29Th July 1956

[Alan Robinson]

I have several books that are highly regarded among sailors, and which go into what amateur mariners regard considerable detail about weather forecasting, and yet I have my reservations about them.

One of them, describing Buys Ballots Law, mentions that “facing the wind in the northern hemisphere, the centre of low pressure is about 90 to 120 degrees to the observer’s rightâ€. My problem with this is that many people I have sailed with go around thinking there is a depression close by, which makes them unnecessarily apprehensive, and spoils the passage for them as they expect to be tossed about before long. Why couldn’t the author simply put that Buys Ballots Law indicates which direction the isobars lay in the observer’s location? There doesn’t have to be a low centre involved when using Buys Ballot.

My question however to the Netweather forum concerns a description of a severe storm on Sunday, July 29^th 1956, which caused great damage to the sailing boats participating in the RORC Channel Race that year. It seems the race started on the evening of Friday 27^th in very reasonable weather. Through Saturday 28^th, the boats made their way over the English Channel to Le Havre, during the morning of which passage a low 998 was located some 700 miles WSW of Land’s End, with fronts extending south and south west. Its track was about ENE. Around 0001 GMT on Sunday 29^th, the Met Office issued gale warnings for sea areas Portland and Plymouth, but not Dover or Wight, which incidentally is where some of the very strongest gusts were experienced later on. At this point, the low had deepened to 985 and was close to Land’s End. By 0600 it was centred just off Barnstaple and had intensified to 977, and at 1000 it was over Gloucester, still 977. As the cold front passed through there was an extraordinarily rapid rise of the barometer.

The odd feature of this storm, which reached Beaufort force 11 at Lizard light, is that the devastating winds were very localised by also very gusty. At Thorney Island, the mean wind was 37 knots, yet the gusts reached 67 knots. One meteorologist – whose rather colourful analysis I have before me – suggests that for one thing, it was almost as though the jet stream had descended to the surface, and for another, that the elevations of Dartmoor, Exmoor, and the Welsh mountains determined the depression’s track, which followed the River Severn.

What I’d like to know from Netweather forum members is a), do they know of any instance when the jet stream has descended to the Earth’s surface? and B) how likely is it that land elevations as modest as Dartmoor and the Black Mountains can affect the track of a vigorous low?

While I am at it, at sea in a small sailing vessel, I keep a keen eye on the barometer, and years ago, I realised that if the glass fell 4mb in 4 hours, I was probably in for an unpleasant puff of wind, and more than this I needed to prepare for a gale. I read however that the Met Office in years gone by would only issue a gale warning if a single observer had recorded a fall of 10 mb in three hours. While I know to my dismay that gales can come on without any drop in pressure, and indeed with a rising barometer, does anyone have a decent rule of thumb for a minimum rate of pressure fall that can be confidently said to precede gale force winds?

Edited January 20, 2011 by Alan Robinson

[knocker]

Regarding the jet stream I would think the answer is no. It's not that unusual for gusts to be much higher than the average wind speed (measured over a period of time) especially at sea. On a few occasions I've seen gusts well in excess of 100kts with the average around 60-70.

[Terminal Moraine]

The gale you mention is one of my earliest weather memories and, although not as severe in this part of the world as in yours, caused a considerable amount of tree damage in these parts.

I was only a small child but I remember seeing the trees in our ( exposed ) garden bending almost double with the force of the wind and being mightily impressed by it.

My parents had pre-planned a trip to Staffordshire to visit relatives on that day and were discussing whether or not we should go due to the danger of falling trees and branches. In the event we did go and I well remember the number of branches, twigs and leaves littering the roads, as well as the occasional part road blockage due to fallen trees.

Apart from my memories of the event I would think it most unlikely that relatively minor topographic features such as Dartmoor or the Welsh hills would have any influence on the track of such a depression although there is the possibility of local wind speed increases due to standing waves over the hills if an inversion is present above the summits. This happened to dramatic effect on the eastern side of the Pennines in Feb' 1962 when parts of Sheffield were devastated by gusts exceeding 90 mph and with parts of Derbyshire and Notts similarly affected ( Another of my early weather memories! )

Edited January 24, 2011 by Terminal Moraine

[Alan Robinson]

The gale you mention is one of my earliest weather memories and, although not as severe in this part of the world as in yours, caused a considerable amount of tree damage in these parts.

In fact, I'm from the Yorkshire coast. My missus since 1975 is Danish, and unfortunately I'm stuck over on this mud streak on the other side of the North Sea. Never mind.

I don't suppose you recall the 1979 gale that overwhelmed the Fastnet Race too do you? I ask, because I am interested in sailors ignoring reasonable warnings in order to race despite the dangers.............not that I am one of them you understand.............I don't set out unless the forcast is less than force 7.

[knocker]

In fact, I'm from the Yorkshire coast. My missus since 1975 is Danish, and unfortunately I'm stuck over on this mud streak on the other side of the North Sea. Never mind.

I don't suppose you recall the 1979 gale that overwhelmed the Fastnet Race too do you? I ask, because I am interested in sailors ignoring reasonable warnings in order to race despite the dangers.............not that I am one of them you understand.............I don't set out unless the forcast is less than force 7.

There is a fair bit of info. on the Fastnet Race here,

http://forum.netweather.tv/topic/56383-the-fastnet-race-disaster/

[Terminal Moraine]

In fact, I'm from the Yorkshire coast. My missus since 1975 is Danish, and unfortunately I'm stuck over on this mud streak on the other side of the North Sea. Never mind.

I don't suppose you recall the 1979 gale that overwhelmed the Fastnet Race too do you? I ask, because I am interested in sailors ignoring reasonable warnings in order to race despite the dangers.............not that I am one of them you understand.............I don't set out unless the forcast is less than force 7.

I remember the Fastnet storm very well. Although it had no direct effect on this area it, understandably, occupied the news bulletins for many days afterwards.