Reference

The Beaufort Scale
The Beaufort Scale, devised in 1805 by Sir Francis Beaufort (1774-1875), is a system for estimating wind strengths without the use of instruments, based on the effects wind has on the physical environment. The behavior of smoke, waves, trees, etc., is rated on a 13 point scale of 0 (calm) to 12 (hurricane).

FORCE	DESC	MPH	EFFECTS

0	Calm	0-1	Land- Smoke rises vertically Water- Like a mirror
1	Light Air	1-3	L- Rising smoke drifts W- Small ripples
2	Light Breeze	4-7	L- Leaves rustle W- Small wavelets, wind fills sail
3	Gentle Breeze	8-12	L- Light flags extend W- Large wavelets, sailboats heel
4	Moderate Breeze	13-18	L- Moves thin branches W- Working breeze, saiboats at hull speed
5	Fresh Breeze	19-24	L- Small trees sway W- Numerous whitecaps, time to shorten sails
6	Strong Breeze	25-31	L- Large tree branches move W- Whitecaps everywhere, sailboats head ashore, large waves
7	Moderate Gale	32-38	L- Large trees begin to sway W- Much bigger waves, some foam, sailboats at harbor
8	Fresh Gale	39-46	L- Small branches are broken from trees W- Foam in well marked streaks, larger waves, edges of crests break off
9	Strong Gale	47-54	L- Slight damage occurs to buildings W- High waves, dense spray, visibility affected
10	Whole Gale	55-63	L- Large trees uprooted, considerable building damage W- Very high waves, heavy sea roll, surface white with spray and foam, visibility impaired
11	Storm	64-74	L- Extensive widespread damage W- Exceptionally high waves, small to medium ships obscured, visibility poor
12	Hurricane	74+	L- Extreme destruction W- Waves 40+', air filled with foam and spray, visibility restricted

Marine Signal Flags

These flags are international signals used by ships at sea to spell out short messages, or more commonly,
used individually or in combination they have special meanings.

Flag

Letter

Meaning

a-flag

Alfa

Diver below (when stationary); Keep clear see note...

b-flag

Bravo

I am taking on, discharging, or carrying dangerous cargo

c-flag

Charlie

"Yes" or "affirmative"

d-flag

Delta

I am maneuvering with difficulty; keep clear

e-flag

Echo

I am altering my course to starboard

f-flag

Foxtrot

I am disabled, communicate with me

g-flag

Golf

I require a pilot

h-flag

Hotel

I have a pilot on board

i-flag

India

I am altering my course to port

j-flag

Juliet

I am on fire and have dangerous cargo; keep clear

k-flag

Kilo

I wish to communicate with you

l-flag

Lima

You should stop your vessel immediately

m-flag

Mike

My vessel is stopped (Not international but commonly used: Doctor on board)

n-flag

November

"No" or "negative"

o-flag

Oscar

Man overboard

p-flag

Papa

All personnel return to ship; about to sail - the Blue Peter

q-flag

Quebec

Ship meets health regs; request clearance into port

r-flag

Romeo

None (previous meaning: The way is off my ship. You may feel your way past me)

s-flag

Sierra

I am moving astern

t-flag

Tango

Keep clear (Not international but commonly used: Request for club launch)

u-flag

Uniform

You are standing into danger

v-flag

Victor

I require assistance (not distress)

w-flag

Whiskey

I require medical assistance

x-flag

Xray

Stop carrying out your intentions and watch for my signals

y-flag

Yankee

I am dragging anchor

z-flag

Zulu

I require a tug

n-flag
c-flag

N + C

There are many flag combinations with additional meanings. Here's one that we hope you won't have to use:

I am in distress

diver-flag

Diver
Down

The red flag with white diagonal stripe, while not international, is commonly used to indicate a diver in the water. Many states now require this flag. It is usually exhibited on a float to mark the diver's approximate location whereas the "A" flag should be used on the vessel.

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