Weather Forecasts 

Checking the weather forecast before putting to sea is one of our obligations under SOLAS V. It is advisable to cross reference a number of weather sources.

It is prudent to always look at more than one forecast, as there is no one stop shop or short cut to building the picture, which enables you to decide whether or not to go out boating and to remember that a forecast is only an indication of what is likely to happen. The closer a forecast is issued to the time it is covering, the more accurate it is likely to be. Be aware that forecasting beyond three days in advance is still considered an inexact science, so treat the last 2 days of any 5 day forecast with caution.

If you look hard enough, you will usually be able to find a web-site which is giving the forecast you want. To build the full picture however, you will need to consider what the forecasters are saying, what the actual weather conditions are and what has already happened.

Forecasts are derived from their source data in different ways. Satellite imagery and weather radar provide a forecaster with real time data for forecasting cloud and rain, but this is not the case with wind.

Actual wind data is only available for specific points, where there is a weather station to collect the data. Wind forecasts are therefore often made using computers which are calculating the figures based on the trend between two known points. These forecasts will give no consideration to the effects a headland, or sea breeze may have on the local conditions and therefore need to be interpreted by the user.

Many of the web-sites to which links are given, derive their forecasts in this computerised way. Whilst pleasing to the eye, easy to read, and offering data for your specific location, they should be used with caution. Be aware of the source of any weather forecast you are using, and treat pin point forecasts with caution, backing them up with information on actual conditions from sources such as the Met Office latest marine observations, help to identify the likelihood of local variations.

Understanding the underlying patterns that drive the weather in your part of the world allows you to understand what is happening when forecasts prove inaccurate or unavailable, and make you much less likely to be caught out. This is why an understanding of weather is a core seamanship skill included in the Yachtmaster syllabus.

A 72 hour weather forecast, tides for 30 days ahead, the inshore waters and the shipping forecast are provided on this site.

Shipping Forecast

The Shipping forecast is broadcast on Navtex 518kHz twice a day and by the BBC four times a day on Radio 4. The content of the Radio 4 transmission and the frequency bands used, vary depending on the time of the broadcast:  

 

Time
(LT - Local Time)
0048 (1) 0520 1201     1754 
Frequency
LW: 198kHZ
(1515m)
FM: 92.4-94.6
LW
FM (2)
LW
FM (2)
LW     LW (3)
FM (4)
Gale Warnings
Summary
Yes Yes Yes Yes 
The General
Synopsis
Yes Yes Yes Yes 
24hr Sea Area Forecasts Yes  Yes  Yes  Yes 
Coastal Station Reports   Yes (5) Yes (6) No  No 
17 are 24 Hour Inshore Waters  Yes  Yes (7)  No  No 

 

(1) Also includes sea area Trafalgar (the area to the south of FitzRoy)
(2) There may be no broadcast on FM during special news programming events
(3) May run up to 1 minute later in the event of special LW programming
(4) Saturday and Sunday only
(5) Long list (approx 23 stations)
(6) Short list (approx 12 stations) 
(7) Concludes with the UK outlook for the next 24 hrs

GALE WARNINGS are issued by the Met Office when winds in any part of a sea area are expected to reach Force 8 or above and / or if gusts of 43 knots or more are anticipated (excluding gusts in thunderstorms). Warnings are broadcast on Radio 4 at the first available programme junction after receipt by the BBC. If this junction does not coincide with a news bulletin, the warning is repeated after the next scheduled bulletin. They are also broadcast on VHF on receipt by the Coastguard Maritime Rescue Co-ordinations Centres (MRCC). Gale warnings are valid for 24 hours unless cancelled. If still in force a "gale continuing" message will be issued. If the forecasters are unsure about the period from 12 to 24 hours the formula "perhaps gale 8 later" can be used in the forecast but no gale warning issued.

STRONG WIND WARNINGS are issued if winds of force 6 or more are expected that have not already been included n the current inshore waters forecast.

COASTAL STATION REPORTS contain actual weather conditions such as wind speed, wind direction, visibility, pressure etc. for specific locations around the country.

Metmaps

Produced by the RYA and Royal Meteorological Society, Met maps are blank maps and tables you can use to record the information from the shipping forecast and create your own synoptic chart. Available in the downloads area of this page, they will be familiar to those who have studied for shorebased schemes in the Yachtmaster syllabus. They can be useful to have aboard on a passage as the order in which the fields are arranged on the sheet correlates to the order in which the information comes out of your radio.

 

 

The RYA can accept no responsibility for the content, accuracy or reliability of the third-party web-sites listed.  

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Article Published: July 17, 2012 15:29

 

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