In The Fog

by Captain Denis J. Blaise,

Instructor, Sea School Northeast

This article by Capt. Blaise originally appeared in Offshore Magazine .

Fog is so common along the Northeast coast that we all learn to handle it or else we are forced to spend many days in harbor. This exercise covers all the Inland and International waters of the Atlantic seaboard.

There are several books on weather for the mariner with long treatises on the nature of fog. We are indebted to Bowditch’s American Practical Navigator, Vol II, for some of the explanations which we simplified and paraphrased from its Glossary.

1. When is fog "fog" or can you differentiate between haze, mist and fog?

a) A dry haze gives the atmosphere a bluish or yellowish appearance. It is made of very fine dust or salt particles which somewhat reduce visibility. A damp haze is made of tiny water droplets creating a veil thinner than fog.

b) Mist is also made up of very small water droplets which create a gray veil over the landscape or the sea. Relative humidity for mist is often less than 95% and it is an intermediary step between haze and fog.

c) Fog is a visible accumulation of the tiny droplets created by condensation which reduces visibility to less than 1/2 nautical mile (1km).

2. What is the name of the most common type of fog along the New England coast in summer?

Advection fog

3. How does this fog come about?

It is created by warm water moist air moving over cold water. As the air cools it can no longer hold as much moisture, and condensation creates the tiny water droplets we call fog.

4. Where does all that warm moist air come from in the summertime?

The summer prevailing wind is SW in New England. That wind picks up its moisture over the Gulf Stream and brings it over the cold coastal waters.

5. Why are the New England coastal waters so cold?

The Labrador current brings cold Arctic water around Newfoundland and Nova Scotia, southwest along Cape Cod, Long Island and all the way to Cape Hatteras.

6. What kind of weather system clears the fog off the New England coast?

A good high pressure with strong westerly or northwesterly winds will give you a nice clear blue sky.

7. In the fall, what may happen when cold NW wind blows over the coastal waters which have been warmed up by the summer sun?

You have fog again! The ocean looks like a hot cup of coffee with steam fog or sea smoke rising from its surface.

8. How would you define smog?

Pollution. Visible pollution in the air, with or without fog.

9. What sound producing devices must you have on board?

If your boat is over 40 feet you must have a whistle and a bell. Under 40 feet, boats are not required to have a whistle and bell but they need to be able to make an efficient sound which sounds like a whistle or a bell. Many states, however, have their own requirement list and, while you may be able to convince a Coastie that the sound from your Key West conch and from beating a pan with a spoon meet the Rules requirements, your local Watery Bear may not be so inclined! Be safe: carry a whistle and a bell regardless of the size of your boat.

10. What’s a fog horn?

A fog horn is found on aids to navigation, like buoys and lighthouses.

11. How long is a short blast on a whistle? and how long is a prolonged blast?

A short blast is a one second; a prolonged blast is four to six seconds.

12. What is the fog signal for a powerboat underway, making way (moving forward through the water, with or without propulsion)?

One prolonged blast every two minutes.

13. What is the fog signal of a powerboat underway, not making way (drifting, but not disabled)?

Two prolonged blasts every two minutes.

14. You hear another boat getting close to you. Can you blow your fog signals more often than every two minutes?

You bet you can... two minutes of silence is a long time when you can’t see who’s about to run you down.

15. Now you hear one prolonged and two short blasts on a whistle. What is it?

The only thing you know for sure is that you need to be very careful. It is a vessel with some sort of handicap like a broken engine, or unable to maneuver because of her work - like a dredge, or fishing nets, or trawling (NOT trolling however), or sailing, or trolling.

16. When you anchor in the fog what signal must you sound?

An anchored boat must sound a rapid ringing of the bell for five seconds every minute.

17. What is the proper fog signal if you are aground?

If aground, you sound three distinct raps on the bell before and after the ringing of the bell, three strokes means "I AM AGROUND".

18. Do you hear all these fog signals on the ocean, in the bay, the river, the harbor? Do you feel self-conscious about blowing your whistle in restricted visibility or ringing your bell when you anchor or run aground in the fog?

NO and YES you say. Well, you’re not alone, but your self-consciousness is misplaced... naahh! that’s a feel-good euphemism... let me say it plainly: YOU ARE WRONG. Are you self-conscious when you put your blinker on to tell other cars you are making a turn? Of course not, it’s required and it’s smart. Proper signals on the water are the same way: it’s the law and it’s safer.

If someone runs into you and you weren't’t sounding the proper fogsigs ( or maneuvering signals, of course), an admiralty lawyer will make minced meat out of you. In court, they’l call your 16- footer a vessel and they’l refer to you as the Master of the vessel... and they’l treat you as what you think of as "one of the big boys" a tug or tanker captain. And if you ignored the Rules of the Road, or claim you did not know them, you've got problems. So avoid expensive headaches: ALWAYS SOUND THE PROPER SIGNALS REGARDLESS OF THE SIZE OF YOUR BOAT. (OK, Enough. Down from my soapbox)

19. Fog is a common cause of restricted visibility. What else are you supposed to do in restricted visibility?

Yes, you must turn your running lights on.

20. Do you ever sound fog signals in an area of unrestricted visibility?

Indeed you do. If you are near an area of restricted visibility, such as a fog bank, the Rules require the proper fogsigs to be sounded.

21. How fast may you travel in the fog?

The Rules state that you proceed at a SAFE SPEED. So it is your judgment, but if you ever hit anybody, that was not a safe speed and those admiralty lawyers...

22. May you turn your engine off to listen for fog signals and buoys like gongs, bells and horns?

No you may not. Your engines must be ready for immediate maneuvering. Send someone to the bow to listen and act as your lookout (another requirement)

23. When you hear the fog signals of another vessel on your port or starboard quarter, what should you do?

You should hold course and speed, because that vessel is behind you.

24. What should you do upon hearing the fog signal of another vessel somewhere ahead of the beam of your boat?

You must slow down to bare steerage way: that is the speed at which you keep the boat on course; or you must take all way off if necessary, and you must navigate with extreme caution until the danger has passed.

25. You feel that you are going to be run down by a vessel you cannot see but whose fogsigs you hear. May you sound Danger/Doubt?

No, you may not sound Danger/Doubt in the fog - or restricted visibility.

26. What is the Danger/Doubt signal?

The Danger/Doubt signal consists of five or more short blasts on the whistle.

27. You finally see the boat coming towards you and about to run you down. Now may you sound Danger/Doubt?

Yes, when in sight (with your eyes, NOT on radar), you may sound Danger/Doubt.

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