Understanding Flybot

What is Flybot?

Flybot is an AI Paragliding Forecast for the UK. It helps paraglider pilots spend more time flying and less time pondering weather forecasts. While checking a detailed forecast is essential before flying, Flybot quickly identifies which sites and dates/times are likely to work.

How to Use Flybot

For the best experience, add Flybot to your mobile home screen! This gives you instant access to forecasts without opening your browser.

Recommended workflow:

1. Add your favorites: Browse to your local sites and click the star button to add them to your favorites (up to 20 sites)
2. Use the dashboard: Open the ⭐ Favorites Dashboard to see quick summaries for all your saved sites at a glance
3. Quick decision-making: Step through your favorite sites on the dashboard to identify the best flying opportunities for the day

Join the Telegram community! Get instant notifications for all flyable sites across the UK delivered to your phone. You can mute specific regional channels if you're only interested in certain areas, but it's an excellent way to discover new sites when you're traveling or exploring different parts of the country.

Interpreting the Forecast Graph

The forecast is displayed as a 6-track timeline showing hourly daytime conditions. Nighttime hours are automatically filtered out.

Track 1: Flyability Score

What it shows: A blue line representing the probability (0 to 100) that conditions are flyable.

• >50: Flyable conditions (shown with green background)
• >30: Potentially flyable - check other parameters carefully
• <30: Low probability of flyable conditions

The higher the score, the better! Low values indicate a lower probability of being flyable. When the score is high and XC Potential >50, the background turns purple indicating XC conditions.

Track 1.5: Mini Wing Suitability

What it shows: An orange line showing suitability for mini wing paragliders (0-100%). Mini wings are small, high-performance paragliders designed for strong-wind ridge soaring in smooth, laminar conditions.

What conditions create mini wing suitability? The model identifies very specific conditions where mini wings excel:

Core Requirements (Coastal and Inland sites):

• Wind Speed: 5.0-9.7 m/s (18-35 km/h) - the "sweet spot" for mini wing soaring
• Wind Alignment: Within ±30° of site takeoff aspect (wind hitting slope directly)
• Low Wind Shear: Smooth vertical wind profile (shear <5 m/s between 10m-500m AGL)
• Low Gusts (Coastal): Gust ratio <1.35 and gust excess <3.5 m/s
• Low Gusts (Inland): Gust ratio <1.25 and gust excess <2.5 m/s (stricter for inland turbulence)

Additional Requirements for Inland Sites:

• No Thermal Activity: Thermal quality stars = 0 (thermals create turbulence incompatible with mini wing flying)
• Slow Thermal Release: Time to release >90 minutes (indicates stable, non-convective conditions)
• Stable Atmosphere: Positive Richardson number (stable air mass, no convection)

Safety Overrides (All Sites):

• Fog: Any significant fog (fog area fraction >0.3) makes conditions unsuitable
• Precipitation: Any rain, drizzle, or snow immediately disqualifies mini wing flying

Why the distinction between coastal and inland? Coastal sites benefit from marine boundary layer flow which tends to be smoother and more laminar, allowing slightly higher gust tolerances. Inland sites are more prone to mechanical turbulence and thermal activity, requiring stricter criteria and explicit checks for stable, non-thermal conditions.

Mini Wing Quality Score (0-1.0): The model also provides a confidence score combining:

• Wind Quality (30%): How close to the ideal wind speed of 7.35 m/s (26 km/h)
• Alignment Quality (30%): How directly the wind hits the slope (closer to head-on = better)
• Gust Quality (40%): How smooth the wind is (lower gusts = higher quality)

Practical interpretation: Mini wing conditions are rare and specialized. When the orange line shows high values (70-100%), experienced mini wing pilots will find ideal conditions: strong, smooth, laminar ridge lift without thermals or turbulence. These are typically stable high-pressure days with brisk winds and no convection.

Track 2: Wind Speed & Direction

Wind Speed (km/h): Large numbers show wind speed at site elevation, color-coded by safety:

• Green (10-20 km/h): Good flying conditions for most pilots
• Orange (20-30 km/h): Experienced pilots and mini wings only
• Red (>30 km/h): Dangerous conditions - avoid flying
• Grey (any speed): Insufficient vertical wind component for ridge soaring (see "Understanding Grey Wind Speed" below)

Gust Difference (+X km/h): Shown in orange below the wind speed. Be cautious when gust differences exceed 10-15 km/h, as this indicates turbulent conditions. Higher gust differences suggest unstable air and increased turbulence risk.

