Metro-02
Meteorology and Flight Planning
(b) Intended to alert pilots that avoidance
by visual or radar detection could be
difficult or impossible
(3) A line of thunderstorms
(a) At least 60 miles long with thunder-
storms affecting at least 40% of the
length
(4) An area of active thunderstorms affecting at
least 3,000 square miles
(a) Thunderstorms having a reflectivity
intensity (VIP LVL) of 4 or greater
and/or having significant satellite
signature affecting at least 40% of the
area outlined
8.
Special Convective SIGMETs - A WST special shall
be issued at any time when either of the following
criteria are met and/or forecast to be met for more
than 30 minutes of the scheduled WST's valid
period
a.
Tornado, hail 3/4-inch or greater, or wind gusts
to 50 kts or greater reported to the NAWAU
forecaster or indicated when previous WST did
not mention severe thunderstorms
b.
Indications of rapidly changing conditions if in
the forecaster's judgment, not sufficiently
described in existing SIGMET
9.
Nonconvective SIGMETs (WS)
Sg 3, fr 13
Fig 17: SIGMET (WS)
a.
Not issued on a regular scheduled basis
b.
Issued whenever any of the following weather
phenomena occur or are forecast to occur and
affect an area of at least 3,000 square miles
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