The value of long, medium and short term forecasts

[ChrisE]

I'll start it then.

I find them all valuable, for different reasons. The LT say 7+ days gives me a feeling for the direction the weather is likely to take, the MT say 3-6 is v useful, in that usually this gives a clearer view of the weekend early enough in the week to make plans. The ST <3 is OK for passage planning. Naturally, the further away the weather is form the forecast the more grains of salt you have to take it with.

That is not to say that they always right or an exact science but a lot better than seaweed or blind hope. But, for someone like me who has to juggle sailing with my and my wife's businesses then the MT usually gives me the lead time I need to make decisions on Monday about sailing at the weekend.

This weekend the forecast changed after 4 days so I missed out on what sounds like a beezer weekend in Cherbourg. On the other hand, the MT forecasts enabled me to have a jolly fine holiday in W. France with iffy, changeable weather.

So, in sum you either take the best soundings and make a decision on them or go with your interpretations of what the weather might do. I'm no expert at Met so prefer the former option and take the consequences of decisons made with the best information at the time.

Still, I'd rather have been in France this weekend than chopping wood but I'm fairly sure that my liver is in better nick than it otherwise would have been.

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[tcm]

Solace for WOOC-in-chief

i think that, if possible to find, it's the change over time of the LT/MT forecasts that gives a real picture for chanel area - the forecast for an area for 8 days away, then 7, 6 etc etc. With these in place, the ST forecast should confirm thoughts , rather than hold any real surprises. So, if the LT forecast had been really calm, but then been upped to 3, then 4, then 5 for cherbourg as the LT became a MT forecast, frexample, it could have been dodgy.

But since it started off sevenish, then went down, that's was good sign and you could have gone, and you are reduced to making wise posts like this as Wimper-Out-Of-Cherbourg-in-chief.

Trouble is, next time it's a forecast 7 you might think hah! not geting dissuaded by that again, but this time it'll be 8 or 9ish....


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[ChrisE]

Some you win...

Yeh, I'll live with sobriquet

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[Twister_Ken]

What motivates a weather person?

Just seems to me that with many of the 'soon, imminent, later' forecasts being observably wrong, that anything longer than 6 hours ahead has to have a degree of doubt cast on its ancestry. On the trip across the 5.00 am shipping forecast advertised something like NW 4 to 5, where as what we got was more like NW'ly 4 veering N 2.

It would help, when making forecasts, if they included a 'certainty' percentage. I found myself wondering whether forecasters deliberately paint the worst case scenario, because if they get it wrong no one is going to complain about things turning out better than expected: whereas if they were too optimistic and things turned out worse than advertised, the phones would ring blue murder. And also wondering whether they spend most of their efforts on land forecasts where 99% of their 'customers' are and where they get the chance to become 'media pesonalities', to the detriment of shipping forecasts.



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[bedouin]

Re: The value of long, medium and short term forec

I tend to find that the medium term forecasts are really worse than useless.

Too often I have postponed or modified sailing plans based on a medium term forecast that turned out to be incorrect, either in terms of the weather or timing.

For the sailing I do the 24 or 48 hour forecasts are all I need to ensure the safety of the boat - anything beyond that is used for convenience to try to determine suitable plans in advance.

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[tcm]

Re: certainty pecentage

um, yes, the french forecasts have a % "fiabilité". Mind you, it's never more than 90%, and often quite a lot lower. I begin wonder if inamongst the excellent people in Meteo France there is either a total dipstick who is always wrong, or perhaps just an awkward sod. Or, perhaps quite few - 10% of them or more at any one time.

Perhaps it ought to be like the Racing Post where all the tipsters hhave ridiculous pseudonyms, presumably so the losers who have bet their house on a tip don't bashem. Weather Post would be much better imho, and more use, cos there only seems a small bunch of nutters in the average bookies, whereas lots of us could easily be interest in a weather forecasting daily paper, with form guides of the seaweed-reading types v large computers v Mrs wassername at the bakers.

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[Peppermint]

Re: Format and area problems

While I like to build up a feel for the weather to come by looking at Atlantic charts I find more defined forcasts, whether by time or area, almost worthless.

I know from talking to weathermen that timing is the toughest thing to call and that the further down the track they're looking the less hope of success they have.

If, and we must have all experienced it, the forecast is repeatedly wrong for the next 12 hours. How wise is it to plan anything based on a longer timescale than that.

On Saturday I'm starting a weeks cruise on a Najad 36. We intend to vist Normandy. Tomorrow I will start taking interest in the weather forecasts and charts to just kind of get into the feel of what's coming along. I'll be completely up to speed on the expected Met by sailing time with a clear view of what to expect. What I expect is that at sometime in the week I'll be surprised.

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[starboard]

Here follows a pretty standard everyday forecast for here on the Clyde.....North West 3 to 4 becoming 5 to 6 maybe locally 7.........if that's not hedging your bets what is...if it blows a 3 the forecast is good or it blows a 7 likewise Mr forecaster will be happy!!!

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[tcm]

Re: Timing

i agree.

I suppose the lt forecasts, taken over sevral days, allow one to build up a pic of the stuff to expect. The LT forecast for last weekends was correct in terms of what was gonna happen, tho they expected the system to hang about for longer. The higher winds came thru sooner than expected, but doesn't mean the LT forecast wasn't worthwhile.

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[ParaHandy]

yer no wrong there ...

but not droite either for the forecast pinned up at cherbourg frequently rates (itself) 100% ... perhaps orra eejits are in s of f or maybe ra further north you get the more intelligent .. eh???

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[tcm]

Re: unlikley

maybe there's only one forecaster around the far north, and is always utterly convinced that he's correct, regardless of what anyone else might say?

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