I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no

On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far

On Wednesday, 4 October 2017 08:37:25 UTC+1, N_Cook wrote:
On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far
The 1 hPa per hour drop is just the threshold for explosive cyclogenisis. It doesn't tell you much about likely strength of wind. Looking at the 1987 storm, the pressure gradient between 51N and 54N on the meridian at 0600UTC was 24 hPa. Tne same measurement at midnight tonight (when the low is in a similar position to 1987) is 16 hPa. So a repeat is unlikely with tonight's storm. Remember also that a pressure gradient doesn't instantaneously give you the wind strength indicated - it takes a finite amount of time for the force exerted by the pressure gradient to accelerate the air to the indicated velocity. The 1987 storm centre had been at 959 hPa for approximately 10 hours before 0600 UTC. Even 6 hours before 0000 UTC, tonight's storm was 4-5 hPa shallower. I think impacts in the Netherlands and Belgium will comfortably exceed anything we experience in the UK tonight. The low tonight isn't anything like 1987 IMHO.

--
Freddie
Fishpool Farm
Hyssington
Powys
296m AMSL
http://www.fishpoolfarmweather.co.uk/
https://twitter.com/FishpoolFarmWx for hourly reports

On 04/10/2017 13:02, Freddie wrote:
On Wednesday, 4 October 2017 08:37:25 UTC+1, N_Cook wrote:
On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far
The 1 hPa per hour drop is just the threshold for explosive cyclogenisis. It doesn't tell you much about likely strength of wind. Looking at the 1987 storm, the pressure gradient between 51N and 54N on the meridian at 0600UTC was 24 hPa. Tne same measurement at midnight tonight (when the low is in a similar position to 1987) is 16 hPa. So a repeat is unlikely with tonight's storm. Remember also that a pressure gradient doesn't instantaneously give you the wind strength indicated - it takes a finite amount of time for the force exerted by the pressure gradient to accelerate the air to the indicated velocity. The 1987 storm centre had been at 959 hPa for approximately 10 hours before 0600 UTC. Even 6 hours before 0000 UTC, tonight's storm was 4-5 hPa shallower. I think impacts in the Netherlands and Belgium will comfortably exceed anything we experience in the UK tonight. The low tonight isn't anything like 1987 IMHO.


Is your historic data , hindsight data from after the event or the data
,as it was, 1 day before the '87 great felling?
ie like for like

On Wednesday, 4 October 2017 14:06:57 UTC+1, N_Cook wrote:
On 04/10/2017 13:02, Freddie wrote:
On Wednesday, 4 October 2017 08:37:25 UTC+1, N_Cook wrote:
On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far
The 1 hPa per hour drop is just the threshold for explosive cyclogenisis. It doesn't tell you much about likely strength of wind. Looking at the 1987 storm, the pressure gradient between 51N and 54N on the meridian at 0600UTC was 24 hPa. Tne same measurement at midnight tonight (when the low is in a similar position to 1987) is 16 hPa. So a repeat is unlikely with tonight's storm. Remember also that a pressure gradient doesn't instantaneously give you the wind strength indicated - it takes a finite amount of time for the force exerted by the pressure gradient to accelerate the air to the indicated velocity. The 1987 storm centre had been at 959 hPa for approximately 10 hours before 0600 UTC. Even 6 hours before 0000 UTC, tonight's storm was 4-5 hPa shallower. I think impacts in the Netherlands and Belgium will comfortably exceed anything we experience in the UK tonight. The low tonight isn't anything like 1987 IMHO.


Is your historic data , hindsight data from after the event or the data
,as it was, 1 day before the '87 great felling?
ie like for like
It is analysed actual data from the time of the event. It isn't forecast data. Even if it was, it wouldn't be "like for like" as models and their methods of assimilating observational data have changed massively since 1987.

--
Freddie
Fishpool Farm
Hyssington
Powys
296m AMSL
http://www.fishpoolfarmweather.co.uk/
https://twitter.com/FishpoolFarmWx for hourly reports

On 04/10/2017 14:12, Freddie wrote:
On Wednesday, 4 October 2017 14:06:57 UTC+1, N_Cook wrote:
On 04/10/2017 13:02, Freddie wrote:
On Wednesday, 4 October 2017 08:37:25 UTC+1, N_Cook wrote:
On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far
The 1 hPa per hour drop is just the threshold for explosive cyclogenisis. It doesn't tell you much about likely strength of wind. Looking at the 1987 storm, the pressure gradient between 51N and 54N on the meridian at 0600UTC was 24 hPa. Tne same measurement at midnight tonight (when the low is in a similar position to 1987) is 16 hPa. So a repeat is unlikely with tonight's storm. Remember also that a pressure gradient doesn't instantaneously give you the wind strength indicated - it takes a finite amount of time for the force exerted by the pressure gradient to accelerate the air to the indicated velocity. The 1987 storm centre had been at 959 hPa for approximately 10 hours before 0600 UTC. Even 6 hours before 0000 UTC, tonight's storm was 4-5 hPa shallower. I think impacts in the Netherlands and Belgium will comfortably exceed anything we experience in the UK tonight. The low tonight isn't anything like 1987 IMHO.


Is your historic data , hindsight data from after the event or the data
,as it was, 1 day before the '87 great felling?
ie like for like
It is analysed actual data from the time of the event. It isn't forecast data. Even if it was, it wouldn't be "like for like" as models and their methods of assimilating observational data have changed massively since 1987.


