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Anticyclonic : Qualifies the circulation of the air in a high. Systematic atmospheric circulation associated with an anticyclone, which is clockwise in the Northern Hemisphere and anticlockwise in the Southern Hemisphere.

Beaufort (scale) : Table establishing a correlation between force and speed of the wind. The force on the scale of Beaufort is spreading out between 0 (speed of the wind between 0 and 1 km/h) and 12 (speed of the wind higher than 118 km/h).
According to the force on this scale are given a definition of the state of the sea and a description of the weather conditions.

Cold front : Any nonoccluded front which moves in such a way that cold air replaces relatively warmer air. On the weather charts, the intersection of this type of surface with the ground is represented by a blue line with triangles. The arrival of a cold front is generally announced by a reinforcement of the winds, and a temporary reinforcement of precipitations. Often, back of the cold front, the wind is irregular in force and in direction, the sky is clearing, the clouds become cumuliform, the visibility improves and showers occur. This is the squally weather.

Complex low : Generally extended trough of low pressure, showing several centers.

Disturbance : As a rule, indicates any weather phenomenon generating a degradation of the weather. Under temperate latitudes, it includes the warm front, the warm sector, the cold front and possibly the occlusion. It is also use to indicate the cloudy area associated with this unit, and even the cloudy zone associated with an isolated cold front.

Floe : Any relatively flat fragment of sea ice about 20 m or more of horizontal size.

Fog patches : Fog of a well delimited local extent that one can observe remotely, most of the time at sea.

Further outlook : Allows schematically to describe the evolution of the weather for the next day(s), stressing the dangerous phenomena (winds over 40 nds).

Growler : Block of ice smaller than a fragment of iceberg, emerging with less than one meter above sea surface and usually extending on a surface from approximately 20 m2. Of white color, but sometimes transparent or bluegreen, the growler is difficult to recognize when it is surrounded by ice of sea or fleets in an agitated sea.

High (anticyclone) : Region of the atmosphere where the pressures are high relative to those in the surrounding region at the same level. It is represented on a synoptic chart by a system of isobars at a specific level, or of contours at a specific pressure, which enclose relatively high values of pressure or contour height.

Hurricane : see "tropical cyclone".

Iceberg : Important ice mass detached from a glacier, of very variable form, emerging more than 5 m above the sea level, and which can be floating or aground. The icebergs can be tabular, domeshaped, inclined, pointed, eroded or of the icebergs of glacier.

Isofronts : Expertised isobaric chart showing for the following days (for example H+ 24, H+48 H, H+72 H) on a broad area, the position of the lows and highs as well as expected disturbances (cold, and warm fronts, occlusions, etc...).

Légende
	Cold front		Stationary front
	Cold frond (little activity)		Stationary front (little activity)
	Warm front		ITCZ
	Warm front (little activity)		Tropical Wave
	Occlusion		Convergence line

ITCZ : Intertropical Convergence Zone : Area of convergence of the trade winds of the northern hemisphere and the southern hemisphere. The squalls and thundersqualls are frequent. Also called doldrums. Shown on the satellite images of the satellites by a zonal band of convective clouds close to the meteorological equator.

Gusts : Sudden, brief increase of the wind speed over its mean value. Gusts can reach an high speed of 50% with that of the moderate wind. The term "gust" is used when the speed of the instantaneous wind exceeds from 10 to 15 kts the mean wind speed value; “strong gusts” when the difference reaches 15 to 25 kts, and "violent gusts" when difference exceeds 25 kts.

Low (depression) : Region of the atmosphere in which the pressures are lower than those of the surrounding region at the same level. It is represented on a synoptic chart by a system of isobars at a specified altitude level (or a system of contours at a specified pressure level) which enclose relatively low values of pressure (or altitude).

Mean wind : By convention, in meteorology, the mean wind is a the average of the wind over 10 minutes and measured 10 meters above the ground. The gusts can exceed by 50% the mean wind. Whatever the hemisphere, it is said that the wind is "veering" when it turns clockwise, and that it is “backing” when it turns anticlockwise.

Occlusion (occluded front) : A composite of two fronts, formed as a cold front overtakes a warm front or quasistationary front.

