Question 1

Your vessel encounters an unexpected Force 9 (severe gale). You are the duty officer. Describe the deck safety management measures you implement immediately.

Accepted Answer

DECK SAFETY IN FORCE 9 — CHIEF MATE: FORCE 9 (SEVERE GALE): mean wind speed 41-47 knots. Wave height 7-10m. Green water on deck. Vessel motion severe. IMMEDIATE DECK SAFETY MEASURES: (1) NO CREW ON DECK: immediately prohibit all non-essential deck work. Post a notice on the gangway/deck access if necessary. This is the primary safety measure; (2) SECURE ALL DECK OPENINGS: hatches, ventilators, air pipes, access panels. Heavy weather clips on all watertight closures; (3) CHECK LASHINGS: if cargo or equipment is on deck — are lashings holding? A visual check from the bridge or covered walkways. No crew to go to open deck to check lashings — assess from the bridge superstructure or enclosed walkways; (4) ANCHOR SECURITY: ensure anchors are properly secured (cat and fish anchors if applicable). An anchor that works loose in heavy weather can cause major bow damage; (5) BILGE ALARM: check that automatic bilge alarms are functioning. Increased ship motion can cause water in unexpected locations; (6) FREE SURFACE: all tanks should be as full or as empty as possible — avoid slack tank conditions that increase free surface effect and reduce GM in heavy weather; (7) SAFETY LINES: if any crew MUST go on deck for essential safety reasons — safety lines rigged on the pathway they will use, two-person rule, suitable PPE; (8) CALL THE MASTER: Force 9 unexpected — the master should be on the bridge; (9) VDR: note the time and conditions in the bridge log; (10) REPORT HAZARDOUS SITUATION: log as an ISM near-miss/hazardous situation if conditions were worse than forecast. No crew on open deck in severe weather: this is a fundamental safety principle. Green water (solid water shipped on deck from breaking waves) has enormous momentum — a wave striking a crew member on deck can sweep them overboard or cause crushing injuries. The force of water at 3-5 knots flow speed on a deck is beyond what any lifeline can reliably hold. The master's standing orders and SMS should specify the wind/sea condition at which deck work is prohibited. Typically: > Force 7 = check before allowing deck work; > Force 8 = essential safety work only with full PPE and safety line; > Force 9 = no routine deck work permitted. Lashing checks in Force 9: the chief mate wants to verify that deck cargo lashings are holding — but this cannot be done safely by sending crew to the open deck in Force 9. Options: (a) visual observation from the bridge; (b) camera monitoring if fitted; (c) wait for an opportune window (temporary reduction in wind) with full safety precautions. The decision to accept that some risk exists vs creating a worse risk (crew on deck in Force 9) must be made by the chief mate/master. Heaving-to (option C): heaving-to is one strategic option in severe weather — but it is NOT automatically required in all Force 9 conditions. A vessel with adequate stability and properly secured cargo may continue to make way in Force 9 on a favourable heading. Heaving-to removes the vessel's ability to make progress and may be appropriate when conditions are so severe that heading becomes untenable — this is a master's decision based on specific circumstances.

Question 2

You are in the Bay of Bengal in October. Barometric pressure has fallen 8mb in 4 hours and a heavy swell is arriving from the SSW despite a cloudless sky. As Chief Mate on watch, what do you suspect and how do you respond?

