Surf Forecast for Shirahama Beach (Izu)
type: Dataset
description: 10-day surf forecast with Strike Scores for Shirahama Beach (Izu), Shimoda, Japan
about: Shirahama Beach (Izu)
  type: TouristAttraction
  geo: GeoCoordinates
    latitude: 34.6667
    longitude: 138.9667
  description: Shirahama is the Izu Peninsula's premier surf beach, a consistent beachbreak that hosts competitions and draws surfers from across the Kanto region. The white sand beach is picture-perfect, and the wave works across a range of conditions, though it needs typhoon swells to really come alive. The scenic Izu Peninsula drive makes the journey worthwhile, and the area offers hot springs (onsen) to warm up after cold-water sessions.
summary:
  best day:
    date: 2026-08-13
    score: 51
    category: Fair
    explanation: Best day in the forecast: 2026-08-13 with a score of 51/100 (Fair)
  firing days count: 0
  overall recommendation: Poor conditions overall: Average score 24/100. Look for spots with better forecasts.
forecasts:
  date: 2026-08-05
  day index: 0
  strike score:
    final score: 18
    category: Poor
    category emoji: 💤
    confidence: 1
    confidence explanation: Very high confidence (0-1 day forecast)
    breakdown:
      swell direction:
        score: 18
        out of: 25
        explanation: Moderate alignment: Swell from 130° is 10° off optimal 140°, workable but not ideal.
      swell size:
        score: 8
        out of: 25
        explanation: Too big: 2.4m exceeds maximum 2.0m. Risk of closeouts.
      swell period:
        score: 20
        out of: 25
        explanation: Good period: 16s is 145% of ideal 11s. Clean, powerful groundswell.
      wind:
        score: 0
        out of: 25
        explanation: Onshore/cross-shore: 33 km/h from 48° (NE). Destroying wave quality. Offshore range: 280°-360°.
    adjustments:
      wind history:
        adjustment: -17
        groomed: false
        morning sickness: true
        explanation: -17 points: Previous days of onshore wind left residual chop ("morning sickness"), reducing wave quality.
      windswell penalty:
        adjustment: -3
        windswell degraded: false
        explanation: Groundswell-dominant conditions (clean, long-period waves).
      secondary swell bonus:
        adjustment: 0
        explanation: No secondary swell bonus.
    summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (130°), size (2.4m), or wind (33 km/h from 48°) is unfavorable. Consider other spots or wait for better conditions.
  conditions:
    swell:
      height m: 2.4
      height ft: 7.9
      direction degrees: 130
      direction cardinal: SE
      period s: 16
      explanation: 2.4m (7.9ft) swell from 130° (SE) at 16s period
    wind:
      speed kmh: 33
      speed mph: 20.5
      direction degrees: 48
      direction cardinal: NE
      explanation: 33 km/h (21 mph) from 48° (NE)
    secondary swell:
      height m: 0.6
      direction degrees: 70
      direction cardinal: ENE
      period s: 8
    windswell:
      height m: 1.1
      period s: 4
      explanation: Local wind-generated waves (choppy, short-period)
forecasts:
  date: 2026-08-06
  day index: 1
  strike score:
    final score: 11
    category: Poor
    category emoji: 💤
    confidence: 1
    confidence explanation: Very high confidence (0-1 day forecast)
    breakdown:
      swell direction:
        score: 11
        out of: 25
        explanation: Moderate alignment: Swell from 164° is 24° off optimal 140°, workable but not ideal.
      swell size:
        score: 2
        out of: 25
        explanation: Too big: 3.0m exceeds maximum 2.0m. Risk of closeouts.
      swell period:
        score: 22
        out of: 25
        explanation: Good period: 15s is 136% of ideal 11s. Clean, powerful groundswell.
      wind:
        score: 1
        out of: 25
        explanation: Onshore/cross-shore: 21 km/h from 55° (NE). Destroying wave quality. Offshore range: 280°-360°.
    adjustments:
      wind history:
        adjustment: -21
        groomed: false
        morning sickness: true
        explanation: -21 points: Previous days of onshore wind left residual chop ("morning sickness"), reducing wave quality.
      windswell penalty:
        adjustment: 0
        windswell degraded: false
        explanation: Groundswell-dominant conditions (clean, long-period waves).
      secondary swell bonus:
        adjustment: 0
        explanation: No secondary swell bonus.
    summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (164°), size (3.0m), or wind (21 km/h from 55°) is unfavorable. Consider other spots or wait for better conditions.
  conditions:
    swell:
      height m: 3
      height ft: 9.8
      direction degrees: 164
      direction cardinal: SSE
      period s: 15
      explanation: 3.0m (9.8ft) swell from 164° (SSE) at 15s period
    wind:
      speed kmh: 21
      speed mph: 13.0
      direction degrees: 55
      direction cardinal: NE
      explanation: 21 km/h (13 mph) from 55° (NE)
    secondary swell:
      height m: 0.6
      direction degrees: 68
      direction cardinal: ENE
      period s: 6
    windswell:
      height m: 0.5
      period s: 3
      explanation: Local wind-generated waves (choppy, short-period)
forecasts:
  date: 2026-08-07
  day index: 2
  strike score:
    final score: 4
    category: Poor
    category emoji: 💤
    confidence: 0.95
    confidence explanation: High confidence (2-3 day forecast)
    breakdown:
      swell direction:
        score: 4
        out of: 25
        explanation: Poor alignment: Swell from 189° is 49° off optimal 140°, barely within workable range 125°-180°.
      swell size:
        score: 1
        out of: 25
        explanation: Too big: 3.3m exceeds maximum 2.0m. Risk of closeouts.
      swell period:
        score: 22
        out of: 25
        explanation: Good period: 15s is 136% of ideal 11s. Clean, powerful groundswell.
      wind:
        score: 1
        out of: 25
        explanation: Onshore/cross-shore: 15 km/h from 84° (E). Destroying wave quality. Offshore range: 280°-360°.
    adjustments:
      wind history:
        adjustment: -21
        groomed: false
        morning sickness: true
        explanation: -21 points: Previous days of onshore wind left residual chop ("morning sickness"), reducing wave quality.
      windswell penalty:
        adjustment: 0
        windswell degraded: false
        explanation: Groundswell-dominant conditions (clean, long-period waves).
      secondary swell bonus:
        adjustment: 0
        explanation: No secondary swell bonus.
    summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (189°), size (3.3m), or wind (15 km/h from 84°) is unfavorable. Consider other spots or wait for better conditions.
  conditions:
    swell:
      height m: 3.3
      height ft: 10.8
      direction degrees: 189
      direction cardinal: S
      period s: 15
      explanation: 3.3m (10.8ft) swell from 189° (S) at 15s period
    wind:
      speed kmh: 15
      speed mph: 9.3
      direction degrees: 84
      direction cardinal: E
      explanation: 15 km/h (9 mph) from 84° (E)
    secondary swell:
      height m: 0.5
      direction degrees: 59
      direction cardinal: ENE
      period s: 5
provider: Strike Mission
date published: 2026-08-05T00:29:50.629Z
temporal coverage: 2026-08-05/2026-08-14
data sources: Open-Meteo Marine API (swell/wave data)
data sources: Open-Meteo Weather API (wind/weather data)

