Lesson 2 - Decoding the Forecast

Key Takeaways:

Synoptic Weather Charts:

  • Show highs (H), lows (L), isobars, and fronts.
  • Tightly packed isobars = strong winds.
  • Wind flows clockwise around highs and counter-clockwise around lows in the Northern Hemisphere.

GRIB Files:

  • Show forecast data (wind, pressure, rain, etc.) in visual format.
  • Need interpretation—no symbols or explanations.
  • Available via apps like Windy and PredictWind.

Best Forecast Tools:

  • Windy: Visual overlays, multiple models.
  • PredictWind: GRIBs, routing, passage planning.
  • Navionics + Weather: Combines navigation and forecast in one.
  • NAVTEX/VHF: Text-based but reliable when offline.

Forecast Models to Know:

  • GFS: Global, free, good for general trends.
  • ECMWF: Higher accuracy, especially in Europe.
  • ICON/AROME: High-resolution, good for local detail.

Strategy:

  • Always compare multiple sources.
  • Update forecasts regularly, especially before departure and en route.
  • Trust your observations alongside data.