Wind force determination scale for children. Storms, squalls, hurricanes, their characteristics, damaging factors

11.03.2020 | Technique

Meteorological hazards are natural processes and phenomena that arise in the atmosphere under the influence of various natural factors or their combinations, which have or may have a damaging effect on people, farm animals and plants, economic objects and the environment.

Wind - This is the movement of air parallel to the earth's surface, resulting from the uneven distribution of heat and atmospheric pressure and directed from a high pressure zone to a low pressure zone.

Wind is characterized by:
1. Wind direction - determined by the azimuth of the side of the horizon from where
it blows, and is measured in degrees.
2. Wind speed - measured in meters per second (m/s; km/h; miles/hour)
(1 mile = 1609 km; 1 nautical mile = 1853 km).
3. Wind force - measured by the pressure it exerts on 1 m2 of surface. The strength of the wind varies almost proportionally to the speed,
therefore, wind force is often measured not by pressure, but by speed, which simplifies the perception and understanding of these quantities.

Many words are used to denote the movement of wind: tornado, storm, hurricane, gale, typhoon, cyclone and many local names. To systematize them, people all over the world use Beaufort scale, which allows you to very accurately estimate the strength of the wind in points (from 0 to 12) by its effect on ground objects or on waves at sea. This scale is also convenient because it allows you to quite accurately determine the wind speed without instruments based on the characteristics described in it.

Beaufort scale (Table 1)

Points Beaufort	Verbal definition wind forces	Wind speed, m/s (km/h)	Wind action on land
Points Beaufort	Verbal definition wind forces	Wind speed, m/s (km/h)	On the land	On the sea
		0,0 – 0,2 (0,00-0,72)	Calm. Smoke rises vertically	Mirror smooth sea
	Quiet breeze	0,3 –1,5 (1,08-5,40)	The direction of the wind is noticeable by the direction of the smoke,	Ripples, no foam on the ridges
	Light breeze	1,6 – 3,3 5,76-11,88)	The movement of the wind is felt by the face, the leaves rustle, the weather vane moves	Short waves, crests do not capsize and appear glassy
	Light breeze	3,4 – 5,4 (12,24-19,44)	Leaves and thin branches of trees sway, the wind flutters the upper flags	Short, well-defined waves. The ridges, overturning, form foam, and occasionally small white lambs are formed.
	Moderate breeze	5,5 –7,9 (19,8-28,44)	The wind raises dust and pieces of paper and moves thin tree branches.	The waves are elongated, white caps are visible in many places.
	Fresh breeze	8,0 –10,7 (28,80-38,52)	Thin tree trunks sway, waves with crests appear on the water	The waves are well developed in length, but not very large; whitecaps are visible everywhere.
	Strong breeze	10,8 – 13,8 (38,88-49,68)	Thick tree branches sway, wires hum	Large waves begin to form. White foamy ridges occupy large areas.
	strong wind	13,9 – 17,1 (50,04-61,56)	The tree trunks are swaying, it’s difficult to walk against the wind	The waves pile up, the crests break off, the foam lies in stripes in the wind
	Very strong wind storm)	17,2 – 20,7 (61,92-74,52)	The wind breaks tree branches, it is very difficult to walk against the wind	Moderately high, long waves. Spray begins to fly up along the edges of the ridges. Stripes of foam lie in rows downwind.
	Storm (strong storm)	20,8 –24,4 (74,88-87,84)	Minor damage; the wind tears off smoke hoods and tiles	High waves. The foam falls in wide dense stripes in the wind. The crests of the waves capsize and crumble into spray.
	Heavy storm (full storm)	24,5 –28,4 (88,2-102,2)	Significant destruction of buildings, trees are uprooted. Rarely happens on land	Very high waves with long curls down with ridges. The foam is blown up by the wind in large flakes in the form of thick stripes. The surface of the sea is white with foam. The crash of the waves is like blows. Visibility is poor.
	Fierce Storm (hard storm)	28,5 – 32,6 (102,6-117,3)	Large destruction over a large area. Very rarely observed on land	Exceptionally high waves. Vessels are hidden from view at times. The sea is all covered with long flakes of foam. The edges of the waves are blown into foam everywhere. Visibility is poor.
		32.7 or more (117.7 or more)	Heavy objects are carried by wind over considerable distances	The air is filled with foam and spray. The sea is all covered with stripes of foam. Very poor visibility.

