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This page provides help wind the many ways of expressing Wind.
Subjects covered here:
Wind Speed Definitions
Marine Warnings
Beaufort Scale
Wind Speed Chart
Northeaster
Windspeed and Sea Height
Direction: In reference to true North, to eight points
of the compass. Winds are described by the direction they come from.
Speed: Generally in
miles per hour (mph), kilometers per hour (kmph), except Marine products which
are in knots.
Gusty: Rapid fluctuations of speed of 10 mph.
|
1 kmph |
= |
.62 mph |
= |
.54 knot |
|
|
light |
- |
<10 mph |
|
1 mph |
= |
.87 knot |
= |
1.62 kmph |
|
|
breezy |
- |
5 to25 mph |
|
1 knot |
= |
1.15 mph |
= |
1.86 km |
|
|
windy |
- |
20 to 30 mph |
|
1 mile |
= |
5280 ft |
|
|
|
|
very windy |
- |
40 to 60 mph |
|
1 nautical mile |
= |
6076 ft |
|
|
|
|
high winds |
- |
40 to 60 mph |
|
|
|
|
|
|
|
damaging winds |
- |
60 mph |
Marine Warnings:
 |
Small Craft Advisory: Forecast winds of 18 to 33 knots;
also issued for hazardous sea conditions. |
|
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Gale Warning: Forecast winds of 34 to 47 knots. |
|
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Storm Warning: Forecast winds of 48 knots or greater. |
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Tropical Storm Warning: Forecast winds of 34 to 63
knots associated with a tropical storm. |
|
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Hurricane Warning: Forecast winds of 64 knots or
greater associated with a hurricane |
Beaufort Scale:
Wind Speed Chart:
|
Force |
Knots |
Description |
|
Km |
Mile/Hour |
Knots |
|
0 |
0-1 |
Mirror
Calm |
|
10 |
6 |
5 |
|
1 |
1-3 |
Gentle
Ripples |
|
15 |
9 |
8 |
|
2 |
4-6 |
Small
Wavelets |
|
20 |
12 |
11 |
|
3 |
7-10 |
Large
Wavelets |
|
25 |
15 |
14 |
|
4 |
11-16 |
Small
Waves |
|
30 |
19 |
16 |
|
5 |
17-21 |
White
Caps |
|
35 |
22 |
19 |
|
6 |
22-27 |
Large
Waves/Spray |
|
40 |
25 |
22 |
|
7 |
28-33 |
Streaking Foam |
|
45 |
28 |
24 |
|
8 |
34-40 |
Gale/Spindrift |
|
50 |
31 |
27 |
|
9 |
41-47 |
Severe
Gale |
|
55 |
34 |
30 |
|
10 |
48-55 |
Storm/White Seas |
|
60 |
37 |
33 |
|
11 |
56-63 |
Violent
Storm |
|
65 |
40 |
35 |
|
12 |
64+ |
Hurricane |
|
70 |
43 |
38 |
|
|
|
|
80 |
50 |
43 |
|
|
|
|
90 |
56 |
49 |
|
|
|
|
100 |
62 |
54 |
Note: Speeds have been rounded off to
nearest full number
Northeaster: Here's my
layman's try at a Northeaster definition. A Northeaster is counter-clock wise
turning cyclone (a storm system circulating around a center) as opposed to a
hurricane which turns right in the northern hemisphere. Northeasters are spawned
by a very curvy Jet Stream that dips very low and then follows the eastern coast
north and finally turning east over and north of Canada. They typically form
near the Bahamas or north of Cuba, along the Appalachians or off Cape Hatteras.
The Jet Stream then drags them northeast ward. Some time a High further north
blocks its path and so it churns over the ocean for a long time sending
beach-eating waves onshore.
WIND SPEED/SEA
HEIGHT RELATIONSHIPS
|
Wind Speed |
Sea Conditions |
|
0-3 KTS |
SEA LIKE MIRROR |
|
4-6 KTS |
RIPPLES, LESS THAN 1 FT |
|
7-10 KTS |
SMOOTH WAVELETS, 1-2 FT |
|
11-16 KTS |
SMALL WAVES, 2-4 FT |
|
17-21 KTS |
MODERATE WAVES, MANY WHITECAPS, 4-8 FT |
|
22-27 KTS |
LARGE WAVES,SPRAY, 8-13 FT |
|
28-33 KTS |
HEAPED SEAS, FOAM FROM BREAKING WAVES, 13-20 FT |
|
34-40 KTS |
HIGH WAVES, FOAM BLOWN IN WELL MARKED STREAKS, 13-20 FT |
|
41-47 KTS |
SEAS ROLL, SPRAY MAY REDUCE VISIBILITY, 13-20 FT |
|
48-55 KTS |
VERY HIGH WAVES, WHITE SEAS, OVERHANGING CRESTS 20-30 FT |
|
56-63 KTS |
EXCEPTIONALLY HIGH WAVES, 30-45 FT |
|
OVER 63 KTS |
AIR FILLED WITH FOAM, SEA COMPLETELY WHITE, OVER 45 FT |
THIS CHART IS BASED ON CRITERIA USED BY THE WORLD
METEOROLOGICAL ORGANIZATION. MARINERS SHOULD REALIZE THAT THESE VALUES ARE
REACHED AFTER WINDS HAVE BLOWN STEADILY OVER A LARGE AREA FOR AN EXTENDED PERIOD
OF TIME. ALSO, THE VALUES GIVEN ARE AVERAGE OBSERVED WAVE HEIGHTS, NOT THE
HIGHEST THAT MAY BE SEEN FOR A GIVEN WIND SPEED.
  
Revised: 07/09/2002
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