<P> Today, hurricane - force winds are sometimes described as Beaufort scale 12 through 16, very roughly related to the respective category speeds of the Saffir--Simpson hurricane scale, by which actual hurricanes are measured, where Category 1 is equivalent to Beaufort 12 . However, the extended Beaufort numbers above 13 do not match the Saffir--Simpson scale . Category 1 tornadoes on the Fujita and TORRO scales also begin roughly at the end of level 12 of the Beaufort scale, but are independent scales--although the TORRO scale wind values are based on the 3 / 2 power law relating wind velocity to Beaufort force . </P> <P> Wave heights in the scale are for conditions in the open ocean, not along the shore . </P> <Table> <Tr> <Th> Beaufort number </Th> <Th> Description </Th> <Th> Wind speed </Th> <Th> Wave height </Th> <Th> Sea conditions </Th> <Th> Land conditions </Th> <Th> Sea state photo </Th> <Th> Associated warning flag </Th> </Tr> <Tr> <Th> 0 </Th> <Td> Calm </Td> <Td> <1 km / h </Td> <Td> 0 m </Td> <Td> Sea like a mirror </Td> <Td> Smoke rises vertically . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> <1 mph </Td> </Tr> <Tr> <Td> <1 knot </Td> <Td> 0 ft </Td> </Tr> <Tr> <Td> <0.3 m / s </Td> </Tr> <Tr> <Th> </Th> <Td> Light air </Td> <Td> 1--5 km / h </Td> <Td> 0--0.2 m </Td> <Td> Ripples with appearance of scales are formed, without foam crests </Td> <Td> Direction shown by smoke drift but not by wind vanes . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 1--3 mph </Td> </Tr> <Tr> <Td> 1--3 knots </Td> <Td> 0--1 ft </Td> </Tr> <Tr> <Td> 0.3--1.5 m / s </Td> </Tr> <Tr> <Th> </Th> <Td> Light breeze </Td> <Td> 6--11 km / h </Td> <Td> 0.2--0.5 m </Td> <Td> Small wavelets still short but more pronounced; crests have a glassy appearance but do not break </Td> <Td> Wind felt on face; leaves rustle; wind vane moved by wind . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 4--7 mph </Td> </Tr> <Tr> <Td> 4--6 knots </Td> <Td> 1--2 ft </Td> </Tr> <Tr> <Td> 1.6--3.3 m / s </Td> </Tr> <Tr> <Th> </Th> <Td> Gentle breeze </Td> <Td> 12--19 km / h </Td> <Td> 0.5--1 m </Td> <Td> Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses </Td> <Td> Leaves and small twigs in constant motion; light flags extended . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 8--12 mph </Td> </Tr> <Tr> <Td> 7--10 knots </Td> <Td> 2--3.5 ft </Td> </Tr> <Tr> <Td> 3.4--5.5 m / s </Td> </Tr> <Tr> <Th> </Th> <Td> Moderate breeze </Td> <Td> 20--28 km / h </Td> <Td> 1--2 m </Td> <Td> Small waves becoming longer; fairly frequent white horses </Td> <Td> Raises dust and loose paper; small branches moved . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 13--18 mph </Td> </Tr> <Tr> <Td> 11--16 knots </Td> <Td> 3.5--6 ft </Td> </Tr> <Tr> <Td> 5.5--7.9 m / s </Td> </Tr> <Tr> <Th> 5 </Th> <Td> Fresh breeze </Td> <Td> 29--38 km / h </Td> <Td> 2--3 m </Td> <Td> Moderate waves taking a more pronounced long form; many white horses are formed; chance of some spray </Td> <Td> Small trees in leaf begin to sway; crested wavelets form on inland waters . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 19--24 mph </Td> </Tr> <Tr> <Td> 17--21 knots </Td> <Td> 6--9 ft </Td> </Tr> <Tr> <Td> 8--10.7 m / s </Td> </Tr> <Tr> <Th> 6 </Th> <Td> Strong breeze </Td> <Td> 39--49 km / h </Td> <Td> 3--4 m </Td> <Td> Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray </Td> <Td> Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 25--31 mph </Td> </Tr> <Tr> <Td> 22--27 knots </Td> <Td> 9--13 ft </Td> </Tr> <Tr> <Td> 10.8--13.8 m / s </Td> </Tr> <Tr> <Th> 7 </Th> <Td> High wind, moderate gale, near gale </Td> <Td> 50--61 km / h </Td> <Td> 4--5.5 m </Td> <Td> Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind; spindrift begins to be seen </Td> <Td> Whole trees in motion; inconvenience felt when walking against the wind . