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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#1
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Graham Easterling wrote:
On 14 Jan, 18:59, "Jack )" wrote: I agree Norman. *As an ex-aviator, I never bothered with terms like gales, strong winds, etc. *It was NUMBERS (30, 45 knots, etc). *Do mariners do the same? *Indeed, I have little idea nor need to know how a gale is defined in terms of actual speeds. Martin. *You used to do the shipping forecasts. *Was it the user or the supplier that wanted the terms gale, etc? Jack The term gale means a lot down here on the tip of Cornwall. A force 8 gale warning and boats think of returning to Newlyn, Force 9 severe gale they stop thinking & do it. Just look at local sites like www.sennen-cove.com/index.htm , which is produced brilliantly by the coxswain of the Sennen lifeboat, and you will see the word gale used appropriately. The beaufort sea descriptions are so useful, and are instantly meaningful when you're by the sea. Like Norman the I hate the phrase 'gusts to gale force', on exposed coasts gusts to gale force occur a good proportion of the days in winter, so is totally meaningless. It just means it's a bit windy. Gale Force is defined as a mean wind speed of 34-40 knots. Therefore, the term "gusts to gale force" would actually mean "gusts to a mean speed of 34-40 knots" which is clearly nonsense. Sorry to be banging on about this so much but it's been a pet hate of mine since an occasion when I had to argue the toss in Court with an obstinate QC who insisted that a gale had occurred because there were wind gusts to 35 knots. The outcome of the case depended on whether or not there had been a gale. Sometimes it matters! Norman -- Norman Lynagh Chalfont St Giles, Buckinghamshire 85m a.s.l. (remove "thisbit" twice to e-mail) |
#2
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![]() Sorry to be banging on about this so much but it's been a pet hate of mine since an occasion when I had to argue the toss in Court with an obstinate QC who insisted that a gale had occurred because there were wind gusts to 35 knots. The outcome of the case depended on whether or not there had been a gale. Sometimes it matters! Norman .... dare we ask who won the case?! Stephen Burt Stratfield Mortimer, Berkshire |
#3
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In message , Norman
writes ..... Gale Force is defined as a mean wind speed of 34-40 knots. Therefore, the term "gusts to gale force" would actually mean "gusts to a mean speed of 34-40 knots" which is clearly nonsense. Sorry to be banging on about this so much but it's been a pet hate of mine since an occasion when I had to argue the toss in Court with an obstinate QC who insisted that a gale had occurred because there were wind gusts to 35 knots. The outcome of the case depended on whether or not there had been a gale. Sometimes it matters! Quite understand the frustration with the lay unscientific approach. I shall perhaps now add to it. I sail dinghies, along with others at a South Coast club. We have an anemometer with dials in the club-house showing wind direction and speed. The race officer will make an assessment of the wind on the water - presumably an attempt at an average - usually with a spread of two Beaufort forces. This is duly marked on the board with the course and other information. Individual sailors have to decide whether to put to sea, and how to rig. We cluster round the instruments, watching the indications for several minutes. The usual description will be along the lines of mostly force so-and-so from such and such a direction, and whatever speed and whichever direction on the gusts. Accuracy is of "top end of four-middle of five" coarseness. It is seen very much as binary. The non-gust component of the wind should be adequate, and the gusts should be tolerable. We can see the state of the sea and the clouds, and usually have various forecasts from the internet. There will be estimates, informed by local experience, of the likely winds on the water, away from the channelling effect of the wind round the clubhouse and the lee of the land. Also, of course, changes in sea-breezes and the passage of systems. This mix of local observation and assessment is perhaps forecasting as a craft rather than a science. Not by any means the Art of Coarse Forecasting. Alan Watts has written compact and useful books on the subject. Average for modelling and scientific reporting, yes. The harm, however, is often in the gusts. Out of curiosity, how did the case come to turn on a gale rather than gusts of such a speed? I hazard a guess hat it was the terms of insurance. -- Peter Thomas |
#4
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"Norman" wrote in
: -------------------- "That rain will be accompanied by strong southerly winds with gusts to gale or severe gale force over southern and southeastern England." -------------------- I was going to comment on that too, Norman!! I'm not keen on the idea of sustained winds. A "gale" in the sustained wind sense can produce a wide range of gusts based upon the underlying surface roughness. Also other meteorological complications like unstable conditions that can really boost the sustained-to-gust windspeed ratio - i.e. a sustained "gale" could give anything from gale force gusts to storm force gusts depending the predicament (and who knows how these sort of sustained- to-gust ratios change when we have "the unknown" like sting jets). I would rather forecasters emphasise the gust speeds. It's the short staccato bursts that are most strongly linked to property damage and avoid the gale/severe gale terminology. IMHO, of course. Richard |
