AIM
4/3/14
7−1−43
Meteorology
7
−
1
−
19. Estimating Intensity of Snow or
Drizzle (Based on Visibility)
a. Light.
Visibility more than
1
/
2
statute mile.
b. Moderate.
Visibility from more than
1
/
4
stat-
ute mile to
1
/
2
statute mile.
c. Heavy.
Visibility
1
/
4
statute mile or less.
7
−
1
−
20. Pilot Weather Reports (PIREPs)
a.
FAA air traffic facilities are required to solicit
PIREPs when the following conditions are reported
or forecast: ceilings at or below 5,000 feet; visibility
at or below 5 miles (surface or aloft); thunderstorms
and related phenomena; icing of light degree or
greater; turbulence of moderate degree or greater;
wind shear and reported or forecast volcanic ash
clouds.
b.
Pilots are urged to cooperate and promptly
volunteer reports of these conditions and other
atmospheric data such as: cloud bases, tops and
layers; flight visibility; precipitation; visibility
restrictions such as haze, smoke and dust; wind at
altitude; and temperature aloft.
c.
PIREPs should be given to the ground facility
with which communications are established;
i.e., EFAS, FSS, ARTCC, or terminal ATC. One of
the primary duties of EFAS facilities, radio call
“FLIGHT WATCH,” is to serve as a collection point
for the exchange of PIREPs with en route aircraft.
d.
If pilots are not able to make PIREPs by radio,
reporting upon landing of the inflight conditions
encountered to the nearest FSS or Weather Forecast
Office will be helpful. Some of the uses made of the
reports are:
1.
The ATCT uses the reports to expedite the
flow of air traffic in the vicinity of the field and for
hazardous weather avoidance procedures.
2.
The FSS uses the reports to brief other pilots,
to provide inflight advisories, and weather avoidance
information to en route aircraft.
3.
The ARTCC uses the reports to expedite the
flow of en route traffic, to determine most favorable
altitudes, and to issue hazardous weather information
within the center’s area.
4.
The NWS uses the reports to verify or amend
conditions contained in aviation forecast and
advisories. In some cases, pilot reports of hazardous
conditions are the triggering mechanism for the
issuance of advisories. They also use the reports for
pilot weather briefings.
5.
The NWS, other government organizations,
the military, and private industry groups use PIREPs
for research activities in the study of meteorological
phenomena.
6.
All air traffic facilities and the NWS forward
the reports received from pilots into the weather
distribution system to assure the information is made
available to all pilots and other interested parties.
e.
The FAA, NWS, and other organizations that
enter PIREPs into the weather reporting system use
the format listed in TBL 7−1−7. Items 1 through 6 are
included in all transmitted PIREPs along with one or
more of items 7 through 13. Although the PIREP
should be as complete and concise as possible, pilots
should not be overly concerned with strict format or
phraseology. The important thing is that the
information is relayed so other pilots may benefit
from your observation. If a portion of the report needs
clarification, the ground station will request the
information. Completed PIREPs will be transmitted
to weather circuits as in the following examples: