Speed & Performance - Discrepancies Between Ships' Data And Independent Weather Bureaus

In the current climate, we are seeing increasing attempts by charterers to withhold hire on the basis that the vessel did not meet its contractual performance warranty.

The law on the issue is well settled; since The "DIDYMI" [1988] it has been accepted that, if a vessel fails to meet its performance warranty in good weather, then it is also deemed to have underperformed during periods of bad weather. Therefore, charterers need only show the vessel underperformed (or over-consumed) during periods of good weather to claim underperformance for the duration of the voyage/charter.

How one measures the number of good weather days becomes complicated when there is a discrepancy between the weather and sea state conditions recorded in the vessel's logbooks, and information from independent weather bureaus, as standard charterparty wordings are silent on which should take precedence.

Historically, the Master's evidence has been preferred, unless he was obviously wrong. This is understandable given that he is on the bridge, and witnesses the weather and sea state continuously, whereas the independent weather information is often only measured daily, or twice daily, using satellite imagery.

However, increasingly, Tribunals are appreciating that the Master's view is subjective, and the independent weather data is becoming more reliable.

In London Arbitrations 3/12 and 4/12, which both concerned the same charterparty dispute, charterers claimed underperformance, and overconsumption. The relevant clause stated (emphasis added):

"Evidence of weather conditions to be taken from the vessel's deck logs and Independent Weather Bureau reports. In the event of a consistent discrepancy between the deck logs and Independent Bureau reports, then the matter to be referred to arbitration, if not settled amicably".

The clause does not state which data is to be preferred, and the phrase "consistent discrepancy" is open to much interpretation.

The factual background was not unique; relying upon independent bureau information, charterers argued the vessel underperformed during good weather on 7 of 20 voyages, and sought to apply that underperformance on all 20 voyages. Owners contested the underperformance by relying upon the passage reports that were taken from the log books.

The Tribunal found that there was a...