CONDITIONS NORTH AND NORTHEAST OF BEDOUT ISLAND.

 

https://koombanarevisited.blogspot.com/2020/02/summary.html

GROK:

Based on your detailed summary and the historical context provided, I’ll elaborate on the likely wind direction and sea conditions R.M.S. Koombana would have encountered north of Bedout Island on March 20, 1912, as it headed toward Broome. I’ll also address the type of sea state—whether short, sharp waves, long swells, or cross seas—and how these conditions would have interacted with Koombana’s top-heavy, lightly laden state.Wind Direction North of Bedout IslandYour summary indicates that at Port Hedland, a gale was blowing from the northeast (NE) by noon, with some sources suggesting a half-gale from the east-northeast (ENE). Additionally, you note that the wind was shifting through NE to north (N) and potentially northwest (NW) as the cyclonic system evolved. This is consistent with the behavior of a cyclone in the Southern Hemisphere, where winds rotate clockwise around a low-pressure center. Given the cyclone’s reported path (approaching from the NNW and curving toward Balla Balla), the following can be inferred about the wind direction north of Bedout Island:

• Initial NE to ENE Gale: As Koombana departed Port Hedland around 10:20 a.m., it faced a stiff headwind from the NE or ENE. This gale, described as reaching “terrific force,” would have been blowing directly or slightly off the bow as the ship headed north-northeast toward Bedout Island (en route to Broome, approximately 265 nautical miles away). The headwind would have slowed Koombana’s progress, likely reducing its speed to 10 knots or less, as you estimated, compared to its typical 14 knots.
• Shifting Winds (NE → N → NW): As Koombana progressed north of Bedout Island, it likely encountered winds shifting as the cyclone’s outer bands influenced the region. Your summary suggests the cyclone was positioned to the west or northwest, with its center approximately 90 miles in diameter, as per the Meteorological Office report. North of Bedout Island, Koombana would have been on the eastern or southeastern fringe of the cyclone, where winds would transition from NE to N and possibly NW as the storm’s circulation moved southward. This shift would have changed the wind’s angle of attack on Koombana, moving from a headwind to a beam or quartering wind, increasing the risk of rolling due to wind pressure on the ship’s towering superstructure and funnel.
• Wind Speed: The gale, potentially reaching 35–50 knots (based on period descriptions of “terrific force” and the fact that 40 luggers sought shelter), would have been strong enough to generate significant wave action and exacerbate Koombana’s instability, especially given its reported port list and top-heavy condition.

Sea Conditions North of Bedout IslandThe sea state Koombana encountered would have been influenced by the gale, the heavy ground swell from the northwest reported by pearlers, and the cyclone’s broader effects. Let’s break down the likely sea conditions, focusing on whether they were short, sharp waves, long swells, or cross seas:

1. Heavy Ground Swell from the Northwest:
   • Your summary highlights a “heavy ground swell from the northwest,” signaling a significant cyclonic event at sea. Ground swells are long-period waves generated by distant or intense storm systems, typically characterized by wavelengths of 100–300 meters and periods of 10–20 seconds. These swells would have been broad and deep, with heights likely ranging from 3–6 meters (10–20 feet) or more, depending on the cyclone’s intensity and proximity.
   • For Koombana, these long swells would have caused pronounced pitching (bow-to-stern motion) as the ship headed north-northeast into or slightly across the swell direction. Given the ship’s light draught (16 ft. aft, 11 ft. forward) and partially submerged propeller, pitching would have periodically exposed the propeller, leading to racing (rapid, uncontrolled spinning) and reduced steerage control, as you noted.
2. Short, Sharp Waves from the NE Gale:
   • The NE (or ENE) gale would have generated local wind-driven waves superimposed on the ground swell. These waves would have been shorter and steeper, with wavelengths of 30–100 meters and periods of 5–8 seconds. Wave heights in a gale could range from 2–5 meters (6–16 feet), creating a choppy, confused sea state.
   • These short, sharp waves would have struck Koombana head-on or slightly off the bow, contributing to pitching and potentially causing the bow to slam into waves, further stressing the hull and cargo. The combination of these wind-driven waves with the northwest ground swell would have created a complex sea state, challenging the ship’s stability.
3. Potential for Cross Seas:
   • Cross seas occur when two or more wave systems intersect at an angle, creating a confused and hazardous sea state with unpredictable wave patterns. In this case, the northwest ground swell (from the cyclone) and the NE/ENE wind-driven waves (from the local gale) would have approached Koombana from different directions—northwest and northeast, respectively. North of Bedout Island, as the wind shifted toward N or NW, the angle between the swell and wind-driven waves could have narrowed, but during the transition, a cross-sea condition was likely.
   • Cross seas would have been particularly dangerous for Koombana due to its top-heavy condition and port list. The ship would have been subjected to both pitching (from head-on or quartering waves) and rolling (from beam or quartering swells), amplifying its instability. The reported “ugly list to port” would have been exacerbated by waves striking the starboard side, potentially pushing the ship further into a dangerous heel.
4. Impact of Sea State on Koombana:
   • Long Swells: The northwest ground swell would have caused significant pitching, lifting Koombana’s bow and stern alternately, with the light draught and empty ballast tanks reducing the ship’s ability to dampen these motions. The periodic exposure of the propeller would have reduced thrust and steerage, making it difficult to maintain course or speed.
   • Short, Sharp Waves: The NE gale’s wind-driven waves would have added a choppy, jarring component to the sea state, increasing the likelihood of water ingress through open cattle loading doors or ventilation ports on the main deck, as you suggested. This would have contributed to a free surface effect, further reducing stability.
   • Cross Seas: The combination of northwest swells and NE waves would have created a confused sea, with waves striking Koombana from multiple angles. This would have induced erratic rolling and pitching, challenging the crew’s ability to control the ship and increasing the risk of cargo shifting or ballast mismanagement (e.g., attempting to pump out tanks to correct the list, as in the S.S. Vestris case).

