Maringret’s zyGrib Page

zyGrib (pronounced “zeegrib” in French) is a very good program. When we first came across it we were frustrated by the lack of a “user’s manual”. To solve our own desires, we wrote the following manual. It is both a hypertext manual for online use as well as being printable to paper.
Note: our manual is for zyGrib version 5.1.0


 

zyGrib

Multi-platform GRIB File Viewer
and
Weather Visualization Software

www.zygrib.org

Version: 5.1.0 for Linux, Mac OS, Windows
Release Date: December 18, 2011
License: GNU GPL v3
Created by: ???
Manual by: Sailing Yacht Maringret
Manual Version: 0.1
Manual Date: 2012-01

Table of Contents

Introduction
Using zyGrib (Quick Start Guide)
zyGrib Button Descriptions
The Menus of zyGrib
zyGrib Menu
File Menu
Data Menu
Altitude Menu
Earth Menu
Options Menu
Help Menu
Glossary of GRIB Data
Glossary

Introduction

Document Scope

This document describes the zyGrib software, it’s usage and features. It has been written for both users new to zyGrib (a Quickstart Guide) and long time users who need a reference of features. It does not cover installing zyGrib, platform differences, GRIB file internals or weather forecasting.

Note: This document was created based on the Macintosh version of zyGrib and may contain some Macintosh specific aspects of zyGrib.

zyGrib Description

zyGrib is a program for the visualization of GRIB files carrying weather forecast information. GRIB files containing time sequenced weather forecast data are retrieved from internet sources based on visual indications and settings in the software. Alternatively GRIB files can be used from the local disk or network. The weather data is then superimposed over geographical maps. Either single displays or time sequences of the data can be presented.

GRIB Files Overview

GRIB is an abbreviation for GRIdded Binary and refers to a method of computer storage of multidimensional numerical data – primarily for use in weather forecasting. GRIB files are used to store both historical data and forecast data. The meteorological institutes of the world use GRIB files to transport and manipulate weather data and these GRIB files are the foundation of the weather forecasts we every day. The format of the GRIB file is defined by the World Meteorological Organization (WMO) and is available for use by any interested parties.

The GRIB file is the format for exchanging meteorological data, that data almost always comes from computer models. There are a number different weather forecasting models, some are:

  • GFS (General Forecast System)
  • NAM (North American Mesoscale)
  • WRF (Weather Research and Forecasting)
  • HRW (High Resolution Model)

zyGrib retrieves GFS produced GRIB files from NOAA (the US National Oceanic and Atmospheric Administration) as well as wave forecast data from the WW3 model at the US FNMOC (Fleet Numerical Meteorological and Oceanography Center).

zyGrib Overview

The zyGrib software has 3 basic parts:

  • geographic map presentation
  • GRIB file retrieval from internet sources or data files
  • presentation of GRIB weather data over top of geographical background maps

Each part will be covered in this manual using the menu choices from the menu bar and buttons at the top of the screen. Pages of options and choices will be discussed in the context of the menu choice which causes them to appear on the screen.

Manual Conventions

There are two main components to the display of zyGrib, the first is the world map, the detail of which can be controlled using various options of zyGrib. This will be referred to as the “background map”. The second is the GRIB data which is displayed over the map. There are multiple data parameters in the GRIB file that can be displayed. All of these are displayed so as to appear to be above the map which appears as the background to the GRIB data display.

The term “right-click” is used to mean clicking the righthand button on a 2-button mouse. For Macintosh users this means Control-click (clicking the mouse button while the Control key is depressed).

Using zyGrib (Quick Start Guide)

zyGrib is a program that takes a data file of weather information that is in the GRIB file format and displays that data over a background map. Usually the information displayed will be current forecast data which predicts the weather behavior. But zyGrib can also use weather data that is now historic, this can be useful to check what the weather did in a similar situation. zyGrib allows a data file to be selected for display or the most current information to be downloaded via the internet.

