By Brian Finch 

Table of Contents

1. Introduction to Downwind Foiling

2. Understanding Ocean Physics

3. Reading Weather Forecasts

4. Optimal Conditions Matrix

5. Forecasting Tools & Apps

6. Community Insights

7. Regional Considerations

8. Safety & Planning

9. Conclusion

Introduction to Downwind Foiling 

Downwind foiling has been revolutionized by athletes like Kai Lenny, who describes it as uniquely qualified pursuit that embraces the glides that attract many into foiling. The sport involves harnessing energy from wind-generated waves and swell to travel from point A to point B purely on water energy, with many describing it as the "grail" of all foiling disciplines.

What Makes Downwind Foiling Special?

• Pure Energy Efficiency: Riders report feeling like they're flying because it's all human powered, with the foil acting like an underwater airplane

• Long Distance Potential: World record holder Olivia Piana completed 287.4 km in under 15 hours along Portugal's west coast

• Unique Conditions Access: Foiling allows you to exploit wind bumps and conditions that traditional boards cannot handle

 

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Understanding Ocean Physics 

The Science of Swell Formation

What is Fetch?

Fetch is the length of water over which a given wind has blown without obstruction. The longer the fetch and greater the wind speed, the more wind energy is transferred to the water surface and the larger the resulting sea state.

Fetch Requirements for Downwinding:

• Minimum: 10-20 km for basic bumps

• Ideal: 50+ km for consistent, organized bumps

• Epic: 100+ km (like Columbia River Gorge conditions)

Wave Period Explained

Swell period is the number of seconds between successive swell crests as they pass the same stationary object. The greater the number of seconds between swells, the larger the resulting wave.

Period Classifications:

• Short Period (3-8 seconds): Local wind waves, choppy conditions

• Medium Period (8-14 seconds): Organized wind swell, good for downwinding

• Long Period (14+ seconds): Groundswell, powerful but less frequent bumps

Swell Formation Process

WIND ENERGY TRANSFER PROCESS:

Stage 1: Initial Disturbance

Wind → Water Surface → Small Ripples

Stage 2: Wave Development  

Sustained Wind + Fetch → Organized Wave Trains

Stage 3: Swell Formation

Waves Leave Storm Area → Sort by Speed → Long Waves Travel Fastest

Stage 4: Swell Propagation

Constant Speed Travel → Thousands of Miles → Minimal Energy Loss

Wind waves are generated when wind speed is faster than wave crest speed, combined with uninterrupted distance (fetch), adequate width, and sufficient duration. As waves move away from storm centers, they sort themselves by speed, with longer wavelength waves traveling faster.

Swell vs. Waves: Key Differences

 

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Reading Weather Forecasts 

Essential Parameters for Downwind Forecasting

Wind Analysis

The best wind for beginners is 18-20 knots. Wingfoiling in light wind is brutally hard when new, while above 23 knots can become gusty and shifty.

Wind Speed Guidelines:

• 12-15 knots: Light conditions, requires large foil and perfect technique

• 15-20 knots: Sweet spot for learning and progression

• 20-25 knots: Ideal for experienced riders

• 25+ knots: Expert conditions, challenging but rewarding

Wind Direction Priorities

1. Cross-shore/Side-shore: Ideal for shore-runner setups

2. Cross-onshore: Good for bump development

3. Offshore: Dangerous - avoid for safety

4. Onshore: Creates backwash, generally poor conditions

Swell Parameters

The most important buoy information is the period range, not just wave height. Opposing tide to wind direction makes waves stand up more and generates more energy in the water.

Optimal Swell Conditions:

• Height: 2-6 feet (0.6-1.8m)

• Period: 8-14 seconds

• Direction: Aligned with or slightly angled to wind

• Interval: Regular, not confused seas

Advanced Forecasting Concepts

Tide Considerations

A tide working against you can slow progress but may increase water flow over the foil, making it easier to get up. Conversely, tide with you assists progress. Opposing tide to wind direction creates better wave formation.

Tide Strategy:

• Outgoing + Onshore Wind = Standing waves, easier takeoff

• Incoming + Offshore Wind = Flatter conditions

• Spring Tides = Stronger current effects

• Neap Tides = More predictable conditions

Water Depth Effects

Deeper water often results in better bumps as well as stronger wind. You need to be around 1km out from beach to get the best wind bumps due to refraction in shallow water.

 

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Optimal Conditions Matrix 

Beginner Conditions

For beginners, the ideal first experience includes fairly steady wind between 15-25 knots, blowing in the same direction as swell. The swell should not be too tight to promote glide and speed.