Breeze (light to strong breeze) sailors call winds that have a speed of 4 to 31 mph. In terms of kilometers (coefficient 1.6) it will be 6.4-50 km/h

Wind speed and direction determine weather and climate.

Strong winds, significant changes in atmospheric pressure and a large number of precipitation causes dangerous atmospheric eddies (cyclones, storms, squalls, hurricanes) that can cause destruction and loss of life.

Cyclone is the general name for vortices with low pressure in the center.

An anticyclone is an area high blood pressure in an atmosphere with a maximum in the center. In the Northern Hemisphere, the winds in an anticyclone blow counterclockwise, and in the Southern Hemisphere they blow clockwise; in a cyclone the wind movement is reversed.

Hurricane - wind of destructive force and significant duration, the speed of which is equal to or exceeds 32.7 m/s (12 points on the Beaufort scale), which is equivalent to 117 km/h (Table 1).
In half of the cases, the wind speed during a hurricane exceeds 35 m/sec, reaching 40-60 m/sec, and sometimes up to 100 m/sec.

Hurricanes are classified into three types based on wind speed:
- Hurricane (32 m/s or more),
- strong hurricane (39.2 m/s or more)
- violent hurricane (48.6 m/s or more).

The reason for such hurricane winds is the emergence, as a rule, on the line of collision of fronts of warm and cold air masses, powerful cyclones with a sharp pressure drop from the periphery to the center and with the creation of a vortex air flow moving in the lower layers (3-5 km) in a spiral to the middle and upwards, in the northern hemisphere - counterclockwise.

Such cyclones, depending on the place of their origin and structure, are usually divided into:
- tropical cyclones found over warm tropical oceans, during the formation stage they usually move to the west, and after formation ends they bend towards the poles.
A tropical cyclone that has reached unusual strength is called hurricane, if he is born in Atlantic Ocean and the adjacent seas; typhoon - V Pacific Ocean or its seas; cyclone – in the Indian Ocean region.
mid-latitude cyclones can form both over land and over water. They usually move from west to east. A characteristic feature of such cyclones is their great “dryness”. The amount of precipitation during their passage is significantly less than in the zone of tropical cyclones.
The European continent is affected by both tropical hurricanes originating in the central Atlantic and cyclones of temperate latitudes.
Storm – a type of hurricane, but has a lower wind speed of 15-31
m/sec.

The duration of storms is from several hours to several days, the width is from tens to several hundred kilometers.
Storms are divided:

2. Stream storms – These are local phenomena of small distribution. They are weaker than vortex storms. They are divided:
- stock – the air flow moves down the slope from top to bottom.
- Jet – characterized by the fact that the air flow moves horizontally or up a slope.
Stream storms most often occur between chains of mountains connecting valleys.
Depending on the color of the particles involved in the movement, black, red, yellow-red and white storms are distinguished.
Depending on the wind speed, storms are classified:
- storm 20 m/sec or more
- strong storm 26 m/sec or more
- severe storm of 30.5 m/sec or more.

Squall – a sharp short-term increase in wind up to 20–30 m/s and higher, accompanied by a change in its direction associated with convective processes. Despite the short duration of squalls, they can lead to catastrophic consequences. Squalls are most often associated with cumulonimbus (thunderstorm) clouds of either local convection or a cold front. A squall is usually associated with showers and thunderstorms, sometimes with hail. Atmospheric pressure during a squall rises sharply due to rapid precipitation, and then falls again.

If it is possible to limit the impact zone, all of the listed natural disasters are classified as non-localized.

Dangerous consequences of hurricanes and storms.

Hurricanes are one of the most powerful forces elements and in their harmful effects are not inferior to such terrible natural disasters as earthquakes. This is explained by the fact that hurricanes carry enormous energy. The amount of it released by an average-power hurricane for 1 hour is equal to the energy of a nuclear explosion of 36 Mt. In one day, an amount of energy is released that would be enough to supply a country like the United States with electricity for six months. And in two weeks (the average duration of a hurricane’s existence), such a hurricane releases energy equal to the energy of the Bratsk hydroelectric power station, which it can produce in 26 thousand years. The pressure in the hurricane zone is also very high. It reaches several hundred kilograms per square meter a fixed surface located perpendicular to the direction of wind movement.

