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.