP.(eg Hautmont, N France, August 2008,
F4,fatalities).
This looks a similar event-radar echoes evolved from a linear feature
which develops a 'Broken-S' signature then the northern segment on
this occasion evolved into an elongated echo with a hook-like feature
resembling a HP supercell.
This suggests there is some persistent, shallow miso/mesocyclone
present.

I will be running the GFS-WRF at 1km for this event. Can keep you
informed if you like ;-).

There is now evidence for a quite linear, intermittent damage track.

Meantime thanks for the reports. Am still very keen for 'unusual' AWS
records from Hampshire -Sussex. Eg Chilbolton met station recorded a
2-3 hPa jump and wind veer, but unremarkable gusts,

best,
David

On 3 Nov, 20:21, Waghorn  wrote:
> On 3 Nov, 18:33, "Will Hand"  wrote:
>
>
>
>
>
> > "Waghorn"  wrote in message
>
> >news:642e7c7d-72a8-48f2-a884-ba682d9f68fe@d21g2000yqn.googlegroups.com...
>
> > > Bit late in the day-but rapidly evolving line convection with Line
> > > Echo Wave Pattern suggests tornado risk for southern coastal
> > > counties.
> > > Maybe alert AWS users could turn logging to every 1 minute.
> > > Please report any wind damage/obs here,
> > > thanks,
> > > David
>
> > Hi David, long time no speak!
>
> > Interestingly I have developed some tornado diagnostics at work running off
> > a 4km model (Jon knows about them!). The diagnostics are based on 0-1km
> > helicity, deep vertical wind shear, CAPE and cloud base height. The
> > forecasts were indicating a high tornado risk in the English Channel and
> > right on the coast from IOW westwards at 12Z with the area moving east and
> > weakening early afternoon. It looked quite impressive, so I am heartened to
> > hear of a possible tornado. Unfortunately they are not available publicly.
>
> > Thanks.
>
> > Will
> > --
>
> Hi Will
>
> GFS yesterday flagged this up as well, with the primary risk along the
> coast and downwind of IoW type event. However, we have seen a number
> of cases now of long tracked tornadoes occuring along triple points/
> wave features with LEWP.(eg Hautmont, N France, August 2008,
> F4,fatalities).
> This looks a similar event-radar echoes evolved from a linear feature
> which develops a 'Broken-S' signature then the northern segment on
> this occasion evolved into an elongated echo with a hook-like feature
> resembling a HP supercell.
> This suggests there is some persistent, shallow miso/mesocyclone
> present.
>
> I will be running the GFS-WRF at 1km for this event. Can keep you
> informed if you like ;-).
>
> There is now evidence for a quite linear, intermittent damage track.
>
> Meantime thanks for the reports. Am still very keen for 'unusual' AWS
> records from Hampshire -Sussex. Eg Chilbolton met station recorded a
> 2-3 hPa jump and wind veer, but unremarkable gusts,
>
> best,
> David- Hide quoted text -
>
> - Show quoted text -

A little north and east of your area, but just on the Hampshire/
Berkshire boundary: here there was showery rain becoming heavy
1100-1215, but nothing particularly noteworthy in intensity. What I
did notice was a very sudden short-lived rapid fall in pressure: from
987.0 mbar at 1209 in a fairly smooth, rapid fall to 985.1 mbar 1221 -
a fall of 1.9 mbar in 12 min, rate almost 10 mbar/h. (1 min AWS
logging to my Campbell Scientific logger.) At this time the wind
dropped and backed a little, from 220-230 deg 6-8 kn mean before and
at the tail end of the showery rain, to 205-210 deg 3-4 kn during the
pressure fall, before resuming much as before.

i mention the pressure fall because you referred to a 2-3 mbar jump at
Chilbolton, which isn't too far SW of here, which contrasts with a
fall - no recovery - here,

The only other notable event of the aftn was a single large-ish gust,
27 kn at 1357, which was much higher than the ones around it - nothing
over 20 kn the rest of the day. (Anemometer at 11 m AGL.)

Hope these notes may be of interest.

