Module 13 - Meteorology
Sketching a Synoptic Chart
What you will learn
Turn a general synopsis and sea-area forecasts into a time-stamped working sketch without pretending to reconstruct an official analysis.
A rough sketch helps spatial reasoning: place named pressure centres and movement, mark reported fronts or troughs, then attach area forecasts to the route.
Start with the issue and valid time. Plot pressure centres only where the synopsis provides a position, pressure or named location, and show the stated movement. Add fronts or troughs only when they are given or visible on a current authoritative chart.
Place the relevant sea areas and route relative to those systems. Add the forecast wind sequence, weather and visibility for the areas that matter. This is enough to expose when an increasing wind or front is likely to meet an exposed leg.
Do not manufacture precise isobars from a few area forecasts. An official surface-pressure analysis or forecast contains more observations and modelling than a voice bulletin. The learner sketch is a decision aid and memory model, not a navigational or meteorological replacement.
| Sketch item | Record | Boundary |
|---|---|---|
| Pressure centre | Position, pressure and movement | Only what the synopsis supplies |
| Front or trough | Type and stated movement | Do not invent detail |
| Sea area | Wind, weather, visibility and timing | Area forecast is not point precision |
| Route | Exposed leg, harbour and alternative | Keep passage decisions visible |
Build a bounded weather sketch
The synopsis reports ‘Low 988, 58 north 12 west, moving northeast, expected 55 north 5 west 995 by 1800’; the route lies in sea areas east of the track.
1. Write the time
Record the forecast issue and the 1800 expected position time.
2. Plot both centres
Mark the reported and expected positions, pressures and northeast movement.
3. Place route and areas
Show the route relative to the low’s track and the applicable sea areas.
4. Add area sequence
Write the forecast wind, weather and visibility beside the relevant leg.
Sense check: The centre pressure rises from 988 to 995 hPa in this synopsis, but the route risk still depends on track, gradient, fronts and local timing.
Common mistake or limitation
- Drawing a precise chart without recording issue and valid times.
- Inventing exact fronts or isobars not supplied by the synopsis or authoritative chart.
- Sketching the system but not relating its movement to the route timetable and alternatives.
Recap
- Time-stamp the sketch and plot only supported system detail.
- Relate pressure-centre movement and area forecasts to the route timetable.
- A learner sketch supports reasoning; it does not recreate the official chart.
Optional quick check
Section 9 of 13
What should be established first on a synopsis sketch?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Meteorology
This public lesson is part of Revision Module 13. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.