Getting Weather Forecasts
Submitted by Frank Singleton on Sat, 02/01/2010 - 12:31
Introduction
Long gone are the days when we had only the shipping forecast on BBC Long wave radio or its foreign equivalents. We now have a bewildering array of forecasts from various sources and by a number of different routes. Broadly speaking, these are:
Marine VHF and MF/SSB, NAVTEX and INMARSAT-C, HF/Single Sideband radio, Public service radio, Internet, Telephone, Marina notice boards, Media, Telephone
There is considerable overlap in that the same service can be obtained by more than one route with the Internet providing the widest range. Taking each in turn -
Under the Global Marine Distress and Safety System (GMDSS), Marine Rescue Co-ordination Centres (MRCC) of most European countries broadcast inshore or coastal forecasts at scheduled times on VHF and/or MF. In all cases the forecasts are produced by the relevant National Weather Service (NWS.) Forecasts are always, at least, for the next 24 hours and usually have an outlook. The period of outlook varies from country to country.
Being produced by forecasters who know the area and have the best data available, these should always be used. Some countries broadcast in English as well as their national language. When this is not the case, it is always worthwhile making the effort to learn enough of the terminology. Ease of use varies with the country; the French are particularly good, others eg the Spanish are less so.
NAVTEX and INMARSAT-C
NAVTEX is the principal method for dissemination of Marine Safety Information; it is a system for broadcasting text over radio.This requires a dedicated, fairly low cost, receiver eg NASA. Furuno, McMurdo.
On NAVTEX 518 kHz, MRCCs broadcast texts of forecasts for "Sea Areas" as used in such as the BBC Shipping forecast ("Bulletins au large" in French.) These forecasts are always in English and, again, produced by the NWS. They should cover 24 hours with a brief 24 hour outlook although not all countries conform. There are usually two forecasts a day.
The UK, alone, produces extended range forecasts for 3 to 5 days ahead on this frequency.
NAVTEX 490 kHz is used for national purposes. Mostly, this is for national language versions of the 518 kHz broadcasts. An exception is the UK which broadcasts inshore forecasts and some coastal actual reports.
INMARSAT-C is, in some senses, an open ocean version of NAVTEX. The areas used in the forecast may be considerably larger than on NAVTEX ("Bulletins au grand large" in French.).
HF/Single Side-Band Radio (SSB)
SSB radio is used in three ways. 
- First there are voice broadcasts of forecasts. These will usually be the same texts as on NAVTEX or INMARSAT-C.
- Secondly, there are charts broadcast on Radiofacsimile by the German Weather service (DWD) or by the Royal Navy (Northwood). These need a computer interfaced with the radio.
- Thirdly, there are forecasts in text on Radioteletype from the DWD. Some of these are inshore forecasts around Germany, some are sea area forecasts. The most useful servive is ofwind, sea state and sometimes weather at a few grid points from the German weather prediction model. Thes are for up to five days ahead and are useful for planning purposes..
To receive Radiofacsimile or RTTY requires a radio linked to a computer and decoding software eg Mscan Meteo, JVComm32, SEATTY. For RTTY, only, the NASA Weatherman is an excellent bit of kit.
Details of Radiofacsimile or RTTY transmissions elsewhere can be found in Admiralty publications or on the NOAA website (a PDF file).
Public service radio on MW and LW.
Few will not be familiar with the BBC Shipping forecast on Radio 4. Other countries have similar broadcasts to these and to the UK general or regional forecasts. Broadcasts from German radio stations are commendably good but, in general, these can be difficult to follow unless you are reasonably fluent or well practiced.
This is an Aladdin's cave of weather information available in Internet cafés, via WiFi, cell phone, satellite phone and, in a limited sense, over marine HF and amateur radio. For several reasons, it is well worth making the effort to be able to use the service whether in harbour, on a buoy or at anchor and, even when at sea if at all possible. Services available fall into four main categories.
- As a back-up to forecasts broadcast on VHF, NAVTEX, INMARSAT-C, HF/SSB radio.
- As a source of GRIB* forecasts, these are usually free and are the output direct from the US Global Forecast System. Some private services, usually on repayment offer more detailed forecasts. These will take more resources to download but are not necessarily appreciably better than the GFS.
- Email for those with bandwidth restrictions. This is an effective way of getting GRIB forecasts and can be used for texts of forecasts on web pages.
- As a source of weather charts.
* NOTE Gridded Information In Binary files are output direct from a computer forecast. Using dedicated software they can be translated into charts of vector winds and other parameters.The example here uses SailDocs Viewfax software; there are several others.
In addition, there are a number of other services such as weatheronline.com, XCWeather.com, Windguru.com, Buoyweather.com. These may look good but are, almost inevitably, simply interpolations from GRIB sources.
There are two types of telephone service, recorded messages in voice or by acsimile and individual briefings. The first is unlikely to offer more than is freely available from other sources eg radio broadcast or Internet but may be more convenient if rather costly. The second can be useful but relatively expensive.
The value depends upon who has produced the forecast and the diligence of the marina staff in updating. Sometimes, forecasts are transcripts of VHF or NAVTEX broadcasts. Sometimes they are forecasts when there has been some human input eg the first 24 hours of a Met Office Marinecall forecast. In both cases these will have the virtues of those broadcasts. In some cases, they will be taken from forecasts produced entirely automatically. These will be generally inferior. Marinas, especially in France and Italy tend to use these latter partly because they are cheaper and they may be visually more attractive. Whatever the source, most important is to check the date/time of issue. It is not unknown for forecasts to be days old or even weeks old.
This is generally a last resort. Remember that morning newspapers go to bed the previous day, sometimes quite early. Forecasts, inevitably, will be old. TV and radio forecasts are more likely to be up to date but are often aimed at the general land based public.
Telephone
Generally, especially when produced by the National Met Service, these will be very similar to the GMDSS information for the first 24 hours or so. They may inclue extrao outlook information. Sometimes produced by private sector companies which may or may not use the "official" texts.
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