date: 2026-08-08
day index: 3
strike score:
  final score: 17
  category: Poor
  category emoji: 💤
  confidence: 0.92
  confidence explanation: High confidence (2-3 day forecast)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 209° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 3
      out of: 25
      explanation: Too big: 2.8m exceeds maximum 2.0m. Risk of closeouts.
    swell period:
      score: 22
      out of: 25
      explanation: Good period: 15s is 136% of ideal 11s. Clean, powerful groundswell.
    wind:
      score: 11
      out of: 25
      explanation: Onshore/cross-shore: 9 km/h from 140° (SE). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: -11
      groomed: false
      morning sickness: true
      explanation: -11 points: Previous days of onshore wind left residual chop ("morning sickness"), reducing wave quality.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (209°), size (2.8m), or wind (9 km/h from 140°) is unfavorable. Consider other spots or wait for better conditions.
conditions:
  swell:
    height m: 2.8
    height ft: 9.2
    direction degrees: 209
    direction cardinal: SSW
    period s: 15
    explanation: 2.8m (9.2ft) swell from 209° (SSW) at 15s period
  wind:
    speed kmh: 9
    speed mph: 5.6
    direction degrees: 140
    direction cardinal: SE
    explanation: 9 km/h (6 mph) from 140° (SE)
  secondary swell:
    height m: 0.9
    direction degrees: 115
    direction cardinal: ESE
    period s: 8

