A Mini Weather-Wiki for GA Flying Companions

Everybody talks about the weather, but nobody does anything about it.

— Mark Twain

If you are the partner or companion of a GA pilot, you have probably noticed that your pilot does more than just talk about the weather. In fact, it might seem that anyone and everyone involved in aviation takes a near-obsessive interest in meteoro­logical matters … and for very good reason. Unlike commercial airliners, which cruise serenely above the worst of the weather, GA airplanes live where the weather is. So the wise GA pilot aims to be a meteo­rological maven.

A full-blown weather course is the stuff of text­books, not magazine articles. Still, you might find it helpful to know what GA pilots consider in the search for “fly-able” weather.

Aviation Weather Data

Pilots do watch broadcast weather reports, but we use them mainly for a broad, big-picture look. For the more detailed information flying requires, we use aviation-specific weather products, both reports and forecasts.

Three of the most commonly-used are the area forecast, the Terminal Aerodrome Forecast (TAF), and the Meteorological Terminal Aviation Routine Weather Report (METAR). The area forecast offers the big pic­ture. Pilots use the TAF to evalu­ate forecast weather conditions for departure, destination, and en route airports at the times those airports will be used. The METAR provides current conditions at those airports.

There’s a lot of information in these and other aviation weather products, but GA pilots focus on three major meteorological elements: wind, ceiling and visibility, and temperatures.

Wind

For GA flying purposes, wind data comes in two flavors: surface winds, which are provided in TAFs and METARs, and winds aloft, provided in a different report.

A GA airplane pilot needs to consider surface winds in terms of both pilot skill and airplane capability. If there is a crosswind — that is, wind blowing from the side of the runway — the pilot needs to be proficient in using the controls to keep the airplane in line with the pavement, and to be sure the flight controls have enough authority to counteract the wind.

Pilots use winds aloft data in flight planning. A flight with a headwind will take longer; one with a tailwind will go faster.

Ceiling & Visibility

Aviation uses ceiling and visibility values to define weather in terms of visual or instrument meteorological conditions. Initial certification allows a pilot to fly under Visual Flight Rules (VFR). Flying under Instrument Flight Rules (IFR) requires additional training and testing, as well as regular practice to retain currency and (most important) proficiency. An instrument-rated pilot who hasn’t practiced enough to stay proficient should not be in IFR weather.

Also, there are some instrument conditions, like thunderstorms, that are off limits to all pilots.

Temperatures

Temperatures — both surface and aloft — pro­vide important information about how the airplane will perform. Hot air is thinner, and that means that both the wing and the engine/propeller have to work harder.

Airplanes perform better in colder air, but not if cold air and clouds combine to produce icing condi­tions. Ice is very dangerous because it reduces lift while adding weight. Unless the airplane is equipped for flight into known icing conditions, the pilot needs to avoid such areas. (FAA Safety Briefing MarApr 2018)