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MET - 2.0 PILOT REPORTS

 

2.1 General

A PIREP is a report pertaining to current weather conditions encountered in flight. It is designed to provide other pilots, dispatchers and weather briefers with up-to-the-minute weather information. In addition, it is an invaluable data source for aviation meteorologists because it either confirms an existing forecast or highlights the requirement for an amendment. A PIREP may also be the only information available regarding areas between reporting stations, particularly those areas whose topography may produce localized weather phenomena (e.g. hills or expanses of water).

Pilots are encouraged to report conditions that differ significantly from those that were forecast. PIREPs that contain critical information on low clouds, reduced visibility, icing, and convective activities such as wind shear, squall line, turbulence, thunderstorms and cumulonimbus clouds are especially useful. PIREPs of hazardous conditions may trigger the issuance of a SIGMET.

For timely distribution, PIREPs should be filed with a flight information centre (FIC) via an en-route frequency or by a toll-free call to an FIC after landing.

Controllers, flight service specialists and CARS observer/communicators may request reports from pilots regarding specific weather conditions or weather conditions encountered during en-route, climb-out or approach phases.

The CFS contains the toll-free FIC telephone numbers in the Flight Planning section of each listed aerodrome, and the recommended contents of a PIREP are listed on the back cover.

2.2 Clear Air Turbulence

Clear air turbulence (CAT) remains a problem for flight operations particularly above 15 000 feet. The best information available on this phenomenon is still obtained from PIREPs, since a CAT forecast is generalized and covers large areas. All pilots encountering CAT conditions are requested to urgently report the time, location, flight level and intensity (light, moderate, severe, or extreme) of the phenomena to the facility with which they are maintaining radio contact. (See Turbulence Reporting Criteria Table, MET 3.7.) A more complete description of CAT and recommended pilot actions can be found in AIR 2.10.

2.3 Wind Shear

Intense down drafts, typically associated with thunderstorms, produce strong vertical and horizontal wind shear components that are a hazard to aviation for aircraft in the approach, landing or takeoff phase of flight (see AIR 2.8). Since ground-based instruments to measure wind shear have not been installed at Canadian aerodromes, the presence of such conditions can normally be deduced only from PIREPs.

Aircrew capable of reporting the wind and altitude, both above and below the shear layer, from Flight Management Systems (FMS) are requested to do so. Pilots without this equipment should report wind shear by stating the loss or gain of airspeed and the altitude at which it was encountered. Pilots not able to report wind shear in these specific terms should do so in terms of its general effect on the aircraft.

2.4 Airframe Icing

Report icing to ATS and, if operating IFR, request a new routing or altitude if icing will be a hazard. Give your aircraft identification, type, location, time (UTC), intensity of icing, type, altitude or flight level, and indicated airspeed. (See the suggested format on the back cover of the CFS.)

The following describes icing and how to report icing conditions:

INTENSITY ICE ACCUMULATION
Trace Ice becomes perceptible. The rate of accumulation is slightly greater than the rate of sublimation. It is not hazardous, even though de-icing or anti-icing equipment is not used, unless encountered for an extended period of time (over 1 hour).
Light The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour).
Moderate The rate of accumulation is such that even short encounters become potentially hazardous, and use of de-icing or anti-icing equipment or diversion is necessary.
Severe  The rate of accumulation is such that de-icing or anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.
*Rime ice: Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.
*Clear ice: Glossy, clear, or translucent ice formed by the relatively slow freezing of large supercooled water droplets.

*Types of icing

2.5 Volcanic Ash

Flight operations in volcanic ash are hazardous (see AIR 2.6). Pilots may be the first line of volcanic eruption detection in more remote areas. Pilots may be able to provide valuable information about the spread of volcanic ash from an eruption; ash can rapidly rise to altitudes above 60 000 feet and exist at hazardous concentrations up to 1 000 NM from the source. Volcanic ash is not detectable on radar. If an eruption or ash cloud is detected, an urgent PIREP should be filed with the nearest ATS unit.

