Home' Afloat : November 2013 Contents Take monthly with water November 2013 55
*Malcolm Riley is the Public and Marine Officer for the Bureau of
Meteorology in Hobart. He has worked in all States with the exception
of Qld and is a Master V. He gives education courses on Marine
by Malcolm Riley*
Many of those in the boating community that undertake long
journeys at sea are familiar with GRIB files. GRIB is an acronym
for General Regularly-distributed Information in Binary form.
GRIB files are used to transfer and store meteorological data and
the format of the files was standardised by the World Meteorological
In a nutshell GRIB files contain large amounts of information
that are stored in relatively small files. For mariners they can provide
detailed forecasts over ocean areas that often only have limited
I have used GRIB files when I have been forecasting in the
Antarctic and when providing forecast support for Tall Ships from
a home base. Accessing these GRIB files is done in a variety of
ways depending on what site you are using. Usually there is some
software to download and a coded message that needs to be sent
to the provider to start the service.
I use the service from Saildocs which has the GRIB viewer
called Viewfax. To get the information you send off a coded email
I leave the subject line blank and have the code in the body of
the email. You just have the codestring only in the body, do not use
a greeting or a signature; it confuses the system.
The codestring to send is:
gfs:10S,35S,140E,160W|1,1|0,6 ,12 . . .180|WIND,PRMSL,
this is and identifier for the Global Forecast
System funded by the US Government.
These are the two latitudes that define the north,
south borders of the forecast area you require. For
southern latitudes the latitude in whole degrees
and S (for south), for northern hemisphere use N
165E,160W| These are the two longitudes that define the east,
west borders of the forecast area you require. For
eastern longitude the longitude in whole degrees
and E (for east), for western hemisphere use W
The number of degrees for each gridpoint. |1,1|
returns gridpoints (wind arrows) every one degree
|3,3| gives a gridpoint wind arrow very 3 degrees.
0,6,12...180| The frequency and duration of the forecasts. In
this case forecasts every 6 hours (0,6,12) out to
... 18 0 hours. You can select 0,12.24 for 12 hour
intervals or 0,24,48 for daily data.
These are the forecast parameters you are
requesting, in this case Wind Speed and
Direction, Mean Sea Level Pressure and
Combined Wave Heights
these vertical lines are dividers between
Once you send off your message it generally only takes a minute
or two before the reply comes back. By using the software maps
such as the one above appear. This is the area that was selected in
the code string and covers the northern tip of NZ, New Caledonia,
Vanuatu and Fiji. The map contains wind feathers/barbs (see Afloat
last month) which are colour coded and the background of the map
shows the colour coded wave heights. As you move your mouse over
the map a spot forecast for that map appears.
There are many different viewers and systems the mariner can
choose from and a list of some can be found at http://weather.
Or google “grib file viewers”.
While it is easiest to download these emails with a satellite
phone/modem on your vessel.
• A cautionary note. These files generally access one computer
model – the United States Global Forecasting System model. Bureau
forecasters have access to many different models that can and do
give different results. h
Australian tropical outlook regions.
2013–2014 Australian tropical cyclone season outlook
Near average tropical cyclone activity is most likely for the Australian region
this season. The tropical Pacific Ocean, which affects tropical cyclone activity in
Australia, is currently neutral (neither El Niño nor La Niña), meaning there is no
strong shift expected in the average number or location of tropical cyclones.
The typical Australian tropical cyclone season:
• has most tropical cyclones between 1 November and 30 April;
• averages around 11 tropical cyclones;
• sees an average of four tropical cyclones cross the coast, though coastal
impacts can be felt when tropical cyclones remain well offshore;
• on average has its first cyclone cross the coast in late December.
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