Your company subscribes to a commercial weather routing service. The routing service recommends a southern route to avoid a forecast depression. As Master, what is your decision-making framework?

A. WEATHER ROUTING — MASTER'S AUTHORITY AND RESPONSIBILITY: NATURE OF WEATHER ROUTING SERVICES: commercial weather routing services (e.g., StormGeo, SPOS, Weathernews) provide: (a) vessel-specific routing recommendations; (b) updated weather forecasts and route revisions en route; (c) port ETA calculations; (d) fuel efficiency optimisation. They are ADVISORY SERVICES — not command authorities. LEGAL RESPONSIBILITY: the passage plan and any alterations to it remain the master's legal responsibility under SOLAS V/34. The routing service has no legal authority over the vessel. A master who follows a routing service recommendation that results in a casualty CANNOT blame the routing service as a complete defence — the master must have exercised independent professional judgement. DECISION FRAMEWORK: (1) ASSESS THE RECOMMENDATION: does it make meteorological and navigational sense? Does it fit with the vessel's stability, cargo, and crew fatigue considerations?; (2) VERIFY WITH INDEPENDENT SOURCES: cross-check the routing service recommendation against: GRIB data (raw model output), Navtex weather forecasts, GMDSS weather bulletins, barometric pressure trend on board; (3) COMPANY POLICY: some companies require masters to follow routing service recommendations unless the master has specific safety objections — check the SMS; (4) MASTER'S OVERRIDE: if the master believes the routing recommendation is unsafe or sub-optimal — the master has absolute authority to deviate and must document the reasons in the OLB; (5) FUEL/COMMERCIAL PRESSURE: if the routing recommendation saves fuel but the master considers it unsafe — commercial pressure does not override the master's safety judgement (ISM 5.3).

B. The routing service is the expert. Once a routing recommendation is received, the master has no further responsibility for route selection — follow the recommendation exactly.

C. Weather routing services are only useful for optimising fuel consumption. For safety decisions, the master should ignore routing service recommendations and use only GRIB data.

D. The routing service bears legal responsibility for the voyage outcome if the master followed their recommendation. Masters should always follow routing advice to transfer liability.

A. PASSAGE PLAN APPROVAL — MASTER'S SOLAS V/34 OBLIGATIONS: SOLAS V/34 LEGAL REQUIREMENT: "Prior to proceeding to sea, the master shall ensure that the intended voyage has been planned using an appropriate chart and appropriate nautical publications for the area concerned, taking into account the guidelines and recommendations developed by the IMO." This is an absolute obligation on THE MASTER — not the chief officer. The master cannot delegate this legal responsibility. WHAT THE MASTER MUST VERIFY IN THE PASSAGE PLAN: (1) APPRAISAL: is the passage planned using the correct, up-to-date charts (latest edition, NTM corrections applied)? Have the relevant nautical publications been consulted (Sailing Directions, Light Lists, Tide Tables, NtM, Notices to Mariners)? Have weather routing service recommendations been considered?; (2) PLANNING: is the passage plan complete from berth to berth? Does it include: (a) waypoints with safe clearing bearings or distances; (b) no-go areas clearly marked; (c) abort points — where is the last point at which the vessel can safely alter to an alternative port?; (d) wheel-over positions for planned alterations?; (e) UKC calculations at minimum water depth points?; (f) speed calculations to ensure arrival at pilot station at the correct tidal window?; (3) EXECUTION CHECKS: are monitoring intervals appropriate to the waters transited? Are danger waypoint checks included?; (4) CONTINGENCY: is there a documented contingency plan for engine failure, medical emergency, severe weather forcing diversion?; (5) MASTER'S SIGN-OFF: the master must sign the passage plan, confirming approval. This signature carries legal weight.

B. SOLAS V/34 is fulfilled as long as a passage plan exists in any form. The master does not need to review the detail — that is the chief officer's responsibility.

C. Passage planning only applies to coastal and restricted waters. For an open-ocean transatlantic passage, a general course line and waypoints are sufficient compliance.

D. The master can delegate the legal obligation for passage planning to the chief officer. If the chief officer is competent, the master's review is optional.

A. UKC CALCULATION AND POLICY APPLICATION: BASIC UKC CALCULATION: Available water depth = Chart depth + Tidal height = 16.2 + 0.8 = 17.0m. Vessel draught = 14.5m. Static UKC = 17.0 - 14.5 = 2.5m. UKC policy requirement = 10% of draught = 1.45m. STATIC RESULT: 2.5m available vs 1.45m required — APPEARS SUFFICIENT. HOWEVER — THE MASTER MUST CONSIDER DYNAMIC UKC FACTORS: (1) SQUAT: at speed in shallow water, the vessel will "sink" relative to the water surface due to Bernoulli pressure reduction. For a vessel of this draught in 17m of water (h/d ratio = 17/14.5 = 1.17 — VERY SHALLOW), squat could be 0.5-1.0m at standard speeds. Use squat formula or company guidance; (2) HEEL ALLOWANCE: if the vessel is turning or wind-heeled, the draught at the low side increases. A 2° list or heel adds ~0.5m to draught at the side; (3) TIDE PREDICTION UNCERTAINTY: is the 0.8m tidal height taken from a standard tidal prediction? In practice, meteorological conditions can reduce tidal height significantly. A strong onshore wind can ADD height; an offshore wind can REDUCE it; (4) CHART DATUM UNCERTAINTY: is the 16.2m from a recent survey? Chart datum may differ from actual current depths in silting areas; (5) WAVE RESPONSE: in swells, the vessel pitches and the bow drops lower — "hogging/sagging" effects; DECISION: with static UKC of 2.5m against 1.45m required — the margin appears sufficient. But with squat at speed potentially 0.5-1.0m, the DYNAMIC UKC may be as low as 1.0-1.5m. If squat approaches 1.0m, the remaining dynamic UKC is 1.5m — which is at the policy limit. RECOMMENDATION: reduce speed to minimise squat, use VHF confirmation of current tidal height, arrive at the shallowest point at maximum tidal height.

B. Static UKC of 2.5m exceeds the 1.45m policy requirement. Proceed at full speed — there are no further calculations required.

C. The 10% policy gives 1.45m minimum UKC. As the static UKC is 2.5m — there is more than adequate margin for all conditions. Squat is only relevant for small vessel operations.

D. Tidal height of only 0.8m is insufficient. Wait for high water (which adds significantly more height) before attempting the passage.