Thursday, March 27, 2014

WEATHER - BEAUFORT SCALE



Beaufort Scale - INTERACTIVE

The Beaufort wind scale is a standard scale, running from force 0 for calm to force 12 hurricane and above for the description of wind speed. Each value represents a specific range and classification of wind speeds with accompanying descriptions of the effects on surface features. It was originally developed as a system for estimating wind strengths without the use of instruments.



It was introduced in 1806 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war frigate of the period, and it was later modified to include descriptions of effects on land features as well. It is currently still in use for this same purpose as well as to tie together various components of weather (wind strength, sea state, observable effects) into a unified picture.

The Beaufort Scale  (for use at sea)
FORCEDESCRIPTIONSEA STATESPEED
knotsm/s
0calmlike a mirror<10.0-0.2
1light airripples, no foam1-30.3-1.5
2light breezesmall wavelets, smooth crests with glassy appearance4-61.6-3.3
3gentle breezelarge wavelets, some crests break, some white horses7-103.4-5.4
4moderate breezesmall waves, frequent white horses11-165.5-7.9
5fresh breezemoderate rather long waves, many white horses, some spray17-218.0-10.7
6strong breezesome large waves, extensive white foam crests, some spray22-2710.8-13.8
7near galesea heaped up, streaks of foam blowing with the wind28-3313.9-17.1
8galefairly high and long waves, crests breaking into spindrift, blowing foam in prominent streaks34-4017.2-20.7
9strong galehigh waves, dense foam streaks in wind, wave-crests topple and roll over, spray reduces visibility41-4720.8-24.4
10stormvery high waves, overhanging crests, dense blowing foam, heavy tumbling sea appears white, visibility poor48-5524.5-28.4
11violent stormexceptionally high waves, hiding small ships, sea covered with foam, crests blown into froth, visibility poor56-6328.5-32.6
12hurricaneair filled with foam and spray, sea white, visibility extremely bad>6432.7