This section is to help new users make their first use of the zyGrib program. Complete descriptions of all options follow later in this manual.

Defining forecast area

GRIB files represent a 3-dimensional matrix of weather data. The height of the data matrix is set by the forecast model while the size of the forecast area is used to extract data from the model which cover different portions of the world – depending on the model being used. The larger the forecast area requested the larger the amount of data that needs to be moved from the serving computer to your computer – this definitely affects the amount of time required to transmit if the data is being moved by radio. Also the number of different layers of the model will affect the data file size.

  1. Start up zyGrib
  2. Use the Zoom
    and Pan  buttons in the menu bar to display the portion of the world you want a forecast for (select an area about the size of 2 or 3 European countries).
  3. Use the mouse to drag a rectangle of the area you want a forecast for.

Downloading GRIB files

  1. Click the GRIB File Download button  in the menu bar.
  2. A window will appear, notice that the coordinates of the area you selected is in the upper 4 fields.
  3. Make sure that the first check box “Wind (10 m) is selected. The various fields in the GRIB data file are listed in the chapter on “Glossary of GRIB File Data.”
  4. Click the Download button.
  5. A progress bar will show the status of the GRIB file download.
  6. Once the file has been downloaded, zyGrib will ask you select a location to store the GRIB file in. Click the Save button when you have selected the location and file name (the default file name will have the date and time in it).

The GRIB file has now been downloaded and is saved on your hard disk. You can now display the data immediately or do so at a later date

Displaying GRIB files

  1. Once the GRIB file has been saved to disk the file name of the GRIB file  will appear as the title of the window; the date of the first forecast in the GRIB file will be displayed in the upper righthand corner of the map display and also as the value of the Forecast Selection popup
  2. Use the Previous & Next buttons  to step through the different forecasts of your GRIB file. Note that the date displayed in the upper righthand corner of the display and the Forecast Selection popup both change as you step through.

Displaying Individual Data Points

When a forecast is displayed the forecast time-sequence for specific locations can be viewed.

  1. Right-Click on the desired location and select Meteotable
  2. A table with the different values for that location from each forecast will be displayed. Values will be displayed for each parameter requested from that GRIB file. If a parameter is not displayed then click on Options and select the desired parameter. If the row for the new parameter is blank then that parameter was not requested when the GRIB file was created.

Adding a Point of Interest

zyGrib provides a facility by which locations can be marked and saved, they then can be used when GRIB files are displayed.

  1. Right-Click on the desired location and select Mark Point of Interest. The latitude and longitude will be displayed and can be changed if needed.
  2. Enter the name you want assigned to this location. You can also assign a colour and text font which will be used to mark the Point of interest on the map.
  3. Click OK to close the window and have the Point of Interest saved.
  4. Clicking on the name of the Point of Interest will display the Meteotable for that location. zyGrib will maintain the Point of Interest until it is deleted.

Making an animation from the GRIB file

The GRIB file you have downloaded is a 4-dimensional file: latitude, longitude, elevation and time. zyGrib can move the date and time setting and produce an animation of the forecast weather behavior.

  1. Click on the Create Animation button
  2. zyGrib will now display a progress bar as it produces all the images to display.
  3. A new view which is the Animation will appear. There will be control buttons for:
    • Close Animation window
    • Save animation images to disk
    • Jump to beginning of animation
    • Play animation
    • Pause animation
    • Loop animation when playing
    • A slider control for speed of playback
    • A slider control that displays or controls the forecast being displayed.
  4. Click on the Save Animation to Disk button  to save image files of the different forecasts.

Interpreting Displayed Data

Forecasting weather is a complex undertaking, interpreting forecast information is equally complex. The GRIB files contain numerical data from a computer program. The zyGrib program and this manual are about getting the GRIB forecast data into a visible form – interpreting it is a very large subject and beyond this manual.

