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Ruzanna · 31-01-2011, 00:48

Capngeo! This is a wonderful idea and looks to be supported by a large community. It's really very important to share wind&weather knowledge. The issue is how to do it effectively.

mrohr · 14-04-2011, 07:36

HI all:Still waiting for this to happen. Maybe topic is too broad,so better weather by region say N. England,Great Lakes,W. Indies,Etc..

**hummingway** · 14-04-2011, 08:18

If I might; we do have cruising destinations already. Perhaps start a weather thread in the destination you are interested in?

Dreaming Yachtsman · 14-01-2012, 05:56

This thread has been around since September 2010 when capngeo suggested creating a weather forum and received what appeared to be nearly unanimous support. What happened to that effort? I would have posted this note on that forum instead of on the much less appropriate "Forum Tech Support & Site Help" sub-forum.

I just stumbled across a new National Weather Service (NWS) site that gives "point" (nominally 2.5 x 2.5 km) forecasts selectable on a "point-and-click" map. (Marine Point Forecasts). It seems very convenient and easy to use. This site does not appear to have been mentioned elsewhere on CF.

Many CF members strongly feel that a cruiser should be able to predict weather based on raw meteorologic data (e.g. 500 Mb charts) and local observations (e.g. clouds, barometric pressure, wind, etc.). I agree with that philosophy but still like to get an expert's opinion or three before leaving the refuge of a marina or protected anchorage. The site mentioned above provides just one more expert opinion to consider.

NWS seems to be making a concerted effort to vastly improve the accuracy of their reports. Refining the present Marine Zones is another example (NOUS41 KWBC DDHHMM).

Lastly, a suggested format for a weather forum: Forum title would obviously be Weather. Sub-forums could include: "Atlantic", "Pacific", "Caribbean", "Indian Ocean", "Resources", "Severe Wx Warnings", etc.

franksingleton · 14-01-2012, 09:56

I am happy to be involved on weather matters generally although my personal direct knowledge is mainly European. However, it would have to be on some form of notification basis. There is a limit to the time that I have to wander around the Internet. I think that CF has a notification by topic system.

Dreaming Yachtsman has brought up some interesting points. This overlong reply might set some thinking – and probably disagreeing.

I must say that I am very cynical about DIY forecasting using 500 hPa charts or any other tools. If you can get such information then either you have internet or Radiofax. In either case, you will certainly not outperform the NWS, ECMWF, the UKMO etc. You have far too little information for a start and computer models are doing ever better.

Speaking as a European waters sailor making much use of the GFS GRIBs together with what comes available via the GMDSS, we can plan with some confidence to at least 5 days. When cruising, I look ahead on a daily basis to 8 days using the GFS. It is not unusual to find good guidance to at least 6 or 7 days. To me, those time scale are most valuable and impossible to achieve by any other way.

That is not to say that a sailor cannot improve on GRIB or GMDSS output. We can and should be using local knowledge, experience and commonsense in interpretation of all forecasts.

I have to say, also, that I doubt the benefit of getting a forecast that claims to be on a 2.5 km grid. Meso-scale models can be run on grids between 1 and 10 km. Some comment on limitations:

But, the smaller the grid, the smaller the area for which the forecast can be run. Meso-scale models can only be run with input from global models. Improvement on the global model is likely to be in areas where topography has a major effect eg through narrow straits.

Small weather detail have short lifetimes. Even if small scale weather could be analysed on a 2.5 km grid, the model will only be able to represent weather on a scale of about 10-12 km – 4 or 5 grid lengths. Weather features of this size will have lifetimes of a few hours, probably less than 6.

Without reading the small print I cannot say whether these 2.5 km forecasts are based on a 2.5 km model or, as is sometimes the case with forecasts on the Internet, interpolated from a larger grid – even from the GFS 50 km output.