Advanced Conditions

Advanced riders can handle lighter conditions once they master pumping technique, but need at least 20 knots of wind and good bumps with proper swell alignment.

Red Flag Conditions (Avoid)

• Confused Seas: Multiple swell directions

• Offshore Winds: Safety hazard

• Storm Conditions: Lightning, heavy rain

• Strong Cross-Currents: Navigation difficulty

• No Fetch: Flat water, no bumps

• Onshore Wind + Short Period: Backwash and chop

 

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Forecasting Tools & Apps 

Primary Forecasting Platforms

1. Windy.com

Provides weather radar, wind and wave forecasts with worldwide animated weather maps, precise spot forecasts, and 50+ weather layers.

Best Features:

• Real-time wind visualization

• Wave height and period data

• Multiple weather models (ECMWF, GFS)

• Mobile app with offline capability

Downwind-Specific Use:

• Check wind consistency over fetch distance

• Analyze swell direction and period

• Verify conditions 6-24 hours ahead

2. Windguru

Special wind and weather forecasts for wind sports, with professional riders worldwide using WindGuru Pro for higher-resolution forecasts.

Best Features:

• Wind sport-specific interface

• Detailed hourly breakdowns

• Historical data comparison

• Pro version with enhanced resolution

3. PredictWind

Ocean racing and America's Cup proven, highest resolution wind and marine forecasts. Ideal for boat-assisted sessions and offshore forecasting.

Best Features:

• Highest resolution available

• Professional marine focus

• Route planning capabilities

• Offshore accuracy

4. Windfinder

Wind and weather reports for over 160,000 locations worldwide, with real-time observations from 20,000+ weather stations.

Best Features:

• Massive location database

• Real-time station data

• Superforecast for detailed local conditions

• Widget support for quick checks

5. Surfline/Surf-forecast

Best Features:

• Swell-focused forecasting

• Break-specific analysis

• Webcam integration

• Regional expertise

Advanced Forecasting Techniques

Model Comparison Strategy

Professional tip: Compare WRF and GFS models when planning sessions—GFS is better for general forecasts, while WRF provides high-resolution, short-term accuracy.

Model Selection Guide:

• GFS: 5-7 day outlook, general trends

• ECMWF: 3-5 day accuracy, European strong

• WRF/NAM: 1-2 day precision, local effects

• ICON: European alternative to GFS

Multi-Platform Verification

Check multiple sources—no single app is 100% accurate.

Verification Protocol:

1. Check 2-3 different forecast platforms

2. Compare buoy data to predictions

3. Analyze webcams for real conditions

4. Consult local knowledge/forums

 

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Community Insights 

Expert Tips from Social Media & Forums

Kai Lenny's Forecasting Wisdom

Kai describes how conditions vary dramatically and how he decides which sport to do based on conditions when he first wakes up, noting that forecasts can change significantly.

Key Insights:

• Don't wait for perfect forecasts - go when it's "good enough"

• Local conditions can vary dramatically from regional forecasts

• Experience with multiple water sports helps read conditions better

Forum Community Tips

Forum discussions reveal that Columbia River Gorge conditions can be easier than North Shore Maui due to consistent opposing current creating groomed bumps. East Coast conditions often require bigger foils (280cm² vs 200cm²) compared to Hawaiian conditions.

Community Wisdom:

• Bigger Foils for Learning: Start with largest foil possible - staying up on foil is key, speed comes later

• Local Knowledge Critical: Always reach out to locals for information on best conditions - nothing beats local knowledge

• Consistency Over Peak Conditions: Regular practice in moderate conditions beats waiting for perfect days

Regional Facebook Groups

Key communities mentioned in research:

• The Swell Riders - Downwind Foiling FB Group (Columbia River Gorge focus)

• Downwind Foiling (General community)

• Regional Groups: Local knowledge sharing

Forecasting Mistakes to Avoid

Common Beginner Errors

1. Waiting for Perfect Conditions: Top tip - do not wait for the windiest or biggest swell forecasts to give it your first goes

2. Ignoring Fetch: Focusing only on local wind speed

3. Underestimating Safety: Not checking backup plans

4. Wrong Equipment: Using too small foils for conditions

Advanced Pitfalls

1. Over-confidence in Light Conditions: Underestimating difficulty

2. Ignoring Tide Timing: Missing optimal current assistance

3. Poor Shuttle Planning: Logistics not matching conditions

 

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Regional Considerations 

World-Class Downwind Locations

Columbia River Gorge, Oregon

The idyllic Columbia River Gorge features a dam-regulated river flowing west toward Portland, perfectly opposing strong winds pushing east - manufacturing perfectly groomed and tightly spaced bumps for miles.

