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Weather ~to~ Sail

• To provide training of the highest quality
• To make a significant contribution to personal safety at sea
• To assist sailors in making the best use of weather and weather windows
• To study micro-scale weather as it affects small craft and passage planning
• To extend knowledge at all levels
• To update knowledge of sources of information
• To emphasise in particular the prediction of wind
• To emphasise the practical application of knowledge

New technology masks the importance of personal skills in prediction. Forecasts sometimes differ, predicted progress of weather systems vary and selecting from the wealth of information is difficult. Technology can go wrong (usually at crucial times!) and no public forecasts predict all events at the mesoscale - the area in which most of us do our sailing.

Learning Material

The course includes: a fully illustrated learning; laminated identification cards of weather features for on deck predictions; a pre-course pack covering fundamental principles, illustrations and recommended reading.

Detailed Course Content

The foundations of the course are the topics set out in the RYA Weather Handbook.

The principles of basic theory

• Global circulation
• Weather systems
• Front formations (cold, warm and occluded) & their development

Common weather features

• Cloud types and weather
• Stable & unstable air
• Convections: gust fronts, updrafts, lulls
• Squall line structure
• Thunderstorm structure
• Types of fog, sea fret, formation and dispersal

Specific features

• Crosswinds
• Sea and land breezes
• Anabatic and katabatic winds
• Wind and local geographic features
• Coastal convergence
• Relationship between wind and waves
• Wave structure: wind, swell, strength, fetch
• Fetch & changes in direction & speed

Weather processes in more detail

• Condensation levels
• Upper air conveyor belts
• Wind, air density and pressure systems
• Coriolis effect
• Pressure gradients
• Geostrophic wind
• Surface wind

Weather forecasting:

• Satellite imagery:
• Meteosat: infra red and visible
• Water vapour imagery
• Surface analysis charts – pressure, temperature, humidity
• Synoptic charts (weather maps)

Local and meso-scale applications:

• Buy Ballots law
• Isobars & wind speed calculation at geostrophic and surface level
• Calculating and forecasting wave height
• Swell propagation and calculation
• ‘On deck’ prediction from readily observable weather features:
• Wind change, crosswinds rules
• Clouds
• Pressure changes, standard & skipper’s scale
• Temperature

Avoidance

• Use of radar for identifying immanent weather
• Bad weather and tropical storm avoidance

Wider horizons

• Global air masses: origins, definitions and behaviour
• Mediterranean weather: the ten winds, typical sea states

Different sources of weather information & recommended websites, including GRIB files

Advanced skills

• Where there is sufficient demand the last session of the day may be split into two groups, with one covering:
• Tephigrams,
• Normands theorem
• Satellite interpretation
• Weather model characteristics
• Surface analysis & Constructing weather charts & forecasts from raw data
• And the other group holding a plenary session, where there will be an opportunity for revision or further explanations of the day’s topics, or for areas of individual interest or particular difficulty to be raised.