date: 2026-08-09
day index: 4
strike score:
  final score: 19
  category: Poor
  category emoji: 💤
  confidence: 0.89
  confidence explanation: Moderate confidence (4-5 day forecast)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 220° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 1
      out of: 25
      explanation: Too big: 3.6m exceeds maximum 2.0m. Risk of closeouts.
    swell period:
      score: 20
      out of: 25
      explanation: Good period: 16s is 145% of ideal 11s. Clean, powerful groundswell.
    wind:
      score: 11
      out of: 25
      explanation: Onshore/cross-shore: 9 km/h from 129° (SE). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: -4
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (220°), size (3.6m), or wind (9 km/h from 129°) is unfavorable. Consider other spots or wait for better conditions.
conditions:
  swell:
    height m: 3.6
    height ft: 11.8
    direction degrees: 220
    direction cardinal: SW
    period s: 16
    explanation: 3.6m (11.8ft) swell from 220° (SW) at 16s period
  wind:
    speed kmh: 9
    speed mph: 5.6
    direction degrees: 129
    direction cardinal: SE
    explanation: 9 km/h (6 mph) from 129° (SE)
  secondary swell:
    height m: 1.2
    direction degrees: 128
    direction cardinal: SE
    period s: 9

date: 2026-08-10
day index: 5
strike score:
  final score: 24
  category: Poor
  category emoji: 💤
  confidence: 0.86
  confidence explanation: Moderate confidence (4-5 day forecast)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 224° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 1
      out of: 25
      explanation: Too big: 3.3m exceeds maximum 2.0m. Risk of closeouts.
    swell period:
      score: 20
      out of: 25
      explanation: Good period: 16s is 145% of ideal 11s. Clean, powerful groundswell.
    wind:
      score: 14
      out of: 25
      explanation: Onshore/cross-shore: 8 km/h from 218° (SW). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: 0
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (224°), size (3.3m), or wind (8 km/h from 218°) is unfavorable. Consider other spots or wait for better conditions.
conditions:
  swell:
    height m: 3.3
    height ft: 10.8
    direction degrees: 224
    direction cardinal: SW
    period s: 16
    explanation: 3.3m (10.8ft) swell from 224° (SW) at 16s period
  wind:
    speed kmh: 8
    speed mph: 5.0
    direction degrees: 218
    direction cardinal: SW
    explanation: 8 km/h (5 mph) from 218° (SW)
  secondary swell:
    height m: 1.1
    direction degrees: 199
    direction cardinal: SSW
    period s: 10
  windswell:
    height m: 0.3
    period s: 2
    explanation: Local wind-generated waves (choppy, short-period)

date: 2026-08-11
day index: 6
strike score:
  final score: 10
  category: Poor
  category emoji: 💤
  confidence: 0.83
  confidence explanation: Low confidence (6-7 day forecast)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 224° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 6
      out of: 25
      explanation: Too big: 2.5m exceeds maximum 2.0m. Risk of closeouts.
    swell period:
      score: 22
      out of: 25
      explanation: Good period: 15s is 136% of ideal 11s. Clean, powerful groundswell.
    wind:
      score: 1
      out of: 25
      explanation: Onshore/cross-shore: 20 km/h from 61° (ENE). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: 0
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (224°), size (2.5m), or wind (20 km/h from 61°) is unfavorable. Consider other spots or wait for better conditions.
conditions:
  swell:
    height m: 2.5
    height ft: 8.2
    direction degrees: 224
    direction cardinal: SW
    period s: 15
    explanation: 2.5m (8.2ft) swell from 224° (SW) at 15s period
  wind:
    speed kmh: 20
    speed mph: 12.4
    direction degrees: 61
    direction cardinal: ENE
    explanation: 20 km/h (12 mph) from 61° (ENE)
  secondary swell:
    height m: 1
    direction degrees: 142
    direction cardinal: SE
    period s: 9
  windswell:
    height m: 0.9
    period s: 4
    explanation: Local wind-generated waves (choppy, short-period)

