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What are GRIB files and buoy reports?

By The Ithaka - Published December 12, 2006 - Viewed 12921 times

What are GRIB files and buoy reports?

John R asks: “What do you mean when you say you’ve ‘downloaded a GRIB file’ or that you’ve gotten ‘a buoy report’?

From Douglas:   On Ithaka, every day, we get weather information in three ways: one, by observing our barometer and baroscope to note pressure changes in the atmosphere that signify coming weather changes and their intensity; two, by tuning our single-sideband radio into the morning cruising net, and listening to the weather forecast; and, three, through our single-sideband radio, where we download to our laptop weather faxes and “GRIB” files that present forecasts and predictions of what the weather is going to do two or three days out.

GRIB is the acronym for Gridded Binary Data -- a format used by meteorological services to exchange weather data. Using a powerful compression technique, these files can contain a boatload of data and still be tiny enough to travel easily on cruisers’ ever-persnickety onboard e-mail systems (connected through SSB). These GRIB files draw from NOAA’s GFS/AVN global model, and include: surface winds; barometric pressure; 500-milibar (upper atmosphere) winds; surface water temperature; and predictions over 12, 24, 36, 48, and 72 hours. Layered onto a graphic display they are easy to read and incredibly valuable. Often, they’re right, too.

When we say we received a “buoy report,” we’re talking about the www.buoyweather.com (subscription) service, which we access through our on-board SSB radio and laptop computer. We receive specially formatted e-mail messages that include five-day wind/wave forecasts. You can also receive automatic daily forecasts, custom weather chart attachments, NOAA buoy reports, official text forecasts, and five-day passage outlooks. It’s an incredible service, and costs only ten cents per message. The company requests a $10 deposit and withdraws against your account.  Buoyweather offers global coverage, and what makes the service so nice is that the user sends in an e-mail identifying either single or multiple latt/long coordinates—depending on one’s needs and interests—and Buoyweather automatically compiles the data for these user-identified “virtual buoys,” all based on a computer analysis of 66 weather charts, and zaps it right back.  Like all weather predictions, there are no guarantees, but it’s a wonderful addition for passage planning. We know a number of people on land who also use the system to keep track of their friends at sea.

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