#5
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On Jan 14, 5:51*pm, "Norman" normanthis...@thisbitweather-
consultancy.com wrote: Aaarrrggghh!!! *One of my pet hates and even the Met Office is at it. The current early warning for heavy rain contains the following gem: -------------------- * "That rain will be accompanied by strong southerly winds with gusts to gale or severe gale force over southern and southeastern England." -------------------- I quote from the Met Office's own document titled "Terms used for describing mean surface wind speed": -------------------- "Beaufort Forces apply ONLY to mean wind speeds (the average over a given period of time - usually one clock hour) and MUST NOT be used in reference to gusts" -------------------- The words in capitals in that quote are as given in the Met Office document. If the Met Office can't get it right and include sensationalist terms in their warnings and forecasts can we blame the media for doing the same. The message would have been correctly conveyed by saying "strong southerly winds with gusts to 40-45 knots", or the mph equivalents. Instead, they are giving the impression that there will be severe gales over southern and southeastern England. Norman -- Norman Lynagh Chalfont St Giles, Buckinghamshire 85m a.s.l. (remove "thisbit" twice to e-mail) I really can't see the problem as far as the average landlubber is concerned and that must constitute the vast majority of the audience. The term "gale force" when referring to gusts is simply a shorthand way of saying 39-46 mph and as long as it is not implied that the mean speed is gale force then I see nothing wrong with it. On Radio 4 the forecast gusts are always given in mph anyway. In my own weather diary, when referring to gusts associated with showers or thunderstorms, I always use Beaufort , eg "heavy shower, gusts to force 7", or "gust to force 8 when cold front went through 2130Z". Will I burn in hell for this? Tudor Hughes |
#6
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![]() * * * * *I really can't see the problem as far as the average landlubber is concerned and that must constitute the vast majority of the audience. *The term "gale force" when referring to gusts is simply a shorthand way of saying 39-46 mph and as long as it is not implied that the mean speed is gale force then I see nothing wrong with it. Tudor Hughes- Hide quoted text - But gusts of 39-46 don't represent a gale, probably typical of a Force 6. In the last 10 years I've recorded 511 days (14% of the total) with gusts of 39mph or over, and I'm in a sheltered spot away from the sea front. It's making the word gale almost meaningless. I suppose by downgrading the use of the word, it allows 'gale' to be used in the inland SE, who would never get a look in otherwise. Graham Penzance |
#7
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![]() "Graham Easterling" wrote in message ... I really can't see the problem as far as the average landlubber is concerned and that must constitute the vast majority of the audience. The term "gale force" when referring to gusts is simply a shorthand way of saying 39-46 mph and as long as it is not implied that the mean speed is gale force then I see nothing wrong with it. Tudor Hughes- Hide quoted text - But gusts of 39-46 don't represent a gale, probably typical of a Force 6.In the last 10 years I've recorded 511 days (14% of the total) with gusts of 39mph or over, and I'm in a sheltered spot away from the sea front. It's making the word gale almost meaningless. I suppose by downgrading the use of the word, it allows 'gale' to be used in the inland SE, who would never get a look in otherwise. Graham Penzance I think you will find that to a shipping forecaster in MO, a gale is winds in the range 39-46mph....... but only in the sense that mean speeeds must be at least 39mph OR gusts at least 46mph (except in the case of isolated gusts). Hence Norman is right that gusts of 35k do not constitute a gale. Norman writes that 'There's no reason why the criteria for issuing warnings of an event have to be the same as the criteria that define the event of the same name has actually happened, though it would certainly be less confusing if they were.' He then gives examples of snow etc over LAND. I concede that public service warnings are a right mixup. However the Severe Warnings are for events that affect large areas, whereas the instantaneous rates are local events. Hence they are not the same thing. For shipping purposes definitions have to be more watertight....... Where are you Jon? Weaman |
#8
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I don't want to be too dogmatic on this topic, mainly because I have