Accepted Answer

TROPICAL CYCLONE APPROACH — RECOGNITION: SIGNS: an 8mb pressure drop in 4 hours plus an anomalous swell from a different direction than the current wind — these are classic early warning signs of a tropical cyclone. October in the Bay of Bengal is the second peak of the cyclone season (post-monsoon, September-December). BAY OF BENGAL CYCLONES: rotate COUNTER-CLOCKWISE (Northern Hemisphere). A swell from the SSW suggests a system to the SSW generating that swell. LOCATING THE CYCLONE: using Buys Ballot's Law (Northern Hemisphere): STAND WITH YOUR BACK TO THE WIND — the low pressure centre is to YOUR LEFT. So if the current wind is from the NNE (facing SSW) — the cyclone centre is approximately to the LEFT (ENE). MANOEUVRING RULES: for a vessel in the DANGEROUS SEMI-CIRCLE (DSC — right-hand semi-circle in Northern Hemisphere): alter to STARBOARD and run with the wind on the starboard quarter to move away from the path. For a vessel in the NAVIGABLE SEMI-CIRCLE (NSC — left-hand semi-circle): bring the wind on the starboard bow and run at best speed. For a vessel ON THE TRACK: bring the wind on the starboard quarter and run. IMMEDIATE ACTIONS: (1) CALL THE MASTER; (2) Obtain the latest GMDSS weather broadcast/NAVTEX; (3) Plot the swell direction and barometric pressure trend on the chart; (4) BEGIN MANOEUVRING in accordance with the semi-circle rules; (5) Secure all deck equipment, hatches, and loose gear; (6) Commence ballasting if stability margin is low. Barometric pressure rate of fall: in tropical regions, the normal diurnal variation in atmospheric pressure is approximately 1-2mb. A fall of 8mb in 4 hours (2mb/hour) is far outside normal variation and indicates the approach of a significant system. This rate of pressure fall is explicitly used in seamanship as a criterion for a developing tropical cyclone. Bay of Bengal cyclones: the Bay of Bengal is one of the world's most active cyclone basins with peak activity in May-June and October-December. Bengali cyclones are noted for their rapid intensification and the shallow Bay of Bengal amplifies the storm surge to devastating heights (the 1970 Bhola cyclone killed 300,000 people partly due to surge). Swell without cloud: tropical cyclones generate long-period swells that travel far ahead of the system — typically 24-36 hours ahead of the centre. The swell arrives before the cloud cover and wind, which is why experienced mariners treat an anomalous heavy swell as a cyclone warning even in clear weather. Buys Ballot's Law: this rule for finding the low pressure centre from the wind direction works in both hemispheres (modified for Southern Hemisphere — centre is to the right when facing into the wind). Every OOW and CM should know this and be able to apply it immediately. Course into swell (option C): course selection in cyclone avoidance is NOT simply "head into the swell." The correct course depends on which semi-circle the vessel is in. Heading directly into the swell might take the vessel toward the cyclone track rather than away from it. Buys Ballot manoeuvre must override the simple "head to sea" instinct.

Question 3

As Chief Mate, you receive a NAVTEX synoptic chart showing a 968mb deep depression 400nm to your NW, moving E at 25 knots. Your position is to the S of the low track. Describe the expected weather sequence.

Accepted Answer

SYNOPTIC CHART ANALYSIS — DEPRESSION WEATHER SEQUENCE: WARM SECTOR DEPRESSION STRUCTURE: the classic mid-latitude depression has: WARM FRONT (ahead of the warm sector), WARM SECTOR, and COLD FRONT. The vessel to the SOUTH of the depression track is in the NAVIGABLE (or "safe") SEMI-CIRCLE and will experience: APPROACHING WEATHER SEQUENCE: (1) VEERING WINDS: as the warm front approaches (from WSW to W to NW) — south of the track; (2) WARM FRONT PASSAGE: (a) Clouds sequence: Cirrus → Cirrostratus → Altostratus → Nimbostratus (the "classical" cloud sequence of an approaching warm front); (b) Rain: continuous moderate to heavy rain with poor visibility; (c) Wind: south to SW, backs slightly as warm front passes; (d) Pressure: steady fall; (e) Temperature: rise; (3) WARM SECTOR: (a) Moderate SW winds; (b) Drizzle and low cloud (sea fog risk if warm, moist air moves over colder sea); (c) Pressure temporarily stabilises; (4) COLD FRONT PASSAGE: (a) Wind veers rapidly from SW to NW or N; (b) Heavy showers, squalls, possibly thunder; (c) Pressure rises sharply; (d) Temperature falls; (e) Visibility clears rapidly; (5) AFTER COLD FRONT: NW winds, showers, good visibility between showers, cumulus cloud. 968mb depression = strong system. At 400nm at 25kt movement = 16 hours to reach the vessel position. Wind force — from distance/isobar spacing on chart: calculate wind force from isobar spacing. 968mb depression = likely Force 9-10 on the south semi-circle at closest approach. 16-hour arrival time: 400nm ÷ 25 knots = 16 hours. This is a real operational planning figure — 16 hours is enough time to: (a) prepare the vessel; (b) ballast/secure; (c) brief the crew; (d) assess whether to divert to shelter or run clear of the track. A CM on watch who correctly identifies this timing gives the master critical decision information. The vessel south of the track: in a Northern Hemisphere depression moving east — the vessel south of the track is in the LEFT (navigable) semi-circle. The warm front WILL pass over the vessel south of the track. The warm sector and cold front will also pass. The CM who says "no warm front because I'm south of the track" is confusing the depression track with the location of the warm front (which extends south of the centre). Isobar spacing and wind force: on a synoptic chart, the spacing between isobars (drawn at 4mb intervals) gives a relative indication of pressure gradient and therefore wind speed. Closely spaced isobars = strong gradient = strong winds. At 968mb in a mid-latitude depression, the warm sector to the south typically shows 4-6mb spacing — equivalent to Force 8-10 (gale to strong gale). Uniform wind Force 12 (option D): incorrect. Wind in a depression varies with location — strongest winds are to the right of the track (dangerous semi-circle) and in the depression core (around the warm/cold front boundary). South of the track, the winds are typically Force 8-10 in a deep system. Force 12 is generally confined to the core of the strongest systems.