Optimal Conditions:

• Wind: 20-35 knots

• Direction: East (upriver)

• Season: April-September

• Tide: Outgoing preferred

Maui, Hawaii

Maui's north shore provides swift currents ideal for downwind SUP hydrofoil, allowing riders to harness ocean energy to gain speed before lifting skyward.

Optimal Conditions:

• Wind: 15-25+ knots

• Direction: Northeast trades

• Season: Year-round, best winter

• Swell: North Pacific groundswell

European Locations

European downwind foiling is expanding rapidly, with locations like Portugal's west coast (world record site) and UK conditions requiring specialized local knowledge.

Considerations:

• More variable conditions than tropical locations

• Shorter weather windows

• Safety considerations in colder water

• Local knowledge absolutely essential

Adapting to Local Conditions

Inland Waters

Lakes offer downwind potential - Swiss rider Balz Müller completed 18km run on Lake Neuchâtel, with fun starting at knee-high chop and 12+ knots.

Lake Forecasting:

• Thermal winds more predictable

• Shorter fetch requires different timing

• Temperature differential important

• Shore shape affects wind patterns

Coastal Variations

North Sea runs require being ~1km from beach to get best wind bumps due to shallow water refraction effects.

Coastal Factors:

• Bathymetry effects on wave formation

• Land mass blocking/channeling wind

• Tidal range variations by location

• Local wind phenomena (sea breeze, etc.)

 

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Safety & Planning 

Pre-Session Checklist

Weather Verification

1. Multi-source Forecast Check: Verify 2-3 platforms agree

2. Trend Analysis: Is weather improving or deteriorating?

3. Backup Plan: Exit strategies if conditions change

4. Communication Plan: Inform loved ones of departure location, time, destination, and contact CROSS (Regional Operational Monitoring and Rescue Center)

Equipment Safety

Essential safety equipment includes VHF radio for coast communication, inflatable PFD with CO2 cartridge and distress flare, bright colored equipment for visibility, and helmet for shock absorption.

Mandatory Gear:

• Leash: Critical connection to board

• PFD: Minimum inflatable belt, consider full jacket

• Communication: VHF radio or waterproof phone

• Visibility: Bright colors, consider strobe light

• Backup Paddle: Or webbed gloves for emergency

Condition-Specific Safety

Light Wind Conditions

• Larger foil required for reliability

• More effort required - manage energy

• Longer time on water - sun protection

• Communication more critical (less power for speed)

Strong Wind Conditions

• Smaller, more manageable foil

• Faster sessions - plan shorter routes

• Higher stakes if equipment fails

• More dangerous if blown offshore

Changing Conditions

Monitor wind conditions noting whether stable, decreasing, or increasing, and whether it will push you in desired direction.

Adaptation Strategies:

• Start conservatively, extend if conditions improve

• Plan multiple exit points

• Monitor weather updates during session

• Have alternative gear sizes accessible

Emergency Protocols

Self-Rescue Techniques

1. Paddle Position: Prone or kneeling to conserve energy

2. Current Awareness: Use tidal flow to advantage

3. Equipment Priority: Board > foil > paddle in importance

4. Energy Management: Steady pace over sprint efforts

Group Protocols

Buddy system essential - stay within sight of pack, use VHF radio communication, share cell phone locations before starting.

Group Guidelines:

• Pre-session briefing on conditions and route

• Skill level matching for group coherence

• Regular check-ins during session

• Established emergency procedures

 

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Conclusion: Mastering Downwind Forecasting

Successful downwind foiling forecasting combines scientific understanding of ocean physics with practical weather reading skills and community wisdom. As Dave Kalama noted, learning to downwind foil was the most humbling experience of his life as a waterman, but the rewards justify the challenge.

Key Success Factors:

1. Understand the Physics: Fetch, period, and swell formation fundamentals

2. Use Multiple Tools: No single forecast source is perfect

3. Build Local Knowledge: Connect with regional communities

4. Start Conservative: Build skills in moderate conditions

5. Prioritize Safety: Equipment and planning prevent emergencies

6. Practice Regularly: Training regularly in good conditions offers the only opportunity to speed up the journey

The Forecasting Mindset

Don't wait for perfect conditions - develop skills to read and adapt to available conditions. The intersection of preparation, knowledge, and opportunity creates those magical sessions where everything aligns.

Remember: Local knowledge beats any forecast model. Use these tools as your foundation, but always seek out and respect the wisdom of experienced local riders.

 

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Resources for Continued Learning:

• Join local Facebook groups and forums

• Follow professional riders on social media

• Practice forecast reading daily, even when not riding

• Build relationships with local downwind community

• Consider formal instruction or workshops

• Keep detailed session logs to improve forecasting skills