Wind Direction Arrow: Small arrow at top shows wind direction:

• Green arrow: Wind direction is within the sites flyable range
• Grey arrow: Wind direction is outside the sites flyable range

Flyable Wind Sectors (Blue Arcs) in the windrose: The wind compass shows blue arcs representing ±30 degrees off the main fall line for the hill. Outside of these zones, the vertical component of rising air will be reduced and there is greater chance of rotor spilling across the site.

Understanding Grey Wind Speed (Soarable Flag)

What does grey wind speed mean? When wind speed is displayed in grey, it indicates that even though the wind direction may be within the flyable range, the vertical wind component is insufficient for ridge soaring.

How is this calculated? The model decomposes the wind vector into components relative to the site's takeoff aspect and slope:

1. Wind Alignment: Calculate how directly the wind is hitting the slope face (head-on = 1.0, crosswind = 0.0, tailwind = negative)
2. Slope Effect: Factor in the slope steepness (steeper slopes produce stronger lift for a given wind speed)
3. Vertical Component: Calculate the upward wind component: Wind Speed × sin(slope angle) × alignment factor
4. Soarability Threshold: If vertical component < 0.5 m/s (~1.8 km/h), the site is marked as non-soarable

Why does this matter? This commonly occurs when:

• Wind is at the edge of the flyable range (shallow angle to slope)
• Wind speed is light but within the "green" range
• Combination of light wind and poor alignment reduces the effective lift

Practical interpretation: Grey wind speed means "the wind direction might technically be OK, but you won't get enough lift to stay up." This is different from a grey arrow (wind outside flyable range) or light green wind (light but adequate vertical component).

Track 3: Wind at 500m AGL

Understanding Wind at 500m AGL vs Ground Level:

Wind Speed Delta: Shows the difference between the wind speed at 500m above takeoff vs takeoff (in km/h):

• Small difference (≤ 10 km/h): Little change in strength with height.
• Moderate difference (10–25 km/h): Increasing wind with height – expect possible turbulence or drift if going XC
• Large difference (> 25 km/h): Wind shear; top-end conditions may feel much stronger than the ground wind suggests

Wind Direction at 500m: The direction arrow shows wind at 500m AGL, colored based on both directional consistency and speed difference with ground wind:

• Green arrow: Small speed difference (<10 km/h) AND angular difference <30° – consistent airflow with height
• Orange arrow: Moderate speed difference (10-25 km/h) OR angular difference 30-60° – expect some wind shear, drift, or turbulence
• Red arrow: Large speed difference (>25 km/h) OR angular difference >60° – significant wind shear, potentially turbulent conditions

Track 4: Thermal Strength Analysis

Thermal Quality Stars (0-3): This is a synthesized rating of pure thermal potential, derived from multiple meteorological components. It is differnt to RASP starts and is unique to Flybot. It is also independent of wind, turbulence, or convective hazards.

• 3 Stars ⭐⭐⭐: Excellent XC Conditions
  • Interpretation: Expect a classic "XC highway" day. Thermals are likely to be strong, wide, well-organized, and frequent, with a high cloudbase providing ample working height for long, efficient glides.
  • Model Notes: The rating achieves a high score by seeing exceptional values in the most heavily weighted components: a very high thermal strength_score (driven by a fast `time_to_release_base`), an excellent height_score (working height >2500m), and good organization_score (ideal lapse rate). The score is often pushed into the top tier by a significant cu_bonus for optimal cloud markers.
• 2 Stars ⭐⭐: Good, Reliable XC Conditions
  • Interpretation: A solid day for cross-country flying. Thermals should be reliable and consistently reach a good working height. Climbs may be more moderate than a 3-star day, but conditions are dependable for planning and executing an XC flight.
  • Model Notes: This rating reflects a well-balanced atmospheric profile. No single component needs to be perfect, but the weighted average of strength, height, organization, and energy (CAPE) is comfortably above the threshold for reliable convection. It indicates conditions without significant limiting factors.
• 1 Star ⭐: Marginal/Weak Thermal Conditions
  • Interpretation: Expect a challenging day of "scratching" for lift. Thermals will likely be weak, narrow, broken, or infrequent. Staying aloft will require skill and patience; XC is improbable.
  • Model Notes: The low rating is caused by one or more critical components scoring poorly. Common causes include: a very low strength_score (long release time), a restrictive height_score (working height <1500m), a poor organization_score (atmosphere is too stable), or a blue_day_penalty being applied due to a lack of cloud markers.
• 0 Stars: No Thermal Activity
  • Interpretation: Soaring and sled rides only. The air is either stable or sinking.
  • Model Notes: This is an override condition. We check `surface_upward_sensible_heat_flux`. If it is below a near-zero threshold (≤10 W/m²), the rating is forced to 0, regardless of any other atmospheric potential.

