BBC coastal forecast vs inshore waters forecast????

[alahol2]

Windfinder has a very nice financial model: it's free. In fact it includes two weather models helpfully entitled Forecast and Super Forecast. Superforecast is the most accurate in my experience (usually quoting about 1 Beaufort above the standard forecast) but it only extends for 3 days.

I believe the two Windfinder forecasts correspond to the two Windguru forecasts (same basic models) but the Windguru equivalent of Super Forecast is a paid-for service.

Ditto, been using Super Forecast all summer, it has definitely been the most accurate this year.

 

[franksingleton]

I missed the start of this thread and have not gone through all posts so I may be repeating what has already been said. This Coastal Forecast has been going for some years now.

The Inshore forecast is written by a human being on the basis of output from the Met office computer models. The Coastal Forecasts is output direct from the Met Office meso-scale model running with a 1.5 km grid length.It should be the same as on the Met Office App that shows rain, temperatures, cloud, wind etc.

As the Met Office start their model runs with the best analysis possible, based on the maximum amount of observational data that can be handled using state of the art analysis programs, it should be the best objective forecast available. Whether on any particular occasion it will be the best can be critically dependent on just what data are received.

 

[webcraft]

I now try to sail to the actual weather rather than the forecast, which is often right in its overall prediction of the sequence and significance of weather events but way out in the timing.

- W

 

[wotayottie]

I now try to sail to the actual weather rather than the forecast, which is often right in its overall prediction of the sequence and significance of weather events but way out in the timing.

- W

On that we agree, Comrade.

 

[franksingleton]

I now try to sail to the actual weather rather than the forecast, which is often right in its overall prediction of the sequence and significance of weather events but way out in the timing.

- W

If you are sailing for an hour or two, fine. If you are making a passage then it is only a matter of time before you become a RNLI casualty.

 

[pvb]

I find XCWeather is pretty good, and has a useful 5-day forecast.

 

[franksingleton]

I find XCWeather is pretty good, and has a useful 5-day forecast.

Sorry to be repetitive, but once again – XCWeather, Passageweather, Magic Seaweed, Windfinder, zyGrib, Ugrib, IPad and Android GRIB Apps and, no doubt, others that I have overlooked all give the same forecast information They all provide the NOAA GFS output. Most do so to 8 days ahead.

Use whichever you find easiest to get and display. My personal choice is zyGrib because it has more options than most and gives more data options than most. The main plus for zyGrib, Ugrib and the Apps is that the output is saved so that you can see them later when you are offline. That would be tedious using the browser services eg XCWeather, Passageweather, Magic Seaweed, Windfinder.

To some extent “accuracy” is in the eye of the beholder. Good in general terms up to 7 days in my experience, but far from invariably so. There is no detail but no model can be expected to give good, small detail beyond a few hours. And, by detail I mean weather features of size less than about 5 miles at the most optimistic.

 

[Bru]

Well i had to laugh today listening to the nice lady at Thames CG still telling us to expect F5/6 as we sat off Holliwell Point in a flat calm. The met for today has been a joke as far as wind strengths are concerned. Must make the Coasties cringe having to read out a forecast so clearly at odds with what's actually happening outside the window

 

[franksingleton]

Well i had to laugh today listening to the nice lady at Thames CG still telling us to expect F5/6 as we sat off Holliwell Point in a flat calm. The met for today has been a joke as far as wind strengths are concerned. Must make the Coasties cringe having to read out a forecast so clearly at odds with what's actually happening outside the window

As a sailior I know that forecasts are far from perfect. As a former professional meteorologist, I am always intrigued by such accounts. But, from long experience, I always want to check what was actually issued by the forecaster. That may or may not be what you heard.

Can you confirm that it was yesterday, Saturday, and at what time you heard Thames coastguard. I will then try to get the original text.

PS. Also, please, where you were when you said that it was a flat calm.

 

[Conachair]

Well i had to laugh today listening to the nice lady at Thames CG still telling us to expect F5/6 as we sat off Holliwell Point in a flat calm. The met for today has been a joke as far as wind strengths are concerned. Must make the Coasties cringe having to read out a forecast so clearly at odds with what's actually happening outside the window

Which sea area was that? Nearest data seems to be an oil platform up past lowestoft which was showing 15Kts sustained yesterday morning, no data for gusts.

