Weather working day
The three weather working day formulations in the Laytime Definitions 2013 and the pro-rata deduction each produces.
A weather working day is a working day, or part of one, during which it is or would be possible to load or discharge cargo without interruption due to weather. It is the most common laytime unit in dry cargo fixtures and the most frequently miscalculated.
The mechanism that generates disputes is the deduction rather than the definition. Under definition 15 of the Laytime Definitions for Charter Parties 2013 an interruption removes from laytime a period calculated by the ratio the interruption bears to the time that would have or could have been worked but for it. It is proportional, not a whole-day switch, and the two 24-hour variants at definitions 16 and 17 compute differently again.
The full article will work each of the three formulations through a statement of facts, cover the interaction with SHEX, SHINC and FHEX conventions, treat the position where the ship is still waiting for her turn, and set out how a weather claim is evidenced from port meteorological records.