Dynamic flight, ridge and wave - expert technical guide

1. Ridge lift / hillside flight

Perpendicular component of the wind

The dynamic descent is generated by the component perpendicular to the crest line of the wind.

  • acceptable angular deviation: up to ± 30 ° from the perpendicular maintains efficiency. At 30 ° the useful component is cos (30 °) ∞ 87% of the total wind. At 45 ° it falls to 71% and it already appears parallel component that breaks the support band.
  • Departure threshold: above 45-60 ° deviation, the ridge ceases to function as a continuous band and is fragmented in local compression areas.

Angle of slope and efficiency

Vz ∞ V · sin (α):

  • 30 ° -45 °: ideal for paragliding and delta wing. Clean maintenance, minimum turbulence.
  • < 20 °: slope, wind just drifting up; only flying gliders or very thin wings.
  • > 60 °: cliff soaring pure; compressed area, intense rotor above the edge.
  • Vertical (90 °, cliff): band < 50m, strong and turbulent.

For paragliding with a 9: 1 plan, Vz > sink rate is required. With α = 30 ° and perpendicular wind 20 km / h (5.5 m / s), theoretical Vz ∞ 2.75 m / s.

Wind window valid for discipline

Paragliding:
- Useful minimum: 12-15 km / h perpendicular (standard EN-B / C)
- Maximum safe: 30-35 km / h perpendicular
- Golden rule: hillside wind < Vtrim − 10 km / h

hang glider

  • Minimum: 18-22 km / h (highest alar load)
  • Maximum: 45-55 km / h perpendicular

The form of the relief

  • Ridge line straight long: uniform band
  • isolated Hill: short band, maximum lift in central crest
  • Bowl / amphitheater: concentrates and amplifies lift (+ 30-50%), also concentrates rotor
  • Cliff: narrow, strong, technical band
  • Spur (spur): component convergence, amplified lift
  • Saddle / col: venturi trap

Double ridge

Optimal separation: 2-4 × first crest height. It can develop low-height wave between both formations.

2. Turbulence and rotor

Sotavent rotor

  • rotor height H vertically
  • Horizontal extension of the dangerous rotor: 5-8 × H with moderate wind; up to 20 × H or more with strong wind or wave setup
  • 20: 1 leeward rule: maintain horizontal distance ≥ 20 × relative height of the obstacle. Operating rule for automatic warnings in the BD.

Signs of dangerous rotor

  1. Wind > L / D of the wing (paragliding: > 35-40 km / h ridge = red flag)
  2. Flags oscillating to leeward
  3. visible in grass / water
  4. Rotary clouds (standing lentilaris rotor, roll clouds)
  5. Gust factor > 1.5
  6. Wind 700 hPa > 2 × surface wind with stability = wave + severe rotor

3. Venturi effect

Typical amplifications in steps / cols:
- Broad Col: + 20-40%
- narrow throat: + 50-100%
- Step between two mountain masses: × 2 or × 3

Cases: Tramontana, Mistral, Bora, Zonda de Cuyo. Cross wind 700 hPa with local geometry: 30 km / h synoptic aligned with a col → 50-70 km / h on surface.

4. Coastal / sea cliff

  • Laminar flow (sea = aerodynamically smooth)
  • Sea breeze amplifies the ridge during the day (local peak 14-17h)
  • Sea breeze can cancel it if a strong offshore synoptic
  • No thermal above the sea (dynamic pure lift)
  • Maritime investment: typical ceiling 300-800 m

5. Wave flight (orographic wave)

Training conditions

  1. Perpendicular wind ≥ 25-30 km / h surface, increasing with height (≥ 50-60 km / h to 700 hPa)
  2. Almost constant direction with height (veering < 30 ° between surface and 500 hPa)
  3. Stratified stability (investment on crest)
      • Froude number Fr = U / (N · h)
  5. Scorer parameter l ² (z): must decline with height (trapping)

Structure of the train

  • Primary wave: right behind the ridge, stronger
  • Secondary: 1-1.5 λ for the wind, 60-70% intensity
  • Tertiary and following: increasingly weak
  • Typical wavelength: 5-20 km

Visual signs

  • ACSL (Altocumulus Standing Lenticularis)
  • Cap cloud on crest
  • Roll / rotor cloud under primary (prohibited area)
  • Foehn gap a leeward
  • summit flags

Reachable heights

  • Paragliding: 4000-6000m usual, records > 8000m with oxygen
  • hang glider: similar, slightly higher
  • Planner: absolute record 23.203m (Perlan 2, 2018)

Accessibility

  • Paragliding: more difficult, needs to enter from thermal / ridge to primary base. Can't cross rotor
  • hang glider: better penetration
  • Planner: the king

6. Glass-off / refund

Mechanics: as the sun falls, W slopes continue to radiate heat as valleys cool. The remaining warm air in the mixed layer is laminated and ascended in a soft pen on the whole side.

