React to The Weather, Or Plan For The Weather

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Snugged up for a bit of unsettled weather.

Being a controlling sort of guy, and a bit of a wimp too, I have always put a lot of effort into getting good weather forecasts and really understanding them, so as to not only get ready for nasty weather, but to really plan our cruises to maximize our enjoyment.

Now, I’m sure many of you are, at this point, saying “duh, doesn’t everyone?” And the answer to that is, “no, they don’t”. Many, perhaps most, cruisers are just looking at the immediate area around them, either via text or radio broadcasts or GRIBs.

By taking this approach, they are practising what I would call tactical weather management—reacting to the weather as it comes.

Get Strategic

On the other hand, probably because many of the places we have cruised have few safe harbours, I have, over the some 25 years I have been doing this, developed an approach to not only pick good weather windows to go to sea, but also, when coastal cruising, to look out as much as two weeks so that we can visit interesting, but often exposed, places when the weather is kind and be snugged down when it’s cruel—a strategic approach.

Hunker Down

For example, as I write, the weather here on the remote Quebec Lower North Shore of the Gulf of St. Lawrence is a bit unsettled, so we picked a nice sheltered anchorage with good hiking possibilities and snugged in for several days of catching up on boat work, writing for AAC, and taking a break from being on the move.

Then Maximize Fun

But, even before we got here five days ago, I could see that settled weather will return next week, so we are planning to visit a couple of isolated communities with less than snug harbours next, and then use the tail end of that pattern, with the associated generally northerly winds—the opposite of the prevailing southerlies (we don’t say “down north” in this part of the world for nothing)—to passage south.

Ocean Passages Too

And this same kind of strategic weather management can be used to plan an ocean passage to minimize nasty weather, although, that said, no amount of weather planning and understanding can guarantee that we won’t need to deal with gales and even storms at sea.

What We Need

There are two parts to doing this kind of cruise-enhancing strategic planning:

  • Getting the required information.
  • Having the skills to analyze it.

The first is easy enough if we have reasonable internet, either via WiFi or cell phone, but, up until a couple of years ago, difficult, time consuming, and expensive without.

And the second used to require a good understanding of upper level (jet stream) patterns and how they affect surface weather, as well as years of experience analyzing the weather in a given area.

Just Got Way Easier

But relatively recently there have been two technical developments that make this strategic planning process far easier than it once was, and that bring it within reach of any cruiser (even when far from internet access) who is willing to expend a little effort and a moderate amount of money.

Those two developments are:

  • The release of the Iridium GO! with associated unlimited data package for $125 a month.
  • The upgrades made to global weather models in the last five years or so that make them quite trustworthy on a detailed basis for 4-5 days and useful on an overview basis for as much as 6-14 days.

Testing The Tools

And the cool thing is that because our current cruise has been to remote places without internet and yet reasonably slow paced and relaxed, I have been able to put some quality time into getting the best from these tools, as well as testing out several software and hardware options.

And that’s what I will share in the next few chapters in this Online Book.

Further Reading

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Bob Tetrault

John, you have my attention. This kind of content is why I’ll always be onboard AAC. One point while you prepare for the next few chapters. As you know I was an early adopter of the GO. The primary reason was not the cost savings but rather the utility of that device. I have my GO mounted in a docking station but with a yank it and the repurposed IPhone nearby would Join me in a liferaft. Not so easy if a laptop is the primary device tethered to it. Battery life and ruggedness being additional qualifiers for bringing them along. I believe you have a portable Iridium phone for your ditch bag. You describe the communication between the GO and IPhone as “clunky”. I can attest to the voice and text being really easy and reliable, not so I presume for the Internet. Is there a way that both utilities can be utilized or enabled at least simultaneously? After all, from the liferaft who needs Internet. In an emergency one doesn’t want to deal with multiple processes, one button push is enough. Ideally the GO would default to the IPhone once separated from the laptop. Have a great cruise home.

Robert Andrew

John, another excellent article. Coincidentally I am in Seattle right now, the home of Starpath. I’m embarrassed to say I have never heard of them before your article (why I’ll keep subscribing to AAC). Since the cost of their online weather course appears to be equal to about 10 years of AAC I’ll take your reference to it as a very strong endorsement of its value? Bob Andrew

Jordan Bettis

Andrew: if you can’t afford the starpath course you can read the text book:


Lee Chesneau is getting an old man. And he is not really in good shape anymore. His wife as a nurse is traveling with him to take care of him. This is sad. It is getting difficult to find seminar with him. I personally urge readers to jump on the next incoming seminars while those are still existing.