Some links on interpreting GRIB weather forecast data are:

  • GRIB on Wikipedia
  • Wind Guru website has a good overview of the different weather models that are used to forecast the weather.
  • Frank Singleton’s What Are GRIB Files?

zyGrib Installation

Installation of zyGrib is covered on the zyGrib website www.zygrib.org.

zyGrib Button Descriptions

Quit Button

Quits the program.

File Open Button

Presents a file selection window for selecting GRIB files from disk.

Forecast Selection Popup

If a GRIB file is currently open and loaded then this popup menu allows a specific forecast to be chosen.

Previous & Next Forecast Buttons

Step forward or backwards through the forecasts of the currently open GRIB file.

Zoom Buttons

There are 4 zoom buttons which zoom the display in to show more detail or zoom it out to show less detail. The first 2 buttons zoom in and out, the 3rd button zoome to shw the current GRIB file, the last button zoome out to show the whole map.

Pan Buttons

Move the map section displayed to the left, right, up or down.

GRIB File Download Button

Open a configuration dialogue for specifying which pieces of data are to be included in the GRIB file request.

MeteoBlue File Download Button

???

GRIB Server Status Button

Opens a status display of the 4 servers used by zyGrib. For each server the most recent forecast date and its most recent time of update is listed, as well as any current activity on the server.

File Information Button

Displays the information for the current GRIB file displayed.

Create Animation Button

Creates a series of images for the forecasts in the current GRIB file, one image for each forecast. A new window with the animation will be opened and offers  the option to save the image files to disk.

The Menus of zyGrib

There are 7 menus in the zyGrib package which are:

  • zyGrib
  • File
  • Data
  • Altitude
  • Earth
  • Options
  • Help

Their purposes are as follows:

The zyGrib menu contains the options for controlling zyGrib in the current computer operating system. These options will be different depending on which computer operating system zyGrib is running on.

The File menu contains the options for managing data files, animation files, the data sources (i.e. the internet computers which serve GRIB files to zyGrib).

The Data menu contains options for managing the GRIB data file and it’s parameters, which parameters are displayed and how.

The Altitude menu contains options for managing what elevation of data in the GRIB file is displayed ranging from surface level to the highest level.

The Earth menu contains options for managing how the background map is displayed. The GRIB data is displayed over the background map.

The Options menu contains the options for managing various parameters that can affect different sections of zyGrib – things like choice of units, fonts and colour to display with, even an angle convertor (e.g. degrees, minutes, seconds, radians, grads).

zyGrib Menu

The zyGrib menu contains the options for controlling zyGrib in the current computer operating system. These options will be different depending on which computer operating system zyGrib is running on.

About zyGrib

Displays information regarding the software version and date, copyright and website.

About QT

Displays information about the QT coding system for C++ that was used in the programming of zyGrib.

Services

On Macintosh systems displays the Mac OS X Services menu.

Hide zyGrib

On the Macintosh system hides the zygGrib system , allowing applications behind it to become visible.

Hide others

On the Macintosh system hides all applications except zyGrib, thereby removing windows which might clutter the screen.

Show all

On the Macintosh system shows all currently running applications.

Quit zyGrib

Quits the zyGrib program.

File Menu

The File menu contains the options for managing data files, animation files, the data sources (i.e. the internet computers which serve GRIB files to zyGrib).

Open

Causes a file selection window to appear so that a GRIB file may be selected from the disk. The GRIB file data will then be displayed over the present map.

Close

Closes the current GRIB file and removes its data from display, leaving the current map.

Download GRIB

Opens a dialogue window to download GRIB file data.

GRIB server status

Opens a status display of the 4 servers used by zyGrib. For each server the most recent forecast date and its most recent time of update is listed, as well as any current activity on the server.

IAC fleetcode NOAA

???

Meteoblue

???

Fast interpolation

???

Load Meteoblue file: Swiss

???

Show area: Swiss

???

