SEA-CRAG RESEARCH PREVIEW

Bosigran

West Cornwall · Granite · Coast-scale guidance, not individual routes

Inputs retrieved 8 Oct 2026, 17:00 BST. Updated each morning and evening, scheduled for 07:00 and 17:00 UK time. Forecasts cover today and the next four days.

Stronger sea-state signal

A strong sea-state signal: waves and spray may affect sea-level climbing. Higher modelled water around 17:00 coincides with a raised sea-state signal. Check official tide times.

Saturday 10 October · 08:00 to 18:42 local time

From 08:00 or sunrise, whichever is later, until sunset. Tide-related turns below cover the full calendar day.

Offshore waves

2 to 2.3 m

Significant wave height, not the largest individual wave.

Swell

1.6 to 1.8 m

Period 7.5 to 8.4 seconds. Longer-period swell can matter even in light wind.

Coastal wind

11.6 to 16.8 mph

Gusts 19.7 to 31.5 mph. Model 10 m open-ground wind, not face or belay wind.

Rain and temperature

0 mm

12.6 to 14.4°C. Rain covers source hours overlapping the daytime window.

Coast and spray

Spray guidance unavailable

  • A notable offshore sea state is forecast.

A representative coastal point is available, but a defensible single coast or face direction has not yet been assigned. Directional spray and shelter claims are withheld.

Spray is an uncalibrated indication, not a probability or a height prediction. A lee wind does not establish shelter from swell.

Predicted astronomical tides

Calculated every five minutes from harmonic constants fitted to the nearby tide gauge's measured record. Some locations can have genuine secondary highs and lows.

    Astronomical tide prediction unavailable. Do not infer constant or low water.

    No local astronomical tide reference is assigned yet. Newlyn is on the other side of the peninsula and has not been validated as a transfer station for Bosigran. Times are predictions, not observations at the crag. Heights are deliberately omitted because they are not tied to a climbing ledge or chart datum here.

    Total water-level model

    Approximate peaks and dips in total sea level, including tide and weather effects. Source resolution is hourly, not a guarantee of timing accuracy.

    • Model level peakAbout 05:00
    • Model level dipAbout 11:00
    • Model level peakAbout 17:00
    • Model level dipAbout 23:00

    The total-water heights use mean sea level, not chart datum. Do not compare them directly with guidebook tidal-access heights.

    Different parts of the crag

    Main cliff base and approaches

    Much of the main cliff begins above the sea, but individual approach and start heights are not surveyed. Nearby sea-level climbing is not covered by this entry.

    Upper cliff and top-outs

    Exposed upper rock can still be affected by wind and spray. This forecast does not establish a safe retreat or guaranteed dry rock.

    How conditions change through the day

    Directions show where wind and waves approach from, relative to the provisional broad coast aspect, not a surveyed climbing face.

    Local time. Water heights are relative to mean sea level (MSL).
    TimeModel waterWavesSwellWind
    08:00-0.5 m MSL
    Falling
    2.3 m
    Unresolved
    1.8 m, 7.8 s
    Unresolved
    16.1 mph
    Unresolved
    09:00-1.7 m MSL
    Falling
    2.2 m
    Unresolved
    1.8 m, 7.8 s
    Unresolved
    13.9 mph
    Unresolved
    10:00-2.6 m MSL
    Falling
    2.1 m
    Unresolved
    1.8 m, 7.8 s
    Unresolved
    15.4 mph
    Unresolved
    11:00-3 m MSL
    Falling
    2.1 m
    Unresolved
    1.8 m, 7.8 s
    Unresolved
    15.9 mph
    Unresolved
    12:00-2.8 m MSL
    Rising
    2 m
    Unresolved
    1.7 m, 7.8 s
    Unresolved
    16.8 mph
    Unresolved
    13:00-1.9 m MSL
    Rising
    2 m
    Unresolved
    1.7 m, 7.9 s
    Unresolved
    15 mph
    Unresolved
    14:00-0.5 m MSL
    Rising
    2 m
    Unresolved
    1.7 m, 8.1 s
    Unresolved
    15.7 mph
    Unresolved
    15:001.1 m MSL
    Rising
    2 m
    Unresolved
    1.6 m, 8.4 s
    Unresolved
    15.2 mph
    Unresolved
    16:002.1 m MSL
    Rising
    2 m
    Unresolved
    1.6 m, 8.4 s
    Unresolved
    15 mph
    Unresolved
    17:002.5 m MSL
    Changing slowly
    2 m
    Unresolved
    1.6 m, 8.1 s
    Unresolved
    13.2 mph
    Unresolved
    18:002.1 m MSL
    Falling
    2 m
    Unresolved
    1.6 m, 7.5 s
    Unresolved
    11.6 mph
    Unresolved
    How this preview works and what is missing

    Astronomical tides use 50 harmonic constituents from TICON-4, fitted to many years of measured tide-gauge data. The Moon and Sun are represented through these astronomical constituents, while local coastal shape is learned from the gauge record. Wind and pressure are not added to that curve.

    Separately, we combine Open-Meteo waves, swell and total sea-level forecasts with local weather and a provisional coast-facing direction. Larger waves, longer periods and waves approaching the coast strengthen the sea-state signal. Onshore wind strengthens the spray signal. These are transparent research rules, not calibrated predictions of wave reach.

    We do not add swell to total wave height because total waves already include swell. We also keep the astronomical tide and weather-affected total-water model separate to avoid counting surge twice.

    • Offshore model guidance, not conditions at a particular ledge. Individual waves can exceed the quoted significant height. Check official tide tables, route access and the sea on arrival; no safe-access window is calculated.
    • Spray signals are provisional rules, not calibrated probabilities or spray-height predictions.
    • The pilot does not resolve bathymetry, wave refraction, reflected waves, surge residuals separately or salt deposits on holds.
    • A sheltered wind direction does not establish shelter from swell. Offshore direction never establishes safe access.

    No climbing score, safe-access interval or notification is produced. These crags are excluded from live rankings. Rock type is descriptive here; salt, seepage and drying are not yet modelled for this pilot.

    Returned marine grid centre: 50.2, -5.6. Small coves, headlands and ledges are not resolved.

    Inspect the research JSON contract