Dug up Roland Stull’s Practical Meteorology again (it’s free and CC-licensed, the whole PDF is online). Started from chapter 1, which is mostly definitions and conventions before the actual physics kicks in. Usually I’d skim this kind of chapter, but a few things in it are the sort of thing that quietly mess you up later if you don’t nail them down now.

The one that got me: meteorologists name wind by where it comes from, but angles in math point toward where something is going. A “west wind” blows from the west, meaning the air itself is moving eastward. So a west wind actually corresponds to a positive U (eastward velocity component). Compass direction also runs clockwise from north (0° at north, 90° at east), while the usual math convention runs counterclockwise from east. Put those two mismatches together and you can’t just drop wind direction into sin/cos and expect a sane answer, you need the actual conversion formulas. Worked example in the book: U = 3 m/s, V = 4 m/s gives speed 5 m/s but a direction of 216.87°, i.e. wind from the SSW, not the NNE you’d guess if you forgot the from-vs-to flip.

Same chapter also defines azimuth, zenith, and elevation angles, for describing where something is relative to an observer (sun, cloud, rainbow, whatever). Azimuth is the compass direction toward the object, measured clockwise from north. That’s the same clockwise-from-north convention as wind direction, but the opposite from/to meaning. So within a single chapter you get two angle systems that look identical but point opposite ways. Worth writing down just so I stop mixing them up later.

The time zone section was more fun than I expected. Standard time zones only exist because 19th century railroads needed to publish schedules that made sense across towns that used to each keep their own local solar noon. UTC (= GMT = “Zulu time”) sits at the prime meridian, and zones are lettered A through Z outward, with the letter Z at Greenwich. There’s a neat trick for reading synoptic weather maps: because of how the US/Canada/Mexico time zones fall relative to Greenwich, a 12 UTC map always lines up with morning local time there, and a 00 UTC map lines up with the previous evening. And “spring ahead, fall back” is apparently the actual mnemonic meteorology textbooks use for daylight saving, not something I made up as a kid.

One stat from a sidebar stuck with me: from 1970 to 2012 there were about 8,835 weather-related disasters, 1.94 million deaths, and $2.4 trillion in losses, with storms alone responsible for 79% of the disasters and 55% of the deaths. Most of the deaths were in less developed countries, most of the economic losses in the richer ones. Makes the “just conventions” chapter feel a little less like paperwork.

Next up: pressure, density, and the ideal gas law.