Weather
Weather allows wind speed, wind direction, pressure, air temperature, sea temperature, wave height, precipitation and currents to be plotted on an open chart. GPSNavX™ uses the standard GRIB (Gridded Binary data) format for weather forecasts. GRIB are output files generated by computer forecasting models. They are tremendously more compact than regular weather charts and because of their size are very well suited for download via wireless means. The largest producer of GRIB weather is NOAA although other organizations such as the military and research institutions also generate GRIB files.  NOAA GRIB files are the best ones suited for marine forecasts.

A GRIB file may be loaded via "Open GRIB..." on the "Weather" menu. GRIB files typically have forecasts for more than one date and/or time. GPSNavX™ will select the closest date to the current date. A different date can be selected on the Weather panel. Use "Show" on the "Weather" menu to turn on or off the weather plot and the Weather panel. "Export GRIB To Google Earth" will create a KML file for the selected forecast time which Google Earth can open.

"Request GRIB" on the "Weather" menu will request via SailDocs a GRIB for the currently opened chart. The chart must be between 3 degrees and 180 degrees in width and height except in the case of the World chart in which case a GRIB of 40 degrees by 40 degrees will be requested. The GRIB will come into your email inbox (Set your email address in the GPSNavX™ Preferences or check "Manual" to manually send the GRIB request) and can be opened in GPSNavX™ with "Open GRIB...". The GRIB will have the requested data and be for 00, 12, 24, 36, 48, 60, and 72 hours. Transfer To KML" will create a file for the selected forecast time which Google Earth can open.

Use "Next Forecast" and "Previous Forecast" buttons to step forwards and backwards in forecast time. Use the "Play" button to cycle through the forecasts. The forecast time is in system local time.

When the Contour is selected, contours for pressure, air or sea temperature, or precipitation rate will be displayed.

When "Barbs" is selected wind speed is indicated by ticks on the wind direction vectors. Each full tick represents a wind speed of ten nautical miles per hour or ten meters per second depending on the "Units" setting in the preferences.

When "Beaufort" is selected wind speed is indicated by the color of the arrow according to this scale..

Force
Color Wind (Knots) Classification
0
  Less than 1 Calm
1
  1 - 3 Light Air
2
  4 - 6 Light Breeze
3
  7 - 10 Gentle Breeze
4
  11 - 16 Moderate Breeze
5
  17 - 21 Fresh Breeze
6
  22 - 27 Strong Breeze
7
  28 - 33 Near Gale
8
  34 - 40 Gale
9
  41 - 47 Strong Gale

10

  44 - 55 Storm
11
  56 - 63 Violent Storm
12
  64 or greater Hurricane

The size and color of the wind markers can be set with the slider and color chooser.

GPSNavX™
only plots the data points contained in the GRIB file, so it may be required to zoom out to see the extent of the GRIB data.


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