Weather services have been reducing grid lengths in the global models with the main benefit of starting with a god analysis and to increase the likelihood of picking up small weather detail that may become large systems in a few days time. The GFS and the UK both now run, effectively, on a 25 km grid. ECMWF uses a smaller grid. Within about 2 years, I expect the GFS and the UK to come down to about 10 to 15 km. That is near the current NAM and the UK NAE. Even now, the UK does not regard the NAE as being “operational”. Looking at its output on www.weatheronlin.co.uk the NAE gives more data but little more information.

They run meso-scale models to help short term detailed prediction such as strong wins, ice on roads or fog on highways etc. However, bearing in mind the time that is bound to elapse between these models being run and their availability to us, the detail modelled on the small scale will have largely disappeared. Benefit would be mainly in local topographical effects which is where the thinking sailor will improve on the forecasts in any case.

Perhaps a couple more comments. Models cannot (yet) deal with convection. They will indicate the probability of showers or thunderstorms but not a specific storm except on the very short scale. Secondly, while models are capable of predicting fairly small sea breeze effects, whether they will do so will always depend on other small scale factors such as cloud cover.

Sorry, I got carried away.

Auspicious · 15-01-2012, 09:47

Thank you for posting Frank. Your website is one of my principal resources for weather.

I do prefer synoptics to GRiBs. There is no substitute for self-sufficiency in my mind.

Capt Phil · 15-01-2012, 11:02

Having a Frank Singleton as a regular poster/critiquer/contributor is a great resource... thanks for your insight and contribution, Frank. Additionally, having a couple of weather routers involved who provide the service for the delivery fleet around the world would also be helpful. I found their service indispensible on west coast of North America deliveries over the years and their accuracy was nothing short of astounding to me. While it cost a couple of $ it was well worth every penny IMHO. Capt Phil

franksingleton · 16-01-2012, 03:41

Quote:

Originally Posted by Auspicious

Thank you for posting Frank. Your website is one of my principal resources for weather.

I do prefer synoptics to GRiBs. There is no substitute for self-sufficiency in my mind.

I would never decry use of synoptic charts. I do think that GRIBs are easier to interpret and can greatly assist in planning. I am all in favour of self sufficiency but do not see how that can extend to drawing your own synoptic charts without access to output from one or more national weather services.

There is no way that you or I sitting on our boats can get enough information to draw a chart, never mind a forecast chart.

To my mind, self sufficiency involves using whatever information can be obtained within the limits of your pocket and abilities. Leaving aside those who go to sea with no form of communications, the minimum is a SSB receiver with broadcasts of GMDSS forecasts.

Once you go further, then you are into the realms of RTTY, Radiofax, email over HF, Iridium etc . Then you have a mass of synoptic charts and GRIBs,

**GordMay** · 16-01-2012, 05:09

See Frank Singleton's Weather and Sailing Pages
➥ Frank Singleton's Weather and Sailing Pages / Franks-Weather | The Weather Window

Auspicious · 16-01-2012, 05:27

Quote:

Originally Posted by franksingleton

I would never decry use of synoptic charts. I do think that GRIBs are easier to interpret and can greatly assist in planning. I am all in favour of self sufficiency but do not see how that can extend to drawing your own synoptic charts without access to output from one or more national weather services.

I fully agree. Radiofax is my weather information of choice. I like to think I am a pretty good weather guy, but forecaster value-added products from professionals are my starting point.

franksingleton · 16-01-2012, 11:28

Quote:

Originally Posted by Auspicious

I fully agree. Radiofax is my weather information of choice. I like to think I am a pretty good weather guy, but forecaster value-added products from professionals are my starting point.

First, not everyone is so comptent.

Secondly, some others will be able to access GRIBs in one way or another. That has to be recognised.

Thirdly, any professional forecast is, in a sense, only a starting point. The thinking sailor can still add value through local knowledge and experience. The starting point has improved greatly over the past 30 years or so. Added value in terms of local effects by an experienced sailor will probably do as well as a meso-scale forecast.