Bookmark and Share Email this page Email Print this page Print

Voyaging weather communications

Sep 4, 2008

By Josh Warren-White

In today’s world one need not be a meteorologist in order to gather weather data and utilize it to make informed decisions for offshore passagemaking. In the information age there is a wealth of just that — information. So where are voyagers getting their weather information and how are they using it?

About two years ago I set sail with my parents aboard their 43-foot cutter, Bahati, from the East Coast of the U.S. on a westward circumnavigation. Since departing, we have covered 12,000 nautical miles through the Caribbean, Panama Canal and across the South Pacific, eventually making our way to New Zealand. Here’s a real-world example of how one voyaging yacht gathers and utilizes weather information to insure (as best we can) safe and successful offshore passages in various regions of the world.

Grib files
Aboard Bahati, we have a fairly simple setup to receive electronic data while offshore: a laptop computer, Pactor-II modem, an old but strong Icom 710 SSB radio and a SailMail email account. As a backup, we also have an Iridium satellite phone and the proper connection cables that allow us to download emails as well as make emergency phone calls. We’ve found similar setups to be quite common among other offshore vessels we’ve met along the way. Some rely entirely on the satellite phone, some on the SSB and many use both.

While on passage, we receive daily weather grib files via email. Thanks to a simple program created by the good folks at Saildocs, any voyager with offshore email capabilities can access free weather data by sending requests to Saildocs (a similar program is also available from MailASail.com). All one needs to do is email Saildocs with simple text commands, which automatically uploads certain files from the Saildocs server that are then provided to the user in an automatic email response.

To request weather information via Saildocs, we have found the most simple and user-friendly approach is the Airmail email client (provided by both SailMail and Winlink to their subscribers — also available as a free download to all amateur radio operators). Airmail has a built in module titled Catalogs under the Window menu. Here, users can make requests for grib files by selecting the area one would like covered on the map and choosing the various parameters desired. You then click Request, which generates a query email to be sent to Saildocs. Making the requests through this Airmail window allows us to not have to learn the scripting language and file names that Saildocs uses to automatically generate our files.

After sending the query and receiving our grib file via email, our next step is reading it. We often use the software program MaxSea to navigate on our laptop computer. Our Raymarine GPS provides the program with data via a serial cable, so in MaxSea we already have our current position, course, hull speed and route plotted on our navigational charts. We simply take the grib files we received via email, import them into MaxSea and overlay them on top of our navigational charts. This gives us a picture of what the NOAA GFS forecast is for our projected position over the following hours and days. There are also numerous free grib-reading software programs available online.

We study the grib files closely, watching the predicted pressure, wind and sea-state for our area. But we also view the data with a critical eye, as we are constantly reminded by marine weather forecasters around the world that grib charts are raw meteorological data. These files are computer generated and do not have the benefit of analysis carried out by a human forecaster. Thus they are limited in their accuracy, especially as the date the prediction is valid for gets further and further from the date it was created. This warning has borne true for us during many passages between Maine and New Zealand. This has led us to the common conclusion that grib charts can be very useful, but are best used in conjunction with forecasts that carry human analysis. So where do we get this human analysis?


One way we get that human analysis while offshore is through narrative text forecasts. These can be gathered from many different sources. Aboard Bahati, we receive them through Saildocs requests just as we do grib files. We simply go into the Airmail program, navigate to the Catalogs module and choose the forecasts for our region from the list provided. Among this list we have automated email access to text forecasts from weather agencies around the world.

We also access text forecasts from marine weather forecasters based in various regions that provide forecasting and routing services to offshore voyagers.

Voice forecasts via SSB
Forecasts with human interpretation are also available as voice broadcasts via SSB and Ham radio (as well as VHF radio in various coastal regions, of course). While in port we often compile lists of frequencies and broadcast times for weather forecasts in the region we will be transiting. These frequency lists are readily available on various Web sites and cruising guides.

Forecasters and weather routers
There are professional and amateur forecasters, routers and meteorologists operating in various regions of the world who specialize in providing weather services to voyagers and offshore sailors. The operating structure of these service providers varies dramatically from business-minded weather routers who charge on an hourly basis to regional weather gurus who charge nothing and work from their homes over amateur radio land-based stations.

We have used both types of forecasters, receiving weather information and advice from all over the map. We have especially found the services provided by the various regional marine weather gurus to be of great help. Sailing from the East Coast of the U.S. out to Bermuda and then down from Bermuda to the Caribbean we used the services of one of the weather-routing businesses: Locus Weather, based in Maine. We also had daily communications with Herb Hilgenberg, a weather forecaster/router who provides attentive, free services over HF radio to vessels sailing in the Atlantic.