Hurricane wind destroys strong and demolishes light buildings, devastates sown fields, breaks wires and knocks down power and communication line poles, damages highways and bridges, breaks and uproots trees, damages and sinks ships, causes accidents in utility and energy networks, in production. There are known cases when hurricane winds destroyed dams and dams, which led to large floods, threw trains off the rails, tore bridges from their supports, knocked down factory chimneys, and washed ships ashore. Hurricanes are often accompanied by heavy downpours, which are more dangerous than the hurricane itself, as they cause mudflows and landslides.

Hurricane sizes vary. Usually, the width of the catastrophic destruction zone is taken as the width of a hurricane. Often this zone is supplemented with an area of storm force winds with relatively little damage. Then the width of the hurricane is measured in hundreds of kilometers, sometimes reaching 1000 km. For typhoons, the destruction strip is usually 15-45 km. The average duration of a hurricane is 9-12 days. Hurricanes occur at any time of the year, but are most common from July to October. In the remaining 8 months they are rare, their paths are short.

The damage caused by a hurricane is determined by a whole complex various factors, including the terrain, the degree of development and strength of buildings, the nature of vegetation, the presence of population and animals in the area of its action, the time of year spent preventive measures and a number of other circumstances, the main one of which is the speed pressure of the air flow q, proportional to the product of the density of atmospheric air by the square of the air flow speed q = 0.5pv 2.

According to building codes and regulations, the maximum standard value of wind pressure is q = 0.85 kPa, which, with an air density of r = 1.22 kg/m3, corresponds to wind speed.

For comparison, we can cite the calculated values of the velocity head used to design nuclear power plants for the Caribbean region: for category I structures - 3.44 kPa, II and III - 1.75 kPa, and for open-air installations - 1.15 kPa.

Every year, about a hundred powerful hurricanes sweep across the globe, causing destruction and often carrying away human lives(Table 2). On June 23, 1997, a hurricane swept over most of the Brest and Minsk regions, as a result of which 4 people were killed and 50 were injured. In the Brest region there were 229 blackouts settlements, 1071 substations were disabled, roofs were torn off from 10-80% of residential buildings in more than 100 settlements, and up to 60% of agricultural buildings were destroyed. In the Minsk region, 1,410 settlements were cut off and hundreds of houses were damaged. Trees in forests and forest parks were broken and uprooted. At the end of December 1999, Belarus also suffered from hurricane winds that swept across Europe. Power lines were broken, and many settlements were without power. In total, 70 districts and more than 1,500 settlements were affected by the hurricane. In the Grodno region alone, 325 transformer substations were out of order, in the Mogilev region even more - 665.

table 2
Effects of some hurricanes

Location of the disaster, year	Death toll	Number of wounded	Associated phenomena
Haiti, 1963		Not recorded

		Not recorded
Honduras, 1974		Not recorded
Australia, 1974


Sri Lanka, 1978		Not recorded
Dominican Republic, 1979
		Not recorded
Indochina, 1981		Not recorded	Flood
Bangladesh, 1985		Not recorded	Flood

Tornado (tornado)- a vortex movement of air, spreading in the form of a giant black column with a diameter of up to hundreds of meters, inside of which there is a rarefaction of air, into which various objects are drawn.

Tornadoes occur both over the water surface and over land, much more often than hurricanes. Very often they are accompanied by thunderstorms, hail and downpours. The speed of air rotation in the dust column reaches 50-300 m/sec or more. During its existence, it can travel up to 600 km - along a strip of terrain several hundred meters wide, and sometimes up to several kilometers, where destruction occurs. The air in the column rises in a spiral and draws in dust, water, objects, and people.
Hazardous factors: buildings caught in a tornado due to vacuum in the air column are destroyed by air pressure from the inside. It uproots trees, overturns cars, trains, lifts houses into the air, etc.

Tornadoes occurred in the Republic of Belarus in 1859, 1927 and 1956.

Beaufort scale - a conventional scale that allows you to visually assess the approximate strength of the wind by its effect on ground objects or by waves at sea. Developed by the English admiral and hydrographer Francis Beaufort. Francis Beaufort) in 1806.