From what I remember of the storm, there was no awareness by anyone
,prior to the 87 storm, about its upcoming severity, during the day before.

Is there an analysis somewhere , of the data available at the time,to
see if there was any pointers at all, prior to the event.
Had French metmen got a better handle on it , the day before , for instance.

Freddie writes:

On Wednesday, 4 October 2017 08:37:25 UTC+1, N_Cook wrote:
On 02/10/2017 20:51, Scott W wrote:
I've written a few lines on October 1987. Similar to my account of the January 1987 cold spell would anyone be interested in adding their account of that night to this blog?

http://wp.me/p2VSmb-2no


second attempt on e-s

A repeat for the Midlands and East Anglia tonight?
GFS has the 1mB/hour drop character in place of cyclogenic upper air
coupling.
I'm surprised no heads-up on this board so far
The 1 hPa per hour drop is just the threshold for explosive
cyclogenisis. It doesn't tell you much about likely strength of wind.
Looking at the 1987 storm, the pressure gradient between 51N and 54N
on the meridian at 0600UTC was 24 hPa. Tne same measurement at
midnight tonight (when the low is in a similar position to 1987) is 16
hPa. So a repeat is unlikely with tonight's storm. Remember also
that a pressure gradient doesn't instantaneously give you the wind
strength indicated - it takes a finite amount of time for the force

I hope you will forgive my pointing out a linguistic detail here. You
mean 'non-zero' not 'finite'. Zero time /is/ a finite time but you want
to exclude that. (Mathematicians might argue that non-zero is not
precise enough because it include negative numbers, but when the context
is informal and the quantity something like time, that would be
pointlessly pedantic.)

exerted by the pressure gradient to accelerate the air to the
indicated velocity.

The wrong phrasing is very tempting in this sort of context because you
are thinking of a division -- it's the acceleration that must be finite
and that requires a change of velocity over a non-zero period of time.

The 1987 storm centre had been at 959 hPa for
approximately 10 hours before 0600 UTC. Even 6 hours before 0000 UTC,
tonight's storm was 4-5 hPa shallower. I think impacts in the
Netherlands and Belgium will comfortably exceed anything we experience
in the UK tonight. The low tonight isn't anything like 1987 IMHO.

BTW, I like and appreciate this sort of posting. That I don't
contribute anything but nit-picking like the above is just due to my not
knowing enough meteorology. It does not mean I don't like reading
about it!

--
Ben.

Reviewing last night's plots, the next time I'll look at the necking in
the near real-time geopotential plots and minimum of the (don't know
what the term is) dam-km product , for the minimum value

A lot of interesting stuff on this paper, about the meteorology and how
the French (in English) handled the 1987 Great Felling

15–16 October 1987 - American Meteorological Society
http://journals.ametsoc.org/doi/pdf/...O%3E2.0.CO%3B2

(hyphen break)

"... Forecasts issued by DMN gave very strong and repeated warnings to
the media, security agencies, and specialized users.
....
Three to 4 days prior to the event, (French) forecasts mentioned the
possibility of a severe storm. ..."

but if the numerical model outputs had been slavishly observed, those
warnings could have neen rescinded.

On Wednesday, 4 October 2017 14:20:22 UTC+1, N_Cook wrote:

From what I remember of the storm, there was no awareness by anyone
,prior to the 87 storm, about its upcoming severity, during the day before.

This was partly a "failing" in the understanding of the meteorology. The enormous, threatening "cloud head" was there and today's meteorologists would view this with a fair amount of horror as it would have signalled the potential for rapid cyclogenesis.

However - if you take a look at the pressure drops in the centre of the storm, it's absolutely nothing remarkable compared to other storms. I did a bit of work for an old company who had digitised all the Atlantic pressure maps going back to 1900 and the 87 storm was maybe about the 50th or 60th most rapid deepener.

The slow, steady development of the storm I think is responsible for the long-lived nature of the sting jet that helped cause such notable damage. When storms rapidly deepen they wrap up quickly and any sting jet signature is fairly quickly overrun by the cold conveyor belt, the traditional source of the strongest winds. This is purely a hypothesis mind...

Richard

On 05/10/17 11:27, N_Cook wrote:
Reviewing last night's plots, the next time I'll look at the necking in
the near real-time geopotential plots and minimum of the (don't know
what the term is) dam-km product , for the minimum value

A lot of interesting stuff on this paper, about the meteorology and how
the French (in English) handled the 1987 Great Felling

15–16 October 1987 - American Meteorological Society
http://journals.ametsoc.org/doi/pdf/...O%3E2.0.CO%3B2


(hyphen break)

"... Forecasts issued by DMN gave very strong and repeated warnings to
the media, security agencies, and specialized users.
...
Three to 4 days prior to the event, (French) forecasts mentioned the
possibility of a severe storm. ..."

but if the numerical model outputs had been slavishly observed, those
warnings could have neen rescinded.


Met Office computer forecast was also going for storms on the Sunday.
When someone asked me in the pub on Monday evening what the weather
would be like on on Friday at Wentworth - he was going to the golf
tournament - I warned him that there'd be storm force winds. In each
successive run of the computer forecast during the week, it looked as
though it was chickening out and if I'd seen the guy on Wednesday
evening, I'd've told him not to worry!


--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
Web-site: http://www.scarlet-jade.com/
“Like sewage, smartphones, and Donald Trump, some things are just
inevitable.� [The Doctor]