Handling Low Visibility When You’re Officer of the Watch
Feb 22, 2023 · 9 mins read ·Jobs at Sea
The safe and efficient navigation of the ship is one of the officer of the watch’s (OOW) most crucial responsibilities.
A ship must navigate through various tidal and meteorological conditions when at sea. Therefore, the navigating officer is responsible for thoroughly studying and planning for the ship’s sailing path in advance.
Limited vision caused by fog, severe rain, or a dust storm is one of the most hazardous situations for a ship.
When a ship’s officer learns about the impending weather, they should take all required steps to ensure that the ship sails through the reduced visibility area without collisions or groundings.
But what are these required steps? What constitutes impending weather that will prompt the OOW to watch?
More importantly, how should the officer of the watch handle low visibility?
Let’s dive deep into that and more in this post.
What is low visibility?
Many factors affect visibility at sea.
The most complex meteorological parameters to forecast are humidity, wind speed, and temperature.
The amount of aerosols (water droplets, ice crystals, or other particles like dust) in the air affects visibility because they reflect incoming light.
Visibility decreases with the presence of more aerosols in the atmosphere. Yet, the aerosol’s shape will also have an impact on visibility. For instance, snow crystals will impair vision more than raindrops.
On average, visibility is higher when winds are coming from the north (in the Northern Hemisphere) than when winds are coming from the south, as the northerly winds frequently bring colder, dryer, and often cleaner air.
What are the usual factors contributing to low visibility? We’ve outlined some of them below:
- Mist and fog
Fog is defined as visibility below 1000 meters, and mist is visibility between 1000 and 5000 meters.
Invisible steam, liquid water droplets, or solid water particles like ice crystals, snow, and hail are all forms of water that are always present in the air.
2. Radiation fog
On land, fog usually develops at night as the temperature drops and dissipates in the morning when the sun heats and dries out the lower atmosphere. This “radiation fog” can only develop when the sky is clear, and the wind is light.
The same method is not feasible over water since water has a far higher heat capacity than land; hence its temperature does not change throughout the day.
However, the radiation fog may spread to the sea, resulting in an all-day low vision for offshore installations.
3. Advection fog
Fog can form when relatively warm, humid air travels over cold water (or land). Advection fog, as it is often known, typically covers a broader region than radiation fog.
It occurs most frequently when the water is still relatively chilly in the spring and early summer. Advection fog will primarily be connected with wind directions between the south and west in northern Europe.
Large amounts of dry airborne particles, such as dust or smoke, can significantly limit visibility. Haze can originate from both natural and artificial causes.
5. Rain, drizzle, showers
Rain rarely causes the visibility to drop below a few kilometers (typically 4-8 km in moderate rainfall). This is because there will be fewer water droplets in the air than in a foggy environment, resulting in less light reflection.
However, drizzle, precipitation with smaller water droplets than rain, frequently comes with mist and reduces visibility to 1 to 5 kilometers.
The visibility may momentarily fall to less than 1000 meters in conjunction with solid showers or thunderstorms.
When it snows, visibility can quickly be decreased to less than 1000m because snow crystals reflect light more than raindrops.
How the OOW should handle low visibility
Again, as the officer of the watch, ensuring your ship and crew will be safe and sound is your number one priority.
Even before you hit low to zero visibility, you should be well-prepared and capable of ensuring safe navigation. Below are some ways to effectively handle low visibility:
- Know the ins and outs of the ship
An effective navigating officer must be familiar with every facet of their ship to avoid any accident. The officer should know the ships’ dimensions and qualities and how they will operate in various situations.
In addition, you must be aware of the stopping distance of the boat at any given RPM in cases with limited vision to control the ship in an emergency.
2. Notify the master
The master must be on the bridge during limited visibility.
Therefore, you must call the master or alert him or her of the navigation situation. Also, the officer needs to alert the engine room and request that the duty engineer staff the engine room in case it is in “unmanned” mode.
3. Appoint enough personnel
It is essential to have a sufficient number of people on the bridge to keep a close eye on the ship’s course.
More people must be hired to serve as “lookouts” around the ship. You must alert the engine room if there is traffic in the vicinity so that there are enough people that the engine is also prepared for a quick maneuver.
4. Keep the fog horn ready
Check that the fog horn is operational for the restricted area. Drain the line before opening the air to the horn if it is air-operated.
5. Decrease speed
Reduce the ship’s speed depending on the visibility. Bring the ship’s RPM to maneuvering if the visibility is poor.
6. Confirm that all important navigational lights and equipment are operable
When there is limited visibility, ensure all necessary navigational lights and equipment operate as intended.
In addition, make sure the navigation charts are correctly reviewed for routing and that a good radar watch is conducted.
7. Cease all other work
Even though it should go without saying, you should never multitask while driving in low visibility, especially if there are plenty of other people on the bridge.
Stop all other deck activities, and tell the crew to enter their respective cabins. In the event of an accident or grounding, this will protect workers on the open deck from harm.
8. Open or close bridge doors
For simple access to the bridge wing, keep the bridge door open and clear of any obstructions. Additionally, shut all bridge openings in dust or sandstorm.
9. Close ventilation
Shut ventilation fans and accommodation or engine room ports to prevent sand particles from entering the bridge, accommodations, and engine room when the ship travels in a sandstorm.
10. Follow all procedures
As stated in COLREG Regulation -19, follow all crucial procedures for restricted visibility.
Moreover, watch radio channel 16 and record all significant ship-related data, such as latitude and longitude, time, speed, etc., in the log book.
The officer of the watch must proceed with the utmost caution and care when navigating the ship through an area with limited sight.
As an officer of the watch, you are integral in ensuring safe voyages—and we’re looking for you!
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