Since 1874, it has been officially adopted for use in international synoptic practice. Since 1926, the Beaufort scale has been supplemented by the wind force in meters per second at a height of 10 meters from the surface. In the USA, in addition to the international 12-point scale, since 1955 a scale expanded to 17 points has been used, used for more accurate gradation of hurricane winds.

Wind strength and average speed				Verbal definition	Manifestation on land	Manifestation at sea	Approximate wave height, m	Visual manifestation
Beaufort points	meters per second	kilometers per hour	nodes	Verbal definition	Manifestation on land	Manifestation at sea	Approximate wave height, m	Visual manifestation
0	0-0,2	0,0-0,7	0-1	Calm	The smoke rises vertically or almost vertically, the leaves of the trees are motionless.	Mirror-smooth water surface.	0
1	0,3-1,5	1,1-5,4	1-3	Quiet wind	The smoke deviates from the vertical direction, the weather vane does not rotate or turn	Light ripples in the sea, no foam on the crests of the waves.	0,1
2	1,6-3,3	5,8-11,9	4-6	Light breeze	The movement of the wind is felt by the face, the leaves rustle, the movement of the weather vane is observed	Short waves with a glassy crest, do not capsize when moving.	0,3
3	3,4-5,4	12,2-19,4	7-10	Light wind	Flags and leaves sway.	Short waves with clearly defined boundaries, wave crests form foam when overturning, and whitecaps appear on some waves.	0,6
4	5,5-7,9	19,8-28,4	11-16	Moderate wind	The wind raises dust and light debris. Leaves and thin branches are constantly in motion.	The waves are elongated, light lambs appear everywhere	1,5
5	8,0-10,7	28,8-38,5	17-21	Fresh breeze	Branches and thin tree trunks sway, bushes sway. The wind can be felt by hand.	Not very large waves, whitecaps are visible everywhere.	2,0
6	10,8-13,8	38,9-49,7	22-27	Strong wind	Thin branches bend, thick tree branches sway, the wind hums in the wires.	Waves are visible across the entire surface, with splashes falling from their foamy crests. Sailing in light boats is not safe.	3,0
7	13,9-17,1	50,1-61,6	28-33	strong wind	The trunks and thick branches of the trees sway. It is difficult to go against the wind.	The waves pile up, the crests break off, and are covered with foam. Sailing on light motor boats is not possible.	4,5
8	17,2-20,7	61,9-74,5	34-40	Very strong wind	The wind breaks dry tree branches, it is very difficult to walk against the wind, it is impossible to talk without screaming.	High long waves with splashes. Rows of foam lie in the direction of the wind.	5,5
9	20,8-24,4	74,9-87,8	41-47	Storm	They bend and break big trees, light roofing is torn off roofs.	High waves with rows of foam. Spray makes visibility difficult.	7,0
10	24,5-28,4	88,2-102,2	48-55	Heavy storm	Trees are uprooted and individual buildings are destroyed. It's impossible to go.	Very high waves with downward curved crests. The surface of the water is covered with foam, small ships disappear from view behind the waves.	9,0
11	28,5-32,6	102,6-117,4	56-63	Fierce Storm	Catastrophic destruction of light buildings, uprooting of trees.	High waves covered with flakes of white foam. Medium ships disappear from view.	11,5
12	>32,6	>117,4	>63	Hurricane	Destruction of stone buildings, complete destruction of vegetation.	Loss of visibility due to splashes, the surface of the water is covered with foam. Destruction of light ships.	12,0

Each a natural phenomenon, having different degrees severity is usually assessed in accordance with certain criteria. Especially if information about it must be transmitted quickly and accurately. For wind strength, the Beaufort scale has become a common international reference point.

Developed by the British rear admiral, a native of Ireland, Francis Beaufort (accent on the second syllable) in 1806, the system, improved in 1926 by adding information about the equivalence of wind strength in points to its specific speed, allows you to fully and accurately characterize this atmospheric process, while remaining relevant and to this day.

What is wind?

Wind is the movement of air masses parallel to the surface of the planet (horizontally above it). This mechanism is caused by pressure differences. The direction of movement always comes from a higher area.

