Weather and meteorology 1LT Jan Kalvoda 22nd Náměšť AFB

Meteorology × Weather Meteorology – theory about wheather Weather – current conditions of atmosfere

Atmospheric phenomena Meteorogical elements Meteorology Atmospheric phenomena Meteorogical elements Rain Hail Fog Rainbow Halo phenomenon Lightning Aurora Temperature Precipitation Wind (speed, direction) Humidity Sunshine duration Snow cover Cloudiness

Pressure areas Depression - An area of low atmospheric pressure Anticyclone - An area of high pressure Ridge - A line of high pressure extending from an anticyclone Trough - A long area of low pressure running out of a depression. Isobar - A line on a synoptic chart joining points of equal pressure.

Wind movement of gases on a large scale Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds. Long-duration winds have various names associated with their average strength, such as breeze, gale, storm, and hurricane.

Fronts and frontal systems Cold front - The boundary between 2 air masses where cold air is overtaking warm air. Air temperature drops and atmosferic pressure grows.

Fronts and frontal systems Warm front - The ground level boundary between warm air and cold ahead of it. Warm air force out cold air and extensive cloudiness risen.

Fronts and frontal systems Occluded front - The boundary when a warm and cold front meet and the warm air is forced up above ground level.

Clouds

Cloud cover Expression Cloud cover Sky clear (SKC) No clouds Few (FEW) The amount of cloud which can be seen in the sky Expression Cloud cover Sky clear (SKC) No clouds Few (FEW) 1-2 oktas Scaterred (SCT) 3 – 4 oktas Broken (BKN) 5 – 7 oktas Overcast (OVC) 8 oktas

Colour codes Surface visibility Cloudbase (5 oktas or more) 8 km 2500 ft Blue 5 km 1500 ft White 3,7 km 700 ft Green 1,6 km 300 ft Yellow 0,8 km 200 ft Amber Less than 0,8 km Below 200 ft Red The visibility and cloud may be good but the airfield cannot be used for some other reason (the runway may be blocked for example). Black

VMC/IMC VMC – visibility more than 5 km, min. cloudbase 1500 ft (in case of 5/8 or more). IMC – any conditions worse than VMC.

Meteorological conditions for SVFR Minimum ground and flight visibility 1500m, for rotar wings, aircraft 800m only. Permanent visual contact with ground Minimum cloudbase 600ft/180m AGL. Out of clouds (Minimum flight hight 500ft/150m AGL)

Meteorological Causes of instrument meteorological Conditions Fog (radiation fog, advection fog) Precipitation (snow, heavy rain) Low Clouds (lifting, cooling) High surface Relative Humidity (RH) common factor in all causes of IMC

Precipitation – Water in any form, liquid or frozen falling from the sky Snow SN Rain RA Drizzle DZ Hail GR Ice pellets PL Snow grains SG Sleet Precipitation (e.g., rain, snow, hail): - light - moderate - heavy

Words associated with precipitation Intermittent Continuous shower Flurry Blizzard Isolated/ Ocassional Scattered Frequent Widespread Freezing Super cooled

Aviation weather hazards

Freezing level × Icing The freezing level, or 0°C (zero degree) isotherm represents the altitude in which the temperature is at 0°C (the freezing point of water) in a free atmosphere.  icing conditions are those atmospheric conditions that can lead to the formation of water ice on the surfaces of an aircraft.

Fog  It is a visible mass consisting of cloud water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud. Generally reported when vis <5km and there is no precipitation reducing visibility Types: radiation, ground, advection, evaporation, steam, ice, freezing, upslope fog.

Mist Mist (BR) is a phenomenon caused by small droplets of water suspended in air.   It is most commonly seen where warm, moist air meets sudden cooling The only difference between mist and fog is visibility.

SQUALL A squall is a sudden, sharp increase in wind speed that is usually associated with active weather, such as rain showers, thunderstorms, or heavy snow.

Turbulence “Bumpiness” in flight Four types Measured as Low-level turbulence (LLT) Turbulence near thunderstorms (TNT) Clear-air turbulence (CAT) Mountain wave turbulence (MWT) Measured as Light, moderate or severe vertical gust

Thunderstorms  is a type of storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as a thunder. Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds, heavy rain and sometimes snow, sleet, hail…

Dry microbursts from high based thunderstorms When precipitation falls through unsaturated air, evaporative cooling may produce dry microbursts Result in very hazardous shear conditions Visual clue: fallstrips (fall streaks that don’t reach the ground) Flight path of plane 45 kt downburst 45 kt headwind 45 kt tailwind

Weather reports

Name of report Content Field of action Issuer Form METAR Regular report (every 1 hour) Actual weather at airport Airport In code METREPORT Local regular weather report Actual weather Spoken words SPECI Exceptional weather report TREND Landing forecast Prediction for 2 hours ahead TAF Aerodrome forecast Prediction for 9/24 hours ahead Airport/ Area service GAMET Area forecast for low level flights Prediction for 5-6 hours ahead Area service AIRMET Information about phenomena missing in GAMET Warning

Name of report Content Field of action Issuer Form SIGMET Information about hazardous phenomena Actual weather and warning Area service In code AD WRNG Airport VOLMET Radio broadcasting for aircraft in air All Big airports ATIS Radio broadcasting for aircraft in air TMA AIREP Weather report from aircraft in the air Actual wethar Aicraft in air

Thank you for your attention… Questions??

Sources Aviation phraseology and terminology for procedures for navigation services Air operational English course Wikipedia