Time to Release: This parameter is a physically-derived estimate of the thermal duty cycle, representing the time required for the ground to heat a surface-layer air parcel to the point of buoyant release. It's a more sophisticated metric for thermal strength than sensible heat flux alone.

How It's Calculated: The model computes this value by solving a simplified energy balance equation:

Time = Energy Required / Rate of Energy Input

1. Energy Required (The Numerator): This is the total energy needed to trigger a thermal. It depends on:
   • Mixing Depth: The depth of the air layer that needs heating, determined by the wind-mixed layer and capped by the LCL. The wind-mixing layer is defined as the volume of air that must be heated before a thermal can form. This captures both realistic parcel depth and the effect of thermal shredding in high wind. In low wind, the mixing layer is shallow and so the sun's energy is concentrated into a small volume, which heats up quickly and reaches its trigger temperature to release a thermal. So time to release is low. In high winds, the mixing layer is much deeper, so the same amount of solar energy has to be distributed through a much larger volume of air. Therefore it takes a much longer time for this layer to heat up to its trigger temperature. So release time is long.
   • Required Temperature Kick: This is dynamically calculated temperature increase needed to overcome atmospheric stability. On an unstable day (high lapse rate), the kick required is very small. On a stable day, a much larger temperature kick is needed to force a parcel to release.
2. Rate of Energy Input (The Denominator): This is the Sensible Heat Flux (H). The model has a robust hierarchy for determining this value:
   • It prioritizes the met offices UK2km paramate `surface_upward_sensible_heat_flux` directly.
   • If unavailable, it calculates `H` using a bulk aerodynamic formula based on the surface-to-air temperature difference and wind speed.
   • As a final fallback, it estimates `H` as a dynamic fraction of incoming solar radiation, adjusted for surface moisture proxies like recent rainfall and relative humidity.

Interpretation: A short release time (<15 min) indicates a rapid thermal cycle with strong and frequent lift. A long release time (>30 min) suggests infrequent, weaker thermals that require more patience to find and utilize. It effectively describes the rhythm of the day.

Colour coded with red: <10 mins (very fast release), orange: 10-20 mins (fast release), green: 20-30 mins (moderate release), blue: 30-60 mins (slow release).

Track 5: Temperature

Temperature at 1000m AGL (top row): Shows how cold it will be at altitude, helping you dress accordingly. Color-coded from icy blue (cold) through green (mild).

Temperature at Site Elevation (bottom row): Ground-level temperature at the site:

• Green: Comfortable temperatures (<20°C)
• Orange: Warm (20-30°C)
• Red: Hot (>30°C)

The temperature spread between ground and altitude is primarily for comfort and clothing planning.

Track 6: Rain, Cloud Base & Cloud Cover

Rainfall (top): Blue raindrop symbols show rainfall intensity:

• 1 drop: Light rain (<1 mm/hr)
• 2 drops: Moderate rain (1-4 mm/hr)
• 3 drops: Heavy rain (>4 mm/hr)
• No drops: No rain - obviously, rain is bad for flying!

Total Cloud Fraction (middle): Shows the % of sky covered by cloud (0 = clear skies, 100 = completely overcast). Higher values indicate more cloud cover, which may affect thermal development, visibility, and the ability to find thermals marked by cumulus clouds.

