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Along-slope Wind System
A closed, thermally driven diurnal mountain wind circulation whose lower branch blows up or down the sloping sidewalls of a valley or mountain. The upper branch blows in the opposite direction, thereby closing the circulation.
Anti-wind
The upper or return branch of an along-valley wind system, as confined within a valley, and blowing in a direction opposite to the winds in the lower altitudes of the valley.
Apparent Wind
The speed and true direction from which the wind appears to blow with reference to a moving point. Sometimes called RELATIVE WIND.
Backing Winds
Winds which shift in a counterclockwise direction with time at a given location (e.g. from southerly to southeasterly), or change direction in a counterclockwise sense with height (e.g. westerly at the surface but becoming more southerly aloft). The opposite of veering winds.

In storm spotting, a backing wind usually refers to the turning of a south or southwest surface wind with time to a more east or southeasterly direction. Backing of the surface wind can increase the potential for tornado development by increasing the directional shear at low levels.
Brisk Wind Advisory
A Small Craft Advisory issued by the National Weather Service for ice-covered waters.
Canyon Wind
A foehn wind that is channeled through a canyon as it descends the lee side of a mountain barrier.
Channeled High Winds
In mountainous areas or in cities with tall buildings, air may be channeled through constricted passages producing high winds. Santa Ana winds and winds through passes from the cold Alaskan interior to the sea are examples of these winds. Channeled high winds are local in nature but can be extremely strong. These winds generally occur in well-defined areas.
Cross-Valley Wind System
A thermally driven wind that blows during daytime across the axis of a valley toward the heated sidewall.
Diablo Wind
Similar to Santa Ana winds in southern California. These winds occur below canyons in the East Bay hills (Diablo range) and in extreme cases can exceed 60 mph. They develop due to high pressure over Nevada and lower pressure along the central California coast.
Down-Valley Wind
A thermally driven wind directed down a valley's axis, usually occurring during nighttime; part of the along-valley wind system.
Extreme Wind Warning
Extreme Wind Warning (EWW) inform the public of the need to take immediate shelter in an interior portion of a well-built structure due to the onset of extreme tropical cyclone winds. An EWW for extreme tropical cyclone winds should be issued when both of the following criteria are met: a. Tropical cyclone is a category 3 or greater on the Saffir Simpson hurricane scale as designated by NHC, CPHC or JTWC. b. Sustained tropical cyclone surface winds of 100 knots (115 mph) or greater are occurring or are expected to occur in a WFO’s county warning area within one hour.
Fall Wind
A strong, cold, downslope wind.
Fire Wind
A thermally driven wind blowing radially inward toward a fire, produced by horizontal temperature differences between the heated air above the fire and the surrounding cooler free atmosphere.
Gap Winds
Strong winds channeled through gaps in the Pacific coastal ranges, blowing out into the Pacific Ocean or into the waterways of the Inside Passage. The winds blow through low passes where major river valleys issue onto the seaways when strong east-west pressure gradients exist between the coast and the inland areas, with low pressure over the ocean.
General Wind
Land management agency term for winds produced by synoptic-scale pressure systems on which smaller-scale or local convective winds are superimposed.
Geostrophic Wind
A wind that is affected by coriolis force, blows parallel to isobars and whose strength is related to the pressure gradient (i.e., spacing of the isobars).
Glacier Wind
A shallow downslope wind above the surface of a glacier, caused by the temperature difference between the air in contact with the glacier and the free air at the same altitude. The glacier wind does not reverse diurnally like slope and along-valley wind systems.
Gradient High Winds
These high winds usually cover a large area and are due to synoptic-scale, extra-tropical low pressure systems.
High Wind
Sustained wind speeds of 40 mph or greater lasting for 1 hour or longer, or winds of 58 mph or greater for any duration.
