Elliot Rappaport, a maritime captain, in his poetically delightful book Reading the Glass: A Captain’s View of Weather, Water, and Life on Ships, had this to say:

Like pilots, roofers, and mountain climbers, mariners are by default obsessed with the weather, immersed in it as part of their daily calculus.

While his list of professions is far from exhaustive, he is right to include pilots high on the list of those whose lives intersect profoundly with the weather. And count me among the obsessed.

But how much must pilots learn and know about the weather?

Weather is the current state of the atmosphere. And on that, pilots are taught in generalities: low barometric pressure brings poorer weather, high pressure fairer weather. Cold air is denser than warm air. Moist air is lighter, counterintuitively, than dry air. We often lack the scientific and technical comprehension of these topics unless we seek them out in independent study.

Two British Airways aircraft parked at London Heathrow on a snowy day.
Photo: bodorka I Shutterstock

Pilots must possess a good working knowledge and understanding of the weather. Pilots need not be meteorologists, and candidly, the training pilots receive about weather is limited to reading aviation-specific forecasts and being generally knowledgeable, but not scientifically knowledgeable, about weather systems and their potential impact on safe flight.

Visibility, ceiling, wind

Airline pilots tend to look at a few key weather features at their departure and arrival points: visibility, ceiling, and wind. This is part of the current data a pilot receives from the airport's ATIS.

Visibility is self-explanatory, measuring forward visibility in statute miles. We like good visibility, generally 6 miles or greater, but in most cases, we are equipped to conduct an approach to a runway with as little as half a mile of visibility.

A ceiling is the lowest base of broken or overcast clouds, expressed in height above the ground. Aviation meteorologists classify sky conditions as clear, few clouds, scattered clouds, broken clouds, or overcast. A ceiling requires broken or overcast clouds, meaning the cloud cover is covering more than half the sky (broken) or essentially all the sky (overcast). Like visibility, we like clear skies but can take off and land with very low cloud layers if necessary.

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The presence of wind has a profound impact on aviation. Somewhat counterintuitively, airplanes take off and land into the wind. The increased flow of air over the wings produced by wind coming towards the aircraft adds significantly to the airplane’s ability to create lift. Wind direction and speed determine which runways we use to depart or arrive. And at times, the wind does not cooperate with any of the runways at a given airport, requiring a crosswind takeoff or landing, a takeoff or landing where the wind is acting perpendicular, or near perpendicular, to the direction of the aircraft. These occurrences are common, making a crosswind takeoff or landing routine, but nevertheless, these events demand additional effort and focus on behalf of the pilot.

An aircraft banking around storm clouds.
Photo: Bruno Ismael Silva Alves I Shutterstock

Storms, turbulence

Once airborne, a pilot grows less concerned with visibility, ceiling, and wind and turns his or her attention toward en route weather, notably storms and turbulence.

Despite the power and capabilities of a modern airliner, Mother Nature is in charge. A feature of the summer months, thunderstorms must be navigated around, either in preflight planning or route changes or route deviations once airborne, by distances far greater than 20 miles. Radar on the airplane, along with helpful direction and advice from air traffic control, aid a pilot in this maneuvering.

Turbulence, unlike thunderstorms, is an invisible risk to safety and passenger comfort. Turbulence may exist at one altitude but not another, encouraging a pilot to adjust the aircraft’s cruise altitude to find smoother air. Here, other pilots, not a forecast, become the most valuable resource, as they relay to air traffic control at what altitudes they experience smooth or rough air - valuable information for the next aircraft along that route.