WEATHER ADVISORY- In aviation weather forecast practice, an expression of hazardous weather conditions not predicted in the area forecast, as they affect the operation of air traffic and as prepared by the NWS.
(See SIGMET.)
(See AIRMET.)
WHEN ABLE- When used in conjunction with ATC instructions, gives the pilot the latitude to delay compliance until a condition or event has been reconciled. Unlike "pilot discretion," when instructions are prefaced "when able," the pilot is expected to seek the first opportunity to comply. Once a maneuver has been initiated, the pilot is expected to continue until the specifications of the instructions have been met. "When able," should not be used when expeditious compliance is required.
WILCO- I have received your message, understand it, and will comply with it.
WIND SHEAR- A change in wind speed and/or wind direction in a short distance resulting in a tearing or shearing effect. It can exist in a horizontal or vertical direction and occasionally in both.
WING TIP VORTICES-
(See VORTICES.)
WORDS TWICE-
a. As a request: "Communication is difficult. Please say every phrase twice."
b. As information: "Since communications are difficult, every phrase in this message will be spoken twice."
WORLD AERONAUTICAL CHARTS-
(See AERONAUTICAL CHART.)
WS-
(See SIGMET.)
(See WEATHER ADVISORY.)
WST-
(See CONVECTIVE SIGMET.)
(See WEATHER ADVISORY.)
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