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Surf Forecasting Simplified In search of the perfect session using modern technology

Surf Forecasting Simplified In search of the perfect session using modern technology. Nathan Cool www.NathanCool.com This presentation and accompanying material at : www.nathancool.com/lmu. Agenda. The pebble in the pond, forecasting principle Tools of the trade: WAMs Data Mining

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Surf Forecasting Simplified In search of the perfect session using modern technology

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  1. Surf Forecasting Simplified In search of the perfect session using modern technology Nathan Cool www.NathanCool.com This presentation and accompanying material at: www.nathancool.com/lmu

  2. Agenda • The pebble in the pond, forecasting principle • Tools of the trade: • WAMs • Data Mining • Weather models • WAMs in-depth • Forecast Accuracy • Dissecting data (automatic data mining)‏ • Forecasting examples • Near-term swell verification • Seasonal Surf Forecasting • Conditions to Consider • Q&A and web resources

  3. The Pebble and the Pond Ripples across the ocean The Principle • Wind (the pebble)‏ • Transfers energy to water • Waves are created • Travel outward • Eventually reaching shore The Practice • Track ocean storms • Measure energy • Measure distance to shore • Wax your board

  4. Old School How we did it back in the day... Pressure Maps, Buoys, and NOAA radio... ...and yes...I once had hair... Tight isobars 1987...skipping work...

  5. The Tools of the Trade Today How the Internet changed everything Wave Analysis Models (WAMs)‏ Model Data Weather Models

  6. Wave Analysis Models (WAMs)‏ Your Tax Dollars at Work • FNMOC • NOAA • NWS

  7. Dissecting a WAM Wave Heights Date Forecast Date Heights Scale/Key

  8. Dissecting a WAM Periods Date Forecast Date Periods Scale/Key

  9. The WAM Crystal Ball A model look at the future Today Tomorrow 48 Hours 144 Hours

  10. Weather Models Your Tax Dollars, Still At Work • FNMOC • NOAA • NWS

  11. WAM Raw Data Grabbing the middle-man How LOLA, SwellWatch, WaveWatch and others do it Data Monitoring Mechanisms Model • Wind data (wind fields)‏ • Sea surface temperatures • Ice concentrations • Bathymetry/obstruction data

  12. WAM Raw Data Number Crunching Behind the Scenes For any point on the planet (“Virtual” Buoys)‏ Thus….

  13. WAM Raw Data Making a near-shore chart Data Charts (Near-shore estimates)‏ Monitoring Mechanisms • Wind data (wind fields)‏ • Sea surface temperatures • Ice concentrations • Bathymetry/obstruction data

  14. A Swell is Born Slide-Shows: Surf forecasting from start to finish 1. Low Pressure Forms 2. Winds Increase (slide show)‏ (slide show)‏ 3. Fetch is created 4. Swell Travels to Coast (slide show)‏ (slide show)‏

  15. Forecasting the Swell Two examples: Winter NW, and Summer SW The essentials • Distance • Angle • Trajectory • Wave Height • Period

  16. A Note About Accuracy Time and Size Calculations Minutes, Seconds, Inches (modeling)‏ Hours, Feet (surf forecasting)‏ Forecast Tolerance

  17. Distance Where in the heck am I ??? • Curvature of the Earth has to be accounted for • Haversine formula • Distance in nautical miles R = earth’s radius (mean radius = 6,371km)Δlat = lat2 − lat1Δlong = long2 − long1a = sin²(Δlat/2) + cos(lat1).cos(lat2).sin²(Δlong/2)c = 2.atan2(√a, √(1−a))d = R.c =((DEGREES(ACOS(SIN(RADIANS(Lat1))*SIN(RADIANS(Lat2))+COS(RADIANS(Lat1))*COS(RADIANS(Lat2))*COS((RADIANS(Lon2-Lon1)))))*69.09))*0.87 Or the easy way... www.WaveCast.com/calculator

  18. Northern Hemi Numbers • Distance: ~2700 nm • Angle (A): ~285° • Trajectory (T): ~20° • Wave Height: ~40 feet • Period: 20 seconds T A 270 ~210 180

  19. Running the Numbers Decay Factor (distance)‏ Decay = (90-((LOG2(Distance)) * (2π)))/100 =(90-((LOG(A2;2))*(2*PI())))/100 Where A2 is the distance in nautical miles

  20. Running the Numbers Angular Spreading Decay Factor (Trajectory)‏ Approx: (100–(θ*0.9))/100 ...or: ((90–θ)+15)/100 0° = no loss 20° = ~15% loss 45° = ~40% loss