The following characteristics are commonly used to describe wind:

speed (measured in meters per second, kilometers per hour, knots and points);
wind force (in points and m.s. - meters per second, the ratio is approximately 1:2);
direction (according to the cardinal points).

The first two parameters are closely related. They can be mutually designated by each other's units of measurement.

The direction of the wind is determined by the side of the world from which the movement began (from the north - north wind, etc.). The speed is determined by the pressure gradient.

Pressure gradient (otherwise known as barometric gradient) is the change in atmospheric pressure per unit distance normal to a surface of equal pressure (isobaric surface) in the direction of decreasing pressure. In meteorology, they usually use the horizontal barometric gradient, that is, its horizontal component (Great Soviet Encyclopedia).

Wind speed and strength cannot be separated. A large difference in indicators between atmospheric pressure zones gives rise to strong and rapid movement of air masses above the earth's surface.

Features of wind measurement

In order to correctly correlate weather service data with your actual position or make a correct measurement, you need to know what standard conditions professionals use.

Wind force and speed are measured at a ten-meter height on an open, flat surface.
The name of the direction of the wind is given by the cardinal direction from which it blows.

Water transport managers, as well as those who like to spend time in nature, often purchase anemometers that determine speed, which is easily correlated with wind force in points. There are waterproof models. For convenience, devices of various compactness are produced.

In the Beaufort system, a description of wave heights associated with a certain wind force in points is given for open sea space. It will be significantly less in shallow waters and coastal areas.

From personal to global use

Sir Francis Beaufort not only had a high military rank in the navy, but was also a successful practical scientist who held important positions, a hydrographer and cartographer who brought great benefit to the country and the world. One of the seas in the Arctic Ocean, washing Canada and Alaska, bears his name. An Antarctic island is named after Beaufort.

Francis Beaufort created a convenient system for estimating wind force in points, available for fairly accurately determining the severity of the phenomenon “by eye,” for his own use in 1805. The scale ranged from 0 to 12 points.

In 1838, a system of visual assessment of weather and wind force in points became officially used by the British fleet. In 1874 it was adopted by the international synoptic community.

In the 20th century, several more improvements were made to the Beaufort scale - the ratio of points and verbal description of the manifestation of the elements with wind speed (1926), and five more divisions were added - points for grading the strength of hurricanes (USA, 1955).

Criteria for estimating wind force in Beaufort points

IN modern form The Beaufort scale has several characteristics that make it possible to most accurately correlate a specific atmospheric phenomenon with its indicators in points.

Firstly, this is verbal information. Verbal description of the weather.
Average speed in meters per second, kilometers per hour and knots.
The impact of moving air masses on characteristic objects on land and sea is determined by typical manifestations.

Harmless wind

Safe wind is determined in the range from 0 to 4 points.

Name	Wind speed (m/s)	Wind speed (km/h)	Description	Characteristic
Calm, complete calm (Calm)		less than 1 km/h	The movement of smoke is vertically upward, the leaves of the trees do not move	The surface of the sea is motionless, smooth
Quiet Wind (Light Air)			The smoke has a slight angle of inclination, the weather vane is motionless	Light ripples without foam. Waves no higher than 10 centimeters
Light Breeze			You can feel the wind blowing on your face, there is movement and rustling of leaves, slight movement of the weather vane	Short, low waves (up to 30 centimeters) with a glass-like comb
Weak (Gentle Breeze)			Continuous movement of foliage and thin branches on the trees, swaying flags	The waves remain short but are more noticeable. The ridges begin to tip over and turn into foam. Rare small “lambs” appear. The height of the waves reaches 90 centimeters, but on average does not exceed 60
Moderate Breeze			Dust and small debris begin to rise from the ground	The waves become longer and rise up to one and a half meters. "Lambs" appear often

A wind of 5 points, characterized as “fresh”, or fresh breeze, can be called borderline. Its speed ranges from 8 to 10.7 meters per second (29-38 km/h, or 17 to 21 knots). Thin trees sway along with their trunks. Waves rise up to 2.5 (on average two) meters. Sometimes splashes appear.

The wind that brings trouble

With a wind force of 6, strong phenomena begin that can cause damage to health and property.