File information

Displays information about the currently open (i.e. displayed) GRIB file, if no GRIB file is open then a message to that effect will be displayed. The following will be displayed:

  • the name of the GRIB data file and its location on the computer
  • the size of the GRIB data file in bytes
  • the name of the weather centre producing the GRIB data, the model used and which grid was used
  • how many forecast dates are included and what the first and last are
  • which parameters or data fields were requested and are present in the GRIB data file
  • what forecast grid corresponds to the requested forecast area, how many forecast points this is and what spacing the points are at on the earth;s surface
  • the lower left and upper right corners of the requested forecast area
  • which run of the model the data came from (this is usually the run most recent prior to the time of request)

This display will change in size depending on if few or many forecast parameters were requested.

Create animation

A new window will open with only the area covered by the GRIB file displayed. zyGrib will now display a progress bar as it produces all the images to display.

  1. A new view which is the Animation will appear. There will be control buttons for:
    • Close Animation window
    • Save animation images to disk
    • Jump to beginning of animation
    • Play animation
    • Pause animation
    • Loop animation when playing
    • A slider control for speed of playback
    • A slider control that displays or controls the forecast being displayed.
  2. Click on the Save Animation to Disk button  to save image files of the different forecasts.

The Animation window can be played in a loop so that patterns in the weather movement can be observed. The slider control for the speed of playback will control the rate of frames in the animation.

Save current image

Saves the current display image to disk. The user will be prompted for the size of the image required and then where the image should be placed on the disk.

Data Menu

The Data menu contains options for managing the GRIB data file and it’s parameters, which parameters are displayed and how. Most often only one parameter can be displayed at the same time. There may be a palette of colours and a legend displayed. If there isn’t, select the option Data➜Options➜Show Colour Scale in the Options sub-menu of the Data menu.

Wind map

Uses colours to display the wind strengths on the background map.

Current map

Precipitation map

Cloud cover

Relative humidity map

Temperature map

Gap temperature-dew point

Snow (snowfall possible)

Snow (depth)

Frozen rain (rainfall possible)

CAPE (surface)

???

Significant wave height

Uses colours to display the predicted wave height. Directional arrows are displayed.

Maximum wave height

Uses colours to display the Maximum wave height. Directional arrows are displayed.

Whitecap probability

Uses colours to display the Whitecap probability. The colours correspond to the probability (between 0 and 100 percent) of white caps occurring.

Wind arrows

Uses arrows to display the wind strengths on the map. The Wind arrows may be displayed over wave data (which include arrows for the wave directions).

Current arrows

Uses arrows to display the current strengths on the map. The Current arrows may be displayed with wind data.

Isobars (MSL)

Causes the pressure isobars to be displayed over the background map. Their appearance can be controlled further by options in the Options sub-menu of the Data menu (Data➜Options)

Pressure Low High

Causes the letters “H” or “L” to be displayed where the Low or High is centred.

Temperature

Isotherms (temperature 0°C)

???

Isotherms (altitude 2m)

???

Options

Options is a sub-menu from the Data menu. It primarily contains options to adjust or alter the main viewing choices made using the Data menu.

Isobars spacing (hPa)

Causes a sub-menu with the values 1, 2, 3, 4, 5, 6, 8, 10 to appear. Select the value for spacing the isobars. Fore example if 5 is selected then the isobars will be displayed at 5 millibar intervals – e.g. 1000 mb, 1005 mb, 1010 mb etc. Smaller isobar spacing values can clutter the display when at a small scale (i.e. a large area is displayed) but may be needed at larger scales in order for isobars to display on a smaller area.

Isotherms 0°C spacing

Causes a sub-menu with the values 10, 20, 50, 100, 200, 500, 1000 to appear.

???

Isotherms 2m spacing ->
Isobar labels

Causes the numeric value of the isobar to be displayed.

Isotherms 0°C labels

Causes the numeric value of the isobar to be displayed.

Isotherms 2m labels

???

