WeatherFax/Barographs onboard

[simonjk]

Hi all,

A great Sailing Weather School today, super to see so many forumites on it.

One thing that interested me (and that I planned to post about in the past) is the lack of use onboard of shortwave radiofax and barographs.

GRIB files seem to be the latest "must have" (although most on the course today weren't sure what GRIB was) and I have to be honest, they really are not what they are cracked up to be - pure model data which can be very, very wrong at times - although may be nice to have.

Weatherfax via SSB gives you much, much more information (analysis and forecast charts), plus if you have RTTY with it you can get forecasts from Hamburg for UK and European sea areas out to 5 days ahead. Simple to use and few draw backs (the biggest being that radio signals can take a hit due to sunspot activity). Software for weatherfax is free, or you might pay £50 or so for a really good version. You plug it into an shortwave receiver, then the laptopo and off you go.

Barographs present so much information to the viewer. You can watch pressure rise and fall, know when you are on the forward or backside of a ridge, predict the oncoming fronts, know when low pressure has passed, predict gales and so much more. A quick skoosh on google showed you can get them for about £240!

No, I am not a barograph manufacturer or a radiofax software producer, just a forecaster who thinks we've lost our way a bit, throwing out the baby with the bath water...yes technology progresses but don't ignore robust, time proven methods.

Not a rant you understand, just what I hope is useful advice.

Have fun,
Simon

 

[vyv_cox]

Well, that's a point of view. Having had weatherfax aboard in the past, I found it useful but tedious to download. Interference often disrupted the reception and, Sod's law always applying, it was always the 24 hour forecast that was illegible, whereas the listing of weatherfax signal times was always perfect.

By contrast a grib file gives pressure, temperature, windspeed and direction, for the next 3 days for free, or 7 days if you pay (with a couple of exceptions) It can be displayed as an animation which I find very useful. It takes almost no time to download and costs a few pence. If you pay for a service you can obtain extremely useful wave predictions that I have found to be accurate and invaluable for longer passages in the Med.

In short, there's no comparison.

 

[snowleopard]

OTOH, there's nothing to beat weatherfax when you're in mid-atlantic, with the possible exception of Herb.

 

[steverow]

I use both Gribs (with Chart Navigator Pro) and WEFAX with JVComm.
The WEFAXES via either Northolt or DWD are consistently more reliable than the grib files in my experience.

Personally I think he is right.


Steve.

 

[vyv_cox]

I'm sure you're right but in the Mediterranean weatherfax is not a fat lot of use.

 

[Danny_Labrador]

I am really interested in this – see my post earlier NAVTEX – could you give me (novice) some detail on the kit that you have and the sources that you get the data from. I need information when sailing in the Med - the daily chart from the marina office leaves you a bit blind.

When I sit at home I can get hold of all the weather data over whatever timescale I want but when I really need it I am having trouble with a source.

Any help much appreciated.

 

[Oldhand]

Think you mean Northwood rather than Northolt as the UK weatherfax source.

 

[steverow]

Yep thats the place, Fleet Oceanographic Centre...sorry.

Steve.

 

[simonjk]

Hi all,

Thanks for the responses, I think it is important to stimulate debate on this one.

Whilst I do not doubt that GRIB files are useful, they are very much "the latest thing". As a meteorologist I use charts generated by the GRIB data many hundres of times a week. I know how these charts are unreliable at times.

You have to have a full understanding and working knowledge of how GRIB files are produced, and on occasions this information can be very, very wrong, the Mediterranean being the perfect example of this. However, I do not doubt that there are much in the way of alternatives here.

My fear is that sailors will come to rely on GRIB too heavily and that, one day, someone will get in real trouble by using it as a main soucre of weather data.

I note with interest the word FREE. It always amuses me that forecasts to 3 days are free and those beyond are not, when it's precisely those longer range forecasts which are by their very nature inaccurate!

Let me give you an example. Late September this year you may remember me posting about a stiong jet coming up the Irish Sea. This was completely missed forecast by the main GRIb model (GFS) which gave 15kt winds off the southwest approaches. The actual speeds were nearer 50kts and there would have been gusts to 80kt.

I wouldn't want to put anyone off GRIB data competely, just to use it in context and prioritise.

Cooments welcome.

Simon

 

[vyv_cox]

I agree with everything you say, although you don't say whether the blow you forecast was predicted by weatherfax?

I have seen data on the accuracy of forecasts according to days ahead. From memory a 5-day forecast is about 5% accurate, so I won't be paying for that, thanks.

We find forecasts in the Western Med to be highly unreliable, whether by Navtex, SMS, French or Italian VHF. I can understand that this is a difficult area to forecast for a variety of reasons. Just for fun this summer we kept a record of forecasts for a couple of weeks and compared them with reality. So far as direction was concerned we would have been better served by assuming every forecast to be out by 180 degrees!

Although we only downloaded grib files fairly infrequently we did find them to give a reasonable indication of the direction of winds and particularly the time when a big blow might end. Last season we were in company with a French yacht that had a sophisticated system for grib file usage. We and he were intending to head north from Menorca at the end of a mistral. His data predicted wave heights of 2.5 metres on the intended day so we waited until the next. I was very impressed with the predictions for our passage, which were spot on. Maybe not that much of a forecast but it saved us 100 miles of discomfort. Unfortunately I omitted to ask him the source of his data and now cannot find wave information for the Med. His laptop-based system gave predictions anywhere on the chart, by use of the mouse.

 

[iangrant]

We used the Grib files crossing the Atlantic last year and they were 100% accurate
One of my crew even woke up in the morning and said "what does the great god grib say today"

I was impressed with the 1 2 and 5 day forecasts for the Atlantic region and how quickly they came in on email.

Having eventually filtered out the ice flows from the SSB Northwood time tables we gave up with mr fuzzy wuzzy

cheers

Ian

 

[simonjk]

I can certainly see that some people do like to use the GRIB files, and of course that is fine.

The Mediterranean is hard enough for a human meteorologist to forecast for, let alone a model. The region is affected so much by local effects, particularly heating, that the best one can do is give an overall indication of conditions.

In the circumstances I mentioned the weatherfax weas more accurate, as on this occasion it would have been RN Northwood transmitting the signal and they use the UK Met Office charts which did forecast the system.

Another thing to note is that because a chart is "fuzzy" it doesn't mean it is inaccurate. It's a bit like looking at various different forecasts until you find one you like!

Once again I stress my concern is not to remove GRIB data as a method of displaying forecasts, rather to encourage the use of weather knowledge and ones own interpretation skills above that offered by raw model output.

Simon

 

[iangrant]

Point taken about the weather chart info - we got the "forecast" from the ARC lot - compared it with the gribs and guess what, the wind arrows lined up with the TS to the north of us and the actual strengths were exactly what it said on the wind instrument where we were!

The ssb reception was ok, good old Northwood keep churning it out - just a bit of a pain receiving the one you want - tuning in at the right time etc..... (in times of "crisis" Northwood de-power the transmitters or switch them to more operational use) Quote "it's only the bloody yachties that use it now anyay" unquote gov spokesman.

cheers

Ian