Chapter 8. FAA Weather Services

Section 1. Pilot Weather Reports

1. GENERAL

1. PIREPs are filed at unscheduled times with stations having sending capability to WMSCR for dissemination on the Service A domestic aviation weather system. Timely dissemination of PIREPs alert pilots to significant weather reports and improves aviation forecasts.
2. Personnel must enter PIREPs into the operational system as individual reports, not appended to a surface observation.
3. Changing weather conditions should dictate increased frequency of PIREP solicitation.

1. RESPONSIBILITY

1. Actively solicit PIREPs when, in your judgment, a report of actual in‐flight conditions is beneficial or when conditions meet criteria for solicitation listed in this section.
2. Assure timely dissemination of the PIREP information.
3. Each facility should make special efforts to solicit PIREPs on departure and arrival weather conditions at airports within their flight plan area.
4. Personnel must not solicit PIREPs when the pilot indicates they are in hazardous weather conditions or during a critical phase of flight.

1. Solicit PIREPs for the affected area(s) when one or more of the following weather conditions exist, are reported, or forecast to occur:

1. Ceilings at or below 5,000 feet.
2. Visibility reported on the surface or aloft is five miles or less.
3. Thunderstorms and related phenomenon.
4. Turbulence of moderate degree or greater.
5. Icing of light degree or greater.
6. Wind shear.
7. Braking action reports less than good.
8. Volcanic eruption, ash clouds, and/or detection of sulfur gases in the cabin: hydrogen sulfide (H₂S) or sulfur dioxide (SO₂).

1. If only H₂S or SO₂ is reported with no reported volcanic ash clouds, ask the pilot if volcanic ash clouds are in the vicinity.
2. The smell of sulfur gases in the cockpit may indicate volcanic activity that has not yet been detected or reported and/or possible entry into an ash-bearing cloud. H₂S, also known as sewer gas, has the odor of rotten eggs. SO₂ is identifiable as the sharp, acrid odor of a freshly struck match.

1. Also, solicit PIREPs regardless of weather conditions when:

1. A NWS or ATC facility indicates a need because of a specific weather or flight assistance situation.
2. Necessary to determine flying conditions pertinent to natural hazards (mountain passes, ridges, peaks) between the weather reporting stations.
3. The station is designated as responsible for PIREPs in an offshore coastal area.

1. In‐flight specialists must solicit sufficient PIREPs to remain aware of flight conditions.
2. To solicit PIREPs within a specific area, broadcast a request on NAVAIDs, transcribed broadcast facilities, or a selected communications frequency.

1. Inform pilots of a need for PIREPs. The following methods may be used to collect PIREPs:

1. During pre‐flight weather briefings.
2. On post‐flight contacts.
3. During regular air‐ground contacts.
4. Broadcast a request on NAVAID frequencies.
5. Request PIREPs from air carrier and military operations offices, military pilot‐to‐forecaster units, and local aircraft operators.
6. Solicit from other air traffic facilities.

1. PIREP CLASSIFICATION

Categorize PIREPs as follows:

1. URGENT. The following weather phenomena must be classified as an URGENT PIREP (UUA):

1. Tornadoes, funnel clouds, or waterspouts.
2. Severe or extreme turbulence (including clear air turbulence).
3. Severe icing.
4. Hail.
5. Low‐level wind shear (LLWS). For the safety of light aircraft, classify low‐level wind shear PIREPs as UUA if the pilot reports airspeed fluctuations of 10 knots or more. Classify reports of low‐level wind shear with airspeed fluctuations less than 10 knots as routine. If airspeed fluctuation is not reported, classify PIREP as UUA.

1. Volcanic eruption, ash clouds, and/or detection of sulfur gases (H₂S or SO₂) in the cabin.

1. If a pilot only reported the smell of H₂S or SO₂ in the cabin and confirmed no volcanic ash clouds were present, classify the report as a ROUTINE PIREP.
2. The smell of sulfur gases in the cockpit may indicate volcanic activity that has not yet been detected or reported and/or possible entry into an ash‐bearing cloud. H₂S, also known as sewer gas, has the odor of rotten eggs. SO₂ is identifiable as the sharp, acrid odor of a freshly struck match.

