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."
12/10/15
WS-
(See SIGMET.)
(See WEATHER ADVISORY.)
WST-
(See CONVECTIVE SIGMET.)
(See WEATHER ADVISORY.)
PCG W-2
Page 724 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures