On a recent voyage I used Weather 4D to view National Weather Service (NWS) Global Forecast System (GFS) weather prediction data, commonly distributed as GRIB files. Of the myriad apps that can be used to display GRIB files, I found Weather 4D to be the most useful way to download and review NOAA’s GFS model GRIB data over cellular or WiFi networks. What sets it apart is the stunning layered display of data elements and its ability to project changes over time, similar to an animated video display. This is a brilliant app that shows wind speed and direction, barometric pressure, temperature, wave height, period and direction, current speed and direction, precipitation and cloud cover.
Weather 4D uses “weather zones” to define the data included in each GRIB file. This zone definition includes the duration of the weather forecast–1 to 8 days–forecast projections in 3-, 6-, 12- or 24-hour increments and a grid resolution of 0.5, 1 or 2 degrees. Data elements include wind speed and direction 10 meters above mean sea level, pressure, precipitation, temperature, waves and ocean current. Zone definitions determine the size of the file downloaded and are dependent on the area size, forecast options and weather elements. Note that large files may take a long time to download and could exceed your cellular plan data limit.
Wind speed can be displayed with traditional wind barbs or as a colored gradient. (A half barb indicates 5 knots, one long barb is 10 knots, two barbs is 20 knots, etc.) Barometric pressure is displayed using continuous blue isobars with labels or in a 3D mode, with highs and lows represented as peaks and valleys on a 3D surface. Wave data includes both wave direction and period, as obtained from FNMOC WW3 Global or Euro. Temperature and rain are shown as colored gradients. Each data element is represented in separate layers. Multiple layers can be combined by selecting the item(s) and display options for some stunning visual presentations.
To visualize changing conditions, Weather 4D allows you to scroll through a weather forecast over its selected timeframe. As you do so the various weather data overlays also change, allowing you to easily visualize the evolving conditions. Each layer has several settings that allow you to customize the display to highlight the weather conditions you are most interested in. This is especially useful for tracking weather systems or noting changes in wind speed and direction.
Due to the fact that a virtually unlimited number of screen-display combinations are available, the screen can become quite busy. During our recent voyage, for example, we regularly monitored the wind speed and direction, baromateric pressures in the area, and wave height and direction. Toggling between temperature, clouds and forecast rain provided yet more information.
With so many features and options at your disposal, Weather 4D can seem overly complex, especially in the beginning. With this in mind when first working with the app, I recommend using a single layer and then experimenting with the display options. If they make an updated version, I would like to seem them add a setting for high/low colored gradients, which would make it easier to visualize the pressure systems. All in all though, for recreational sailors and coastal cruisers, Weather 4D provides a beautiful way to manage and view GRIB files. I give Weather 4D 4½ stars. Weather 4D is available on iOS for $10.99. s
Name: Weather 4D & Weather 4D Pro iOS
Available on: iOS & Android devices (weather4d.com/en)
Price: $10.99 & $33.99 (Pro)
Score: 4 1/2 stars
