The Art of Dredging

Dredging and shipping


GRIB (GRIdded Binary) is a mathematically concise data format commonly used in meteorology to store historical and forecast weather data. It is standardized by the World Meteorologial Organization.


“ZYGRIB” is new software,  for reading and displaying “GRIB” datafiles.

ZyGrib, ready to download GRIB-data from the net.


You open ZYGRIB, select an area, a grid mesh, and the meteo parameters  you wish to see,  for a period of up to seven days.The software retrieves it from the net.

This data is generated by mainframe computers, who run weather prediction programs every few hours, fed with meteo input from the field.

The ZYGRIB package can be found on  and it’s freeware.

I found ZYGRIB less straightforward to use than UGRIB (can be found on, also freeware, just need to register).

 UGrib, displaying Grib-data fro the Guylf of Biscay


Both programs  are sufficient for sea passages, they use rather small data packages (typically less than 100kB), which make them useful onboard ships with bandwidth impaired internet access.





It isparamount to understand that GRIB data are only the result of models that simulate the atmosphere using current data. They are never 100% correct, and with unusual situations (major storms) significant errors are seen.

The atmosphere is not yet completely understood by science, and weather is -to a certain degree- random.

To my personal experience (in South Korea), GRIB-data proved spooky correct for 36-48 hours ahead, but deviating for longer forecasts.

In Sachalin (Russian Federation) however, GRIB was less reliable, mainly because that area was not dotted with meteo sensors, providing scanty input in computer models. (“Garbage-in-is-garbage-out”-principle.)

GRIB-data should not be used as stand-alone forecast, but always in conjunction with data from other sources, synop-charts, etc… (see also ….)



Marc Van de Velde

October 2009


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