NOAA-GFS: Duplicate first cumulative record

???

FNMOC-WW3: Duplicate missing wave records

???

Numeric data interpolation

Causes the displayed data to be interpolated between discrete data points in the GRIB data file which gives a smoothed appearance with the colours still being in bands. All colours used will appear in the legend.

Smooth colours

Causes the displayed data to be interpolated and then the banding also to be interpolated so the colours appear in smooth transitions. This means that colours used are not in the legend. The advantage of this display is that gradual trends in the data can be seen without the coloured banding distracting from the data.

Wind barbs

Causes “feathers” to appear on the shafts of the wind arrows. Each

½ feather represents 5 knots of wind speed while each full feather represents 10 knots. There can be up to 5 feathers on the shaft which would represent 50 knots of winds. Winds greater than 50 knots are shown with a triangle against the shaft and then the system of ½ and full feathers which allows up to 100 knots of wind to be displayed. Below are the symbols for 5 knots, 15 knots and 65 knots of wind strength.

Wind arrows on Grib grid

The default display places wind arrows so that they fill the display, this often requires values to be interpolated from the values in the GRIB data file. By selecting “Wind arrows on Grib grid” wind arrows will only be displayed where the software model generated values – i.e. no interpolated values will be displayed.

Current arrows on Grib grid

The default display places current arrows so that they fill the display, this often requires values to be interpolated from the values in the GRIB data file. By selecting “Current arrows on Grib grid” current arrows will only be displayed where the software model generated values – i.e. no interpolated values will be displayed.

Show Grib grid

???

The keyboard shortcut is zX

Show colour scale

Causes a palette of colours and a wind strength legend to be displayed. This is related to the display of the wind map (see Data➜Wind Map in the Data menu).

The keyboard shortcut is zY

Show values panel

Causes a table of values to be displayed, these values will change as the cursor moves over the map. pending on the latitude and latitude of the cursor the numbers display will show the values of the GRIB file for the location at the elected time.

The keyboard shortcut is zV

Altitude Menu

The Altitude menu contains options for managing what elevation of data in the GRIB file is displayed ranging from surface level to the highest level.

Sea Level

Values displayed are for sea level (which is consistent world wide).

Surface

Values displayed are for surface level which will vary from below sea level through to higher elevations inland.

Sigma 995

1m above ground

Values displayed are for 1 metre above surface level.

2m above ground

Values displayed are for 2 metres above surface level.

3m above ground

Values displayed are for 3 metres above surface level.

10m above ground

Values displayed are for 10 metres above surface level.

925 hPa (~760 m)

850 hPa (~1460 m)

700 hPa (~3000 m)

500 hPa (~5600 m)

300 hPa (~9200 m)

200 hPa (~11800 m)

Atmosphere

Geopotential altitude 925 hPa

Geopotential altitude 850 hPa

Geopotential altitude 700 hPa

Geopotential altitude 500 hPa

Geopotential altitude 300 hPa

Geopotential altitude 200 hPa

Spacing (m)

A sub-menu of 1,2, 5, 10, 20, 100

Geopotential labels

Earth Menu

The Earth menu contains options for managing how the background maps are displayed. The GRIB data is then displayed over these maps.

Map Quality

Causes a sub-menu of choices:

  • Resolution 1 (25 km)
  • Resolution 2 (5 km)
  • Resolution 3 (1 km)
  • Resolution 4 (200 m)
  • Resolution 5 (100 m)

These options define how accurate the map contours will be, the higher the resolution (i.e. smaller the resolution distance) the more accurate the background map will be. Note that the higher resolution the maps the more memory will be used by zyGrib. zyGrib comes with Resolution 1 (25 km) background maps installed, the increased detail background maps can be downloaded separately from the xyGrib website. Instructions for downloading and installing the higher resolution background maps are on the  zyGrib website.