1. Any other weather phenomena reported which are considered by the specialist as being hazardous, or potentially hazardous, to flight operations.

1. ROUTINE. Classify as ROUTINE (UA) all PIREPs received except those listed above.

1. DATA TO BE INCLUDED IN PIREPs

Include the following reports of flight conditions, as appropriate:

1. Height and coverage of cloud bases, tops, and layers.
2. Flight visibility.
3. Restrictions to visibility and weather occurring at altitude.
4. Air temperature and changes to temperature with altitude or range.
5. Direction and speed of wind aloft.
6. Duration and intensity of turbulence.

1. Extent, type, and intensity of icing.

1. Weather conditions and cloud cover through mountain passes and over ridges and peaks.
2. Location, extent, and movement of thunderstorms and/or tornadic activity.
3. Excessive winds aloft, low‐level wind shear, and other phenomena bearing on safety and efficiency of flight.

1. PIREP FORMAT

Using TEIs as described below, prepare PIREPs for system entry in the following format:

1. UUA or UA. Message type - urgent or routine PIREP.
2. /OV.

1. Location in reference to a VHF NAVAID or an airport. Use the three or four alphanumeric identifier. If appropriate, encode the identifier, then three digits to define a radial and three digits to define the distance in nautical miles.

1. Route segment. Two or more fixes to describe a route.

1. Latitude and longitude. Alternatively, the location may be reported as a latitude and longitude pair (in degrees and minutes) for cases of crewed aircraft flying in overseas/over water locations where it is impracticable for the pilot to report using distance and direction from a NAVAID or airport, or for UAV or UAS flying anywhere in the world. UAV or UAS should not use latitude and longitude for the coastal waters of the U.S., unless it is impracticable to report using distance direction from a NAVAID or an airport.

1. /TM. Time. Enter the time that the reported phenomenon occurred or was encountered. Report time in four digits UTC.

1. /FL. Altitude/flight level. Enter the altitude in hundreds of feet (MSL) where the phenomenon was first encountered. If not known, enter UNKN. If the aircraft was climbing or descending, enter the appropriate contraction (DURC or DURD) in the remarks/RM TEI. If the condition was encountered within a layer, enter the altitude range within the appropriate TEI describing the condition.

1. /TP. Type of aircraft. Enter the aircraft type. If not known, enter UNKN. Icing and turbulence reports must always include the aircraft type. Do not consolidate observations from numerous aircraft types into one PIREP.

1. /SK. Sky condition. Report height of cloud bases, tops, and cloud coverage as follows:

1. Enter the height of the base of a layer of clouds in hundreds of feet (MSL) using three digits. Enter the top of a layer in hundreds of feet (MSL) preceded by the word “TOP.” If reported as clear above the highest cloud layer, enter a space and “SKC” following the reported level.

1. Use authorized contractions for cloud cover.

1. Cloud cover amount ranges will be entered with a hyphen and no spaces separating the amounts (for example, BKN-OVC).

1. Unknown heights are indicated by the contraction UNKN.

1. If a pilot indicates he/she is in the clouds, enter IMC in the remarks.

1. When more than one layer is reported, separate layers by a solidus (/).

1. /WX. Flight visibility and weather. Report weather conditions encountered by the pilot as follows:

1. Flight visibility, if reported, will be the first entry in the /WX field. Enter as FV followed by a two‐digit visibility value rounded down, if necessary, to the nearest whole statute mile and append “SM” (FV03SM). If visibility is reported as unrestricted, enter FV99SM.
2. Enter flight weather types using one or more of the standard surface weather reporting codes contained in TBL 8-1-1.

1. Intensity of precipitation (- for light, no qualifier for moderate, and + for heavy) must be indicated with precipitation types, except ice crystals and hail, including those associated with a thunderstorm and those of a showery nature.
2. Intensity of obscurations must be ascribed as moderate or + heavy for dust and sand storms only. No intensity for blowing dust, blowing sand, or blowing snow.