--
Stephen Burt
Stratfield Mortimer, Berkshire

On 3 Nov, 20:48, Stephen Burt  wrote:
> On 3 Nov, 20:21, Waghorn  wrote:
>
>
>
> > On 3 Nov, 18:33, "Will Hand"  wrote:
>
> > > "Waghorn"  wrote in message
>
> > >news:642e7c7d-72a8-48f2-a884-ba682d9f68fe@d21g2000yqn.googlegroups.com...
>
> > > > Bit late in the day-but rapidly evolving line convection with Line
> > > > Echo Wave Pattern suggests tornado risk for southern coastal
> > > > counties.
> > > > Maybe alert AWS users could turn logging to every 1 minute.
> > > > Please report any wind damage/obs here,
> > > > thanks,
> > > > David
>
> > > Hi David, long time no speak!
>
> > > Interestingly I have developed some tornado diagnostics at work running off
> > > a 4km model (Jon knows about them!). The diagnostics are based on 0-1km
> > > helicity, deep vertical wind shear, CAPE and cloud base height. The
> > > forecasts were indicating a high tornado risk in the English Channel and
> > > right on the coast from IOW westwards at 12Z with the area moving east and
> > > weakening early afternoon. It looked quite impressive, so I am heartened to
> > > hear of a possible tornado. Unfortunately they are not available publicly.
>
> > > Thanks.
>
> > > Will
> > > --
>
> > Hi Will
>
> > GFS yesterday flagged this up as well, with the primary risk along the
> > coast and downwind of IoW type event. However, we have seen a number
> > of cases now of long tracked tornadoes occuring along triple points/
> > wave features with LEWP.(eg Hautmont, N France, August 2008,
> > F4,fatalities).
> > This looks a similar event-radar echoes evolved from a linear feature
> > which develops a 'Broken-S' signature then the northern segment on
> > this occasion evolved into an elongated echo with a hook-like feature
> > resembling a HP supercell.
> > This suggests there is some persistent, shallow miso/mesocyclone
> > present.
>
> > I will be running the GFS-WRF at 1km for this event. Can keep you
> > informed if you like ;-).
>
> > There is now evidence for a quite linear, intermittent damage track.
>
> > Meantime thanks for the reports. Am still very keen for 'unusual' AWS
> > records from Hampshire -Sussex. Eg Chilbolton met station recorded a
> > 2-3 hPa jump and wind veer, but unremarkable gusts,
>
> > best,
> > David- Hide quoted text -
>
> > - Show quoted text -
>
> A little north and east of your area, but just on the Hampshire/
> Berkshire boundary: here there was showery rain becoming heavy
> 1100-1215, but nothing particularly noteworthy in intensity. What I
> did notice was a very sudden short-lived rapid fall in pressure: from
> 987.0 mbar at 1209 in a fairly smooth, rapid fall to 985.1 mbar 1221 -
> a fall of 1.9 mbar in 12 min, rate almost 10 mbar/h. (1 min AWS
> logging to my Campbell Scientific logger.) At this time the wind
> dropped and backed a little, from 220-230 deg 6-8 kn mean before and
> at the tail end of the showery rain, to 205-210 deg 3-4 kn during the
> pressure fall, before resuming much as before.
>
> i mention the pressure fall because you referred to a 2-3 mbar jump at
> Chilbolton, which isn't too far SW of here, which contrasts with a
> fall - no recovery - here,
>
> The only other notable event of the aftn was a single large-ish gust,
> 27 kn at 1357, which was much higher than the ones around it - nothing
> over 20 kn the rest of the day. (Anemometer at 11 m AGL.)
>
> Hope these notes may be of interest.
>
> --
> Stephen Burt
> Stratfield Mortimer, Berkshire

Thanks stephen, the Chilbolton trace is complex and rather interesting
(I used the term 'pressure drop' rather loosely)- a ~1 hPa rise then a
sharp drop of 2-3 hPa and then a sharp recovery. I'd like to compare
yours. Could you send me a trace, also RH, wind direction, gusts, rain
rate ? Any use would be fully acknowledged of course.
Best,
David
davidDOTwaghornATgmailDOTcom

On 3 Nov, 20:21, Waghorn  wrote:

> Meantime thanks for the reports. Am still very keen for 'unusual' AWS
> records from Hampshire -Sussex. Eg Chilbolton met station recorded a
> 2-3 hPa jump and wind veer, but unremarkable gusts,

Were they scanning today? Wonder if someone had the chance to alert
them early enough?

Richard

"Richard Dixon"  wrote in message 
news:22a0e3f0-1a43-4ded-b82b-17a08e389fb7@l2g2000yqd.googlegroups.com...
> On 3 Nov, 18:33, "Will Hand"  wrote:
>
>> Interestingly I have developed some tornado diagnostics at work running 
>> off
>> a 4km model (Jon knows about them!). The diagnostics are based on 0-1km
>> helicity, deep vertical wind shear, CAPE and cloud base height. The
>> forecasts were indicating a high tornado risk in the English Channel and
>> right on the coast from IOW westwards at 12Z with the area moving east 
>> and
>> weakening early afternoon. It looked quite impressive, so I am heartened 
>> to
>> hear of a possible tornado. Unfortunately they are not available 
>> publicly.
>
> That must feel quite heartening. What sort of % tornadic risk doid the
> diagnostic spit out, Will? I'm presuming low but not insignficant?
>
> Richard

It's basically a gridded index Richard, and they were high values over large 
areas indicating a real risk of somewhere getting hit, particularly as the 
synoptics were favourable as David has pointed out. At 9 hours lead time it 
was a good heads-up, much stronger signal at 3 hour lead time.

Will
--