High Wind Advisory
This product is issued by the National Weather Service when high wind speeds may pose a hazard. The criteria for this advisory varies from state to state. In Michigan, the criteria is sustained non-convective (not related to thunderstorms) winds greater than or equal to 30 mph lasting for one hour or longer, or winds greater than or equal to 45 mph for any duration.
High Wind Warning
This product is issued by the National Weather Service when high wind speeds may pose a hazard or is life threatening. The criteria for this warning varies from state to state. In Michigan, the criteria is sustained non-convective (not related to thunderstorms) winds greater than or equal to 40 mph lasting for one hour or longer, or winds greater than or equal to 58 mph for any duration.
High Wind Watch
This product is issued by the National Weather Service when there is the potential of high wind speeds developing that may pose a hazard or is life threatening. The criteria for this watch varies from state to state. In Michigan, the criteria is the potential for sustained non-convective (not related to thunderstorms) winds greater than or equal to 40 mph and/or gusts greater than or equal to 58 mph.
Hurricane Force Wind Warning
A warning for sustained winds, or frequent gusts, of 64 knots (74 mph) or greater, either predicted or occurring, and not directly associated with a tropical cyclone.
Hurricane Force Wind Watch
A watch for an increased risk of a hurricane force wind event for sustained surface winds, or frequent gusts, of 34 knots 64 knots (74 mph) or greater, but its occurrence, location, and/or timing is still uncertain.
Jet Wind Speed Profile
A vertical wind speed profile characterized by a relatively narrow current of high winds with slower moving air above and below. A large wind (speed) shear occurs above and below the jet axis.
Katabatic Wind
A wind that is created by air flowing downhill.
Local Convective Wind
In fire weather terminology, local thermally driven winds arising over a comparatively small area and influenced by local terrain. Examples include sea and land breezes, lake breezes, diurnal mountain wind systems and columnar convective currents.
Marine Small Craft Wind Warning
A marine warning issued by Environment Canada Atmospheric Environment Branch for winds which are forecasted to be in the 20-33 knot range inclusive.
Maximum Sustained Surface Wind
When applied to a particular weather system, refers to the highest one-minute average wind (at an elevation of 10 meters with an unobstructed exposure) associated with that weather system at a particular point in time.
Mesoscale High Winds
These high winds usually follow the passage of organized convective systems and are associated with wake depressions or strong mesohighs.
Mid-Flame Wind
Wind measured at the midpoint of the flames, considered to be most representative of the speed of the wind that is affecting fire behavior.
Mountain Wind System
The system of diurnal winds that forms in a complex terrain area, consisting of mountain-plain, along-valley, cross-valley and slope wind systems.
Mountain-Plain Wind System
A closed, large-scale, thermally driven circulation between the mountains and the surrounding plain. The mountain-to-plain flow making up the lower branch of the closed circulation usually occurs during nighttime, while the plain-to-mountain flow occurs during daytime.
Peak Wind Speed
The maximum instantaneous wind speed since the last observation that exceeded 25 knots.
Plow Wind
A term used in the midwestern United States to describe strong, straight-line winds associated with the downdrafts spreading out in advance of squall lines and thunderstorms. Resulting damage is usually confined to narrow zones like that caused by tornadoes; however, the winds are all in one direction (straight-line winds).
Predominant Wind
The wind that prevails and generates the local component of the significant sea conditions across the forecast area. This is the wind included in all marine forecast products and is defined as a 10-meter wind, except over the nearshore marine zones where it is defined to be the wind at a 3-meter height.
Prevailing Winds
A wind that consistently blows from one direction more than from any other.
Radius of Maximum Winds
The distance from the center of a tropical cyclone to the location of the cyclone's maximum winds. In well-developed hurricanes, the radius of maximum winds is generally found at the inner edge of the eyewall.
Relative Wind
The wind with reference to a moving point. Sometimes called APPARENT WIND. See also APPARENT WIND, TRUE WIND.
