Meteorology applied to thermal flight - Expert technical report

1. Thermal types

Fixed thermal: recurring points on stable topographic triggers - dark rocks, quarries, dry crops, villages, asphalt parkings. Low albedo (0.10-0.15) + low heat capacity. Vertical column of competition tasks because they are predictable.

Column thermal: stationary mature thermal, 100-300m diameter, core compact core > 4 m / s surrounded by descending ring. Typics in low cutting (shear < 10 kt / km vertical). they climb at 360 ° closed.

Bubble thermics: discrete bubbles that are regularly deposed, diameter 50-150m, short life (3-8 min). Common 1-last hour and in thin BL (< 1000m AGL). They require reactive flight.

Dust diabls: vertical vortices axis on very hot surfaces, ΔT solo-air > 15 ° C. Diameter 5-50m, rotation 10-25 m / s. Dangerous near ground but mark exceptional thermal at 100-200m AGL.

shear thermal: deformed / tilted by cutting > 15 kt between ground and top BL. Core moved; they require "derivative-and-search" to leeward. Severe cutting → broken thermal (broken), effective climb -30-50%.

Convergence Thermics: continuous line of ascending over mass border. Streets of tens of km, climate sustained 1-2 m / s allowing straight flight without turning (ridge-soaring without relief).

2. McCready / Speed to Fly

Formula: V _ stf = f (polar, MC, wind, sink areas), where MC = expected rate next thermal.

Typical polar paragliding (glide ratio max 9-11 at 38 km / h, min sink 1.0 m / s at 28 km / h):
- MC = 0 (expected weak thermal): min sink (28 km / h)
- MC = 2 m / s: ~ 42-45 km / h (1 / 3-1 / 2 bar)

Application to prognosis: w * → PG useful climb: 'climb _ util ∞ 0.5-0.7 × w *' (mean vs core + focused efficiency).

Example: w * = 3 m / s → climb 1.8 m / s → MC 1.5 → STF 40 km / h → task speed ~ 25-30 km / h (considering rising fraction).

3. Trigger Temperature

Concept: T minimum surface that breaks night investment and reaches free convection level (LFC).

Calculation: from the morning survey (12Z analysis / 06Z planned), project dry adiabatic from surface to cross environmental profile. T _ trigger = that superficial T.

Field rule: T _ trigger ∞ T _ 850hPa × (P _ sup / 850) ^ 0.286 + 3 ° C (+ 3 ° superheat floor-oriented).

Variable to predict trigger time:
- incident radiation SW _ down (W / m ²) - integral from dawn
- T2m time forecast
- Smoke ground 0-7cm (soil moisture): delayed wet soil (Bowen ratio)
- Low cloud coverage
- Slope aspect: slope S advance trigger 1-2h over N in spring

shot time = hour where T2m planned reaches T _ trigger. Typically 10: 30-12: 00 Mediterranean spring, 09: 30-10: 30 continental summer.

4. Non-standard pro indicators in Open-Meteo

w * (Deardorff convective speed)

"'
w * = [g · (H / (¥· cp · T)) · z _ i] ^ (1 / 3)
"'
H = surface sensitive heat flow, z _ i = height BL. It gives feature speed updraft layer mixed.

Paragliding thresholds:
- w * < 1 m / s: low day
- 1.5-2.5: normal day
- > 3: strong day
- > 4: powerful day with OD risk

It is derived from 'sensitive _ heat _ flux' + 'boundary _ layer _ height' in Open-Meteo.

Thermal Index (IT)
IT = T _ plot (z) − T _ environment (z) at 850 hPa or top BL.
- IT ≤ − 2 ° C: vigorous convection
- 0 to − 2: weak
- > 0: stable (no thermal)

RASP / Dr. Jack classic indicator.

B / D ratio (Blue / Developed)

Cook dry BL height / condensation height (LCL).
- B / D > 1: blue day (no clusters, top BL)
- B / D < 1: heat-marking clusters
- < 0.7: OD risk
- Ideal 0.8-1.0: dispersed clusters marking without overdevelopment

Buoyancy / Shear ratio
Bulk Ri convective: Ri _ B = (g / θ) · Δθ · z _ i / (Δu ² + Δv ²)
- Ri _ B > 10: clean columnar thermal
- 3-10: usable inclinations
- < 3: broken / unorganized

Over-development signs

  • CAPE > 800 J / kg with CIN < 20 J / kg
  • Lifted Index < − 4
  • K-index > 30
  • Humidity mid-level (500-700 hPa) increasing during the day
  • Precious water > 25mm (continental)
  • Mass-flux convergence to mid-high BL
  • Cloud top height > 1.5 × z _ i

paragliding -polar planning calculations

Integrate L / D vs V polar with 3D wind field (u, v to BL heights) for possible planning distance from each point. Final planning maps and task viability. It requires wind 1500 / 3000 / 5000 m AGL hours.