A volcanic ash forecast chart is produced when required (see MET 3.21).

2.6 Pilot Estimation of Surface Wind

Surface wind direction and speed is information critical to effective pilot decision making for takeoff and landing. Where neither wind measuring equipment nor a wind direction indicator (see AGA 5.9) is available, the wind direction and speed can be estimated by observing smoke, dust, flags or wind lines on bodies of water.

Pilots on the ground may estimate wind speed and direction by using anything that is free to be moved by the influence of the wind. The descriptions in the Beaufort Wind Scale found in Table 1 have been found to be particularly useful and are widely used.

Wind direction can also be estimated accurately by simply facing the wind. Such estimates should only be provided to the nearest eight points (i.e., north, northeast, east) of the compass. The best estimate is obtained by standing in an open area clear of obstructions. Should this not be possible, estimation errors may be so large that pilots using the information should exercise caution. The direction and speed of low-lying clouds can be an indicator of surface winds but should also be used with caution because of the possibility of wind shear near the surface.

Pilots who relay reports of winds based on estimation should ensure that the intended user of the information is aware that it is based on estimation so that appropriate precautions can be taken.

Estimating Wind Speed

The speed may be estimated by using the Beaufort Scale of Winds, which relates common effects of the wind and equivalent speeds in knots

Table 1: Beaufort Wind Scale
Descriptive Term Beaufort Force Speed Range (knots) Knots Average Specification for
estimating wind
over land 		Specification for estimating wind over sea (probable wave height in metres*)
Calm 0 Less than 1   Smoke rises vertically Sea is like a mirror (0)
Light Air 1 1–3 2 Direction of wind shown by smoke Ripples with the appearance of scales are formed, but with out foam crest (0.1)
Light Breeze 2 4–6 5 Wind felt on face; leaves rustle; ordinary vane moved by wind Small wavelets, still short but more pronounced; crests have a glassy appearance and do not break (0.2 to 0.3)
Gentle Breeze 3 7–10 9 Leaves and small twigs in constant motion; wind extends light flag Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses (0.6 to 1)
Moderate Breeze 4 11–16 14 Raises dust and loose paper; small branches are moved Small waves becoming longer; fairly frequent white horses (1 to 1.5)
Fresh Breeze 5 17–21 19 Small trees in leaf begin to sway; crested wavelets form on inland waters Moderate waves, taking a more pronounced long form; many white horses are formed, chance of some spray (2 to 2.5)
Strong Breeze 6 22–27 25 Large branches in motion; whistling heard in telephone wires; umbrellas used with difficulty Large waves begin to form; the white foam crests are more extensive everywhere, probably some spray (3 to 4)
Near Gale 7 28–33 31 Whole trees in motion; inconvenience felt in walking against wind Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind (4 to 5.5)
Gale 8 34–40 37 Breaks twigs off trees; generally impedes progress Moderately high waves of greater length;edges of crests begin to break into the spindrift; the foam is blown in well-marked streaks along the direction of the wind (5.5 to 7.5)
Strong Gale 9 41–47 44 Slight structural damage occures to roofing shingles, TV antennae, etc. High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble and roll over; spray may affect visibility (7 to 10)
Storm 10 48–55 52 Seldom experienced inland; trees uprooted; considerable structural damage Very high waves with long, overhanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy and shock-like; visibility affected (9 to 12.5)
Violent Storm 11 56–63 60 Very rarely experienced; accompanied by widespread damage Exceptionally high waves (small and medium sized ships might be lost to the view behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; visibility affected (11.5 to 16)
Hurricane 12 Above 63     The air is filled with foam and spray; sea completely white with driving spray; visibility seriously affected (16+)

* Wave height is representative of conditions well away from shore and in deep water when winds of that strength have persisted for an extended period of time. The wave height figure does not give the maximum wave height nor does it take into account the effects of swell, air temperature or currents.

Date modified:
2012-02-24