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  Topic Review (Newest First)
02-06-2012 12:55 PM
Originally Posted by SVAuspicious View Post
GRiBs are evil.

I sense that that they are more usual offshore as they do not seem to factor in land and sea breezes especially well. I also like the weatherfax, but will use all tools available to me before heading out into bluewater.
02-06-2012 12:47 PM
SVAuspicious GRiBs are evil.
02-06-2012 11:47 AM
Originally Posted by jackdale View Post
Here is the technical answer - Guide to GRIB
I read through the link and still do not understand what data is being used to gernerate the grib chart. It seems that direct measurements of wind and waves is not the primary means to generate the chart. It seems satelites are used to measure maybe wind, waves, and barometric pressure. But how does a satelite measure these?
02-03-2012 08:45 AM
SVAuspicious I use a software tool named Visual Passage Planner. VPP has the current pilot chart data by month. If you punch in the polars for your boat it will give quite reliable predicted passage duration estimates.

Jimmy Cornell has just announced a global package of updated pilot charts. See Noonsite for links.
02-02-2012 09:29 PM
jimmalkin All above are perfectly appropriate direction to get your answers - I can only add (sign up for a trial) is a great single source for forecasting that combines information from the usual multitude of weather prediction and ocean activity sources and puts them together allowing you to get lat/long specific forecasts for any given location.
01-11-2012 05:48 PM
Originally Posted by casey1999 View Post
Can someone explain how the Grib files are produced? I understand the files are all computer generated but what is the input? Do they use a satelite to get the input information? And what is the input information? If it is say Barometric pressure, how does a satelite measure barometric pressure?
Here is the technical answer -
01-11-2012 12:55 PM
casey1999 Can someone explain how the Grib files are produced? I understand the files are all computer generated but what is the input? Do they use a satelite to get the input information? And what is the input information? If it is say Barometric pressure, how does a satelite measure barometric pressure?
01-11-2012 10:35 AM
Them, rather than it

Originally Posted by davidpm View Post
Well I've downloaded it not trying to figure out how to get it big enough to read.
Note that the pilot charts are monthly by ocean basin so you might need to dowload several. Also Cornell's book is a compilation of data from many sources including pilot charts. It is certainly the pre-eminent data source for planning passages. When we recently planned our trip from Oz to North America, it was a matter of we have to be here (for us South Africa) at a certain time and that means we have x weeks to get from here to there. There is a reason that people going to various parts of the world all go at pretty much the same time - and why another time might be quite dangerous.

A semi-politcal comment about Cornell's book. We buddy-boated with friends from Florida all the way to Oz, with several times when we went different places. We each started with a new Cornell. When I bought mine in Toronto I did not know, and the bookseller did not say, that there was a new edition out so I had one edition older. By the time we go to Brisbane, John's binding was falling apart and mine was still in almost new condition. The new edition is printed and bound in China, while my older one was done in the US. It is sad when we get crappy quality and people here lose jobs. I would bet the difference in price would be less than $5.
01-11-2012 08:57 AM
speciald I use the MaxSea weather routing application. Grib files, polars of your boat, what the projected weather are are all used to produce a sailing route. The Gribs can be downloaded from their website enroute to update the routing underway. It has worked very well for me in passages to and from the Caribbean in the last 7 years. It is an expensive program, unfortunately, but works. It is also part of the Furuno Nav-net system.
01-10-2012 10:59 PM
jackdale For passage planning I use the following as well.

NOAA weather fax

GRIB files

Both are available from Internet, but offshore weatherfax can be accessed via SSB > Modem > laptop and GRIB files can be accessed via email either SSB or Sat Phone. GRIB readers run the whole gamut of cost from free (UGRIB) to expensive (Expedition)

Get familiar with them at home online.

I use the North East Pacific weather fax

Northeast Pacific WX Briefing Package

For Internet based GRIB files I use UGRIB

For email based GRIB files see Requesting grib files from Saildocs (2010-07-08)

I also have a slew of Android apps that I use for weather.

Also if you are going to cross the Gulf Stream, you may wish to use a routing service.

There are also weather routing services both free and for fee available.
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