Prince William Sound is infamous for sudden, blinding advection fog during the peak summer cruising months. As warm, moist air from the Gulf of Alaska moves over the glacial-fed, ice-cold waters of the Sound (which hover between 40°F and 46°F year-round), the air is chilled to its dewpoint, condensing instantly into “pea-soup” fog.
Navigating safely when visibility drops to zero requires disciplined radar utilization, strict compliance with international sound signal mandates (COLREGS), and highly active watchkeeping.
🌫️ Critical Fog Safety Protocols
When entering a fog bank, immediately execute these three critical procedures:
1. Reduce Speed Instantly
The most critical rule of fog navigation is to travel at a safe speed appropriate for the conditions. Under Navigation Rule 6, safe speed cannot be reduced to a fixed knot value or stopping-distance formula. The operator must determine the appropriate safe speed by considering all prevailing circumstances, including visibility, traffic density, vessel maneuverability, wind, sea state, current, proximity of navigational hazards, and the limitations of available navigation equipment (such as radar). High-speed transit in fog is a major cause of catastrophic hull collisions with floating ice growlers, reefs, or other vessels.
2. Assign a Dedicated Lookout
Do not rely solely on the flybridge or enclosed cabin.
- The Position: Navigation Rule 5 requires a proper lookout by sight, hearing, and all available means. Assign a dedicated lookout in a secure position that provides the best practical ability to see and hear while remaining protected from falls, spray, cold exposure, ice, and abrupt vessel motion. Do not place a lookout at the extreme bow if doing so exposes them to falling or going overboard in rough water or during maneuvering.
- The Duties: The lookout must keep watch and listen specifically for approaching foghorns, the roar of glacial calving waves, or the low rumble of breaking surf on unseen reefs. Provide them with a handheld VHF radio to report immediately to the helmsman.
- Acoustic Awareness: Turn off cabin stereos, silence non-essential chatter, and open side doors or hatches to maximize acoustic awareness.
3. Coordinate Navigation Tools & Sensors
Use radar, AIS, visual and auditory lookouts, charts, sound signals, and safe-speed judgment together. Radar is a powerful tool to detect targets in restricted visibility, but it must be used in conjunction with all other available means:
- Tuning and Gain: Adjust gain and clutter controls (sea clutter, rain clutter) to optimize target detection according to your radar manufacturer’s instructions. Note that tuning parameters are highly dependent on the sea state and manufacturer protocol.
- AIS Integration: Turn on your AIS transponder (if equipped) to broadcast your position and track commercial tankers, AMHS ferries, and large charters transiting the Valdez Narrows or Passage Canal.
- Running Lights: Ensure your port/starboard navigation lights and white all-around masthead/stern lights are illuminated.
🔊 COLREGS Fog Sound Signals
Under the International Regulations for Preventing Collisions at Sea (COLREGS), all vessels operating in restricted visibility must sound acoustic horns at precise intervals.
Sound Blast Definitions:
- Prolonged Blast: 4 to 6 seconds duration (represented below by
▬▬▬). - Short Blast: Approximately 1 second duration (represented below by
●).
🎛️ Standard Fog Sound Signals Reference
Under international and inland collision regulations (COLREGS Rule 35), vessels operating in restricted visibility must sound sound signals to indicate their state. Memorize these standard horn patterns:
| Vessel Status | Required Signal Pattern | Frequency Requirement | Operational Purpose |
|---|---|---|---|
| Power Underway & Making Way | 1 Prolonged Blast (▬▬▬, 4–6s) | At intervals of not more than 2 minutes | Alert surrounding vessels of active movement. |
| Power Underway but Stopped | 2 Prolonged Blasts (▬▬▬ ▬▬▬, 2s gap) | At intervals of not more than 2 minutes | Warn vessels that you are drifting and making no way. |
| Sailing or Restricted Maneuverability | 1 Prolonged + 2 Short Blasts (▬▬▬ ● ●) | At intervals of not more than 2 minutes | Includes sailboats, towing vessels, and commercial fishers. |
| Vessel Anchored (< 100m) | Rapid Bell Ringing (🔔, 5s duration) | At intervals of not more than 1 minute | Ring bell rapidly in the forepart of the vessel. |
[!WARNING] Safety Notice: Sound signal definitions and requirements vary depending on your specific vessel category and location. Operators must study the official COLREGS and Navigation Rules prior to navigation in fog.
🎛️ Radar Adjustments for Glacial Ice
Standard radar configurations will frequently miss growlers—waterlogged chunks of glacial ice that sit nearly flush with the surface. Follow this specific PWS tuning protocol:
- De-select Auto-Clutter: Auto-tuning algorithms are designed for oceanic swell, not glacial ice chunks. Turn off auto-clutter and adjust manual controls.
- Increase Rain & Sea Clutter Slightly: This will suppress close-in waves, but do not turn it up too high, or you will erase small targets like kayaks and 5-foot growlers.
- Pulse Width: If your radar allows, set it to Short Pulse (SP) when navigating in ice fields. This provides the highest target resolution at close ranges (under 1.5 NM).
- Compare Radar vs. Charts: If your radar shows an echo that is not on your digital chart, assume it is a massive growler or a small skiff and alter course instantly.