been away from issuing both sea and land warnings for over 4 years now, and inevitably things change. Therefore read on with that caveat in mind:.... Here some thoughts though based on my experience, web pages on the Met Office site and other sources. First, the criteria for *gusts* are still available in the Glossary under each heading (Gale, Severe Gale and Storm): use this link:- http://booty.org.uk/booty.weather/uswfaqfr.htm [ use the detailed index ] However, as has been made clear, these were, as far as I am aware, introduced for the convenience of bench MARINE forecasters to define and analyse situations where gales (or higher) were expected/occurring, and are based on the well-known "Ratio of maximum gust to mean hourly speed for open sea" relationship [Shellard], of *1.3. Whether it is *right* to use this I'll leave to others to debate, but for practical purposes, and over *OPEN* sea (i.e. within the domain of the Shipping Forecast / High Seas etc.), then they proved a useful guide. The first complication arises because the Shipping Forecast is *not* intended for inshore waters use, where of course the wind regime can differ markedly, both in terms of the mean speed and gust structure, than that found beyond 12 miles out. (I can't remember if the limit was 6 or 12 miles - I think the latter as the Inshore Waters forecast explicitly defined it's range as up to 12 miles from shore.) They were NOT intended to be used in the post-analysis of events for climatology or similar as is clear in the complete absence of the mention of gusts in this table:- http://www.metoffice.gov.uk/weather/...fortscale.html However, annoyingly (to me at any rate), they *were* used in the gale warning verification scheme. The Beaufort Scale was not originally intended for land use: for a history, see he- http://www.metoffice.gov.uk/educatio.../beaufort.html but as that text makes clear, early in the 20th century, a 'land-based' form was developed. Again, as far as I am aware, gust speeds were not explicitly involved. The problem comes, literally, as you come closer inshore, and certainly when dealing with wind behaviour over land. Offices with responsibility for coastal/sea area warnings (e.g. Dunstable then Bracknell then Exeter & the various MMOs/Weather Centres) would have the scale in front of them with the 'gust equivalents', but they would also be issuing public service scripted forecasts; there was a certain amount of 'leakage' from the scale designed for use with the marine community in mind and the procedures for land use. The phrase "gusts to gale force" has never been officially sanctioned, as it is meaningless. Gale force, whether used over the sea or over land, is defined as a *mean* wind speed for a defined period of time, usually 10 minutes. The phrase was often used when I started PS work in the 1970s, but even then attempts were made to stamp it out, and I thought we'd got rid of it completely with an *explicit* instruction to mention specific values for gusts rather than vague (to the public) terms such as 'severe gales'. Indeed, as was pointed out, the PS definition of a 'severe gale' is nothing like that for the Beaufort Scale:- http://www.metoffice.gov.uk/weather/..._warnings.html Using this definition (repeated gusts to 70 mph or more), you would be into F11 on the *marine / operational* version of the Beaufort Scale, whereas that scale's 'Severe Gale Force 9' would have gusts 47 to 54 mph: so there is no linkage between the two there. It gets even worse with 'Storms', but you get the idea. -- Martin Rowley E: W: booty.org.uk |
#9
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On Tue, 15 Jan 2008 00:47:49 -0800 (PST), Graham Easterling wrote:
In the last 10 years I've recorded 511 days (14% of the total) with gusts of 39mph or over, and I'm in a sheltered spot away from the sea front. It's making the word gale almost meaningless. I suppose by downgrading the use of the word, it allows 'gale' to be used in the inland SE, who would never get a look in otherwise. Agreed, we think twice about going out into a true gale, it is hard work to walk against or even just to stand still as you have to brace against it. Conversatation has to shouted due to the noise in your ears and the roar of the air around objects. Anything loose and not significantly heavy will be blown away. People who visit us frequently comment about the wind and that's when it's only an F5 (19 to 24 mph), we don't think that as windy at all... These comments either come as they enter or when looking out of the window watching the trees sway about. -- Cheers Dave. pam is missing e-mail |
#10
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On Mon, 14 Jan 2008 17:15:32 -0800 (PST), Tudor Hughes wrote:
I really can't see the problem as far as the average landlubber is concerned and that must constitute the vast majority of the audience. Except the average lanlubber then goes away thinking that a much lower mean wind speed is a "gale" when it isn't. You do have to think twice about going out in a gale, most places in Britain rarely have real gales. You only have to look around at all the loose stuff and flimsy fences to see that. In my own weather diary, when referring to gusts associated with showers or thunderstorms, I always use Beaufort , eg "heavy shower, gusts to force 7", or "gust to force 8 when cold front went through 2130Z". Will I burn in hell for this? I don't know but it might come back to haunt you is that "gust to force 8" a 39mph gust or 46mph one? "Gusts to force 7" is that a few just above 32mph, most between 32 and 38 mph with none above 39,are there a few above 39, how many how far? I'm not expecting precision, I normaly use low/mid/upper tens mph for gust speeds. -- Cheers Dave. pam is missing e-mail |
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