GRIB Files on a Tablet

What this page is about

This page is based largely on my experience testing Apps on an iPad .Mostly, these are “work in progress” and this page will inevitably lag behind events


GRIB Apps are, effectively Tablet or Smartphone versions of the File Transfer Protocol system used by zyGrib.

In most cases there is a small charge for the App but all are free to use – except, of course, for communications costs.

Weather models

The usual source is the NOAA, MCEP GFS (Global Forecast System.) Occasionally the CMC (Canadian) GEM model can be used. A wide range of weather elements is available. The GFS uses a 13 km grid (about 1/8 of a degree but issues the data on a 0,25 degree grid – about 25 km.

Some Apps offer limited area models such as the US Navy COAMPS and the WRF.

Wave and current models

There are both WW3 and FNMOC wave forecasts available. Some are for specific areas such as the Mediterranean. Current predictions may be available for inshore areas as well as oceans.


All the elements on offer are obvious except, perhaps for CAPE. This is an index of instability and indicates thunderstorm or lightning risk.

Length of forecast

The GFS runs out to 14 days with the first 8 days being output on a 0.25 degree grid. From 8 to 14 days data are only available on a 2.5 degree grid and 12 hourly. Skill decreases rapidly after7 days so that it is unwise to make plans beyond 6 or 7 days ahead.

List of Apps on this page

Some of these Apps piggy-back on the Saildocs service. They are all the same data albeit with different presentations and some variation in the selection of elements, sea state and current.

For weather, few give more than Saildocs. Most give less either in number of days or resolution or both. Most Apps interpolate between the GFS grid point values making it appear that they are providing more information.

For iPad

For iPad and Android

For Android

For iPad, Android and Windows

For all platforms

Examples of iPad, images will be similar to those on iPhones and are taken from my iPad2. Android examples are taken from the relevant sites.




This is a free facility of the well-known iNavX navigation package.

Elements available –

Wind, Air and Sea temperature, Wave height, Precipitation.

These are chosen separately and the software generates an email for each to Saildocs. The reply email should arrive within one minute with an attachment that can be opened with whatever GRIB software you have - including overlaying on the navigation chart..

This is a rather simple, somewhat clumsy service that, by default, gives information over a 20 degree lat/lon area covering the area currently in use on your iPad screen..

Forecast periods can be chosen up to 7 days from the GFS and COAMPS. With a little care it is possible to edit the email to change the times, elements requested and the default area. See my Saildocs page. Deleting the words “sent from mu iPad” will avoid annoying failure messages.

Displays on the iNavx charts look like -


 Weathertrack samples


 inavx ipad



Weathertrack has a wide, possibly the widest choice of options.

Elements -

Wind, Pressure, CAPE, Rain, Snow, Dew point, Cloud Cover, Wave (s Height/Direction/Period, ), Currents, (available as auto-renewable subscription.), Air- and Sea Temperature, Relative Humidity.

Forecasts are up to 16 days (depending on the model), Choice of ,models GFS, COAMPS; severs wave models including for the Mediterranean.

In addition to GRIB data, there are many other options including synoptic charts, weather actuals and much more. It is nearly a one-stop forecast service.

Two slight drawbacks. First, the chart projection is distorted in northern latitudes, Secondly, pressure and wind apart, it is impossible to overlay elements. Charts look like this









By contrast, iGrib produced by a Cruising Association member, is fairly basic and probably the most intuitive to use.

Elements –

Winds, Pressure, air Temperature, Precipitation, CAPE and , Cloud. Wave predictions are planned and other elements may be added.

There are no latitude/longitude lines.

Displays of iGrib panels look like this

Self select area panel

 iGrib area selection

Winds & Pressure

 iGrib winds and isobars

Winds, Pressure & rain

 iGrib winds, isobars, rain




Weather4D is another with a wide choice of options. It also has the option of using email to Saildocs. for use when bandwidth is limited. This is a most useful facility as the file can be opened with other viewers. This includes th iNavX chart plotter App.

Elements –

Wind, Pressure, Cloud, Precipitation, Air temperature, CAPE, Waves (Height/period/direction). Currents

Forecasts up to 10 days (depending on data model), Choice of ,models GFS, GEN, COAMPS, WRF. For waves there are WW3 Global and European Wave models. There are My Ocean global, Biscay and Mediterranean current models.

Elements can be overlaid although it can be difficult to view. A particularly nice feature is the presentation of a time sequence of wind speed and direction overlaid on the charts of wind. These are some samples -

Baltic winds

 Weather4D winds

Winds & Isobars

 eather4D Grib winds


 eather4D general weather






This has a fairly large range of elements. The chart projections are good with latitude/longitude lines. It does interpolate between grid point values giving a slightly misleading appearance of precision.

Elements -

Wind, Precipitation, Pressure, Air temperature, Cloud, Relative humidity, CAPE, Waves (including Mediterranean and Black Sea,) Current (Atlantic only)

Forecasts up to 8 days from the GFS, COAMPS, WW£ (including the Mediterranean.)

These are examples -

Winds, isobars, waves





 pocketgrib meteogram 1




This is a free service primarily for windsurfers with the emphasis on conditions at specific locations.

The wind data are from the GFS and WRF for pre-selected areas. In some cases the WRF presentation has too much of the area over land for it to be useful to off-shore sailors.

These are some examples –

WRF winds


Time sequence


Wind graph




Not being an Android user, my knowledge of this App is limited to their site.


Wind, Pressure, Temperature, Cloud, Humidity, Precipitation, Waves.

Forecasts up to 16 days from the GFS.

These are examples -


 Android winds


 android pressure


 android rain



GRIB version

Routeing version Attach: sailgribroute.grb

Unusually, there are free versions that give forecasts for up to two days. These can be upgraded for a small charge to full versions. There is a GRIB version and a Weather Routeing one.


Wind, Pressure, Precipitation, Cloud, Air Temperature, Wave (height/direction/period), CAPE, Tidal or oceanic currents

Depending upon the model forecasts are available up to 14 days ahead from the GFS, COAMPS and WW3 wave model.

SailGrib offers a variety of presentation formats to suit most tastes. These are some examples -

Winds & isobars

A Winds & isobars

Enhanced wind display

  Enhanced wind display

Saildocs request panel

  Saildocs request panel





This is more of a teaching or demo aid than a useful tool for sailors. It does enable you to take a genuinely global view of the weather. It provides forecasts out to 5 days using the ECMWF model. For that reason it is useful as a comparison with the GFS output used by most of the other apps listed here


North Atlantic


Global view


Western Med



Many will have used PassageWeather as an easy way to get vector wind charts from the GFS and other models. There is now a mobile version.which can be used with most platforms.

Area selection is from a list that mirrors the chart on the main website. Chart selection similarly. It can also be used on a PC without all the advertising blurb.

Examples are shown here -

Select area

 passageweather Select area

Select chart

 passageweather Select charts

GFS Chart

 passageweather GFS

Other Apps

There are many weather Apps – use Google to see what is available. Most will simply be different presentations of GFS and WRF output with no human input. The only real differences are likely to be the gimmicks employed to make them attract users. Few will have anything substantive for sailors.

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