Pilot to Metro Service. Military weather units operate a Pilot to Metro Service (PMSV) at selected Air Force, Army, and Navy airfields to provide aircrews a direct contact with weather forecasters or observers. The primary purpose of PMSV is for communicating various types of weather information to pilots. PMSV is also used to update the Flight Weather Briefing Form (DD-175-1) and to receive pilot weather reports (PIREPS) of significant or hazardous weather phenomena, which are entered into weather telecommunications networks for dissemination.

PMSV facilities manned by forecasters are listed as "Full Service" while PMSV facilities manned by weather observers are listed as "Limited Service". When an observer responds to a call, they will identify themselves as an observer, state that no forecaster is available, and relay only surface observations, radar observations, terminal forecasts and military weather advisories. If additional forecast information is necessary, the observer will refer the aircrew to a full service PMSV facility where a forecaster is on duty. The radio call for PMSV is "METRO", e.g., "Travis METRO". When requesting terminal weather, advise the forecaster/observer of your ETA.

A Pilot Report (PIREP) is an aircrew report of weather conditions at altitude. PIREPs are extremely important to operations. Airborne crews can see a broader horizon and experience phenomena, which may be hidden from the weather observer’s ground view point. For example, cloud bases and tops, turbulence and icing may only be evident to airborne crew. While ground observations contain valuable information, they may not meet the need for information on weather conditions at altitude. Weather technicians use PIREPs to service other aircrews and to aid forecasting. PIREPs are transmitted over selected navigational aids and weather data nets. Air traffic controllers will relay PIREPs to other affected aircrews and weather technicians.

The PIREP format includes a "message type" (UUA: severe; UA: regular) and text element indicators preceding data groups. Indicators consist of a slash (/), two letters, and a space (except for "FL" which is not followed by a space. Aircraft position is relative to an omni-range transmitter TACAN, VORTAC, /VOR) with a six digit group giving the relative bearing (first three digits) and distance (last three digits) from the omni-range. "DURGC" (during climb) or "DURGD" (during descent) indicates PIREPS received by aircraft taking-off or landing.

Indicators:

/OV Indicates aircraft position, time of observation, and altitude

/TM Time of observation (Z)

/FL Altitude (flight level)

/TP Type of aircraft

/SK Sky cover

/WX Visibility and weather (visibility to nearest mile)

/TA Temperature (C)

/WV Wind direction and speed (six digits)

/TB Turbulence (includes intensity, type, and altitude)

/IC Icing (includes intensity, type, and altitude)

/RM Remarks clarifying coded elements and adds significant data

A. Hail (GR or GS)

B. Low-Level Wind Shear (LLWS)

C. Severe icing

D. Severe or extreme turbulence, including Clear Air Turbulence (CAT)

E. Tornado, funnel cloud, or waterspout (FC).

F. Volcanic Eruption and/or Ash (VA), in the air or on the ground.

G. Any condition that, in the judgment of the person entering the PIREP into the system, would present an extreme hazard to flight.

Example: Regular PIREP from 315 degrees and 45 miles from Scott AFB, 2224Z, at an unknown flight level. Aircraft is a C-9, observed a broken line of thunderstorms aligned north to south with occasional lightning from cloud to cloud and from cloud to ground. Cloud bases are at 3,000 ft, unknown total sky cover and cloud tops at 34,500 ft.

BLV UA/OV BLV 315045/TM 2224/FL UNKN/TP C9/RM BKN LN TSTMS N-S OCNL LTGCCCG 030 UNKN 345.

Severe Weather Forecast Alert (AWW). AWW is a preliminary message used to alert airmen that a Severe Weather Bulletin (WW) is being issued. AWW defines an area of possible severe thunderstorms or tornado activity.

Example: MKC AWW 655 WW 279 SEVERE TSTM NY PA NJ 1630Z-1700Z. 70 STATUTE MILES EITHER SIDE OF LINE 10W KMSS TO 20E KABE. AVIATION COORDS 60 NM EITHER SIDE 16O NW KSLK - 35 W KEWR. HAIL SURFACE AND ALOFT. SURFACE WIND GUSTS 65 KNOTS. MAX TOPS TO 540. MEAN WIND VECTOR 19020. REPLACES WW 278. OH PA NY

Convective SIGMET. Convective SIGMETs (WST) are issued by time and region, and are associated with thunderstorms. WSTs are issued hourly as required. They are valid for two hours or until superseded. Bulletins consist of an observation and/or a forecast. WSTs cover one of three areas: Eastern (E), Central (C), and Western (W), defined by longitudinal boundaries of 87 and 107 degrees West. Hourly, an Outlook is issued for each region. The Outlook is a 2-6 hour projected thunderstorm activity discussion listed at the end of the WST and is updated as required. WSTs are issued for:

1. Severe thunderstorm with surface winds greater than or equal to 50 knots

2. Hail greater than or equal to 3/4 inches in diameter

3. Tornados

4. Embedded thunderstorms

5. A line of thunderstorms

6. Thunderstorms greater than or equal to VIP 4 affecting 40% or more of a 3,000 square mile area

Example:

WSUS42 KMKC 201852

WSTW

MKCW WST 201855

CONVECTIVE SIGMET...NONE

OUTLOOK VALID 202055-210055

TS ARE NOT EXPD TO REQUIRE WST ISSUANCES.

Airmen's Meteorological Information (AIRMET). AIRMETs are issued only to amend the area forecast concerning weather phenomena which are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualification. AIRMETs concern weather of less severity than that covered by SIGMETs or convective SIGMETs. AIRMETS must affect at least a 3,000 square mile area.

Sierra Bulletin (reserved for IFR and mountain obscuration)

1. Ceilings less than 1000 feet and /or visibility less than 3 miles affecting over 50% of the area

2. Extensive mountain obscuration

Tango Bulletin (reserved for wind related phenomena)

1. Moderate turbulence

2. Sustained surface winds of 30 knots or more

1. Moderate icing