That was an eye opening for me: his approach on the 500mb storm trac map is so modern. Classic weather training classes based on surface analysis are way behind. I really do not understand why more than 20 years after his first publication most marine weather course do not even considering talking about this. And not many books mention his analysis either.

This is where I can realize that AAC include lots of great and valuable content.

Unfortunately, Lee’s web site has not been maintained over at least the last 2 years, and it is very hard to get in touch with him.


Mariner’s Weather Handbook from Steve and Linda Dashew also includes a large section dedicated to the 500mb charts. Lee Chesneau and Joe Sienkiewicz contributed largely to that section of the book. It is easier to read than Lee’s book and does not include the section about route planning for commercial vessel.
A free PDF version of the book is available for download at

Stefa Katamay

The approach and language used in David Burch’s book Modern Marine Weather will appeal to ACC readers. David Burch is the brain’s behind Starpath. He covers 500mb content thoroughly and in an easy to read and understand manner.

M Dino Kubik

John, have you come across a Barometer App for an iPhone 6 or later that has an alarm. I hear a cumulonimbus cloud passing over head but hidden in a cold front will drive pressure down over a matter of seconds. I’m thinking about repurposing an old aiPhone 6 into a Barometric Pressure Logger and an alarm feature would be a great feature.

M Dino Kubik

I’m on it. Thanks

Rob Gill

Hi Dino,

From meteorology study as a navigator 40 years ago (I may be a little hazy), sudden dramatic changes in pressure like you describe (say even 3 millibar) around cumulonimbus “thunderheads” are not uncommon, but I believe are more usually associated with sudden rises in barometric pressure, caused by very rapidly descending cold and damp air with precipitation or hail.

From personal experience, I can relate that cold front embedded thunderheads can take you from dead calm to 60 knots in an instant, and in such cases I’m not sure an alarm function would be that useful. I can also say the last thing on my mind like John, was looking at the barometer.

A sudden blast of wind (near vertically down in our case) will press you over at anchor at a truly impressive angle, alarming if you are deeply asleep as happened to us. And then sheets of heavy rain hitting your deck will wake even the dead. On passage, you certainly won’t need the alarm to announce such a front’s arrival.

Occasionally though, I believe if the surrounding air is hot, a thunderhead can trigger rising air around it with a suddenly falling barometer, but I think I’m right in saying this would usually occur over the land, not the sea; but maybe the Red Sea? Anyone?

Over our Christmas break I bought the Starpath App, Marine Barograph for i-phone. If I leave the app open in the foreground, it continues recording barometric pressure against time with a cool graph. If I leave it open in the background (not on the main screen) it can “loose the plot” after some while. Not sure why yet and a bit annoying.

But great for tracking approaching wether systems like the two that have belted NZ in the last month, with tragic consequences. I really like the “at-a-glance” information that only a barograph provides. Kind of cool also for after the event analysis – in Cyclone Gabrielle last week, safely at home, I awoke to see we got down to 965 mb overnight. That wasn’t even the system’s centre, and it had transitioned into NZ’s cooler water becoming an “extra tropical”, or a “mid-latitude” cyclone.

Tilting the screen to landscape mode, gives you just the detail of the barograph plot. And you can select different time scales from 30 minutes to 384 hours which is nice too.

No alarm, but a very cool app for any mariner who follows barometric pressure (does anyone not)?

M Dino Kubik

Thanks Rob:

Gotta laugh at “..mariner who follows barometric pressure (does anyone not).” as there are a number of expensive brass barometers mounted deep in the living areas of boats more as a work of art than anything you can see from the helm. In fact, very few of the barometers availabe for sale have a hand-set keeper dial.

We have a Trintec aneroid barometer with a set-by-hand keeper pointer is in the pilothouse of our LM 28. It is reset as part of the Predeparture Check List and is visiable from the cockpit.

I’m taking John’ advice and getting a weather station.

The LM 28’s VP 2003 engine is fully enclosed in a fibreglass casket with a sliding top. The engine is under the cockpit floor and has only a temperture alarm. I know.. it is called “An Idiot’s Light” not an “Idiot Light”. Would not hurt to hang the weather station’s outdoor temperature sensor a foot from the exhaust elbow to monitior temperature changes. We shoot the temperature of the wet exhaust leaving the through hull with a remote thermometer a few times each day.

I was looking at the StarPath app and if i had an alarm I was thinking of upgrading from the free one I installed form the AppStore.