Definition
The sudden, sharp increase in surface wind speed that occurs at the leading edge of a thunderstorm's outflow, marking the arrival of cold downdraft air spreading out along the ground ahead of the storm. The first gust typically brings an abrupt wind shift, a rapid temperature drop, and wind speeds that can exceed the prevailing wind by 25 knots or more.
Plain English
The first strong burst of wind you feel when a thunderstorm's cool downdraft hits the ground and rushes outward ahead of the storm. The wind suddenly speeds up, changes direction, and the air feels noticeably cooler.
Context Anchor
Used in thunderstorm weather discussions, especially when judging changing wind near an airport before takeoff or landing.
Derivation
Gust means a sudden rush or blast of wind. In this term, first points to the initial arrival of that blast, not necessarily the strongest wind that will occur.
Why Pilots Care
It produces sudden wind shifts and speed changes that can affect aircraft performance during takeoff and landing, requiring pilots to add extra airspeed margin and be ready for control inputs.
Grounding Statement
Picture standing on a calm, warm ramp as a thunderstorm approaches: suddenly the wind slams in from a new direction, the temperature drops, and dust kicks up. That sharp arrival is the first gust.
Intuition Check
Do not assume first gust means the strongest gust. It means the first noticeable blast of wind as storm outflow reaches you.
Example Sentence 1
The tower reported the first gust from the approaching thunderstorm shifted the wind from 180 at 8 knots to 240 at 35 knots within seconds.
Example Sentence 2
On short final the pilot added five knots to approach speed to compensate for the expected first gust.