Projection

Causes a sub-menu of:

  • ZyGrib
  • Mercator
  • Miller
  • Central Cylindric
  • Equal cylindric

As the world has a curved surface it is problematic to display a map of the world on a flat surface. Part of flattening the curved map causes distortion in the map. This geometric problem is unavoidable, rather than a solution there are a number of alternatives which specify how the distortion occurs. The primary goal with any map projection is that the inescapable distortion is consistent and predictable. The distortion is the least in the equatorial regions and greatest at the poles.

zyGrib offers 5 different projections for the background maps. The GRIB data displayed is not changed of affected, only the shape of the background map is affected.

Great circle distance

When measuring distances along the earth’s surface the shortest path is not a straight line but rather what is known as a “Great Circle Route.” When an area on the background map is created in zyGrib by pressing the left mouse button down and dragging to create a rectangle, the selected area is shown as a darkened area on the background map. If the menu option Great Circle Distance (Options➜Great Circle Distance) is selected then a white line from the first point of the rectangle to the last point (which will be diagonal across the darkened region) is shown in white. The Great Circle Distance for that line is shown at the bottom of the display along with the latitude and longitude for the starting and ending corners. The angle of bearing fromthe first to second point is also shown. If the option is not selected then the distance will not appear on the screen and the white line across the darkened are will also not appear.

The distance between any two points onthe background map can be derived by enabling the menu option Great Circle Distance and then using the mouse to drag a region with the initial corner of the rectangle on the first point and the final corner of the rectangle on the second point. This method can be used to determine distance between sailing waypoints.

Longitudes-latitudes grid

Causes a grid of the lines of longitude and latitude to be overlaid on the displayed map and GRIB data.

Boundaries

Causes the boundaries of countries to be displayed. The displayed qualities of these lines can be altered using the Graphical Parameters option in the Options menu (Options➜Graphical Parameters).

Rivers

Causes principal rivers to be displayed. The displayed qualities of these lines can be altered using the Graphical Parameters option in the Options menu (Options➜Graphical Parameters).

Country Names

Causes country names to be displayed. The displayed qualities of the names can be altered using the Fonts option in the Options menu (Options➜Fonts).

Cities names

Cause a sub-menu of:

  • None
  • Level 1 (>= 1000000)
  • Level 2 (>= 100000)
  • Level 3 (>= 10000)
  • Level 4 (>= 1000)
  • Level 5 (>= 0)

Using this menu control is available to display cities of varying populations or no cities at all. The displayed qualities of the names can be altered using the Fonts option in the Options menu (Options➜Fonts).

Point of interest

One of the most powerful features in zyGrib’s management of background charts is the use of Points of Interest (POI). POI allow any point on the earth’s surface to be identified and given a name. Selecting the POI menu option will cause POI to be displayed if they are not displayed and will hide them if they are displayed. POIs can be waypoints for a planned route or any other location that is of interest and which you want to be able to refer to easily in the future.

The keyboard shortcut is zN

Using and Managing Points of Interest

Points of Interest (POI) can be created, deleted and changed at any time. The main purpose for a POI is to mark a point on the earth’s surface which can be returned to easily. Note that the Point of Interest option in the Earth menu (Earth➜Point of interest) must be enabled in order to view POIs. However POIs may be created without being visible (they will disappear once created until they are enable in the Earth menu.

Clicking on a POI will produce a “meteo table”, an excerpt of which is below:

Add Point of Interest

A new POI can be added by right-clicking the background map at the desired location. A dialogue will appear:

By filling in a meaningful name, setting the latitude and longitude, selecting a colour and font style the POI can be configured as needed. Click the OK button to have the POI stored. The POI will be stored with the program on the current computer, moving to another computer requires any POIs to be recreated.

Delete Point of Interest

As with the previous dialogue for adding a POI, once an existing POI is selected by clicking on it the dialogue will appear. Click on the “Delete This POI” button to remove the POI.

