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AIM

10/12/17

7

−1−18

Meteorology

NOTE

1. Terminal control facilities have the option to limit the
AWW, convective SIGMET, SIGMET, or CWA broadcast as
follows: local control and approach control positions may
opt to broadcast SIGMET or CWA alerts only when any
part of the area described is within 50 miles of the airspace
under their jurisdiction.

2. In areas where HIWAS is available, ARTCC, Terminal
ATC, and FSS facilities no longer broadcast Inflight
Weather Advisories as described above in paragraph a. See
paragraphs b1 and b2 below.

b. Hazardous Inflight Weather Advisory Ser-

vice (HIWAS).

HIWAS is an automated, continuous

broadcast of inflight weather advisories, provided by
FSS over select VOR outlets, which include the
following weather products:  AWW, SIGMET,
Convective SIGMET, CWA, AIRMET (text [WA] or
graphical [G

−AIRMET] products), and urgent

PIREP. HIWAS is available throughout the contermi-
nous United States as an additional source of
hazardous weather information. HIWAS does not
replace preflight or inflight weather briefings from
FSS. Pilots should call FSS if there are any questions
about weather that is different than forecasted or if the
HIWAS broadcast appears to be in error.

1.

Where HIWAS is available, ARTCC and

terminal ATC facilities will broadcast, upon receipt,

a HIWAS alert once on all frequencies, except
emergency frequencies. Included in the broadcast
will be an alert announcement, frequency instruction,
number, and type of advisory updated; for example,
AWW, SIGMET, Convective SIGMET, or CWA.

EXAMPLE

Attention all aircraft. Hazardous weather information
(SIGMET, Convective SIGMET, AIRMET 

(text [WA] or

graphical [G

−AIRMET] product)

, Urgent Pilot

Weather Report [UUA], or Center Weather Advisory
[CWA], Number or Numbers) for (geographical area)
available on HIWAS or Flight Service frequencies.

2.

Upon notification of an update to HIWAS,

FSS will broadcast a HIWAS update announcement
once on all frequencies except emergency frequen-
cies. Included in the broadcast will be the type of
advisory updated; for example, AWW, SIGMET,
Convective SIGMET, CWA, etc.

EXAMPLE

Attention all aircraft. Hazardous weather information for
(geographical area) available from Flight Service.

3.

HIWAS availability is notated with VOR

listings in the Chart Supplement U.S., and is shown
by symbols on IFR Enroute Low Altitude Charts and
VFR Sectional Charts. The symbol depiction is
identified in the chart legend.