Points	Name	Wind speed (m/s)	Wind speed (km/h)	Wind speed (sea speed)	Description	Characteristic
	Strong Breeze				Thick tree branches sway strongly, the hum of telegraph wires can be heard	Large waves form, foam crests acquire significant volume, and splashes are likely. The average wave height is about three meters, the maximum reaches four
	Strong (Moderate gale)				The trees are completely swaying	Active movement of waves up to 5.5 meters high, overlapping each other, scattering of foam along the line of wind movement
	Very strong (Gale)				Tree branches break due to the pressure of the wind, making it difficult to walk against the direction of the wind	Waves of considerable length and height: average - about 5.5 meters, maximum - 7.5 m. Moderately high long waves. Sprays fly up. The foam falls in stripes, the vector coincides with the direction of the wind
	Storm (Strong gale)				The wind damages buildings and begins to destroy roof tiles	Waves up to ten meters with an average height of up to seven. The foam stripes become wider. Overturning ridges scatter in spray. Visibility is reduced

Dangerous wind force

Winds with a force of ten to twelve are dangerous and are characterized as a strong and violent storm, as well as a hurricane.

The wind uproots trees, damages buildings, destroys vegetation, and destroys buildings. The waves emit deafening noise from 9 meters and above, and are long. At sea, they reach dangerous heights even for large ships - from nine meters and above. Foam covers the water surface, visibility is zero or close to this.

The speed of movement of air masses ranges from 24.5 meters per second (89 km/h) and reaches from 118 kilometers per hour with a wind force of 12 points. Severe storms and hurricanes (winds equal to 11 and 12 points) occur very rarely.

Additional five points to the classic Beaufort scale

Since hurricanes are also not identical in intensity and degree of damage, in 1955 the United States Weather Bureau adopted an addition to the standard Beaufort classification in the form of five scale units. Wind strength from 13 to 17 points inclusive - these are clarifying characteristics for destructive hurricane winds and accompanying phenomena environment.

How to protect yourself when disaster strikes?

If a storm warning from the Ministry of Emergency Situations occurs in an open area, it is better to follow the advice and reduce the risk of accidents.

First of all, you should pay attention to the warnings every time - there is no guarantee that an atmospheric front will come to the area where you are, but you also cannot be sure that it will bypass it again. All items should be removed or securely secured to protect pets.

If a strong wind catches a fragile building - garden house or other lightweight structures - it is better to close the windows on the side of air movement and, if necessary, strengthen them with shutters or boards. From the leeward side, on the contrary, open it slightly and fix it in this position. This will eliminate the danger of an explosive effect from the pressure difference.

It is important to remember that any strong wind can bring with it unwanted precipitation - in winter there are blizzards and blizzards, in summer dust and sand storms are possible. It should also be taken into account that strong winds can occur even in absolutely clear weather.

IA website.

Beaufort scale

0 points - calm
Mirror-smooth sea, almost motionless. The waves practically do not run onto the shore. The water looks more like a quiet lake backwater than a sea coast. There may be haze over the surface of the water. The edge of the sea merges with the sky so that the border is not visible. Wind speed 0-0.2 km/h.

1 point - quiet
There are light ripples on the sea. The height of the waves reaches up to 0.1 meters. The sea can still merge with the sky. You can feel a light, almost imperceptible breeze.

2 points - easy
Small waves, no more than 0.3 meters high. The wind speed is 1.6-3.3 m/s, you can feel it with your face. With such wind, the weather vane begins to move.

3 points - weak
Wind speed 3.4-5.4 m/s. Slight disturbance on the water, whitecaps appear occasionally. The average wave height is up to 0.6 meters. The weak surf is clearly visible. The weather vane spins without frequent stops, leaves on the trees, flags, etc. sway.

4 points - moderate
Wind - 5.5 - 7.9 m/s - raises dust and small pieces of paper. The weather vane spins continuously, thin tree branches bend. The sea is rough and whitecaps are visible in many places. Wave height is up to 1.5 meters.

5 points - fresh
Almost the entire sea is covered with whitecaps. Wind speed 8 - 10.7 m/s, wave height 2 meters. Branches and thin tree trunks sway.

6 points - strong
The sea is covered with white ridges in many places. The height of the waves reaches 4 meters, the average height is 3 meters. Wind speed 10.8 - 13.8 m/s. Thin tree trunks and thick tree branches bend, telephone wires hum.