  21. Northern Hemi Numbers • Distance: ~2700 nm • Angle (A): ~280° • Trajectory (T): ~20° • Wave Height (Wh): ~40 feet • Period (p): 20 seconds T A • Distance Decay (dd) = ~80% • Angular Decay (ad) = ~15% Height (h) = ((Wh – dd) – ad)‏ Face Height = h * (p * 0.1)‏ Time = Distance / (p * 1.5)‏ Height = (40’ – 80%) - 15% = 6.8’ (40 * 0.2) * 0.85 = 6.8' Face Height = 6.8 * (20 * 0.1) = ~13.6' (best case)‏ Time = 2700 nm / (20 * 1.5) = 90 hours (~3.75 days)‏

  22. When the waves arrive... Shoaling Considerations 6.8' seas * (20 * 0.1) = ~13.6' face max Face Height Approximations Steep Shoaling: h * (p * 0.1)‏ Slow-sloped Shoaling: h * (p * 0.075)‏ So… Steep Shoaling: = 6.8 * 2.0 = ~13.6' face height Slow-sloped Shoaling) = 6.8 * 1.5 = ~10.2' face height

  23. When the waves arrive... Shoaling Considerations: Tidal Depth Tides, depth, conditions, change hour to hour Normal, Average Tides Abnormal “Tidal Swing”, from lunar event 7' depth difference over 8 hours

  24. When the waves arrive... Obstructions & Island Shadowing in SoCal (1 of 2)‏ Obstruction Energy Skirts Past SoCal Islands Block Energy Also

  25. When the waves arrive... Obstructions & Island Shadowing in SoCal (2 of 2)‏ More swell north of Pt. Conception, less swell in SoCal... ...due to NW angle

  26. When the waves arrive... 1/22/2011 • No loss from angular decay • No obstructions • Size amplified by refraction Jacob Trette Moments before going over the falls at Mavs.

  27. Tracking A Southern Hemi From the Southern Ocean to SoCal • Distance: ~5200 nm • Angle (A): ~210° • Trajectory (T): ~45° • Wave Height: ~36 feet • Period: 15 seconds A To SoCal T Trajectory 270 ~210 180

  28. Tracking A Southern Hemi The Numbers for SoCal • Distance: ~5200 nm • Angle (A): ~210° • Trajectory (T): ~45° • Wave Height (Wh): ~36 feet • Period (p): 15 seconds A To SoCal T • Distance Decay (dd) = >85% • Angular Decay (ad) = ~30% Height (h) = ((Wh – dd) – ad)‏ Face Height = h * (p * 0.1)‏ Time = Distance / (p * 1.5)‏ Trajectory Height = (35’ – 85%) - 30% = 3.7' Face Height = 3.7 * (15 * 0.1) = 5.5 feet Time = 5200 nm / (15 * 1.5) = 231 hours (~ 9 days)‏

  29. Indicators Near-term verification by buoys

  30. Indicators Near-term verification by CDIP Now-cast Model But, initialized at Pt. Conception 9-Period Bands Buoy history

  31. Seasonal Forecasting ENSO • El Niño: • Winter (good)‏ • Low pressure dominates Gulf • Improves storm track • Summer (bad)‏ • Stronger southern hemi jetstream • Less chance for storms to drift north • More Pacific hurricanes • Blows out Atlantic hurricanes • La Niña: • Winter (bad)‏ • High pressure blocking in Gulf • Less favorable storm track • Summer (good)‏ • Weaker southern hemi jetstream • Better chance for storms to drift north • Fewer Pacific hurricanes • Better chance for Atlantic hurricanes

  32. Seasonal Forecasting ENSO : El Niño 1997-98

  33. Seasonal Forecasting ENSO : El Niño's effect on the jetstream : the results, 1998

  34. Seasonal Forecasting ENSO : This year's La Niña Jetstream/ storm track Strong high pressure

  35. Seasonal Forecasting ENSO : La Niña and Omega Blocking

  36. Seasonal Forecasting Southern Hemi Jetstream Bend in jetstream guides storms/swells

  37. Conditions to Consider Wind Swell Pressure Wind Fetch

  38. Conditions to Consider Coastal Eddy, Southerly Winds, Onshore Flow Pressure Wind Northerly Winds Coastal Eddy Trapped Between Islands and Land

  39. Conditions to Consider Santa Ana, when the low passes and high takes over High circulating clockwise as low moves east Offshore winds

  40. Conditions to Consider Santa Ana, thermal gradients Tight Thermal Gradients Normal Thermal Gradients

  41. Thank You! Q&A www.NathanCool.com/lmu • Presentation • Swell Calculator (Excel)‏ • Forecast Discussion Group

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