View Point of Interest

Click on a POI to view its Meteotable:

A time view of the forecast values for that location (i.e. that POI) will appear. By sliding to the right more forecast values may be viewed. The Options button is described in the next section, the Save button will generate a image file of the table. Use the Close button to close the Meteotable display.

Manage Displayed GRIB Parameters

The GRIB data file parameters that are displayed can be selected by clicking the Option button:

The list of GRIB data file parameters will be listed in the lefthand column. Click on one or more parameters and then the arrow button pointing to the right to move them to the righthand column which is the list of parameters that will be displayed. Note that a parameter may be selected for display which is not in the GRIB data file, in that case the parameter will display with empty values. To stop a parameter from being displayed, click on it and then click the arrow button pointing to the left. The order of parameters can be arranged by dragging values in the righthand column into the desired order. Click the OK button when done and the Meteotable display will be updated, an example is below:

Note that the GRIB data file parameter “Snow” has been selected but as it is not in the data file the display is empty.

Increase map scale

Causes the display to zoom in on the map, the zoom is centred on the middle of the displayed area.

Reduce map scale

Causes the display to zoom out from the map, the zoom is centred on the middle of the displayed area.

Zoom (selected zone or Grib file)

The Zoom function zooms the display to display a specific area:

IF a GRIB data file is loaded then the display will be set to show the GRB file data area as large as possible (with a slight border around the outside).

If an area is currently selected on the display (by selecting a rectangle by dragging the mouse) then that area will be displayed as large as possible (with a slight border around the outside). If a GRIB data file is loaded does not affect the display of a selected area.

If no area is selected and no GRIB file is loaded then the display will not change.

Show whole map

Causes the view of the background map to be zoomed out as much as possible so that the complete world map is shown.

Left, Right, Up, Down

These 4 buttons allow the displayed background map and GRIB data (if any is presently being displayed) to move to the left, right, upwards and downwards. Each click of the button will move the background map ¼ across the screen. Four clicks will move the screen 100% in the relevant direction.

Options Menu

The Options menu contains the options for managing various parameters that can affect different sections of zyGrib – things like choice of units, fonts and colour to display with, even an angle convertor (e.g. degrees, minutes, seconds, radians, grads).

Internet Parameters

???

Angle Converter

Defining areas on the earth’s surface is based on 3-dimensional angular geometry. Different applications such as surveying, engineering, popular maps use different systems to express the angular dimension of an angle. The angle converter allows conversions between any 2 of the following:

  • degrees with minutes & seconds (e.g. 45° 15’ 00’’)
  • degrees with decimal minutes (e.g. 45° 15.25’)
  • decimal degrees (e.g. 45.25416667°)
  • radians (e.g. 0.78983421 rd)
  • grades (e.g. 50.28240741 gr)

Radian and grades will normally be used only by technical users.

Date Selector

This option causes a clickable timescale to appear along the bottom of the main display window. The timescale is an alternative to clicking on the

Forecast Selection Popup or the Previous & Next Forecast Buttons.

Units

zyGrib can display values in any common unit of measure. The units to be used for displaying values can be set for:

  • Wind Speed
  • Current Speed
  • Temperature
  • Distances
  • Coordinates
  • Longitude
  • Latitude
  • Time Zone
  • Geopotential Altitudes
  • Isotherm O°C

Fonts

For ease of use and rapid identification of information types zyGrib allows different fonts to be used for the display of different items. For example City Names can utilize a different font than Isobar Labels or Country Names. Also different sized cities can be in different fonts. In addition to different fonts a different font style can also be selected: regular, bold, italic and bold italic. The fonts can be set for the following:

  • Main font
  • Dates list
  • Menus
  • Status bar
  • Temperature
  • Isobars
  • Pressure high & low
  • Cities (level 1) (population more than 1,000,000)
  • Cities (level 2) (population more than 100,000)
  • Cities (level 3) (population more than 10,000)
  • Cities (level 4) (population more than 1,000)
  • Cities(level 5) (population below 1,000)
  • Country names

Depending on the scale of the display map there can be a lot of information displayed and selecting fonts can help to differentiate different types of information.

