Furuno’s NX-300 and the Grundig Globe Traveler both capitalize on free weather data on the airwaves.

Window on the Weather

Passagemakers can find different sources for WX information as their voyage progresses and adjust their plans based on current data.

Time was when any skipper worth his salt would start listening to weather forecasts and poring over synoptic charts days ahead of any serious passage. Now it seems most of us just click onto our favorite Web site.

There are plenty. For passagemaking, my favorite is an ad-supported one called PassageWeather.com that pulls together the basics —wind, waves, weather, and visibility—for the next week in a simple, no-frills view. Pay sites like ClearpointWeather.com and BuoyWeather.com offer all sorts of high-tech fish-hunting extras, such as charts showing chlorophyll concentrations and surface-height anomalies.

The definitive U.S. weather site, however, is Weather.gov. It’s the National Weather Service’s own free gateway to a mass of solid weather information, including text forecasts and satellite and radar images. There’s a cut-down version (mobile.weather.gov) for cell phones and PDAs, and a WAP (wireless application protocol) version (cell.weather.gov) for the dumbest of dumbphones.

But the big snag with relying on the Web for weather information is not what’s available, it’s how you get it. Wi-Fi hot spots are all very well, but their range is usually very limited. Range extenders such as Wave Wi-Fi’s Rogue Wave and Digital Yacht’s WL510 are great for expanding a hot spot’s coverage to several miles, but they can’t really be counted upon to pull in weather information while you’re on a long passage.

Once out of Wi-Fi range, you’re into cell phone territory. Two factors limit the range of cell phones and mobile broadband modems. One is that portable equipment uses low-powered transmitters and tiny aerials; the other is that they’re close to sea level and thus their range is highly limited.

Both problems can be overcome to some extent by using signal amplifiers such as Digital Antenna’s PowerMax or Shakespeare’s CruiseNet, but sooner or later you will run up against one of the unbreakable laws of physics: Radio waves at cell phone frequencies cannot bend over the horizon. Their effective range depends on the height of the cell tower and of the onboard antenna, but it’s unlikely to be more than about 20 miles or so offshore.

Beyond that, we’re into the realm of satcom. If you really can’t do without phone and Internet, it may be a worthwhile investment. But if you plan to use it only to get an offshore weather forecast a few days a year, it’s probably an unnecessary extravagance.

An outstanding alternative could be called “one-way” satcom, the satellite weather services broadcast by Sirius XM. Originally two separate companies, Sirius and XM joined forces three years ago. But there are still technical differences between the signals transmitted by their satellites, so which service you get depends on which receiver you buy. That depends on the chartplotter you connect to: Furuno, Lowrance, Simrad, and Raymarine use Sirius, while Garmin uses XM. Whichever service you have, expect Web site-like weather information and forecasts anywhere up to about 200 miles off the U.S. coast, at prices that are broadly in line with those of the subscription Web sites.

Lower down the radio spectrum where frequencies are measured in kilohertz instead of megahertz, the “line of sight” rule doesn’t apply. For the boater on a budget who can do without colorful graphics, there’s lots of information to be gleaned from a world-band radio such as a Sangean ATS505 or Grundig Globe Traveler, costing $150 or so.

Medium Frequency (MF) radio waves curve around the surface of the earth, absorbed and weakened as they go, but forecasts broadcast by the Coast Guard on 2670 kHz can be picked up about 150 miles offshore during the day and twice that distance at night. High-frequency (HF) radio waves travel even farther, bouncing off electrically charged layers in the atmosphere. But the Coast Guard’s schedule of high-seas forecasts is complicated because HF frequencies have to be changed to suit daily changes in the atmosphere, and reception is never as clear as you’d expect on VHF. But it’s free, it’s worldwide, and you can pick it up on the same world-band radio.

At the risk of sounding geeky, you could even load an HF fax-decoding program such as SeaTTY or Mscan Meteo onto your laptop, connect it to the same radio, and download satellite photographs and synoptic charts. The squeaks and whistles you hear in HF voice broadcasts translate into smudges and streaks on the fax image, but some people find that learning to live with the quirks of HF fax becomes a fascinating hobby in its own right.

Out at the unfashionable end of the radio spectrum, at 518 kHz, there’s a gem of a service called Navtex that broadcasts navigational information and weather forecasts in a form that can be picked up and decoded by a dedicated Navtex receiver and reassembled into a printed message on screen. Navtex receivers such as the Furuno NX300 typically cost a few hundred dollars, but the service itself is free and the process of receiving messages is almost entirely automatic: You don’t even have to tune it. Just set the kinds of messages you want, switch it on, and wait. It doesn’t matter if you miss a message because each one is repeated until it’s out of date and is saved in the receiver’s memory.

There are more than 100 Navtex transmitters around the world, each with a range of several hundred of miles,and covering most of the coastlines of the developed world out to a couple of hundred miles offshore. And for those who cross oceans, there’s another big advantage to the Navtex information system: The standard broadcasts are always in English!

This article originally appeared in the September 2011 issue of Power & Motoryacht magazine.