Cloud Base Category (bottom): Text shows cloud base height category:

• High: Cloud base >800m - good conditions
• Medium: Cloud base 300-800m - decent local flying
• Low: Cloud base 100-300m - may be too low for comfortable flying
• Very Low: Cloud base <100m - definitely too low

Cloud base category is calculated from cloud_base_height_2p5_oktas (cloud base at 2.5 oktas coverage).

XC Potential

When XC Potential >0.5 and Flyability >0.5, the flyability track background turns purple. This indicates good cross-country flying conditions.

Note: XC Potential is still a work in progress. It uses a different model trained on conditions where pilots have exceeded 10km flights.

Current Time Indicator

When viewing "Today" forecast, a red dotted vertical line shows the current time, helping you see what conditions are happening right now.

Data Sources & Updates

Forecast Model: Met Office UK2km forecast (4-hour delay)

Update Frequency: Hourly

Machine Learning: Our models are trained on historical flight records and site-specific characteristics to predict flyability and XC potential.

How the Model is Built

We start by assembling two streams of data: high-resolution Met Office UKV (2-km) forecast fields and observed paragliding activity from OGN/PureTrack. The weather stream is collated across many daily CSVs, lightly cleaned (rows with extensive gaps dropped; remaining NaNs imputed), and then enriched with per-site metadata (take-off aspect and elevation) from our Flybot annotations table. Each weather record is joined to the nearest site and hour, and then aligned to flight logs aggregated by site and hour—so for every "site × hour" we know the forecast conditions and whether pilots actually flew (and whether anyone went XC).

On top of the raw meteorology we build a stack of pilot-centric features. These include wind–topography interactions (headwind and crosswind components relative to each site’s take-off aspect), vertical wind shear metrics between standard heights (10–100–250–500–1000 m AGL), gust diagnostics (gust ratio/excess), cloud and visibility categories, precipitation flags, thermal proxies (dew-point spreads, near-surface lapse rates, CAPE variants), and simple stability/turbulence indicators (e.g., Richardson bulk number). The result is a wide, engineered dataset where each row is a forecast snapshot of “how flyable this site-hour looked” in the dimensions pilots actually care about.

Labelling is necessarily noisy in a sport constrained by people’s availability and risk appetite, so we use a positive–unlabelled (PU) learning setup. “Positive” means we observed pilots on site that hour; anything else starts unlabelled. We then mark a subset of obvious “no-go” hours as reliable negatives using conservative heuristics (e.g., very strong wind or gusts, any precipitation, or very poor visibility). We also reduce confounding by matching negatives to positives with similar wind direction at the same site, and we split train/validation by site groups to test on genuinely unseen sites. Features are standardised column-wise. A compact neural network is trained with a PU/PNU-style loss so it learns the boundary between “conditions with observed flying” and everything else without pretending all missing activity is a true negative. In parallel, we train a separate Random Forest classifier for cross-country propensity using flights > 10 km as positives, giving a probability that conditions are supportive of XC.

End-to-end, the pipeline (current code version v_19) ingests forecasts, enriches them with terrain/site context, aligns them to observed behaviour, engineers domain features, constructs PU-appropriate training sets with group-aware splits, scales inputs, and trains the models (flyability and XC) ready for scoring future forecasts. The output is a site- and hour-specific probability that conditions will be flyable, plus a complementary XC-likelihood signal to help pilots plan their day.

Submit a New Site

Missing your favourite site? We'd love to add it to our forecast coverage! Submit the site details and we'll include it in our list of forecasted locations.

What we need:

• Site name - The common name pilots use for the site
• Location coordinates - Latitude and longitude (decimal format preferred)
• Grid reference - OS Grid Reference (e.g., SK 1234 5678)
• what3words address - The what3words location for easy navigation
• Site elevation - Height in metres above sea level
• Flyable wind directions - Which wind directions work for the site
• Site description - Brief description of the site, access notes, and any special characteristics
• Site characteristics - Is it a club site? Members only? Tow launch? Site fee? Any other relevant details
• Links - Site guide URL or other relevant links (optional)

Please provide as much detail as possible to help other pilots. The more information you share, the more useful the forecast and site information will be for the community.

Support the Project

Flybot is a passion project built for the UK paragliding community. If you find it useful and want to support continued development, hosting costs, and new features, consider buying me a coffee!

Your support helps keep Flybot free and accessible for all pilots. Every contribution, no matter how small, makes a difference and is greatly appreciated.