Graphical Parameters

For ease of use and rapid identification of information types zyGrib allows different colours and line thicknesses to be used for the display of different items. For example the Sea Colour can utilize a different colour than the land Colour and the colours can be chosen to suit the user’s preferences. Different users can select different colours.  Line thickness can be set for drawn entities such as boundaries and rivers. This allows what the user judges to be more important to be more easily visible.

The colours can be set for the following:

  • Background colour
  • Sea colour
  • Land colour

The line thickness can be set for the following:

  • Sea border line
  • Boundaries
  • Rivers
  • Isobars
  • Isotherm O°C

Additionally Cloud Cover can be displayed as White or Black for percentage cloud cover.

Language

The language that zyGrib uses to display information and interact with the user can be set to one of the following:

  • Arabic
  • German
  • English
  • Spanish
  • French
  • Italian
  • Dutch
  • Russian
  • Czech

More languages may be added in the future.

Help Menu

The Help menu causes the system-specific help files to be displayed. The exact format of the help files will depend on the system. At present zyGrib does not have any application specific help facility.

Glossary of GRIB Data

zyGrib uses 3 different sources for GRIB data files, each of which defines a different set of data fields:

  • NOAA – GFS standard model
  • NOAA – GFS altitude model
  • FNMOC – WW3 wave model

The fields for each of the 3 GRIB file formats are defined below.

NOAA – GFS Standard model data fields

  • Wind (10m)
  • Mean sea level pressure
  • Temperature (2m)
  • Temperature min (2 m)
  • Temperature max (2 m)
  • Isotherm 0 degrees C
  • CAPE (surface)
  • Wind gust (surface)
  • Cloud cover (total)
  • Relative humidity (2 m)
  • Total precipitation
  • Snow (snowfall possible)
  • Snow (depth)
  • Frozen rain (rainfall possible)

NOAA – GFS Altitude model data fields

  • 925 hPa
  • 850 hPa
  • 700 hPa
  • 500 hPa
  • 300 hPa
  • 200 hPa

FNMOC – WW3 Waves model data fields

  • Significant height
  • Maximum waves
  • Swell
  • Wind waves
  • Primary waves
  • Secondary waves
  • Whitecap probability

Glossary

  • Altitude – 200 hPa (~11800 m), 300 hPa (~9200 m), 500 hPa (~5600 m), 700 hPa (~3000 m), 850 hPa (~1460 m), 925 hPa (~760 m)
  • Boundaries
  • Current arrows
  • Current arrows on Grib grid
  • Current map
  • Fast interpolation
  • Gap temperature-dew point
  • Geopotential Altitude – Geopotential altitude 200 hPa, Geopotential altitude 300 hPa, Geopotential altitude 500 hPa, Geopotential altitude 700 hPa, Geopotential altitude 850 hPa, Geopotential altitude 925 hPa
  • Great circle distance
  • GRIB
  • GRIB Grid
  • IAC fleetcode NOAA
  • Isobar labels
  • Isobars (MSL)
  • Isobars spacing
  • Isotherms (altitude 2m)
  • Isotherms (temperature o C)
  • Longitudes-latitudes grid
  • Map Projection – ZyGrib, Mercator, Miller, Central Cylindric, Equal cylindric
  • Meteoblue
  • Point of interest
  • Precipitation map
  • Relative humidity map
  • Rivers
  • Sigma 995
  • Temperature map
  • Wind arrows
  • Wind arrows on Grib grid
  • Wind barbs
  • Wind map
  • Wind Speed
  • Current Speed
  • Temperature
  • Distances
  • Coordinates
  • Longitude
  • Latitude
  • Time Zone
  • Geopotential Altitudes
  • Isotherm O°C