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Author Topic:   Using GRIB Forecast Tools
jimh posted 08-14-2011 10:34 AM ET (US)   Profile for jimh   Send Email to jimh  
On our recent eight-day cruise of Northern Lake Huron and Georgian Bay, I was able to obtain weather forecast information from on-line resources using the GRIB format. I used my laptop computer and the excellent POLAR VIEW NS application to select the region of interest, download the GRIB data, and display the weather information on my chart. The GRIB data typically gives a seven day forecast. I was able to obtain GRIB data whenever I could get a Wi-Fi connection to the internet. I began the trip with data I downloaded just before departure from home, and I refreshed the data one or two times during the week.

The weather data provided by GRIB was very useful and seemed quite accurate. For example, on the one morning when we awoke to rain and fog, the GRIB model predicted those conditions and precisely for the area where we were. On GRIB the whole of Georgian Bay looked clear, but rain was forecast for the Killarney area, precisely where we were that morning. I was very impressed.

I had meant to get some screen grabs of those forecasts, but POLAR VIEW had expired them after seven days and deleted them. You'll just have to take my word for it.

Here is a screen grab showing the GRIB forecast for this coming Wednesday, August 17, for the Great Lakes region.

Graphic: GRIB forecast for Great Lakes on August 17, 2011

As you can see, this would not be a good day to transit Georgian Bay from East to West--you'd have a 20-knot Southwest head wind and perhaps some rain. There is a low pressure system in the region, apparently a bit farther North and with a 1007 or lower center. This will also not be a good day for making any Westing in the North Channel: 15-knot headwinds are predicted. And for Northern Lake Superiod--watch out for those sustained 20-knots Westerlies.

For more on the GRIB system, see .

For more on POLAR VIEW, visit the POLAR NAVY website, .

jimh posted 08-14-2011 10:44 AM ET (US)     Profile for jimh  Send Email to jimh     
The attraction of GRIB had escaped my attention until I began using POLAR VIEW. The POLAR VIEW application makes acquiring and displaying the GRIB forecast extremely simple and fast. Even with rather slow and flaky WiFi connections in Georgian Bay, obtaining the GRIB data only required a few seconds of download time. The GRIB format is very concise.

Interpretation of the display requires some familiarity with Meteorologic symbols, but most boaters traveling offshore and in remote areas should already have the requisite background needed to interpret the display. For more on the map interpretation see

jimh posted 08-14-2011 10:46 AM ET (US)     Profile for jimh  Send Email to jimh     
As I have mentioned elsewhere, I should remark about the weather during our cruise. For the last three days of the cruise the voice weather forecast was quite simple: Weather fair; winds light. No GRIB model needed for interpretation of that data!
jimh posted 08-14-2011 03:32 PM ET (US)     Profile for jimh  Send Email to jimh     
I should also mention that the GRIB forecast data I was downloading was provided at no charge, presumably from NOAA.

When planning our 70-mile run from Little Current to Tobermory, we initially intended to depart early, around 9 a.m., as a general measure to get out on the water before the wind had a chance to build up. As it happened, the GRIB data for that day showed that the wind strength would actually be light and decreasing during the day, with the wind forecast for around 8 p.m. to go to calm conditions. Based on that, we changed our starting time to about 11 a.m., which gave us a leisurely morning in town and a chance to have a GAM with another Boston Whaler boater who had just joined our fleet.

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