The Offshore Voyaging Reference Site

Five Tips For Choosing Weather Information to Believe…And Pay For

As many of you know, Morgan’s Cloud is spending the winter in the water this year. This has, shall we say, focused me on the weather and the best ways of deciding what precautions we need to take for each winter storm, up to and including sleeping on the boat, which I have done twice so far. (Yeah I know, anal-retentive, what was your first clue?)

Anyway, the process has got me using a lot of weather resources on a regular basis. But no, this is not a comparative article to pick the best resource, but rather a set of guidelines that I have developed over some 35 years of being a weather-freak that will be useful as you decide what weather resources to use (and pay for) and how much weight to credit to each.


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Tim

Thanks for this. This is quite relevant since I have just purchased an Iridium Go for the purpose of weather forecasts when we set off on our circumnavigation in April from the UK!

You reference Predict Wind which is simple enough as it is a “service” accessible via their App / program. However GFS which is a model, how would one go about getting that forecast via a very low bandwidth sat system like the Iridium Go? I think it tops out at around 5kbs.

Marc Dacey

I think that’s part of the puzzle. When one is tied into a winter berth, both the resources and the consequences of a screw-up differ in quantity and relevance. Offshore, you can get reasonably adept, with instruction and experience, at reading GRIBs and interpreting the 500 mb chart as it pertains to your course. I recently attended a Lee Chesneau seminar and it was interesting listening to the three or four people out of 60 or so in attendance who made little “oh, crap” noises when a “weather bomb in the making” isobar slide was shown.

Even 12 hours’ notice of getting kicked should generally be enough to dictate your course of action offshore, and being your own weather forecaster is to my mind, more seamanlike than hiring a custom forecaster for a cruiser. Were I a racer, however, especially offshore, I wouldn’t hesitate to hire a forecaster, because unless it’s survival conditions, we aren’t stopping and heaving to…we are always going to bash or run unless the boat or crew fails.

Marc Dacey

Not enough, no, but better than looking behind you and asking “what’s the dark grey line?”

I was exaggerating for effect; even weather bombs can be, if not predicted, at least suggested, some time in advance, but not usually five days.

One of the more instructive examples of “rapid development not forecast” I can recall is the Queen’s Birthday Storm of 1994.

Neil McCubbin

If you have a GO!, I feel the best approach is to bite the bullet and pay the $128US/month for unlimited text and Email.
We did this for 5 months from Scotland to the Caribbean, in 2016/7, stopping only when we hauled-out for the summer in Grenada.
We got lots of GRIB data, including the rain, swell etc, since the marginal cost was zero.
We happily downloaded GRIBs for wide areas, again because of no-cost.
We also had lots of social Email.
We did not use the free minutes for voice calling, because the recipient gets hit with anything from about $3 to $10 a minute. (I did have fun using my free voice minutes to fight with T-Mobile over an abusively large mobile phone bill that arrived as we left the Cape Verdes. I do not care what it cost them to answer)
The GO! sent a text message of our position and speed every hour, again at no cost.
I am just home from crossing with the ARC Europe in another boat, equipped with an Iridium phone, paying by the minute. The skipper limited himself to one, fairly small area, GRIB/day, receiving the (rather disappointing) weather forecasts from the ARC, and half a dozed very short personal emails. His average cost/month was slightly more than ours, but he missed all the advantages we had.

Jim Patek

Thanks for this update John. I am still using UUPLus, Saildocs and Viewfax after all these years having learned about it from your writing and I have seen no reason to change. The ultimate low bandwidth/low cost solution. I crosscheck it with the pinpoint virtual weather buoy concept provided by Buoyweather, another application suited for sat phones (mostly GFS) depending on where you are and many times incredibly accurate. This one costs $79.95 per year. So far, so good.

And let us not forget good old Passageweather (GFS), still the go to website for those of us sitting at the quay (with wifi) waiting for a weather window.

All the best,

Jim

Jim Patek

I agree. Wrong choice of words and I should have been more precise. The Buoyweather text Passage Forecast for the location of where you hope to be as each day of your passage progresses for up to seven days is a convenient and inexpensive way of distilling a small scale map down to your location (and, at local time). Models other than GFS are available but I have not used them.

Myles

Have you considered Sirius XM Marine weather service?

Myles

Yep, I have to agree…and when I had a question for customer support it was not impressive.

Chuck B

I was excited about this option until I realized it had limited coverage. It’s a great idea – constant streaming of high-fidelity weather data via satellite – with some interesting possibilities relative to low-bandwidth options like sat phone and SSB. But it would require worldwide satellite coverage to be truly valuable to cruisers.

Chris

Hi John,

Here is my two cents on this topic. On board Haiyou, our Garcia Exploration 45, we use a variety of forecasting tools, but the one we come back to most often is the Weather4d app from Olivier Bouyssou. John hold on… I know what you are thinking, keep reading please. In addition to the sexy visual effect you refer to in your post, it also offers a choice of various forecasting model ( 16 in all- but some might be different version of the same) including GFS and GEM , but also Arpege ( for a fee) and a number of other one I have never heard of : NAM, Arome, WFR. All can be downloaded through our iridium while offshore.

However when we are close enough to shore to get a mobile/wifi connection we always check the local marine weather forecast and more often than not it is the most accurate. This was proved to us once again last autumn when we were looking for a 3-day window to sail back from Western Norway to Holland. While all the models were consistent in forecasting the major lows moving in succession to the north of us, they were, it seems, incapable of forecasting the secondary lows developing in the North Sea with previsions changing wildly every 6 or 12 hours. In the end we relied on the Norway met office forecast at http://www.yr.no which was spot on and we enjoyed a fast broad reach to Ijmuiden.

I suspect some of the answers might also have been buried in the 500 mb weather chart and I have on my to do list to learn how to interpret these.

Best Regards
Chris

Rusty Gesner

PredictWind Grib Offshore does indeed include GFS (and CMC) in addition to their PWG and PWC. In addition to being able to check multiple models, another big advantage to me is that PWG and PWC optionally forecast Swell. Without swell each model is for 5 days about 7.1kB, and swell adds 22.6kB. A 3 day forecast is about 2/3 of that.
(GRIB HiRes, which is much more data intensive is in only PWG and PWC.)
Maybe you can look at a traditional GRIB and completely visualize, but PredictWind’s animated colored representations sure make visualization easy.

Rusty Gesner

I should add that example was for 6 hour interval 100km resolution and a 400x600nm area, both of which affect the amount of data. I generally like to do a much larger area at 24 hr interval for 7+ days to see what is coming, and then a small area at 50km resolution to see local details.