The web companion to The Sailor's Weather Atlas: read the wind off the book's pressure charts, work out waves and apparent wind, practise naming clouds, revise with flashcards and the quiz, keep a barometer log, and look at live model data for any place.
Pressure charts
The scenes from the book. Tap or click anywhere on the chart to read the computed surface wind and pressure there; move the time slider to watch the pattern move.
Tap the chart to read the wind at a place.
The winds are the book's engine: geostrophic wind from the isobar spacing, corrected for curvature, then slowed and turned towards low pressure by friction (70% and 15° over the sea). Hills, headlands and sea breezes are not modelled.
Calculators
The book's formulas, for quick answers on deck. Every result is a model value; use it to judge the size of things, not as a forecast.
Cloud trainer
Name the cloud. The pictures are the book's drawings of the ten genera; each comes in three versions.
The ten genera
Flashcards
The book's chapter flashcards with spaced repetition. A card you know moves up a box and comes back later; a card you miss goes back to box 1.
Chapters · all chapters
Keys: Space shows the answer, K means you knew it, M means you missed it. Progress is saved in this browser.
Quiz
The end-of-chapter questions. Answer in your head (or out loud), then check.
Barometer log
Log the barometer (and the wind) on passage. The log gives the three-hour tendency in the shipping forecast's words and draws the trace. Entries stay in this browser.
Live model data
Hourly pressure, wind, gusts and waves from weather models for any place, fetched from Open-Meteo. This is raw model output for your own study: it is not an official forecast and carries no warnings.
Weather data by Open-Meteo.com (CC BY 4.0). Your position is sent only to Open-Meteo, only when you press Fetch.
RYA syllabus
Every weather item in the RYA Day Skipper, Coastal Skipper/Yachtmaster Offshore and Yachtmaster Ocean theory syllabi, with the chapters that cover it. Tick items you are confident about. The RYA revises its syllabi: check the current version before a course or exam.