What's a GRIB?

While racing and cruising over the oceans, many of our YachtPals have been sending us updates which mention GRIBs.  We've gotten a few emails on the subject (always appreciated), and we've been made to realize the need to clear this GRIB thing up for our readers.  While we're at it, we thought we might as well give you some links to the FREE technology available for weather prediction, which you can then use yourself.  Careful, it can become addictive playing with GRIBs, but it's probably better for the brain than watching TV.

GRIB is short for GRIdded Binary.  It's a style of data that saves bandwidth, and in regard to weather, GRIBs can give you days of predictions over a wide area using even the most minimal data connections.  Weather GRIBs are something like a shorthand, where the Earth is sectioned off into grids, and the information can be packaged so as to send only the data for the grids you wish.  It's a brilliant system, since the info can be so small it is easily sent via SSB/HAM or even Iridium, and it has, for many skippers, replaced or heavily augmented the WeatherFAX.

The GRIB info is based on computer models, thus it gives predictions and not observations.  The accuracy is pretty astounding, and is, in fact, what most meteorologists use in making local predictions.  So, with the GRIBs in hand, you are your own weatherperson - exactly what you need when you're out in the ocean yourself, or even if you're just planning your weekend.  Of course, you won't be any better than your local weatherperson, but more on that later.

The first step is to download a GRIB viewer.  There are several software packages that will read GRIBs, and even navigation software that will lay the weather data over your charts - which can be really nice.  To make things simple, we'll use the grib.us software (UGRIB) and service, as it's nicely packaged reader and downloader, and it's free.  As for the GRIB data, it's also free (thanks to the US taxpayers).

First off, we're talking Windows here, so MAC and Linux folks: look to Parallel and Wine (if you don't know what that means, you're probably going to get in over your head).  Now, for the download you can either go here anonymously, or you can go to http://grib.us and register to download - it should be the same software either way.  You're going to need to download and install the software on your computer, and then run UGRIB.  Pretty simple.

Once the software opens, you'll see a map of the world.  Choose an area by drawing a box on the map with your mouse.  Choose the number of days, the interval (in hours), the resolution and the parameters in the box marked 'GRIB data options' on the left.  Choose your connection and download folder in the box below this, and on the box above, hit the 'Download Grib File' button.  Voila, once downloaded, you can view the weather data.  Even more interesting: use the "Create Animation" button on the top of the screen to make a movie of the weather prediction.

So now, when people report that they are referring to the GRIB's, you can too.  Cool, eh?  As for the accuracy mentioned above, the GRIB info is based on the most accurate computer models available, but that's not saying much.  Those familiar with chaos theory know that computer weather predictions helped launch this entire branch of science - the butterfly effect and all that.  So, a couple of days out and these are pretty accurate, while a week away is more of an educated guess than a prediction - just like your local "extended forecast" - but at least you won't have to stay up until 11:25 for it.

GRIB files can also be downloaded via email, and are small enough for Pactor/SSB/HAM or satellite rigs to retrieve.  So, up-to-date weather info. can be gathered from nearly anywhere on the globe.  Sailmail provides a wonderful service for this, and is well worth a look if you're heading out of the range of standard communications.  If you're not off the grid, however, please spare the SailMail servers the work, and get your GRIB's online whenever possible.

-Brad Hampton exclusively for YachtPals.com