Ridge :Region of the atmosphere in which the pressure is high relative to the surrounding region at the same level. It is represented on a synoptic chart by a system of nearly parallel isobars or contours, approximately Ushape, which are concave towards an anticyclone.

Sea state : state of the surface resulting from the superposition of the different swell waves and the waves generated by the winds (sea of the wind). To describe the state of the sea, one uses the average height of the third of the highest waves : H1/3. The terms used for the description of the state of the sea are those of the Douglas scale (see left).

Secondary cold front : In the cold air of the disturbance, a secondary cold front materializes the arrival of an even colder air mass and results in a reinforcement of the squalls.

Shallow low : Low whose pressure in the center remains high in the absolute (higher than 1010 hPa, for example) but is weaker than in the neighbourhoods.

Squalls : Atmospheric phenomenon characterized by an abrupt and large increase of wind speed with a duration of the order of minutes which diminishes rather suddenly. It is often accompanied by showers or thunderstorms. The occurrence of strong gusts is higher leeward the cloud.

Storm : Under the temperate latitudes, phenomenon generating wind forces of 10 Beaufort (48 55 kts)

Swell : TAny system of water waves which has left its generating area.

Trade wind : Persistent winds, mainly in the lower atmosphere, which blow over vast regions from a subtropical anticyclone to the equatorial regions. Their predominant directions are NE in the Northern Hemisphere and SE in the Southern Hemisphere.

Tropical cyclone : Under the tropical latitudes, the cyclone is an about circular isolated depression, whose diameter lies between 300 and 1000 km. The pressure at the center can be very low. At the center lies a zone of calm, with often clear sky: it is the eye of the cyclone. Around the eye, the winds are extremely violent, exceeding 64 kts (approximately 120 km/h, force 12 Beaufort). These phenomena are called hurricanes in North Atlantic and in the Northeast Pacific and typhoons in the Northwest Pacific.

Tropical depression : under the tropical latitudes, swirling phenomenon of wide extent generating winds lower than 34 nds.

Tropical storm : Under the tropical latitudes, phenomenon generating wind forces of 8 to 11 Beaufort (from 34 to 63 kts)

Tropical wave : Trough moving westward in the flow of trade wind and often developing a squall line.

Trough : An elongated area of relatively low atmospheric pressure.

TU or UTC (Universal Time Coordinated) : Legal time base around the world: it is the same time everywhere in the world at a given moment. 00H00 UTC correspond to 00h00 Greenwich time.

Variable cyclonic : Said of the variation of the direction of the winds around and near the center of a low. It turns anticlockwise in northern hemisphere and clockwise in southern hemisphere.

Trough : An elongated area of relatively low atmospheric pressure.

Warm front : : Any nonoccluded front which moves in such a way that warm air replaces cold air.

Waving front : : Cold front showing an undulation. Its presence in such a front is often announced because it exists a risk that a small depression deepens at the "top" of the undulation, generating an aggravation of the weather.

Wind chill : Index used to determine the relative discomfort resulting from a specific combination of wind speed and air temperature. The felt temperature corresponds to the feeling felt on the skin in calm weather.

Wind force : Number on a progressive scale (Beaufort scale) corresponding to the effects produced by winds within a particular range of speeds. As for the speed of the gusts, it is always expressed in kts. In the weather bulletins, the force of the average wind may also be qualified by an adjective going from weak to violent. It doesn’t exist any standardized definition of the corresponding speeds of wind. Nevertheless, one can advance the following correspondence:


- light wind = 0 to 6 kts (force 0 to 2 Beaufort)
- moderate wind = 7 to 21 kts (force 3 to 5)
- fresh wind = 22 to 27 kts (force 6)
- strong wind = 28 to 40 kts (force 7 and 8))
- very strong wind = 41 to 47 kts (force 9)
- violent wind = higher than 47 kts (force 10 and more)


On the weather charts, a shaft indicates the direction from where comes the wind; it is provided with barbs straight lines corresponding to the wind force : halfbarb for five kts, barb for ten kts. A solid triangle replaces the barbs to indicate fifty kts.

Wind sea : Waves raised by the wind blowing in the immediate neighbourhood of an observation site at the time of observation.