1. When more than one form of precipitation is combined in the report, the dominant type must be reported first.

1. When FC is entered in /WX, FUNNEL CLOUD is spelled out on /RM. When +FC is entered in /WX, TORNADO or WATERSPOUT is spelled out in the /RM TEI.

1. State the size of the hail in remarks in ¼” increments or any hail less than ¼” is stated as “GR less than ¼”.
2. The proximity qualifier VC (Vicinity) is only used with TS, FG, FC, +FC, SH, PO, BLDU, BLSA, and BLSN.

1. When more than one type of weather is reported enter in the following order: 1) TORNADO, WATERSPOUT, OR FUNNEL CLOUD; 2) Thunderstorm with or without associated precipitation; 3) Weather phenomena in order of decreasing predominance. No more than three groups in a single PIREP.
2. Weather layers must be entered with the base and/or top of the layer when reported. Use the same format as in the /SK TEI.

1. /TA. Air Temperature. Report outside air temperature using two digits in degrees Celsius. Prefix negative temperatures with an M (for example, /TA 08 or /TA M08).
2. /WV. Wind direction and speed. If reported, wind direction from which the wind is blowing must be coded using three figures. Directions less than 100 degrees must be preceded by a “0”. For example, a wind direction of 90 degrees is coded as 090. The wind speed must be entered as a two or three digit group immediately following the wind direction. The speed must be coded in whole knots using the hundreds digit (if not zero) and the tens and units digits. The wind group always ends with “KT” to indicate that winds are reported in knots. Speeds of less than 10 knots must be coded using a leading zero. For example, a wind speed of 8 knots must be coded 08KT and a wind speed of 112 knots must be coded as 112KT.

1. /TB. Turbulence. Report intensity, type, and altitude as follows:

1. Intensity. Enter duration if reported by the pilot (INTMT, OCNL, CONS) and intensity using contractions LGT, MOD, SEV, or EXTRM. Separate a range or variation of intensity with a hyphen (for example, MOD-SEV). If turbulence was not encountered, enter NEG.
2. Type. Enter CAT or CHOP if reported by the pilot.
3. Altitude. Report altitude only if it differs from value reported in /FL. When a layer of turbulence is reported, separate height values with a hyphen. If lower or upper limits are not defined, use BLO or ABV.

1. IC. Icing. Report intensity, type and altitude of icing as follows:

1. Intensity. Enter intensity first using contractions TRACE, LGT, MOD, or SEV. Separate reports of a range or variation of intensity with a hyphen. If icing was not encountered, enter NEG.
2. Type. Enter the reported icing type as RIME, CLR, or MX.
3. Altitude. Enter the reported icing/altitude only if different from the value reported in the /FL TEI. Use a hyphen to separate reported layers of icing. Use ABV or BLO when a layer is not defined.

1. When icing is reported always report temperature in the /TA TEI.

1. /RM. Remarks. Use this TEI to report a phenomena which is considered important but do not fit in any of the other TEIs. This includes, but is not limited to, wind shear (including low‐level wind shear) reports, thunderstorm lines, coverage and movement, size of hail (¼” increments), lightning, clouds observed but not encountered, geographical or local description of where the phenomenon occurred, International Standard Atmospheric (ISA) reports and contrails. Report hazardous weather first.

1. Wind shear.

1. Describe wind shear to the extent possible (see paragraph 8-1-8).
2. Wind shear (including low‐level wind shear) may be reported as plus (+), minus (-), or both (+/-) depending on how it affects the aircraft.
3. If the location and/or altitude are different than the /OV and/or /FL fields, include the location and/or altitude in the remarks.
4. When low‐level wind shear is reported, enter it as the first remark in the /RM TEI.

1. FUNNEL, CLOUD, TORNADO, and WATERSPOUT are entered with the direction of movement if reported.

1. Thunderstorm. Enter coverage (ISOL, FEW, SCT, NMRS) and description (LN, BKN LN, SLD LN) if reported. Follow with “TS,” the location and movement, and the type of lightning if reported.

