Definition
In aviation weather and turbulence reporting, a qualifier indicating a condition of high intensity that causes large, abrupt changes in altitude or attitude, momentary loss of aircraft control, and may produce structural damage. Applied to turbulence, icing, and thunderstorm intensity categories, 'severe' sits one level below 'extreme' and one level above 'moderate.'
Plain English
A weather condition strong enough to throw the aircraft around hard, briefly take control away from the pilot, and possibly damage the airplane.
Context Anchor
Seen in icing forecasts, pilot reports, and weather discussions that describe how quickly ice is forming on an aircraft.
Derivation
From Latin 'severus,' meaning strict or harsh. In aviation it keeps that sense of harshness but is tied to specific, defined intensity criteria rather than a subjective impression.
Why Pilots Care
Determines whether to continue, divert, or request an altitude change because severe conditions increase workload and risk of momentary loss of control.
Grounding Statement
Picture ice continuing to build on the airplane even while the ice-protection system is on; that is the practical meaning of severe icing.
Intuition Check
Severe does not just mean “pretty bad” here. In an icing report, it means the ice buildup is beyond what the airplane’s ice-protection equipment can adequately control.
Example Sentence 1
The PIREP reported severe turbulence at 12,000 feet, so the crew requested a lower altitude to exit the affected area.
Example Sentence 2
Severe icing was forecast above the freezing level, requiring the pilot to exit the clouds promptly.