- V8V2222 -
HF/SSB radio email and voice services

GRIB synoptic weather charts

GRIB charts provide up-to-date synoptic weather charts via HF/SSB radio email. GRIB chart file attachments are small size and downloadable via either of BRUNEI BAY RADIO's email services; BBRemail or SailMail. They are read and displayed by software incorporated within AirMail, the on-board HF/SSB radio email software.

The displayed file gives a comprehensive synoptic weather chart, including wind barbs showing wind speed and strength. This feature is particularly useful in low latitudes where isobars are often far apart and small changes in pressure create large changes in the wind. The most recent versions of AirMail also include wave height information displayed as coloured shading, and coloured wind speed arrows based on the wind speed. 
 

This GRIB chart service is a major advance on traditional HF/SSB radio weather faxes because:

1. Vessels can request and collect the GRIB file when on-board duties and HF/SSB propagation permit.

2. GRIB charts an display the predicted synoptic situation up to 10 days in advance.

3. Vessels select the forecast area, level of detail and future predictions that suits their requirements.

4. SPOT forecasts are available which give a tabulated list of predicted  weather factors, such as barometric pressure, wind speed and direction, rainfall etc. The wave height and direction information is especially useful for surf charter vessels, or choosing a comfortable anchorage.

5. The desired area for a GRIB chart is chosen using pages incorporated within the on-board AirMail software. The correctly formatted GRIB request email is generated by the software and automatically e-mailed to the server when the next transfer connection is established. The computer gathers the requested information from the NOAA weather database and e-mails the data back as an attached GRIB file.

6. The on-board software's GRIB selection page includes the ability to enter course and speed, and request a subscription for up to 14 days. The shore server automatically sends predictions each 12 or 24 hours (as requested) and the area displayed moves forward to match the course and speed. 

7. The received GRIB files area displayed on-board by AirMail with a background of the major landforms. Some navigation software will take these GRIB files and overlay their weather details on electronic charts.  

8. The software and GRIB chart service is included with subscriptions to SailMail and BBRemail.

Obtaining GRIB weather charts via HF/SSB radio has become far simpler and more reliable than weather faxes because:

1. Many free-to-air weather fax services have closed, become unreliable or the frequency and power of transmission has reduced, since the introduction of GMDSS. 

2. There is no need to study transmission schedules and sit by the radio at a fixed time.

3. GRIB charts can be received with other HF/SSB radio email messages when propagation and onboard demands permit.

SailMail and BBRemail allow GRIB file attachments up to 30kB (Pactor 3).   The more future "pictures" requested and the larger the geographic area, the bigger the file.

How to get the software:   

The latest versions of AirMail integrate all the needed software to select, request and display GRIB charts, the the great colour displays of wave and wind information. .

GRIB chart database:

The chart information comes from the very extensive  NOAA (the USA's National Oceanic and Atmospheric Administration) database. This data includes input from thousands of stationary wave buoys around the world , satellite images, weather radars and more. It also includes the actual weather data sent by vessels at seas; including yachts that use the free  YOTREPS position report service. 

The same NOAA data is also used by Navies, commercial forecasting and routing services, merchant ships etc.

Making it work:

1. In the Airmail software, select Windows - Catalogs. Click (left mouse button twice) on the Catalog folder icon to expand it to Saildocs, and click (left mouse button twice) on that to expand it to Grib Files. Click (left mouse button once) on that folder and bingo, you get a map of the world. (Having done this expansion of folders/directories once, the system remembers, so next time you click on Windows - Catalogs, it immediately displays the map.)

2. Move the mouse pointer over the map. Press and hold the left button at the point you want to be the top-left corner of the area of land/sea you want the grib file to cover. Move the pointer across and down to the bottom right corner of the area.  There will be a blue shaded box created to show you the area.  

3. Look at the Grib Parameters section. Check the approx file size - make sure it's less than 30 kB (Pactor 3 users). 

4. Look at the Request from Saildocs section. You can choose one only send, or set up a regular send. REMEMBER, the NOAA information base is MASSIVE and it can take up to 6 hours to recalculate the new information to create updated predictions. The source database is updated twice daily. So the new information gathered from around the world at the 0000 UTC update may not be available for SailDocs to access till about 0600 UTC. Similarly the new information gathered at the 1200 UTC update may not be available till about 1800 UTC. If you request a GRIB chart at say 0500 or 1700 you may get a chart based on old information. It’s best to request at about 0700 to 0800 and 1900 to 2000, to get updated predictions based on the latest information. 

5. The standard GRIB chart request includes the predicted isobars and wind speed/direction for 24 hours, 48 hours, and 72 hours after the latest update (ie: either 0000 or 12000 utc). This gives a useful view into the future. BUT, the NOAA database may not always include local storms (including localised tropical storms/cyclones/typhoons, or sudden fronts), especially when they are just starting. So it's also important to access local storm warning information via some other method. 

6. On some extremely uncommon occasions, the NOAA system has a problem and the data is not available, or not completely available. 

Important note regarding standards used in all meteorological publications; including METAREA forecasts and GRIB charts. These standards were highlighted in the 1998 Sydney to Hobart race when yachts faced unexpected extreme conditions: 

1. Wind speed refers to the average speed over a 10-minute period. Gusts may be up to 40 percent stronger than the average speed.  (Wind speeds figures are recorded/estimated at 10 metres above the surface.)

2. Wave and swell height information is based on the significant wave heights standard. This is the average of the highest one third of waves. The likely maximum wave height can be up to twice the significant wave height.

Back to top

Call-sign: V8V2222    SelCall ID: 2222

For enquiries click here to email BRUNEI BAY RADIO

Brunei Bay Radio 
PO Box 2234
Bandar Seri Begawan  BS8674
BRUNEI DARUSSALAM

Phn: +673 2 262676     Fax: +673 2 262675

Unit 105, 1st Floor, PGGMB Building
Jalan Sungai Kianggeh
Bandar Seri Begawan BS8111
BRUNEI DARUSSALAM
 

Copyright © 1999 - 2010, Intrepid Management Services Sdn Bhd