1. Lightning. Enter frequency (OCNL, FRQ, CONS), followed by type (LTGIC, LTGCC, LTGCG, LTGCA, or combinations), if reported.

1. Electric discharge. Enter DISCHARGE followed by the altitude.

1. Clouds. Use remarks when clouds can be seen but were not encountered and reported in /SK.

1. Volcanic activity. Volcanic eruption, ash clouds, and/or sulfur gases are urgent PIREPs. Reports of volcanic activity must include as much information as possible (for example, the name of the mountain, ash clouds observed and their movement, the height of the top and bottom of the ash clouds, etc.).

1. If a pilot detected the smell of sulfur gases (H₂S or SO₂) in the cabin and reported volcanic ash clouds, include “VA” in Weather and “H2S,” “SO2,” or “SULFUR SMELL” in remarks.

1. If a pilot only detected the smell of sulfur gases (H₂S or SO₂) in the cabin and confirmed there were no volcanic ash clouds, classify the PIREP as Routine and include “VA” in Weather and “H2S NO ASH,” “SO2 NO ASH,” or “SULFUR SMELL NO ASH” in Remarks.

1. If a volcanic activity report is received from other than a pilot, enter Aircraft “UNKN,” Flight Level “UNKN,” and in Remarks “UNOFFICIAL.”

1. Plain language. If specific phraseology is not adequate, use plain language to describe the phenomena or local geographic locations. Include remarks that do not fit in other TEIs like DURC, DURD, RCA, TOP, TOC, or CONTRAILS.

1. When a PIREP from a pilot identifying themselves as a “SKYSPOTTER” aircraft is received, personnel must include the additional comment “/AWC” at the end of the remarks section of the PIREP.

1. If ISA is reported.

1. REPORTING TURBULENCE IN PIREPs

1. Turbulence reports must include location, time (UTC), altitude/FL or range of altitudes, aircraft type, intensity, duration (occasional, intermittent, and continuous), and whether in clouds or clear air. The degree of turbulence, intensity, and duration is determined by the pilot.
2. Turbulence intensity based on aircraft reaction.

1. Light turbulence. Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw).
2. Light chop. Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude.
3. Moderate turbulence. Turbulence that is similar to “light turbulence” but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed.
4. Moderate chop. Turbulence that is similar to “light chop” but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude.
5. Severe turbulence. Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control.
6. Extreme turbulence. Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage.

1. High level turbulence (normally above 15,000 feet MSL) not associated with cumuliform cloudiness, including thunderstorms, should be reported as CAT preceded by the appropriate intensity, or light or moderate chop.

1. REPORTING AIRFRAME ICING IN PIREPs

1. Icing reports must include location, time (UTC), altitude/FL or range of altitudes, aircraft type, outside air temperature, intensity, and type of icing.
2. Icing types.

1. Rime ice. Rough, milky, opaque ice formed by the rapid freezing of small supercooled water drops/droplets after they strike the aircraft. The rapid freezing results in air being trapped, giving the ice its opaque appearance and making it porous and brittle. Rime ice is more regular in shape and conformal to the airfoil than glaze ice.
2. Clear ice (also known as glaze ice). Ice, sometimes clear and smooth but usually containing some air pockets, which results in a lumpy translucent appearance. Clear ice results from supercooled drops/droplets striking a surface but not freezing rapidly on contact. It is denser, harder, and sometimes more transparent than rime ice. With larger accretions, the ice shape typically includes “horns” protruding from unprotected leading edge surfaces. It is the shape, rather than the clarity or color, which is most likely to be accurately assessed from the cockpit.
3. Mixed. Simultaneous appearance or a combination of rime and glaze ice characteristics. Since the clarity, color, and shape of the ice will be a mixture of rime and glaze characteristics, accurate identification of mixed ice from the cockpit may be difficult.

