Definition
Thunderstorm-related weather that poses a serious threat to aircraft, including severe or embedded thunderstorms, lines of thunderstorms, thunderstorms producing hail three-quarters of an inch or greater in diameter, and thunderstorms producing surface winds of 50 knots or greater. It is the type of weather that triggers a Convective SIGMET (WST).
Plain English
Thunderstorm activity that is dangerous to fly through or near — strong storms, lines of storms, storms hidden in cloud layers, storms with large hail, or storms producing very strong surface winds.
Context Anchor
Pilots encounter this phrase in weather briefings and Convective SIGMET discussions, especially when deciding whether a thunderstorm area must be avoided.
Derivation
‘Convective’ comes from the Latin convehere, meaning ‘to carry together.’ In weather, it refers to the vertical movement of air — warm air rising and cooler air sinking. Thunderstorms are the most powerful form of this vertical motion, which is why thunderstorm hazards are grouped under the term ‘convective.’
Why Pilots Care
These conditions can cause structural damage, loss of aircraft control, or sudden loss of performance, so pilots must identify and avoid them for flight safety.
Grounding Statement
Picture a hot, moist air mass building into a thunderstorm: the air rises hard, falls hard, and can create violent wind, rain, hail, and lightning around the cloud.
Intuition Check
Hazardous does not mean merely uncomfortable or inconvenient here; it means significant enough to threaten safety of flight. Convective does not mean any cloudy weather; it means weather driven by strong vertical air movement, usually thunderstorms.
Example Sentence 1
The Convective SIGMET warned of hazardous convective weather along our route, so we requested a deviation 50 miles to the south.
Example Sentence 2
Before departure the briefer highlighted hazardous convective weather developing along the planned route, leading to a delay until conditions cleared.