Weather Sources (in Response to a Reader’s Questions)

Steve and Linda answer a reader’s questions about sources for weather data.

There are so many weather sources available today that sometimes I think it was easier in the olden days – when the only data available came from the barometer, wind direction and speed, swells, and clouds. It was amazing that somehow most of us cruised safely with only the data we could glean from what we saw around us to help in weather tactics. And it may come as a surprise to you that today we still use the local data to make a final decision on what the longer range data tells us.

So what do we do for information today? I’ll break this answer up into two categories – first when we have a land-based Internet connection, and second when we’re aboard.

The trouble with land-based information is there is so much of it. So we use the SetSail weather links to get us to the appropriate regional sites for tropical or extra-tropical weather. We usually look at the surface and 500mb forecast data, and then check out the water vapor satellite images (the latter are extremely valuable in ascertaining if the 500mb data is on track) – the 500mb data being the key to nasty to eliminating nasty surprises!

We also use the SetSail-MaxSea “chopper” to download data from the various models. This is the same as onboard, except that we request larger files than we do when the connection is slow or costly.

We have found that for normal high latitude patterns, the “chopper” model files are great – and the ability to turn these into weather movies or use them with the routing software is a real advance. If we are concerned with serious weather, however, we definitely want to see what the professional forecasters are saying and so look for the web-based weather fax downloads.

At sea the situation changes. Here it is a question of what sort of e-mail capability we have. Assuming we are out of range for Globalstar or Iridium (or don’t have them on board) we use our Furuno weather fax. There are a couple of keys to making any fax work. First is a good antenna – that’s the key to picking up weak signals. Second in knowing the time of day and frequency to watch. It usually takes a week or more to find the best combination – especially when there are several stations to monitor.

The minute we have access to a satellite phone, it becomes a question of the risk factors. We’ve found that we can download most of the NOAA fax files from the web in about a minute per file. That puts the cost at a buck a fax (or less, as prices tumble). It is a lot if you are sitting and/or the weather fax receiver is working. But if you are crossing the Gulf Stream, and want the latest data, the price is cheap.

Even less costly is to use the SetSail-MaxSea “chopper” to request weather data files using either SailMail, Ham WinLink, or the satellite phone. The files come in so quickly that we typically use the satellite phone once or twice a day for this. If it is not working, we switch to SailMail and the SSB radio.

The amount of weather data coming aboard each day is staggering compared to what we used to have. If we were still navigating with a sextant, we would not have time to absorb even a fraction of the data, let alone decide what to do with it. However, with GPS and electronic charting, there is a lot more time to look at the weather data, and then compare it to what we see on deck.

Posted by Steve Dashew  (October 31, 2002)

Comments are closed.