1. Icing intensity.

1. Trace. Ice becomes noticeable. The rate of accumulation is slightly greater than the rate of sublimation. A representative accretion rate for reference purposes is less than ¼ inch (6 mm) per hour on the outer wing. The pilot should consider exiting the icing conditions before they become worse.
2. Light. The rate of ice accumulation requires occasional cycling of manual deicing systems to minimize ice accretions on the airframe. A representative accretion rate for reference purposes is ¼ inch to 1 inch (0.6 to 2.5 cm) per hour on the unprotected part of the outer wing. The pilot should consider exiting the icing condition.
3. Moderate. The rate of ice accumulation requires frequent cycling of manual deicing systems to minimize ice accretions on the airframe. A representative accretion rate for reference purposes is 1 to 3 inches (2.5 to 7.5 cm) per hour on the unprotected part of the outer wing. The pilot should consider exiting the icing condition as soon as possible.
4. Severe. The rate of ice accumulation is such that ice protection systems fail to remove the accumulation of ice and ice accumulates in locations not normally prone to icing, such as areas aft of protected surfaces and any other areas identified by the manufacturer. A representative accretion rate for reference purposes is more than 3 inches (7.5 cm) per hour on the unprotected part of the outer wing. By regulation, immediate exit is required.

1. REPORTING WIND SHEAR IN PIREPs

1. Wind shear is aircraft dependent.
2. Wind shear reports must include location, time (UTC), altitude/FL or range of altitudes, aircraft type, and description of wind shear. If the location and/or altitude is different than the /OV and/or /FL fields, include the location and/or altitude in the remarks.
3. Wind shear may be reported as plus (+), minus (-), or both (+/-) depending on how it affects the aircraft.
4. Wind shear descriptions.

1. Severe wind shear. A rapid change in wind direction or velocity which causes airspeed changes greater than 15 knots and/or vertical speed changes greater than 500 feet per minute.
2. Low‐level wind shear. Wind shear within 2,000 feet of the surface. When low‐level wind shear is reported, enter it as the first remark in the /RM TEI.
3. Vertical wind shear. Wind shear in a vertical direction.
4. Increasing headwind shear. Wind shear in which headwind increases causing an airspeed increase.
5. Decreasing headwind shear. Wind shear in which headwind decreases causing an airspeed loss.
6. Decreasing tailwind shear. Wind shear in which tailwind decreases causing an airspeed increase.
7. Increasing tailwind shear. Wind shear in which tailwind increases causing an airspeed loss.

1. PIREP HANDLING

1. Record PIREP data directly into the operational system, on FAA Form 7110-2, or on other material deemed appropriate (for example, 5” x 8” plain paper).
2. Upon receipt of a PIREP, accomplish the following:

1. Urgent.

1. Deliver to the ARTCC weather coordinator as soon as possible.
2. Enter into the operational system or on Service A as soon as possible.
3. Use in weather briefings, as appropriate.

1. Routine.

1. Transmit through the operational system or Service A as soon as practicable.
2. Use in weather briefings, as appropriate.

1. To assure proper dissemination of PIREPs to all system users, the encoding procedures listed below must be followed:

1. Identify each element by a TEI.
2. Ensure each report includes TEIs for message type, location, time, altitude/flight level, aircraft type, and at least one other to describe the reported phenomena.
3. Precede each TEI, except message type, with a space and a solidus (/).
4. Follow each TEI, except altitude/flight level, with a space.
5. Insert zeros in reported values when the number of digits in the report is less than the number required by the format.
6. Use only authorized aircraft designators and contractions.
7. In the location TEI, include any three character alphanumeric identifier to describe locations or routes. Use only authorized identifiers from FAA Order JO 7350.9, Location Identifiers.
8. Omit entries of TEIs, except as listed in subparagraph 8-1-9c2, for which no data was reported.

1. PIREPs must be coded to ensure the PIREP is stored and subsequently distributed with the surface observation location nearest the condition being reported. If more than one METAR location is appropriate, select the location that provides the greatest distribution and/or prominence, such as a major hub airport.