Maybe the forecasters windows have to be much bigger than yours

 

[Burnham Bob]

We had a forecast for force 3-4 for a local race yesterday afternoon here in Burnham on Crouch. There was so little wind the course was shortened and lots of us retired!

 

[Bru]

We had a forecast for force 3-4 for a local race yesterday afternoon here in Burnham on Crouch. There was so little wind the course was shortened and lots of us retired!

V Exactly

The inshore waters forecast, to the best of my recollection, issued at 06:00 UTC on Saturday morning had, for Gibraltar Point to North Foreland, a strong wind warning (yeah right!) and a forecast wind of F4 or F5 occasionally F6 at first, dropping to F3/4 later

Off Holliwell Point, on the edge of the Ray Sand, that morning it was as flat a flat calm as a flat calm could possibly be! Honestly, it was hilarious!

 

[Conachair]

V Exactly

The inshore waters forecast, to the best of my recollection, issued at 06:00 UTC on Saturday morning had, for Gibraltar Point to North Foreland, a strong wind warning (yeah right!) and a forecast wind of F4 or F5 occasionally F6 at first, dropping to F3/4 later

Off Holliwell Point, on the edge of the Ray Sand, that morning it was as flat a flat calm as a flat calm could possibly be! Honestly, it was hilarious!

So what about the data from a rig off Lowestoft showing 15Kts sustained sat morning, does that not count?

 

[Bru]

So what about the data from a rig off Lowestoft showing 15Kts sustained sat morning, does that not count?

So what? Even 15kts isn't a strong wind and we were supposed to have strong winds in the South and it was flat calm as far as the eye could see!

And yes, that is a problem with the inshore forecast of course - it covers far too long a stretch of coastline. It would be perfectly possible to have strong winds in the Wash and light winds in the Thames Estuary but that's not what was forecast yesterday morning.

 

[franksingleton]

It looks to me like the old problem of the forecast having to use a few words to cover Gibraltar Point to North Foreland for a 24 hour period. From what was quoted, it is clear that the strong winds – F6 were at first with an expected decrease to F3-4 overall. To criticise the forecast, you would have to look at the whole area for the whole period and not just the part where you happened to be for the short period you were there

Verification of Inshore and Shipping forecasts is something that I have been trying to urge the Met Office to make public. It is a near impossible task but one that they are addressing. I have seen a draft of a paper to be published developing a methodology to assess accuracy of wind forecasts in GMDSS texts. I hope that it will be openly available. A rather cursory reading seemed to imply that the average error in predictions was within the noise level of the wind. One of my more pithy statements is that the wind does not know itself to within one Beaufort force.

We sailors tend to forget is that wind can vary greatly in both space and time. Sailing this year in the La Rochelle to Lorient area we had a number of forecasts from Météo France that did not impress. We saw some from Météo Consult that were worse. Having sailed in 7 or 8 countries in recent years, I am all too well aware that the UK Met Office is not alone in facing the kind of criticisms being aired here.

 

[maxi77]

It looks to me like the old problem of the forecast having to use a few words to cover Gibraltar Point to North Foreland for a 24 hour period. From what was quoted, it is clear that the strong winds – F6 were at first with an expected decrease to F3-4 overall. To criticise the forecast, you would have to look at the whole area for the whole period and not just the part where you happened to be for the short period you were there

Verification of Inshore and Shipping forecasts is something that I have been trying to urge the Met Office to make public. It is a near impossible task but one that they are addressing. I have seen a draft of a paper to be published developing a methodology to assess accuracy of wind forecasts in GMDSS texts. I hope that it will be openly available. A rather cursory reading seemed to imply that the average error in predictions was within the noise level of the wind. One of my more pithy statements is that the wind does not know itself to within one Beaufort force.

We sailors tend to forget is that wind can vary greatly in both space and time. Sailing this year in the La Rochelle to Lorient area we had a number of forecasts from Météo France that did not impress. We saw some from Météo Consult that were worse. Having sailed in 7 or 8 countries in recent years, I am all too well aware that the UK Met Office is not alone in facing the kind of criticisms being aired here.