Saffir-Simpson Hurricane Wind Scale
The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 categorization based on the hurricane's intensity at the indicated time. The scale provides examples of the type of damage and impacts in the United States associated with winds of the indicated intensity. In general, damage rises by about a factor of four for every category increase. The maximum sustained surface wind speed (peak 1-minute wind at the standard meteorological observation height of 10 m [33 ft] over unobstructed exposure) associated with the cyclone is the determining factor in the scale. The scale does not address the potential for other hurricane-related impacts, such as storm surge, rainfall-induced floods, and tornadoes.
Santa Ana Wind
In southern California, a weather condition in which strong, hot, dust-bearing winds descend to the Pacific Coast around Los Angeles from inland desert regions.
Solar Wind
The outward flux of solar particles and magnetic fields from the sun. Typically, solar wind velocities are near 350 km/s.
Steering Winds
Same as Steering Currents; A prevailing synoptic scale flow which governs the movement of smaller features embedded within it.
Straight-line Winds
Generally, any wind that is not associated with rotation, used mainly to differentiate them from tornadic winds.
Sustained Wind
Wind speed determined by averaging observed values over a two-minute period.
Thermal Wind
It is a theoretical wind that blows parallel to the thickness lines, for the layer considered, analogous to how the geostrophic wind blows parallel to the height contours. The closer the thickness isopleths, the stronger the thermal wind. Cold air is always located to the left of the thermal wind (as you face downstream) and the warm air is located on the right. Since thickness contours are tighter on the cold side of thermal wind, your lower thickness values will be found on the left side of the thermal wind. The speed and direction of the thermal wind are determined by vector geometry where the geostrophic wind at the upper level is subtracted from the geostrophic wind at the lower level.
Trade Winds
Persistent tropical winds that blow from the subtropical high pressure centers towards the equatorial low.
Transport Wind
The average wind over a specified period of time within a mixed layer near the surface of the earth.
True Wind
Wind relative to a fixed point on the earth. Wind relative to a moving point is called APPARENT or RELATIVE WIND.
Up-valley Wind
A diurnal thermally driven flow directed up a valley's axis, usually occurring during daytime; part of the along-valley wind system.
VAD Wind Profile
A radar plot of horizontal winds, derived from VAD data, as a function of height above a Doppler Radar. The display is plotted with height as the vertical axis and time as the horizontal axis (a so-called time-height display), which then depicts the change in wind with time at various heights. This display is useful for observing local changes in vertical wind shear, such as backing of low-level winds, increases in speed shear, and development or evolution of nearby jet streams (including low-level jets). This product often is referred to erroneously as a VAD.
Variable Wind
Same as Variable Wind Direction; a condition when
(1) the wind direction fluctuates by 60° or more during the 2-minute evaluation period and the wind speed is greater than 6 knots; or
(2) the direction is variable and the wind speed is less than 6 knots.
Variable Wind Direction
A condition when
(1) the wind direction fluctuates by 60° or more during the 2-minute evaluation period and the wind speed is greater than 6 knots; or
(2) the direction is variable and the wind speed is less than 6 knots.
Veering Winds
Winds which shift in a clockwise direction with time at a given location (e.g., from southerly to westerly), or which change direction in a clockwise sense with height (e.g., southeasterly at the surface turning to southwesterly aloft). The latter example is a form of directional shear which is important for tornado formation. Compare with backing winds.
Vertical Wind Shear
the change in the wind's direction and speed with height. This is a critical factor in determining whether severe thunderstorms will develop.
Very Windy
30 to 40 mph winds.
Wasatch Wind
A strong easterly wind blowing out of the mouths of the canyons of the Wasatch Mountains onto the plains of Utah. Also called canyon wind.
Whirlwind
A small, rotating column of air; may be visible as a dust devil.