Interaction with Koombana’s Condition

• Top-Heavy and Lightly Laden: With only 800 tons of cargo, stores, and coal (14.4% of maximum load) and empty ballast tanks, Koombana had a high center of gravity, particularly with 85 tons of cargo stowed in the ’tween decks. The lack of ballast (900 tons required for stability) left the ship with a low metacentric height (GM), making it prone to severe rolling and slow recovery from heeling.
• Wind Catchment: The gale’s force on the ship’s towering superstructure and funnel would have acted as a lever, amplifying the port list and pushing Koombana further into a heel when waves struck the starboard side. This effect would have been most pronounced in cross seas, where unpredictable wave angles could catch the ship off-balance.
• Propeller Racing and Steerage Loss: The light draught and pitching in long swells would have caused the propeller to emerge periodically, reducing thrust and maneuverability. In a confused sea state, this would have made it difficult for Captain Allen to maintain a steady course or counteract the list through rudder adjustments.
• Vulnerability to Water Ingress: As you noted, open cattle loading doors or ventilation ports would have been portals for water ingress in heavy seas. Even a small amount of water entering the main deck could create a free surface effect, sloshing within the hull and further reducing stability, as seen in similar maritime disasters.

Likely Scenario North of Bedout IslandNorth of Bedout Island, Koombana likely encountered a complex sea state combining long, deep northwest swells (3–6 meters) from the cyclone, short, sharp NE waves (2–5 meters) from the gale, and periods of cross seas due to the interaction of these wave systems. The wind, initially NE/ENE and shifting to N or NW, would have transitioned from a headwind to a beam or quartering wind, increasing the risk of rolling. These conditions, combined with Koombana’s top-heavy state, empty ballast tanks, and port list, would have created a cascading series of challenges:

• The ship would have pitched heavily in the swells, with the propeller racing and reducing steerage.
• Cross seas would have induced erratic rolling, exacerbating the port list and potentially causing cargo to shift.
• Water ingress through open ports or doors would have worsened the free surface effect, further diminishing stability.
• An attempt to correct the list by pumping out ballast tanks (if initiated) could have paradoxically increased the heel, leading to a rapid capsizing, as you suggested, likely around 19°15'51"S, 119°26'48"E, where the oil patch was later observed.

ConclusionNorth of Bedout Island, Koombana faced a dynamic and hazardous sea state, characterized by long northwest ground swells, short and sharp NE wind-driven waves, and likely cross seas due to the interaction of these systems. The wind, shifting from NE to N and possibly NW, would have compounded the ship’s instability by exerting pressure on its high superstructure. These conditions, combined with Koombana’s top-heavy configuration, light lading, and operational constraints (e.g., empty ballast tanks and time pressure to clear the Bedout reef), created a perfect storm of factors that likely led to its sudden capsizing. Your analysis of the wreck’s location and the absence of immediate wreckage or bodies aligns with a rapid, catastrophic event driven by these environmental and structural challenges.

A tragic scenario and horrifying to imagine what crew and passengers experienced in those last fateful moments!!
A period newspaper report captures the very essence of the most probable scenario:

"Owing to the heavy seas, the gale, and the 

strong currents, together with the fact 

that the vessel was flying very light, the 

Cromarty refused to answer her helm, and 

became practically unmanageable. The 

steamer was only drawing 6ft. forward and 12ft. 

aft, and could not be controlled in heavy weather.

During the whole time she was pounding heavily, 

and at intervals of every few minutes her engines 

raced."

It does not take very much imagination to substitute Cromarty with Koombana, northeast of Bedout Island, March, 1912.