7 points - strong
The sea is covered with white foamy ridges, which from time to time are blown off the surface of the water by the wind. The height of the waves reaches 5.5 meters, the average height is 4.7 meters. Wind speed 13.9 - 17.1 m/s. The middle tree trunks sway and the branches bend.

8 points - very strong
Strong waves, foam on every crest. The height of the waves reaches 7.5 meters, the average height is 5.5 meters. Wind speed 17.2 - 20 m/s. Walking against the wind is difficult, talking is almost impossible. Thin branches of trees break.

9 points - storm
High waves on the sea, reaching 10 meters; average height 7 meters. Wind speed 20.8 - 24.4 m/s. Large trees bend, medium branches break. The wind tears off poorly reinforced roof coverings.

10 points - severe storm
Sea white. The waves crash onto the shore or against the rocks with a roar. The maximum wave height is 12 meters, the average height is 9 meters. The wind, with a speed of 24.5 - 28.4 m/s, tears off roofs and causes significant damage to buildings.

11 points - severe storm
High waves reach 16 meters, with an average height of 11.5 meters. Wind speed 28.5 - 32.6 m/s. Accompanied by great destruction on land.

12 points - hurricane
Wind speed 32.6 m/s. Serious damage to permanent structures. The wave height is more than 16 meters.

Sea state scale

Unlike the generally accepted twelve-point wind rating system, there are several ratings of sea waves.

The generally accepted ones are British, American and Russian assessment systems.

All scales are based on a parameter that determines the average height of significant waves.

This parameter is called Significance Wave Height (SWH).

The American scale takes 30% of significant waves, the British 10%, and the Russian 3%.

The height of the wave is calculated from the crest (the top point of the wave) to the trough (the base of the trough).

Below is a description of wave heights:

0 points - calm,
1 point - ripple (SWH< 0,1 м),
2 points - weak waves (SWH 0.1 - 0.5 m),
3 points - light waves (SWH 0.5 - 1.25 m),
4 points - moderate waves (SWH 1.25 - 2.5 m),
5 points - rough seas (SWH 2.5 - 4.0 m),
6 points - very rough seas (SWH 4.0 - 6.0 m),
7 points - strong waves (SWH 6.0 - 9.0 m),
8 points - very strong waves (SWH 9.0 - 14.0 m),
9 points - phenomenal waves (SWH > 14.0 m).

The word “storm” does not apply in this scale.

Since it determines not the strength of the storm, but the height of the wave.

A storm is defined by Beaufort.

For the WH parameter for all scales, it is the part of the waves that is taken (30%, 10%, 3%) because the magnitude of the waves is not the same.

At a certain time interval there are waves, for example, 9 meters, as well as 5, 4, etc.

Therefore, each scale had its own SWH value, where a certain percentage of the highest waves is taken.

There are no instruments to measure wave height.

Therefore, there is no exact definition of the score.

The definition is conditional.

On the seas, as a rule, the wave height reaches 5-6 meters in height and up to 80 meters in length.

Visual range scale

Visibility is the maximum distance at which objects can be detected during the day and navigation lights at night.

Visibility depends on weather conditions.

In metrology, the influence of weather conditions on visibility is determined by a conventional scale of points.

This scale is a way of indicating the transparency of the atmosphere.

There are day and night visibility ranges.

Below is the daily visual range scale:

Up to 1/4 cable
About 46 meters. Very poor visibility. Dense fog or snowstorm.

Up to 1 cable
About 185 meters. Bad visibility. Thick fog or wet snow.

2-3 cables
370 - 550 meters. Bad visibility. Fog, wet snow.

1/2 mile
About 1 km. Haze, thick haze, snow.

1/2 - 1 mile
1 - 1.85 km. Average visibility. Snow, heavy rain

1 - 2 miles
1.85 - 3.7 km. Haze, haze, rain.

2 - 5 miles
3.7 - 9.5 km. Light haze, haze, light rain.

5 - 11 miles
9.3 - 20 km. Good visibility. The horizon is visible.

11 - 27 miles
20 - 50 km. Very good visibility. The horizon is clearly visible.

27 miles
Over 50 km. Exceptional visibility. The horizon is clearly visible, the air is transparent.