Prediction:
- Strong heating + mixed layer > 2000m AGL
- Weak synoptic wind (< 15 km / h in 850 hPa)
- Clear sky at sunset
- stable gradient on mixed layer
- Duration: 30-90 min from 1-2h before sunset

Classical areas: Annecy, Organyà, Bir Billing, Roldanillo. Lift 0.3-1.0 m / s but very extensive - 20-40 km in calm.

7. Brisas

Sea breeze

  • Cats: ΔT tierra-sea > 3-4 ° C
  • Speed: 10-25 km / h front, 5-15 km / h inland
  • Penetration: 20-50 km (temperate), 100-200 km (arid)
  • Home 10-12h, peak 14-17h, sunset end
  • Sea breeze front: convergence with land flow - linear lift area, aligned clusters. Important XC tool.

Valley / anabatic

  • Home: 1-2h after sunrise
  • Speed: 5-20 km / h
  • Duration: up to 1-2h before sunset

Katabatic / night drainage

  • Speed 5-15 km / h valleys, 30-50 km / h glaciers (fall windows)
  • Danger: evening landings / landings, chaotic convergence, cold current channeled

8. Specific meteor variables for ridge / wave

What should be in BD and overlay:

  • Wind 10m (operating area)
  • Wind 80-100m AGL (crest)
  • Wind 925 / 850 / 700 / 500 hPa (vertical structure, veering, shear)
  • Vertical kernels: > 10 kt / 1000ft probable turbulence; > 15 kt critical
  • Froude number: Fr = U / (N · h). 0.5-1.5 favored wave
  • Scorer parameter l ² (z): decline with height = caught wave
  • Brunt-Väisälä N: layer stability
  • Pressure tendency 3h / 6h: fast fall = front
  • Hélicity / SRH
  • Richardson number Ri = N ² / (dU / dz) ²: Ri < 0.25 turbulence KH
  • Base / top investment and ΔT investment
  • CAPE / CIN
  • relative level humidity (RH 700 hPa > 70% = visible lenticular)

9. Source

  • RASP (Dr. Jack): WRF-derived, outputs BL wind / top, star, bsratio, CU / OD potential, wave lift. Free regional networks.
  • SkySight: own WRF, wave layer overlay, rotor probability, convergence zones, BL top. Resolution 2-6km, 15min.
  • Gliderweather.com / TopMeteo: sailing flight, excellent wave.
  • Meteo-Paragliding: outputs wave, shear, wind by layers.
  • Windy: ECMWF / ICON / GFS / AROME multimodel.

10. Webcams and local stations

Decisive in Dynamic because models fail in fine topography.

  • Holfuy.com: global network, accessible API. de facto standard in European PG. Integrate.
  • FFVL Balises: French network, Public API, 5 min.
  • Windy station network / PWS: added personal stations.
  • Netatmo: domestic network, limited API.
  • Pioupiou: PG / kite specific ultra-light sensors.
  • Meteociel / Infoclimat: webcams Europa.
  • Windguru stations: kite / windsurf, valid for coastal.

Recommendation for BD: each spot should have * holfuy _ id , * ffvl _ balise _ id , * webcam _ url , * live _ widget . Model serves for 24-72h; station + webcam decide go / no-go in last 2h. Realtime model confidence score = key differentiator.

Operational summary for termika.app

Cross:
- Perpendicular wind + slope + vertical shear → ridge lift score
- Froude + Scorer + veering → wave score
- Brisa + glass-off → time modes
- Holfuy / FFVL as ground truth
- Rule 20: 1 → warnings automatic rotor

Differentiator: combine thermal + dynamic + wave + breeze in a single time score per spot.
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