Surf Forecasting SimplifiedIn search of the perfect session using modern technologyNathan Coolwww.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 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

The Pebble and the PondRipples across the ocean Wind (the pebble) Transfers energy to water Waves are created Travel outward Eventually reaching shore Track ocean storms Measure energy Measure distance to shore Wax your boardThe PrincipleThe Practice

Old SchoolHow we did it back in the day...Pressure Maps, Buoys, and NOAA radio......and yes...I once had hair...Tight isobars1987...skipping work...

The Tools of the Trade TodayHow the Internet changed everythingWave Analysis Models (WAMs)Model DataWeather Models

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

Dissecting a WAMWave HeightsHeightsScale/KeyDateForecast Date

Dissecting a WAMPeriodsPeriodsScale/KeyDateForecast Date

The WAM Crystal BallA model look at the futureTodayTomorrow48 Hours144 Hours

Weather ModelsYour Tax Dollars, Still At Work FNMOC NOAA NWS

WAM Raw DataGrabbing the middle-manHow LOLA, SwellWatch, WaveWatch and others do itMonitoring MechanismsDataModel Wind data (wind fields) Sea surface temperatures Ice concentrations Bathymetry/obstruction data

WAM Raw DataNumber Crunching Behind the ScenesFor any point on the planet(Virtual Buoys)Thus.

WAM Raw DataMaking a near-shore chartDataCharts(Near-shore estimates)Monitoring Mechanisms Wind data (wind fields) Sea surface temperatures Ice concentrations Bathymetry/obstruction data

A Swell is BornSlide-Shows: Surf forecasting from start to finish1. Low Pressure Forms

2. Winds Increase3. Fetch is created4. Swell Travels to Coast(slide show)(slide show)(slide show)(slide show)

Forecasting the SwellTwo examples: Winter NW, and Summer SWThe essentials Distance Angle Trajectory Wave Height Period

A Note About AccuracyTime and SizeMinutes, Seconds, Inches(modeling)Hours, Feet(surf forecasting)CalculationsForecast Tolerance

DistanceWhere in the heck am I ??? Curvature of the Earth has to be accounted for Haversine formula Distance in nautical miles=((DEGREES(ACOS(SIN(RADIANS(Lat1))*SIN(RADIANS(Lat2))+COS(RADIANS(Lat1))*COS(RADIANS(Lat2))*COS((RADIANS(Lon2-Lon1)))))*69.09))*0.87R = earths radius (mean radius = 6,371km) lat = lat2 lat1 long = long2 long1 a = sin(lat/2) + cos(lat1).cos(lat2).sin(long/2) c = 2.atan2(a, (1a)) d = R.c www.WaveCast.com/calculatorOr the easy way...

Northern Hemi Numbers Distance: ~2700 nm Angle (A): ~285 Trajectory (T): ~20 Wave Height: ~40 feet Period: 20 seconds270180~210AT

Running the NumbersDecay Factor (distance)Decay = (90-((LOG2(Distance)) * (2)))/100=(90-((LOG(A2;2))*(2*PI())))/100

Where A2 is the distance in nautical miles

Running the NumbersAngular Spreading Decay Factor (Trajectory)0 = no loss20 = ~15% loss45 = ~40% lossApprox: (100(*0.9))/100...or: ((90)+15)/100

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)

Distance: ~2700 nm Angle (A): ~280 Trajectory (T): ~20 Wave Height (Wh): ~40 feet Period (p): 20 secondsATNorthern Hemi Numbers

When the waves arrive...Shoaling Considerations6.8' seas * (20 * 0.1) = ~13.6' face max

Face Height ApproximationsSteep Shoaling: h * (p * 0.1)Slow-sloped Shoaling: h * (p * 0.075) SoSteep Shoaling: = 6.8 * 2.0 = ~13.6' face heightSlow-sloped Shoaling) = 6.8 * 1.5 = ~10.2' face height

When the waves arrive...Shoaling Considerations: Tidal DepthNormal, Average TidesAbnormal Tidal Swing, from lunar eventTides, depth, conditions,change hour to hour7' depth differenceover 8 hours

When the waves arrive...Obstructions & Island Shadowing in SoCal (1 of 2)Energy Skirts Past SoCalIslands Block Energy AlsoObstruction

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

When the waves arrive...1/22/2011Jacob TretteMoments before goingover the falls at Mavs. No loss from angular decay No obstructions Size amplified by refraction

Tracking A Southern HemiFrom the Southern Ocean to SoCal Distance: ~5200 nm Angle (A): ~210 Trajectory (T): ~45 Wave Height: ~36 feet Period: 15 secondsTo SoCalTrajectory270180~210TA

Tracking A Southern HemiThe Numbers for SoCal Distance: ~5200 nm Angle (A): ~210 Trajectory (T): ~45 Wave Height (Wh): ~36 feet Period (p): 15 secondsTo SoCalTrajectoryTA Distance Decay (dd) = >85% Angular Decay (ad) = ~30%

Height (h) = ((Wh dd) ad)Face Height = h * (p * 0.1)Time = Distance / (p * 1.5)

Height = (35 85%) - 30% = 3.7'Face Height = 3.7 * (15 * 0.1) = 5.5 feetTime = 5200 nm / (15 * 1.5) = 231 hours (~ 9 days)

IndicatorsNear-term verification by buoys

IndicatorsNear-term verification by CDIP9-Period BandsBuoy historyNow-cast ModelBut, initialized at Pt. Conception

Seasonal ForecastingENSO El Nio: 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 Nia: 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

Seasonal ForecastingENSO : El Nio 1997-98

Seasonal ForecastingENSO : El Nio's effect on the jetstream : the results, 1998

Seasonal ForecastingENSO : This year's La NiaJetstream/storm trackStrong highpressure

Seasonal ForecastingENSO : La Nia and Omega Blocking

Seasonal ForecastingSouthern Hemi JetstreamBend in jetstreamguides storms/swells

Conditions to ConsiderWind SwellPressureWindFetch

Conditions to ConsiderCoastal Eddy, Southerly Winds, Onshore FlowPressureWindNortherly WindsTrapped Between Islands and LandCoastal Eddy

Conditions to ConsiderSanta Ana, when the low passes and high takes overHigh circulating clockwiseas low moves eastOffshore winds

Conditions to ConsiderSanta Ana, thermal gradientsNormal Thermal GradientsTight Thermal Gradients

Q&Awww.NathanCool.com/lmu Presentation Swell Calculator (Excel) Forecast Discussion GroupThank You!

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