5. Convergences

Sea breeze

Fresh sea air border ↔ continental hot.
- Indoor thermal gradient > 8 ° C, synoptic wind < 15 kt
- Convergence produces line CU aligned perpendicular coast
- Advance 20-80 km / day according to synoptic
- Key variable: surface divergence

Valley breeze / anapatic
- Get up sunny valley earrings
- Convert to headers and crest
- Maps: parallel wind component valley axis, growing in tomorrow
- Systematic slope thermal production and divisional convergence

Mountain-plain boundary

  • Anabatic flow convergence mountain ↔ plain
  • Common Pyrenees / Alps face S late
  • Maps: maximum vertical speed lined with pediemonte
  • XC flight of hundreds of km following the line

Dry line

  • Dry mass border (continental) ↔ wet (sea / Gulf)
  • No large thermal contrast but dewpoint > 8 ° C in 50 km
  • Dry side: higher BL, stronger thermal
  • Line shoots powerful convection
  • Visible on 2m or theta-e surface maps

Visualization in forelast maps

Combine:
- Surface convergence
- Vertical speed 850 / 700 hPa
- horizontal gradients theta / dewpoint
- streets of clouds on synthetic satellite

SkySight has specific "overlay convergence.".

6. Emagram / Vertical Scanning - Pilot Reading XC

  1. T surface max vs ambient curve: dry adiabatic to intersection top thermal BL (z _ i).
  2. Surface dew point: saturated adiabatic LCL (cloud base). Gap LCL − z _ i: if day is blue or with CU.
  3. Investments: dT / dz > 0 or < attenuated dry adiabatic sections. Substitution (anti-cyclone) = hard roof.
  4. Side Hodograph: wind by level. Changes > 30 ° in dir between surface and top BL = broken thermal.
  5. Humidad mid-level: dry 700-500 hPa = CU do not grow (good). Wet = probable OD.
  6. CAPE / CIN: CAPE 200-800 J / kg ideal. CIN > 50 trigger delay but allows accumulation (explosive days).
  7. Equilibrium Level (EL): height max deep convection if there is OD.

Fast interpretation: dry adiabatic profile developed up to 2500-3500m AGL, soft investment ceiling, dry air up, wind < 20 kt turned < 30 °.

7. Investments

Low-level inversion (nocturnal / radiative)

Radiative ground cooling. Thickness 100-500m. It must be broken to start convection - it defines time of shooting. Persistent valleys (winter thermal investments) can last all day.

Capping inversion
Hunting in anti-cyclonic dorsal. BL peak (1500-3500m AGL per station). Define daily thermal ceiling.
- ΔT > 3 ° C in 200m: it breaks with powerful convection (breakthrough)
- ΔT < 1.5 ° C: porous, strong thermal drill → "chimneys"
- ΔT ~ 2-3 ° C: firm cover

Trade-wind inversion

Persistent subtropical, Hadley cell. Low ceilings 1500-2500m (Canary Islands, Hawaii, Caribbean). Very stable. Define local flight style (ridge + low thermal).

Top operating XC

top _ op = min (dynamic z _ i, investment base)

8. Over-Development and closing time

Signs announcing OD
- CU grows vertical faster than horizontal (aspect ratio < 1)
- Fuse CU → cumulonimbus: anvil
- Dark sky → cut radiation → heat flux collapse → switch off in 20-40 min
- Gust fronts, outflow boundaries: surface wind rachted changing dir
- Virga (evaporating tip): fresh BL
- Increased humidity 925 / 850 hPa during the afternoon

Closing time mechanisms
1. Convective Shadow: nubosity > 70% short radiation
2. Precipitation: cold / humidify BL, destroys adiabatic profile
3. Synoptic front / pulse: cold / wet air height elevates LI, shoots OD
4. Decline evening: after max solar (14-15h summer), H falls, w * decreases as H ^ (1 / 3). Thermals disappear 1-2h before sunset.

Monitoring real time

  • Time CAPE
  • Total cloud cover trend
  • Cloud top height trend
  • Surface convergence
  • Wet 700 hPa

Mapping to pro platform variables

  • 124; Variable - 124; SkySight - 124; RASP Dr. Jack - 124; meteor - paragliding - 124; Open- Meteum necessary - 124;
  • 124; --- - 124; --- - 124; --- - 124; --- - 124; --- - 124;
  • 124; Thermal strength - 124; "Thermal strength" - 124; 'wstar _ bsratio' - 124; "Ascendances" (m / s) - 124; 'sensitive _ heat _ flux + bl _ height' - 124;
  • 124; Thermal top - 124; "Thermal Top" - 124; 'hbl' - 124; "Plafond" - 124; 'boundary _ layer _ height' - 124;
  • 124; Cloud base - 124; "Cu Base" - 124; 'bl _ cloud base' - 124; "Base cumulus" - 124; T2m + Td2m (Espy) - 124;
  • 124; Cu depth - 124; "Cu Depth" - - 124; - 124; - Cloud top − LCL - 124;
  • 124; B / S ratio - 124; "BS Ratio" - 124; 'wstar _ bsratio' - 124; "Turbulence" - 124;

Minimum operating variables that termika.app should compute

By point × hour:

w_star             # m/s, Deardorff
z_bl               # m AGL, top BL
cloudbase_lcl      # m AGL, base CU
TI_850             # °C, Thermal Index a 850 hPa
trigger_time       # hora local, inicio convección útil
cutoff_time        # hora local, fin thermal diurna
od_risk_index      # 0-100, riesgo overdevelopment (OD)
shear_bl           # kt/km, cortante vertical BL
convergence_flag   # bool, línea convergencia presente
top_operativo      # min(z_bl, base_inversión) m AGL
stf_optimo         # km/h, speed-to-fly McCready
glide_achievable   # km, planeo final polar + viento

All derived from Open-Meteo without APIs paid. Thermika.app: compute them with a documented and open recipe (most services hide them after paywall).
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