On 13/01/2016 08:48, xmetman wrote:
On Wednesday, 13 January 2016 04:46:22 UTC, Tudor Hughes wrote:
On Tuesday, 12 January 2016 16:47:45 UTC, N_Cook wrote:
On 12/01/2016 14:58, Richard Dixon wrote:
On Tuesday, 12 January 2016 14:52:42 UTC, N_Cook wrote:
... to discover its affect on the North Sea sea levels.
The particular path is from the Icelandic area coming south , close to
north of Scotland but passing west of it, and west of Ireland before
going NW, west or southwest, ie not over the UK. Preferably in the last
20 years.
Any ideas how to go about it, other than squandering bandwidth on
weterzentral.de

This might be a useful starting point.

http://data.giss.nasa.gov/stormtracks/

Richard


Many thanks for that, what a useful resource. I've not found an example
in a winter quarter of the years I've chosen so far , but that is
probably associated with my conjecture.

Local marine flooding approx 100 years ago , on dates
27 oct 1909
26 dec 1912
05 Nov 1916
27 nov 1924
were more extreme than in the following decades to the present.
Looking at reanalysis of the synoptics for those periods, the associated
lows were not that extreme, but they took a track that just does not
happen these days, let alone 4 in 15 years, from the north, west of
Ireland and then turning into the English channel. Plenty of lows go
into the English Channel but don't produce historically excessive sea
levels, 1703 and 1824 events were probably due to true huricanes.
My conjecture is , due to the longer transit time via the North Sea,
close passage west or Scotland induces a positive surge into the North
Sea, that passes through Dover and attenuated going west through the
English channel but sums to the normal sort of west to east surge in the
channel associated with a low going into the channel from the west, so a
double-whammy.
Once I have a date I can check the BODC UK tide gauge data for North Sea
residuals
Incidently storm Frank seems to have induced a negative surge in the
North Sea inverse-barometer effect (from its south to north passage west
of Scotland) producing an east to west attenuated surge approx -0.7m in
our channel area that exactly cancelled an otherwise expected +0.7m
west to east surge in the Solent area, caused by the same Frank passage
in the Atlantic, taking 2 paths around the UK but temporally coincident
in the Solent.

A complicating factor in all this is the natural resonance of the North Sea which can be amplified by the wind if the timing is right, i.e. the speed of movement of the Low. My actual knowledge of this effect is a bit skimpy but it was implicated in the North Sea Floods of Jan 1953.

Tudor Hughes, Warlingham, Surrey.

I have 2.5°x2.5° gridded data and I was going to set myself a programming task of tracking highs an lows (yes I am quite sad but you have to fill the days). Finding the crude position of highs and lows wouldn't be the problem but keeping track of the low/high would using 6 hourly charts would be difficult to automate and require some human input I reckon.


Probably require a lot of hands-on interpretation.
I've now checked sep to feb 1980 to 1998.
Excluding 19-20 Sep 1994 which at 1005mB is barely perceptible on the
Reanalysis synoptics as a low track, this is the only one that comes near
28-29-30 Jan 1986. Unfortunately I only have North Sea BODC data for the
1990s
On the original source of this project, storms of 1909,1912,1916,1924
and their track paths. A few weeks back I was talking to an
oceanographic expert on the north Atlantic including early 20C , he was
not aware off the top of his head , locked-in inferred SST or jetstream
anomalies coincident with that period.
Another sideways input from an ex-polar researcher
"(Iceland ,skirting Ireland,Eng channel track lows)sounds like they were
polar lows caught up in the flow around a larger older low pressure
system. If so they would be likely to be tighter with regard to
pressure gradient than the recent secondary lows we have been
experiencing. Looking at their (GISS) definition of a “storm” they
should detect polar lows. However polar lows are essentially mesoscale
phenomena originating in a poorly observed region so there is the
possibility that the reanalysis might miss the initial stages of the low
resulting in a system which does not then qualify under their 36 hour
rule. Polar lows were (I think) unknown until satellite imagery showed
their existence. Prior to that, ones which came south (rather than
forming and decaying in the Iceland/Faeroes region) would probably have
been classed as secondary lows, i.e. developing further South rather
than in the area where they originally developed.
What I think I am saying is to warn that the GISS system may not detect
all storms of the type you are looking for."