Shipping Forecast “accuracy” assessment?

[franksingleton]

I always mistrust assessments of services and products, especially when provided by the supplier. Smarter forecasts, safer seas: Met Office advances maritime forecast accuracy is no exception. This is not because I doubt the honesty of the assessment but because I doubt the value of any statistical assessment of an area forecast.

Objective assessments of computer model output are an essential part of model development and maintenance. Any change to a model or introduction of a new or modified data input is vital before operational implementation.

However, any assessment of an areal forecast is a hostage to fortune and to the vagaries of individual perception and memory. Although I never wrote a shipping forecast, I was, for a 10 year period, responsible for all marine and other forecasts when on duty. I am all too aware of the problems inherent in writing a forecast for 24 hours covering such a large area in a limited number of words.

Of course, in these days of GRIB output, the usage of the shipping forecast has changed greatly from my days at Bracknell. To me, at least, the shipping forecast is a last resort fallback whose only value is as a warning service.

 

[Stemar]

Since I rarely go offshore, I don't bother with the shipping forecast any more. I use the Met Office app and a couple of others for the forecast for a nearby location. I know I'm likely to get a force or so more a mile or two offshore, but a forecast 6 means I'm staying in port unless I've got a very good reason to be out there, and Jazzcat will cope fine with a 7 - it just isn't as much fun as when I was younger.

 

[NormanS]

When I started cruising on the West Coast of Scotland, the Shipping Forecast was all there was. Many's the time that I've fallen asleep over "Sailing By". Two sea areas for the whole of the West Coast, and only for the next 24 hours! Thank goodness we've got better things now.
If there is a remote chance of F8, even at the furthest edge of the sea area, then the forecast will (rightly) give F8. But how useful is that forecast, when possibly most of the area may be expected to have much quieter conditions? Bearing that in mind, I would say that the Shipping Forecasts are probably quite accurate, but for most of us, irrelevant. We can get much more local forecasts, with much longer outlooks.

 

[franksingleton]

In the OP, I was conflating two issues. First was how meaningful, even useful, is the assessment of accuracy of such a broad brush forecast. Claims of improvement, even if justified, are hostages to fortune.

My second point, really, is that the shipping forecast now has little relevance, particularly since the closure of R4 LW. For many, as the previous two posts say, the Inshore Waters forecast is more useful. For those of us who make longer passages, services using GRIB output are more useful. All I like to see otherwise is a warning service primarily for gales. Perhaps warnings should include fog.

As for wind strength, my personal rule has long been “6 ever, 7 never.” But it does depend on direction. We do not mind reaching or running in a 7/8 even some 9 although not for choice. We certainly do not want to be hard on the wind in such situations!

 

[RunAgroundHard]

I find the shipping forecast is, in general, accurate and good enough for my west coast sailing. While having great detail can be useful, I find it a chore with limited benefits. It becomes chasing tails, did the forecast meet the actual experience, how many tenths of a knot out, minutes of a degree wrong was the wind strength and direction. To hell with that, I don't go sailing to be a slave to the accuracy of data, or not, nor do I need such detail to make decisions. I have been using the shipping forecast and inshore waters forecast for decades. I do like the convenience of an App and not being constrained by broadcast times, that to me has the greater utility. Having said that, I am not going to ignore detailed, localised forecast data at my finger tips, especially where my experience of an area is good.

 

[Neeves]

Based in Australia

As you know our Bureau of Meteorology covers local 'inshore; forecast and huge areas of blue water.

Much depends on what you mean by accuracy ad what time scale you are talking of. Its a forecast its not a certainty

The 24 hour forecast is usually sufficiently accurate (but misses on fine detail certainly for blue water forecasts). They miss intensity of small storm cells.

The 24-48 hour period is good enough to tell you can go - beyond 48 hours a senior forecaster suggested it was science but science fiction.

Jonathan

 

[Laser310]

an important aspect of text forecasts is that they still mostly have human input.

There are some text forecasts that are (I think) AI generated from NWP model results, but the shipping forecast is still made by humans, who can look at the various NWP models and also use their forecasting experience to produce a forecast.

Even offshore, I try not to rely only on gribs from NWP. This means both text forecasts and human-produced surface forecasts.

edit - so on reading the linked article, I see that they are moving towards incorporating automated text generation for the shipping forecast.

 

[franksingleton]

Much depends on your type of sailing. Off the mooring and back, the main consideration is wind strength. Beat out and run back or vice versa. For any form of passage making, wind direction is critical but the shipping forecast winds cover a large span in that SW covers anything between S and W. SW-W covers from S to NW. St Peter Port, north about Guernsey to Dartmouth is mainly 320 degrees. A SW forecast may sound OK but might well be just a little too tight for many family cruising yachts. The shipping forecast is an uncertain tool. GRIBs will give far better guidance.
Cruising for weeks or days requires continual monitoring of forecasts for the next 10 days if you are to avoid being stuck in a port that you do not want to be in, in weather you do not want to go out in.
All too easily you can have difficult decisions and, sometimes have to look for the least worst option. The Met Office extended range forecast can help but is only issued once a day. A GRIB forecast is much more useful.
Of course, I am not saying that you should ignore shipping or similar forecasts. Take seriously any warnings. Use GRIBs to tell you more.

 

[RunAgroundHard]

Yet Frank, that’s exactly what was done when I started sailing, used the shipping forecasts. I managed back then, and still manage like that mostly today.

 

[winch2]

Local for me too and to be fair Met Coastal always seems about right, tho Im constantly gazing upwind towards the incoming clouds,....just in case.

 

[franksingleton]

Not that many years ago, yachts did not have engines. Few of us could have thought about sailing except in a limited way or in enclosed waters such as the Broads. Engines became the norm but sailing away from a home port was always hazardous because it was all too easy to get weather bound in a distant port. Improved prediction has opened up extended cruising to many with far greater safety than, say, 50 years ago. As someone who first cruised in the 1970s and has enjoyed extended cruising over the past 35 years the freedom made possible by improved forecasting is marked.
We used to say that there are bold sailors, there are old sailors but few old, bold sailors. Due to a combination of better boats, better aids and better forecasts there are, I suspect, more old bold sailors than previously.