World Met Organisation

Wing Commander Rajagopal

Meteorological Organisation

World Meteorological Organisation (WMO)

  • World Meteorological Organisation (WMO) is a part of the United Nations Organisation that facilitates worldwide cooperation in consultation with the International Civil Aviation Organisation (ICAO).
  • World Weather Watch (WWW) coordinates using:
    • Global Observing System (GOS)
    • Global Telecommunication System (GTS)
    • Global Data Processing System (GDPS)
  • World Area Forecast System (WAFS) centres are located in London and Washington with 19 regional centres.
  • RWAFC, New Delhi provides global aeronautical en-route weather forecasts to meteorological offices.
  • WAFC prepares digital and gridded global forecasts four times daily and issues them within 6 hours of origin.
  • Forecasts contain:
    • Upper Winds
    • Temperature
    • Humidity
    • Maximum Wind
    • Icing
    • Turbulence
    • Cumulonimbus (CB) Clouds
    • Flight Level and Tropopause Temperature
  • WAFC also prepares SIGWX forecasts for radioactive material release and volcanic activity.

India Meteorological Department (IMD)

  • IMD has six Regional Meteorological Offices located at:
    • Delhi
    • Mumbai
    • Kolkata
    • Chennai
    • Guwahati
    • Nagpur
  • IMD Websites:
    • https://mausam.imd.gov.in
    • https://imd.gov.in
  • Meteorological Watch Offices (MWO) at Delhi, Mumbai, Kolkata, and Chennai provide meteorological services to their respective Flight Information Regions (FIR) and issue SIGMET.
  • Tropical Cyclone Advisory Centres (TCAC) monitor tropical cyclones and issue advisories on position, movement, pressure, and wind.
  • Aerodrome Meteorological Offices (AMO) are located at major airports and provide 24-hour weather watch.
  • AMOs issue:
    • METAR
    • SPECI
    • RVR
    • Weather Forecast
    • TAF
    • Landing Forecast
    • Aerodrome Warning
    • Briefing
    • VOLMET
    • ATIS
    • Radar Images
    • Satellite Images
  • Aeronautical Meteorological Stations (AMS) observe current weather and provide aeronautical forecasts during watch hours.

Meteorological Briefing

Notice Period for National Flights

  • AMO: 3 hours notice.
  • AMS: 18–24 hours notice.

Notice Period for International Flights

  • New Delhi, Kolkata, Mumbai, Chennai, Nagpur, Banaras, Guwahati, Hyderabad, and Thiruvananthapuram: 3 hours notice.
  • Other AMOs: 12 hours notice.
  • AMS: 18–24 hours notice.

Online Briefing System (OLBS)

AMOs provide an Online Briefing System (OLBS) consisting of:

  • Wind and Temperature (FL50 to FL530)
  • TAF (9 HR and 30 HR)
  • National and WAFC SIGWX Charts
  • METAR of major airports
  • Satellite Imagery
  • Radar Products
  • Synoptic Features
  • Route Forecast (T3 Format) for low-level flights
  • Local and Area Forecasts for airports in FIR
  • Take-off Data
  • SIGMET Warnings

Exchange of Meteorological Messages

  • VOLMET – Meteorological information for aircraft in flight.
  • D-VOLMET – Data Link VOLMET providing METAR, SPECI, TAF (9 HR), SIGMET, and AIRMET.
  • VOLMET Broadcast – Continuous broadcast of METAR, SPECI, TAF (9 HR), and SIGMET on VOLMET HF.
  • Broadcasts are made from Mumbai and Kolkata every 30 minutes.
  • ROBEX – Routine OPMET bulletin exchange for METAR, SPECI, and AIREP of international and alternate aerodromes outside India.
  • ATIS – Automatic Terminal Information System continuously broadcasting current weather information every half hour.
  • Current Weather Displays are computer-based systems used inside Meteorological Offices and ATC.

Meteorological Instruments

  • Surface Pressure (hPa, mb, inHg): Mercury Barometer, Aneroid Barometer, Barograph
  • Upper Air Pressure: Radiosonde, Dropsonde
  • Air Temperature (°C): Mercury or Alcohol Thermometer
  • Dew Point: Dry and Wet Bulb Thermometer
  • Relative Humidity (%): Dry and Wet Bulb, Hygrometer, Psychrometer
  • Humidity Mixing Ratio (g/kg): Hygrograph
  • Precipitation: Rain Gauge, Snow Gauge, Hyetograph
  • Wind: Wind Vane, Anemometer
  • Upper-Level Wind: Optical Theodolite, Pilot Balloon, RAWIN
  • Cloud Base: Searchlight, Laser Ceilometer, Balloon, Nephoscope, Alidade
  • Visibility: AVRA, Transmissometer, Scopograph, Forward Scatterometer
  • Cloud Observation: Weather Satellites, Radar

Pre-Flight Meteorological Briefing

  • Pre-flight meteorological briefing provides written, printed, and digital weather information up to 3 hours before departure.
  • Includes:
    • Upper Winds
    • Temperature
    • Maximum Wind
    • Jet Stream
    • Tropopause Height
  • Oral briefing is provided when the required notice period is inadequate.
  • Notice period:
    • AMO: 3 hours
    • AMS: 12 hours
  • Reports: METAR, SPECI, TREND, AIREP, SIGMET, VA
  • Forecasts: En-route Weather, TAF, Take-off Forecast, Wind Shear Warning
  • Charts: SIGWX Charts
  • Imagery: Satellite and Ground Radar
  • Low-level flight briefing (up to FL100, FL150 in mountainous regions) includes:
    • Poor Visibility (<5000 m)
    • Clouds affecting flight
    • SIGMET/AIRMET information

Meteorological Briefing Documentation

  • Flight documentation is issued in Chart or Tabular format.
  • Tabular Format (MET T3) for routes up to 500 NM.
  • Cross Section Format (MET T4) for routes beyond 500 NM.
  • Documentation includes:
    • Synoptic Situation
    • Surface Pressure Data
    • En-route Weather Outlook
    • Cloud Amount and Type
    • Upper Winds and Temperature
    • Freezing Level
    • Tropopause Data
    • Surface Visibility
  • Significant En-route Weather (High-Level Flights):
    • Thunderstorms (TS)
    • Cumulonimbus (CB)
    • Squall Line
    • Hail
    • Icing
    • Precipitation
    • Widespread Duststorm/Sandstorm (DS/SS)
    • Marked Mountain Waves
    • Moderate or Severe Turbulence
  • Additional Information for Low-Level Flights:
    • Fog
    • Precipitation
    • Weather likely to reduce visibility below 5000 m