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 32--38 mph </Td> </Tr> <Tr> <Td> 28--33 knots </Td> <Td> 13--19 ft </Td> </Tr> <Tr> <Td> 13.9--17.1 m / s </Td> </Tr> <Tr> <Th> 8 </Th> <Td> Gale, fresh gale </Td> <Td> 62--74 km / h </Td> <Td> 5.5--7.5 m </Td> <Td> Moderately high waves of greater length; edges of crests break into spindrift; foam is blown in well - marked streaks along the direction of the wind </Td> <Td> Twigs break off trees; generally impedes progress . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 39--46 mph </Td> </Tr> <Tr> <Td> 34--40 knots </Td> <Td> 18--25 ft </Td> </Tr> <Tr> <Td> 17.2--20.7 m / s </Td> </Tr> <Tr> <Th> 9 </Th> <Td> Strong / severe gale </Td> <Td> 75--88 km / h </Td> <Td> 7--10 m </Td> <Td> High waves; dense streaks of foam along the direction of the wind; sea begins to roll; spray affects visibility </Td> <Td> Slight structural damage (chimney pots and slates removed). </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 47--54 mph </Td> </Tr> <Tr> <Td> 41--47 knots </Td> <Td> 23--32 ft </Td> </Tr> <Tr> <Td> 20.8--24.4 m / s </Td> </Tr> <Tr> <Th> 10 </Th> <Td> Storm, whole gale </Td> <Td> 89--102 km / h </Td> <Td> 9--12.5 m </Td> <Td> Very high waves with long overhanging crests; resulting foam in great patches is blown in dense white streaks along the direction of the wind; on the whole the surface of the sea takes on a white appearance; rolling of the sea becomes heavy; visibility affected </Td> <Td> Seldom experienced inland; trees uprooted; considerable structural damage . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 55--63 mph </Td> </Tr> <Tr> <Td> 48--55 knots </Td> <Td> 29--41 ft </Td> </Tr> <Tr> <Td> 24.5--28.4 m / s </Td> </Tr> <Tr> <Th> 11 </Th> <Td> Violent storm </Td> <Td> 103--117 km / h </Td> <Td> 11.5--16 m </Td> <Td> Exceptionally high waves; small - and medium - sized ships might be for a long time lost to view behind the waves; sea is covered with long white patches of foam; everywhere the edges of the wave crests are blown into foam; visibility affected </Td> <Td> Very rarely experienced; accompanied by widespread damage . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 64--72 mph </Td> </Tr> <Tr> <Td> 56--63 knots </Td> <Td> 37--52 ft </Td> </Tr> <Tr> <Td> 28.5--32.6 m / s </Td> </Tr> <Tr> <Th> 12 </Th> <Td> Hurricane force </Td> <Td> ≥ 118 km / h </Td> <Td> ≥ 14 m </Td> <Td> The air is filled with foam and spray; sea is completely white with driving spray; visibility very seriously affected </Td> <Td> Devastation . </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> ≥ 73 mph </Td> </Tr> <Tr> <Td> ≥ 64 knots </Td> <Td> ≥ 46 ft </Td> </Tr> <Tr> <Td> ≥ 32.7 m / s </Td> </Tr> <Tr> <Th_colspan="8"> References: Met Office, Royal Meteorological Society, Encyclopædia Britannica </Th> </Tr> </Table> <Tr> <Th> Beaufort number </Th> <Th> Description </Th> <Th> Wind speed </Th> <Th> Wave height </Th> <Th> Sea conditions </Th> <Th> Land conditions </Th> <Th> Sea state photo </Th> <Th> Associated warning flag </Th> </Tr>

Description given to zero on the beaufort scale