While in the Caribbean we regularly used the services of Chris Parker, who has a similar setup to Herb’s, but also provides email forecasts and operates through a modest yearly or monthly subscription fee.

Then in the South Pacific region, for support with the potentially difficult passage south to New Zealand, Bob McDavitt provides excellent forecast and routing services to offshore vessels, mostly through email communication.

Here is an example of how McDavitt’s forecasting support helped us through a tense situation: Like many other vessels in the region, our intention was to sail Bahati to New Zealand in order to wait out the South Pacific cyclone season. Heading south from the equatorial islands, as you get higher in latitude into what is commonly known as the variables, storms can whip up quickly and give even the most seasoned sailors a good beating. For us, what appeared to be a benign eight-day passage, turned into a nail-biting 14-day ordeal, when an unanticipated cyclonic low-pressure system started to bear down on the rhumb line.

We were among a number of boats sailing from Tonga to New Zealand on similar routes and quickly began tense morning conferences on the SSB radio to share weather information and discuss each other’s strategy for riding out the strong blow coming down from the northwest. These radio conferences (often referred to as nets) can be very helpful to share information and strategy between vessels, though they often come with a heavy dose of group hysteria that ultimately may not help the situation.

With the aid of Bob McDavitt, who was watching the storm develop in real time via satellite, we were able to radically change course in order to encounter the frontal boundary of the system in its early, less-developed stages and then skirt around the backside of it, remaining in the least dangerous sector. We were studying the NOAA GFS grib files, which painted a terrifying picture of winds topping near hurricane strength. But Bob was looking at many different models and came to the conclusion that the GFS model was predicting the storm too early and too strong. In the end, his prediction was correct. It blew, but not at hurricane force. Either way, we were grateful to be in the least dangerous sector of the system, even if it added an extra week to the voyage. It was in situations like this that we were quite glad to have local expert knowledge and a very attentive and patient friend on our team.

Each of these regional maritime forecasters carries with them a detailed knowledge of the region in which they operate and provide personalized service that voyagers can count on. That said, we take their advice as just that — advice.

A route to the Galapagos
Some time ago we enlisted the services of a professional weather router based in the U.S. to help us find the best window to sail from Panama to the Galapagos Islands, 1,000 miles off the coast of Ecuador, which is classically a challenging stretch of ocean often riddled with calms and countercurrents. We had already started the passage once and had been forced back to Panama due to major issues with our charging system, so we were familiar with the frustrations this stretch of ocean could dish out.

Four days into the passage, it became clear that the conditions were considerably different then the router had predicted. They were actually playing out as the grib files were predicting, in contradiction to the forecast and routing advice we received via email from the land-based professional. Five days into the passage — 300 miles off the coast of Colombia and still 500 miles from our intended destination on the island of Santa Cruz, Galapagos — we had to make the call to defer from the advice of the router and follow a different course. If we had followed the advice given, we would have traveled further south along the South American coast, then turned due west around the equator. Upon turning west we would have hit headwinds for days, forcing us to use the last bit of our precious fuel fighting our way off the coast. Instead we stuck to the southwesterly rhumb line, made a couple of extra tacks and had a pleasant nine-day passage, arriving with fuel to spare. This was a key lesson in the necessity of making our own decisions utilizing all of our available resources. Even professionals can be wrong, especially when it comes to something as unpredictable as predicting weather. Bob McDavitt’s own caveat says it all: “Weather is a mixture of chaos and pattern.”

Putting it all together
In preparation, during the week or so leading up to an offshore passage, we typically begin talking to forecasters and routers, downloading grib files and text forecasts, listening to the weather broadcasts for the region and getting a feel for the weather patterns of the area, while starting to look for a favorable window and route for our desired passage.

Once we are finally at sea, I spend a good portion of my day (aside from eating, sleeping, fishing and actually sailing) gathering and processing weather information. At the end of the day we sit down together as a group with the information provided to us by the regional forecasters, with the local knowledge that only they have, and couple it with the information we have received through data, text and voice transmissions and make our decisions for ourselves. Our lives and the safety of our vessel are in our hands and we are ultimately responsible for the decisions that we make while offshore. Luckily, in this day and age we have access to ample resources to inform these difficult decisions.

Josh Warren-White is a graphic designer who recently returned to San Francisco, California after sailing 12,000-plus nautical miles from the East Coast of the U.S. through the Caribbean, the Panama Canal and across the South Pacific to New Zealand, aboard his parents’ boat, 43-footer Bahati. Josh can be reached at jwarrenwhite@gmail.com. Stories, photos and position reports from the voyage of the Bahati can be found at www.Bahati.net.

Related media