Meteorology and weather interpretation
Meteorology questions are about reading the sky and the glass, not reciting a forecast: what is coming, how fast, and where you should be when it arrives.
Pressure and wind
Wind flows from high to low pressure, deflected to the right in the northern hemisphere. Closely spaced isobars mean strong wind. A fall of more than about 1 hPa per hour signals an approaching front or low; a rapid rise after a squall line means the worst is passing.
Beaufort, roughly
F0–1 calm to light air (0–3 kn), F2–3 light to gentle breeze (4–10 kn), F4–5 moderate to fresh (11–21 kn) - whitecaps, and reefing time for small boats; F6 strong (22–27 kn); F7 near gale (28–33 kn) - spray, difficult on open water; F8 and above gale. On lakes the sea builds faster than the wind figure suggests when the wind blows against an existing wave pattern or along a long fetch.
Alpine and lake effects
Föhn is a warm, dry, gusty downslope wind, classic on Lake Uri and Lake Geneva; it arrives suddenly and can make a lake dangerous within minutes. The Bise is a cold, steady north-easterly on Lake Geneva. Valley and lake breezes build during the day and fade at dusk. In summer, cumulus over the Jura or the Alps in late morning often grows into a cumulonimbus by afternoon, bringing squalls, heavy rain and lightning.
Reading the signs
Cirrus thickening to altostratus with a halo, pressure falling steadily, wind backing and freshening: a warm front is close, bringing rain and a veer. Towering cumulus with a dark flat base and an anvil: get to shelter now.
Worked example
At 10:00 the pressure is 1018 hPa; by 14:00 it is 1012, the wind has backed from SW to S and cirrus has thickened into a sheet. That is a fall of 1.5 hPa per hour with a classic warm-front sequence: rain within a few hours, then a veer to W or NW behind the front. Reef now and pick a harbour for the afternoon, not later.
Traps
Planning on the morning forecast alone; ignoring Föhn warnings; being caught on a lee shore by a thunderstorm gust front; confusing veering with backing.