Thread: TS Ophelia
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Old October 12th 17, 03:02 PM posted to uk.sci.weather
Graham Easterling[_3_] Graham Easterling[_3_] is offline
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Default TS Ophelia

On Thursday, October 12, 2017 at 10:30:42 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

On Wednesday, October 11, 2017 at 10:52:46 PM UTC+1, Freddie wrote:
There is a massive variety of ensemble solutions for Sunday and Monday, and
there just isn't enough confidence in the outcome to say anything more than
the bland statement. The MetO had to issue a chart for this time, but to be
honest it could be well wide off the mark. The models will have a much
tighter range of solutions in a couple of days time when extra-tropical
transition is underway. One thing we can be certain of - the storm won't be
a hurricane by the time it makes landfall in the UK, if indeed it does hit
our shores at all.

--
Freddie


Looks very much like Eire will take a hammering though, the forecast track is
becoming more consistent.

The swell forecast has been upped considerably to the SW of Ireland over the
last 24 /36 hours. See
http://magicseaweed.com/UK-Ireland-S.../1/?type=swell for Monday.

Forecast significant peak swell height of 50', The significant wave height is
mean wave height (trough to crest) of the highest third of the waves (H1/3).
The highest swells will be 30% or more higher than that, so really big by any
standards. Personally, I'm a little surprised how big the forecast swell size
is, considering the speed feature will be moving.



I haven't checked but perhaps the predicted forward movement is such that it
matches the speed of propagation of the waves thus effectively lengthening the
fetch of the strongest winds. Or, even more complicated, as the forward motion
increases perhaps the very strong wind field 'catches up' with swell that has
previously propagated away from the storm.


--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
Twitter: @TideswellWeathr


Yes, seems a likely explanation. This was 2004 when a depression moved north at just the right speed to generate an exceptional swell in Mount's Bay. http://www.turnstone-cottage.co.uk/PzStorm.PDF

Current forecast for Sennen on Monday
Noon 3' 10sec
3pm 6-7' 19sec
6pm 20' 17sec
The sudden onset risks catching a few people out.

With the wind offshore in the cove, it should look impressive.

Assuming it happens as forecast!

Graham