Weather & Tides

Weather

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 look at more than one forecast. There is no one stop shop or short cut to building the picture which enables you to decide whether or not to go boating. Remember that a forecast is only an indication of what is likely to happen.

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

Nowadays 5 day forecasts are reasonably accurate but treat the last 2 days of any 5 day forecast with caution. Check the forecast regularly to assess the forecasters' certainty in their predictions. Weather systems do not always develop in the way that the computer models calculate.

Source data

Forecasts are derived from source data in different ways. The starting point is from numercial weather prediction models run by computers. The forecaster then uses other data such as satellite imagery and weather radar and actual measurements to provide their best prediction i.e. the forecast.

Some online forecasts purely display the computer generated information in an easy to read web page format, however they should be treated with caution.  Despite claiming accurate forecasts for specific locations such as a headland, they can not give consideration to the effects of that headland, or sea breezes on the local conditions; these need to be considered by the user.

Many of the websites 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, you should back these up with sources such as the Met Office latest marine observations, to help 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.

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:  

* It is sometimes necessary for the BBC to alter the times. Where changes are notified to the Maritime and Coastguard Agency (MCA) in advance they are generally published at https://www.gov.uk/government/publications/maritime-safety-information-leaflet.

(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 in the past by the RYA and Royal Meteorological Society, Metmaps are blank maps and tables you can use to record the information from the shipping forecast and create your own synoptic chart.  This 2003 version of Metmaps has been retained as, although out of date, some people still find it useful. 

Weather related websites

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

AccuWeather: https://www.accuweather.com/
MCA MSI leaflet:https://www.gov.uk/government/publications/maritime-safety-information-leaflet
Met Office: https://www.metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea
Met Office surface pressure charts: https://www.metoffice.gov.uk/weather/maps-and-charts/surface-pressure/
NASA MSFC Earth Science Office: https://weather.msfc.nasa.gov/
National Data Buoy Center: https://www.ndbc.noaa.gov/
Oceanography and Marine Meteorology: http://weather.gmdss.org/
Frank Singleton: http://weather.mailasail.com/Franks-Weather/Home
Theyr.com: https://www.theyr.com/
WaveNet: https://www.cefas.co.uk/data-and-publications/wavenet/
Weather Online: https://www.weatheronline.co.uk/
Windfinder: https://www.windfinder.com/
Windguru: https://www.windguru.cz/
XCWeather: https://www.xcweather.co.uk/

Tides & Tidal Predictions

Essential to passage planning, one of your obligations under the SOLAS V regulations, tidal predictions allow you to establish the best time to transit certain parts of our coastline.

Sites such as the UKHO's Easytide (after you have completed a simple registration procedure) offer access to free worldwide tidal predictions for up to 7 days ahead.

Please note: When using online tide tables, be aware that different website publishers adhere to different conventions in adjusting for seasonal time differences.

Most printed UK tide tables list times throughout the year as UT (Greenwich Mean Time), but some online tables automatically adjust to BST for the relevant summer months and some do not. The time difference applied is often shown in the top line of the tidal data.

Tides related websites

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

Tides.INFO: https://www.tides.info/
UKHO EasyTide: http://www.ukho.gov.uk/EasyTide/EasyTide/index.aspx

Related page on the RYA website

Maritime Safety Information (MSI)