Compare an entered official significant-wave forecast with a compatible observed or buoy Hs record while retaining period, direction and observation age.
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Compare one current official significant-wave-height forecast with a compatible observed/buoy Hs record while retaining period, direction and observation-age context.
Keep zone/station, time, units and Hs definitions compatible.
Enter official Hs, observed Hs, peak period, primary direction and observation age.
Sees the signed difference and ratio without a fabricated maximum-wave prediction.
Recognize that period, direction, source quality and recency matter.
Review retained context and then consult the underlying current forecast, warnings and observation record.
Does not reduce sea character to height alone.
Keep vessel limits, depth/current, wind wave, swell and individual-wave risk above arithmetic.
Use current responsible-authority products and qualified local judgment externally.
Never treats matching Hs as permission to depart or cross a bar.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
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The result subtracts the entered official significant-wave height from a compatible entered observed or buoy significant-wave height and reports signed and absolute differences.
Peak period, primary direction and observation age remain visible because equal heights can describe materially different conditions and old or mismatched records can mislead.
Significant wave height is the mean height of the highest one-third. Individual waves can be substantially higher, so this tool does not multiply Hs into a deterministic maximum or forecast new conditions.
Updated: August 2026
Enter compatible time- and unit-aligned Hs records, then inspect whether the observation is above, below or equal to the official value.
Keep peak period, primary direction and observation age beside the height comparison before consulting the full forecast, spectrum and warnings.
Use current responsible-authority forecasts plus vessel limits, depth/current, bar or surf conditions and local experience; never use this comparison as departure permission.
Align zone or station, timestamp, units and Hs definition, and verify the observation's quality and age.
Hs is an average of the highest one-third, not a maximum. Individual waves can be substantially higher.
This tool reconciles one entered official Hs value with one compatible observed or buoy Hs record and keeps period, direction and age visible. It does not forecast waves, determine a maximum individual wave or assess vessel operability, bar conditions or permission to depart.