How to Gather and Understand Sea Weather Forecasts before Setting Sail
New York (USA), October 28, 2012
Understanding the Weather Forecasting for Sailing
It is very important to gather and understand weather forecasts before setting sail. You should collect information from different sources and analyze them to get a clear picture. You should not confine to a single forecast to decide whether to set sail.
Informal weather predictions have been prevalent for long. With development of science and technology, weather forecasts have become more accurate and systematic since the nineteenth century. Weather forecasts are made by collecting quantitative data about the present state of atmosphere.
Scientific analysis of this data projects how the atmosphere will evolve or change over specified period. Current weather, barometric readings, sky, and wind conditions together help build a weather forecast model.
Weather Forecast Sources
Weather forecasts are available from different sources like satellite recordings, websites, meteorological stations, and others. VHF radio available through Coastguard Maritime Rescue Coordination Centers (MRCC), Radio 4 broadcasts, National Weather Service, broadcast agencies like The Weather Network, Weather Channel, AccuWeather, and other news bulletins provide necessary weather forecasts. Coastal stations provide reports of actual weather like wind direction, wind speed, pressure, visibility, and similar factors for specific locations in a country.
Weather radar and satellite imagery provide forecasts for rain and clouds. Wind data are available only from specific weather stations that collect data regarding wind movements. Wind forecasts depend on computerized specific trends between two accepted and recognized points. However, these forecasts do not mention effects of winds on land or sea breezes and have to be interpreted properly. You should follow any specific weather forecast implicitly. Always check and compare different forecasts with actual weather, latest observations, and data available from local met office.
Forecast is only an indication of what the weather could be over a period. Weather forecasts for beyond three days should be considered cautiously. Weather can change drastically over three days. Immediate forecasts are more reliable. After availing forecasts, you should be able to decipher them to understand what is actually predicted. You should have a clear understanding of core seamanship skills.
Meteorological offices issue gale warnings if sea winds are expected to reach or cross Force 8 or above. Similarly, if gusts of 43 knots or more are expected other than gusts in thunderstorms, warnings are issued to those venturing out in sea. These warnings remain valid for twenty-four hours unless canceled.
If winds continue to blow with same force, ‘gale continuing’ message is issued. If there is any doubt about wind force, ‘perhaps gale 8 later’ forecast is issued. This is not a gale warning. If wind force is 6 or expected to be more, strong wind warnings are issued.
Analyzing Weather Forecasts
Before setting sail, weather forecasters have to disseminate available meteorological data. This data is normally available in GRIB format. It provides information about past weather of particular area, prediction of weather in immediate future, and sea state data. You can understand all implications of available data in GRIB format by using navigation and route planning software.
GRIB data is available in binary format. GRIBs contain small subset of surface data like wind speed, wind direction, wave strength, wave heights, surface pressure, and direction. You can receive further concentrated format by analyzing available data for specific location, rather around position of your yacht. GRIB data can be transmitted over single sideband radios and satellite phones.
The simplest technique is to predict next day’s weather depending on today’s weather conditions. This technique remains valid only if weather follows a steady pattern like summer season of the tropics. Another technique is to use barometers to study and understand barometric pressure. If pressure changes are vast, weather changes drastically. A sharp drop in pressure indicates formation of a low-pressure with strong possibility of rains. An increase in pressure indicates clearer skies.
Weather forecasting within the next six hours is nowcasting. This weather prediction technique is very accurate indicating specific characteristics like thunderstorms, showers, wind speeds, and others. Analog technique implements specific weather event of the past to predict weather forecasts for the future. Ensemble forecast involves use of different forecasts to understand possible errors and thereby assess what the weather could be in the future.
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