date: 2026-08-12
day index: 7
strike score:
  final score: 38
  category: Poor
  category emoji: 💤
  confidence: 0.8
  confidence explanation: Low confidence (6-7 day forecast)
  breakdown:
    swell direction:
      score: 6
      out of: 25
      explanation: Poor alignment: Swell from 98° is 42° off optimal 140°, barely within workable range 125°-180°.
    swell size:
      score: 18
      out of: 25
      explanation: Marginal size: 1.9m is 0.6m from ideal 1.3m.
    swell period:
      score: 25
      out of: 25
      explanation: Perfect period: 12s is at or above ideal 11s. Long-period groundswell with maximum power.
    wind:
      score: 1
      out of: 25
      explanation: Onshore/cross-shore: 19 km/h from 52° (NE). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: 0
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: -3
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Poor conditions at Shirahama Beach (Izu). Either swell direction (98°), size (1.9m), or wind (19 km/h from 52°) is unfavorable. Consider other spots or wait for better conditions.
conditions:
  swell:
    height m: 1.9
    height ft: 6.2
    direction degrees: 98
    direction cardinal: E
    period s: 12
    explanation: 1.9m (6.2ft) swell from 98° (E) at 12s period
  wind:
    speed kmh: 19
    speed mph: 11.8
    direction degrees: 52
    direction cardinal: NE
    explanation: 19 km/h (12 mph) from 52° (NE)
  secondary swell:
    height m: 0.6
    direction degrees: 174
    direction cardinal: S
    period s: 9
  windswell:
    height m: 1
    period s: 4
    explanation: Local wind-generated waves (choppy, short-period)

date: 2026-08-13
day index: 8
strike score:
  final score: 51
  category: Fair
  category emoji: 😐
  confidence: 0.8
  confidence explanation: Very low confidence (8-10 day forecast, conditions may change)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 216° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 21
      out of: 25
      explanation: Good size: 1.7m is within 15% of ideal 1.3m.
    swell period:
      score: 25
      out of: 25
      explanation: Perfect period: 11s is at or above ideal 11s. Long-period groundswell with maximum power.
    wind:
      score: 18
      out of: 25
      explanation: Onshore/cross-shore: 6 km/h from 79° (E). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: 0
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Surfable but not special at Shirahama Beach (Izu). The 1.7m swell from 216° is workable, but conditions aren't ideal. Fine if you're local, but not worth a dedicated trip.
conditions:
  swell:
    height m: 1.7
    height ft: 5.6
    direction degrees: 216
    direction cardinal: SW
    period s: 11
    explanation: 1.7m (5.6ft) swell from 216° (SW) at 11s period
  wind:
    speed kmh: 6
    speed mph: 3.7
    direction degrees: 79
    direction cardinal: E
    explanation: 6 km/h (4 mph) from 79° (E)
  secondary swell:
    height m: 0.7
    direction degrees: 214
    direction cardinal: SW
    period s: 8
  windswell:
    height m: 0.3
    period s: 2
    explanation: Local wind-generated waves (choppy, short-period)

date: 2026-08-14
day index: 9
strike score:
  final score: 46
  category: Fair
  category emoji: 😐
  confidence: 0.8
  confidence explanation: Very low confidence (8-10 day forecast, conditions may change)
  breakdown:
    swell direction:
      score: 0
      out of: 25
      explanation: No alignment: Swell from 208° is outside workable range 125°-180°. Wrong swell direction for this spot.
    swell size:
      score: 19
      out of: 25
      explanation: Marginal size: 1.4m is 0.1m from ideal 1.3m.
    swell period:
      score: 25
      out of: 25
      explanation: Perfect period: 11s is at or above ideal 11s. Long-period groundswell with maximum power.
    wind:
      score: 16
      out of: 25
      explanation: Onshore/cross-shore: 6 km/h from 147° (SSE). Destroying wave quality. Offshore range: 280°-360°.
  adjustments:
    wind history:
      adjustment: 0
      groomed: false
      morning sickness: false
      explanation: No significant wind history adjustment.
    windswell penalty:
      adjustment: 0
      windswell degraded: false
      explanation: Groundswell-dominant conditions (clean, long-period waves).
    secondary swell bonus:
      adjustment: 0
      explanation: No secondary swell bonus.
  summary: Surfable but not special at Shirahama Beach (Izu). The 1.4m swell from 208° is workable, but conditions aren't ideal. Fine if you're local, but not worth a dedicated trip.
conditions:
  swell:
    height m: 1.4
    height ft: 4.6
    direction degrees: 208
    direction cardinal: SSW
    period s: 11
    explanation: 1.4m (4.6ft) swell from 208° (SSW) at 11s period
  wind:
    speed kmh: 6
    speed mph: 3.7
    direction degrees: 147
    direction cardinal: SSE
    explanation: 6 km/h (4 mph) from 147° (SSE)
  secondary swell:
    height m: 0.7
    direction degrees: 214
    direction cardinal: SW
    period s: 8

Strike Mission
type: Organization