Good Weather Analysis: How to Defend a Speed Claim

A speed and consumption claim turns on a deceptively simple question: did the vessel meet its warranted speed in good weather? Get the definition of “good weather” right and most disputes resolve themselves.

What counts as good weather

A wind force ceiling (often Beaufort 4) defined in the charter party.
A sea/swell height limit, sometimes including a current allowance.
A minimum continuous duration so brief lulls do not qualify.

The step-by-step analysis

Isolate the good-weather periods using independent metocean data, then compare achieved speed and consumption only within those windows against the warranty. NAVGreen automates exactly this: every voyage is matched against NOAA/ECMWF data so the good-weather sample — and the resulting claim or defense — is verifiable rather than asserted.

FAQ

What is good weather in a speed claim?

It is the period when wind and sea stay below the limits defined in the charter party (commonly up to Beaufort 4) for a minimum continuous duration. Only these periods are used to assess warranted speed and consumption.

Whose weather data is authoritative?

Disputes usually hinge on independent hindcast data such as NOAA or ECMWF rather than the ship’s own logs, because an independent source is harder to contest.

See how NAVGreen does this for you

Run a real scenario on your own voyages and trade lanes.

Charter Party Performance Monitoring