Wind
The horizontal motion of the air past a given point. Winds begin with differences in air pressures. Pressure that's higher at one place than another sets up a force pushing from the high toward the low pressure. The greater the difference in pressures, the stronger the force. The distance between the area of high pressure and the area of low pressure also determines how fast the moving air is accelerated. Meteorologists refer to the force that starts the wind flowing as the "pressure gradient force." High and low pressure are relative. There's no set number that divides high and low pressure. Wind is used to describe the prevailing direction from which the wind is blowing with the speed given usually in miles per hour or knots.
Wind Advisory
Sustained winds 25 to 39 mph and/or gusts to 57 mph. Issuance is normally site specific. However, winds of this magnitude occurring over an area that frequently experiences such winds
Wind Chill
Reference to the Wind Chill Factor; increased wind speeds accelerate heat loss from exposed skin, and the wind chill is a measure of this effect. No specific rules exist for determining when wind chill becomes dangerous. As a general rule, the threshold for potentially dangerous wind chill conditions is about -20°F.
Wind Chill Advisory
The National Weather Service issues this product when the wind chill could be life threatening if action is not taken. The criteria for this warning varies from state to state.
Wind Chill Factor
Increased wind speeds accelerate heat loss from exposed skin. No specific rules exist for determining when wind chill becomes dangerous. As a general rule, the threshold for potentially dangerous wind chill conditions is about -20°F.
Wind Chill Warning
The National Weather Service issues this product when the wind chill is life threatening. The criteria for this warning varies from state to state.
Wind Couplet
An area on the radar display where two maximum wind speeds are blowing in opposite directions.
Wind Direction
The true direction from which the wind is blowing at a given location (i.e., wind blowing from the north to the south is a north wind). It is normally measured in tens of degrees from 10 degrees clockwise through 360 degrees. North is 360 degrees. A wind direction of 0 degrees is only used when wind is calm.
Wind Field
The three-dimensional spatial pattern of winds.
Wind Gust
Rapid fluctuations in the wind speed with a variation of 10 knots or more between peaks and lulls. The speed of the gust will be the maximum instantaneous wind speed.
Wind Radii
Term used in National Weather Tropical Cyclone Forecast Advisory products (TCM). Wind radii are the largest radii of that wind speed found in that quadrant. Quadrants are defined as NE (0-90), SE (90-180), SW (180-270), and NW (270-0). As an example, given maximum 34 knot radii to 150 nm at 0 degrees, 90 at 120 degrees, and 40 nm at 260 degrees, the following line would be carried in the forecast/advisory: 150NE 90SE 40SW 150NW.
Wind Rose
A diagram, for a given locality or area, showing the frequency and strength of the wind from various directions.
Wind Shear
The rate at which wind velocity changes from point to point in a given direction (as, vertically). The shear can be speed shear (where speed changes between the two points, but not direction), direction shear (where direction changes between the two points, but not speed) or a combination of the two.
Wind Shear Profile
The change in wind speed and/or direction usually in the vertical. The characteristics of the wind shear profile are of critical importance in determining the potential for and type of severe weather.
Wind Shift
A change in wind direction of 45 degrees or more in less than 15 minutes with sustained wind speeds of 10 knots or more throughout the wind shift.
Wind Shift Line
A long, but narrow axis across which the winds change direction (usually veer).
Wind Sock
A tapered fabric shaped like a cone that indicates wind direction by pointing away from the wind. It is also called a "wind cone."
Wind Speed
The rate at which air is moving horizontally past a given point. It may be a 2-minute average speed (reported as wind speed) or an instantaneous speed (reported as a peak wind speed, wind gust, or squall).
Wind Waves
Local, short period waves generated from the action of wind on the water surface (as opposed to swell). Commonly referred to as waves. In a National Weather Service Coastal Marine Forecast or Offshore Forecast, wind waves are used when swells are described in the forecast.
or
Waves generated by the local wind blowing at the time of observation.
Windward
The side toward the wind. Compare with leeward.
Windy
20 to 30 mph winds.

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     Page last Modified: 25 June, 2009 1:01 PM