Meteorology for the Soaring Pilot Joerg Stieber Canadian Advanced Soaring

Why do we need to know this? Macro weather –Weather systems (Highs, Lows, fronts) –Rain or shine Micro weather –Why are the cu here and not there? –Local effects like convergence, lake effect, etc. Canadian Advanced Soaring profound of the weather is the basis for reaching your goals as a XC Pilot. A profound understanding of the weather is the basis for reaching your goals as a XC Pilot.

The Atmosphere Think of it as an ocean of air All weather relevant to gliding occurs below 35,000ft (Troposphere) Different airmasses and their properties –Temperature –Humidity Warm air can hold more moisture than cold air Percent of saturation (public weather) Dew point: Temperature at which an airmass is saturated (aviation reports) Canadian Advanced Soaring

Fronts Fronts are boundaries between different airmasses They pass over us as airmasses move like currents in an ocean –Cold Front Cold air displaces warm air –Temperature drop, gusty NW winds, likely rain, possibly thunder, quick passage – clear behind –Warm Front Warm air displaces cold air –Thickening layers of clouds, steady rain, slow passage Canadian Advanced Soaring

Cold Front Canadian Advanced Soaring Ground Good soaring conditions conditions Tephi 18 – 24 hrs

Warm Front Canadian Advanced Soaring Ground

Weather Systems Low Pressure System –Cyclone –Unstable airmass, rises – clouds and precipitation –Inflow counter clock wise (northern hemisphere) – Mixing of different airmasses - fronts High Pressure System –Anticyclone –Airmass sinks (0.2 kts) –Clockwise outflow Canadian Advanced Soaring Isobars

Weather Maps Canadian Advanced Soaring

How Thermals Work Sun heats the ground (not the air) Ground transfers heat to the lowest layers of air A pocket of hot air develops at ground level Eventually the pocket of hot air takes off Canadian Advanced Soaring 20 C 25 C 20 C

The parcel of air cools as a result of expanding as the pressure drops with height –adiabatic lapse rate – dry / wet Environmental lapse rate ~ -2C per 1000ft Canadian Advanced Soaring 9 C 15 C

Canadian Advanced Soaring Unstable 15 C

Canadian Advanced Soaring Unstable 15 C 17 C

Canadian Advanced Soaring Questions??

Temperature Ground Inversion Inversion Dry Adiabatic Lapse Rate Trigger Tephigram Back to Cold Front Back to Cold Front

The Tephigram Temperature and humidity over altitude The tephigram shows if a particular airmass is stable or unstable and allows us to forecast –thermal strength –depth (height) of convection –trigger temperature –Clouds –Overdevelopment The easiest to use is the NOAA Java based plot at: Canadian Advanced Soaring

Skewed Tephi

4 Different Tephis 4 Different Tephis (Dave Springford) Blue soaring day Good soaring day Over-development Cu spreading out Canadian Advanced Soaring

Convection without Clouds Convection without Clouds the dreaded blue day Canadian Advanced Soaring parcel rises while unstable (along dry adiabatic LR) parcel stops rising before saturating moisture content of parcel Ground temp from daytime heating Saturation point follow mixing ratio (Dave Springford)

Convection with Clouds Convection with Clouds Fair weather Cu Canadian Advanced Soaring temperature profile of airmass includes upper level inversion parcel rises while unstable along dry adiabatic LR parcel saturates here moisture content saturated parcel continues to rise along wet adiabatic LR parcel stops rising clouds between 825 and 875 mb (Dave Springford)

Canadian Advanced Soaring

Over Development (CBs) Canadian Advanced Soaring temperature profile of airmass does not include inversion until 40,000 ft parcel rises while unstable parcel saturates saturated parcel rises along wet adiabatic LR clouds between 825 and < 200 mb (Dave Springford)

Canadian Advanced Soaring Towering Cu - Precip Showers are still flyable but one has to keep a close eye on the weather and pick the route carefully

CBs – Thunderstorms CBs – Thunderstorms Better make sure the plane is secure! Canadian Advanced Soaring

CBs – Thunderstorms CBs – Thunderstorms Better make sure the plane is secure! Canadian Advanced Soaring

(Dave Springford)

Canadian Advanced Soaring

Questions??

Looking a Week ahead Looking a Week ahead Any good Days coming up? Long-term forecast (5 – 7 days) –Public forecast: – –Unisys 10 day forecast: Forecast maps for days 2-3 –Intellicast Dr. Jack/XC Skies for days NAM & RUC – Canadian Advanced Soaring Unisys Map Dr Jack Jump to Day

Canadian Advanced Soaring

Good Weather Systems Canadian Advanced Soaring (Dave Springford) Back to Week ahead

Canadian Advanced Soaring SW Ontario

On the Day of the Flight Look out the window –You should see clear blue sky or small low cu (after a recent cold front) –The air should feel fresh and cool Public forecast –WX, max temperature, dew point, any change later? –Cloud base in ft AGL = 400*(Tmax – Tdewp) (if the thermals go that high) Tephi for Kitchener/London (16z, 18z, 21z) –Airmass, height of inversion, cu?, winds aloft Satellite Picture – clear? Nav Canada – Prog Charts (18z) –change in airmass expected? Dr. Jack or XC-Skies –thermal strength, height, cu, boyancy/shear (18z, 21z) Canadian Advanced Soaring

Special Situations Cloud streets –On windy days – form upwind/downwind Lake effect –Wind off the lakes L. Ontario (E-wind), Erie (S-wind), Huron NW Sea breeze –General wind direction 5 – 10 kts off-shore Convergence Canadian Advanced Soaring Cloud Street Lake Effect Convergence

Cloud Street Canadian Advanced Soaring Back

Canadian Advanced Soaring Back

Lake Effect due to easterly wind Seabreeze along Lake Huron Convergence on the Niagara Peninsula Lake Effect & Convergence

Convergence West of London Canadian Advanced Soaring

Internet Sources The first thing you need is a public forecast from Environment Canada to give a general weather pictureEnvironment Canada –Sun or rain?For what Period? –Max temp for the day?Dewpoint? –Wind direction? Next an overall picture of the frontal systems in NA is helpful –I use either Intellicast or UnisysIntellicastUnisys A satellite picture can also help –the GOES Satellite picture is good: –Weatherundergound: A clouds and weather forecast from NavCanada is also helpfulNavCanada (check the IR too) (Dave Springford)