I tend to agree most of the official coastal forecasts use to few words to cover the sea area covered. On my trip to Portugal in the end relied much more on services such as GRIBs and Passage Weather. Both I found if taken as an instant snapshot were also inaccurate, but if you monitored the forecast info for the area you were interested in for a few days if the forecast was stable over this period then you could place some trust in it.

It is noticeable that many marinas and harbours now display such unoffical forecasts either with the official or in some cases in pace of the official forecast

 

[Blue5]

I think from memory the 06:00 forecast from Saturday for Selsey to Portland also started with a F5-6 and was probably associated with the weather clearing to the SE but as it was also giving a reduction to F3-4 it appeared that this was just a possibility at the start of the period.

A cursory glance at the pressure charts also suggested the winds were decreasing during the day.

 

[franksingleton]

I tend to agree most of the official coastal forecasts use to few words to cover the sea area covered. On my trip to Portugal in the end relied much more on services such as GRIBs and Passage Weather. Both I found if taken as an instant snapshot were also inaccurate, but if you monitored the forecast info for the area you were interested in for a few days if the forecast was stable over this period then you could place some trust in it.

It is noticeable that many marinas and harbours now display such unoffical forecasts either with the official or in some cases in pace of the official forecast

What you are saying is what I have said on a number of occasions on these forums and do so when I give talks. I think that many sailors overlook the purpose of the GMDSS products eg the Shipping and Inshore forecasts and their counterparts around the world. They are classed as Marine Safety Information. At best they can only give a general view and their prime purpose is safety.

There is nothing “Unofficial” about GRIBs. These are from the NOAA National Center for Environmental Prediction – the GFS. They have the same standing as forecasts from ECMWF and GRIB type information on the Weatheronline site. You just have to remember they are not checked or verified by a human being. They will tend to under-estimate wind strengths - often by about one Beaufort or 20%.

I always do my planning, whether passage making or deciding where I want to be in the next few days, on the basis of the GFS with a sideways look at UK synoptic charts - http://weather.mailasail.com/Franks-Weather/Latest-Uk-Forecast-Charts-5-Days and the ECMWF. On a daily basis, when cruising, I always refer to the local inshore forecast. This is primarily to see whether there are any hazards that I should know about. Also to see what the human forecaster thinks as he will have seen his own country’s computer output as well as that from other countries, including the GFS. Forecasters do not work in a vacuum.

Lastly, and again, Passageweather gives the same information as GRIBs. zyGribm Ugrib and their App counterparts are more convenient because they are saved for future reference.

 

[Bru]

It looks to me like the old problem of the forecast having to use a few words to cover Gibraltar Point to North Foreland for a 24 hour period. From what was quoted, it is clear that the strong winds – F6 were at first with an expected decrease to F3-4 overall. To criticise the forecast, you would have to look at the whole area for the whole period and not just the part where you happened to be for the short period you were there .

Wasn;t there for a short period, was there for the entire 24 hour period of the forecast in question and then some either side

Sure, the area covered is far too large but they do split the forecast into North and South when there is significant variation and that they did on Saturday morning. The strong winds were forecast to be in the South. I was in the South. There wasn't any wind! Yes, it was forecast to decrease but there wasn't anything TOO decrease!!

 

[franksingleton]

Wasn;t there for a short period, was there for the entire 24 hour period of the forecast in question and then some either side

Sure, the area covered is far too large but they do split the forecast into North and South when there is significant variation and that they did on Saturday morning. The strong winds were forecast to be in the South. I was in the South. There wasn't any wind! Yes, it was forecast to decrease but there wasn't anything TOO decrease!!

OK. I yield.

I just try to see it from the point of view of the poor person who has the best computer forecast possible and who has to paraphrase that into a few words. All I can suggest is to use the US GFS GRIBs with a look at the relevant Inshore Waters forecast. That is what I do. I don’t get it right all the time. I just minimise the chances of getting it wrong.

Added later -


In my talks, I often finish by saying that using any weather forecast involves using pragmatism, realism and commonsense.