Most weather forecasts present a general picture of what to expect in your area over a given period of time. We rely on such forecasts to provide basic information, but the actual weather and sea conditions we experience don’t always tally with the general view.
It is not necessarily the forecasters’ fault if the conditions we experience don’t tally with the forecast, as it is the local tides, topography and sea breezes that interact with the basic picture and give rise to the actual conditions we experience out on the water.
Before deciding whether it is safe for your vessel and crew to go afloat, it is a good idea to study all available forecasts. A major part of making that decision is done through observation and being able to assess where in the forecast weather pattern you actually lie. Has that predicted front passed through yet, what are the clouds telling you, what is the wind strength, how has it changed through the last few hours and what is the barometer doing? Study your charts and estimate when and where you can expect wind against tide. Are the elements going to clash severely and if so when is this going to happen? Will you need to avoid being in that area or will the conditions be manageable? Below are some weather forecasting tips to help you reach your decision.
Sources of weather forecasts
It is a good idea to gather as much reliable information as you can. Sources of weather forecasts include:
- National meteorological offices.
- Internet – good source for GRIB forecasts (Gridded Information in Binary files),eg UGrib, weather charts, web services eg Windguru also back-up to VHF, NAVTEX, INMARSAT-C and SSB radio.
- MSI (Marine Safety Information) broadcasts on VHF and SSB radio.
- Public service broadcasts on radio and tv.
- NAVTEX, Weatherfax and INMARSAT-C.
- Harbour and marina offices.
- Local knowledge -talking to locals in the know, for example fishermen, can help you decide.
With information gathered, compare a number of pressure charts to see how the weather patterns have been forecast to evolve in your area over a number of days. This will help you to judge when fronts will pass through, what local conditions will be as a result and how this tallies with your planned departure and route plan.
Before you go
Before departure, download forecasts to cover the anticipated length of your passage. Be prepared to delay your departure or change your destination if the weather forecast is unfavourable. Once committed to going, ensure that you have the means to get regular, reliable weather forecasts if you are at sea for any length of time. This will allow you to change your plans and head for a safe haven if the forecast is for stormy weather, and to take advantage of detailed weather information when planning your route.
- Study the Beaufort scale and use it to judge wind strengths.
- Practice how to interpret barometric pressure charts.
- The barometer is arguably the most useful forecasting tool. Keep a note in the log to monitor change in barometric pressure.
- Learn how to observe cloud formations to forecast the weather.