Here are the results for the letter f
- 1) Fahrenheit- The standard scale used to measure temperature in the United States. On this scale, the freezing point of water
is 32°F and the boiling point is 212°F. To convert a Celsius temperature to Fahrenheit, multiply it by 9/5 and
then add 32:
°F = (°C * 9/5) + 32
2) Fog- Water droplets suspended in the air at the Earth's surface. Fog is often hazardous when the visibility is reduced to ¼ mile or less.
- F Corona
- In solar-terrestrial terms, of the white-light corona (that is, the corona seen by the eye at a total solar eclipse), that portion which is caused by sunlight scattered or reflected by solid particles (dust) in inter-planetary space.
- F Region
- In solar-terrestrial terms, the upper layer of the ionosphere, approximately 120 to 1500 km
in altitude. The F region is subdivided into the F1 and F2
regions. The F2 region is the most dense and peaks at altitudes
between 200 and 600 km. The F1 region is a smaller peak in
electron density, which forms at lower altitudes in the daytime.
- F Scale
- Abbreviation for Fujita Scale, a system of rating the intensity of tornadoes; for detailed information, see the definition for that term.
- Forecast Area
- Federal Aviation Administration
- In hydrologic terms, the external surface of a structure, such as the surface of a dam.
- In solar-terrestrial terms, a bright region of the photosphere seen in white light, seldom
visible except near the solar limb.
- (abbrev. F) The standard scale used to measure temperature in the United States. On this scale, the freezing point of water is 32°F and the boiling point is 212°F. To convert a Celsius temperature to Fahrenheit, multiply it by 9/5 and then add 32:
°F = (°C * 9/5) + 32
- It is usually used at night to describe less than 3/8 opaque clouds, no precipitation, no extremes of visibility, temperature or winds. It describes generally pleasant weather
- the season of the year which is the transition period from summer to winter occurring as the sun approaches the winter solstice. In the Northern
Hemisphere, fall customarily includes the months of September, October and November.
- Fall Line
- A skiing term, indicating the line of steepest descent of a slope.
- Fall Wind
- A strong, cold, downslope wind.
- Same as Virga; streaks or wisps of precipitation falling from a cloud but evaporating before reaching the ground. In certain cases, shafts of virga may precede a microburst.
- AVN MOS Guidance (older version)
- A pattern of plume dispersion in a stable atmosphere, in which the plume fans out in the horizontal and meanders about at a fixed height.
- Unit of water depth equal to 6 feet.
- Flight Advisory Weather Service
- (Great Lakes Freeze-Up/Break-Up Outlook) - A National Weather Service product to keep mariners informed of the projected freeze-up date or break-up date of ice on the Great Lakes.
- Federal Snow Sampler
- In hydrologic terms, a snow sampler consisting of five or more sections of sampling tubes, one which has a steel cutter on the end. The combined
snowpack measuring depth is 150 inches. This instrument was formerly the Mount Rose Type Snow Sampling Set.
- Feeder Bands
- Lines or bands of low-level clouds that move (feed) into the updraft region of a
thunderstorm, usually from the east through south (i.e., parallel to the inflow). Same as inflow bands.
This term also is used in tropical meteorology to describe spiral-shaped bands of convection
surrounding, and moving toward, the center of a tropical cyclone.
- Federal Emergency Management Agency. An agency of the federal government having responsibilities in hazard mitigation; FEMA also administers the National Flood
- Ferrel Cell
- In the general circulation of the atmosphere, the name given to the middle latitude cell marked by sinking motion near 30 degrees and rising motion near 60 degrees latitude.
- 1. The area in which ocean waves are generated by the wind. Also refers to the length of the fetch area, measured in the direction of the wind.
2. In hydrologic terms,
- The effective distance which waves have traversed in open water, from their point of origin to the point where they break.
- 2. The distance of the water or the homogenous type surface over which the wind blows without appreciable change in direction.
- A National Weather Service convective precipitation descriptor for a 10 percent chance of measurable precipitation (0.01 inch). Few is used interchangeably with isolated.
- Few Clouds
- An official sky cover classification for aviation weather observations, descriptive of a sky cover of 1/8 to 2/8. This is applied only when obscuring phenomenon aloft are
present--that is, not when obscuring phenomenon are surface-based, such as fog.
- Flash Flood Guidance
- (Also abbrev. F) - Fog - water droplets suspended in the air at the Earth's surface. Fog is often hazardous when the visibility is
reduced to ¼ mile or less.
- In solar-terrestrial terms, a linear pattern in the H-alpha chromosphere of the sun, as seen
through an H-alpha filter, occurring near strong sunspots and
plage or in filament channels.
- Field (Moisture) Capacity
- The amount of water held in soil against the pull of gravity
- Field Moisture Deficiency
- The quantity of water, which would be required to restore the soil moisture to field moisture capacity.
- A mass of gas suspended over the photosphere by magnetic fields
and seen as dark lines threaded over the solar disk. A filament
on the limb of the sun seen in emission against the dark sky is
called a prominence.
- Filament Channel
- A broad pattern of fibrils in the chromosphere, marking
where a filament may soon form or where a filament recently
- Fill Dam
- In hydrologic terms, any dam constructed of excavated natural materials or of industrial wastes
- The opposite of deepening. A general increase in the central pressure of a low pressure system.
- 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.
- Any source of heat, natural or man made, capable of igniting wildland fuels; flaming or glowing fuel particles that can be carried naturally by wind, convection currents, or gravity into unburned fuels.
- Firn (Snow)
- In hydrologic terms, old snow on top of glaciers, granular and compact and not yet converted into ice. It is a transitional stage between snow and ice.
Also called Neve.
- Firn Line
- In hydrologic terms, the highest level to which the fresh snow on a glacier's surface retreats during the melting season. The line separating the
accumulation area from the ablation area
- First Law of Thermodynamics
- The law of physics that states that the heat absorbed by a system either raises the internal energy of the system or does work on the environment.
- Flanking Line
- A line of cumulus or towering cumulus clouds connected to and extending
outward from the most active part of a supercell, normally on the southwest side. The line normally
has a stair-step appearance, with the tallest clouds closest to the main storm
- In solar-terrestrial terms, a sudden eruption of energy on the solar disk lasting minutes to
hours, from which radiation and particles are emitted
- A sudden, brief illumination of a conductive channel associated with lightning, which may contain multiple strokes with their associated stepped leaders, dart leaders and return strokes.
- Flash Flood
- A rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam). However, the actual time threshold may vary in different parts of the country. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters.
- Flash Flood Guidance
- (FFG) Forecast guidance produced by the River Forecast Centers, often model output, specific to the potential for flash flooding (e.g., how much rainfall over a given area will be required to produce flash flooding).
- Flash Flood Statement
- (FFS) In hydrologic terms, a statement by the NWS which provides follow-up information on flash flood watches and warnings.
- Flash Flood Table
- In hydrologic terms, a table of pre-computed forecast crest stage values for small streams for a variety of antecedent moisture conditions and rain
amounts. Soil moisture conditions are often represented by flash flood guidance values. In lieu of crest stages, categorical
representations of flooding, e.g., minor, moderate, etc. may be used on the tables.
- Flash Flood Warning
- Issued to inform the public, emergency management, and other cooperating agencies that flash flooding is in progress, imminent, or highly likely.
- Flash Flood Watch
- Issued to indicate current or developing hydrologic conditions that are favorable for flash flooding in and close to the watch area, but the occurrence is neither certain or imminent.
- Flash Multiplicity
- The number of return strokes in a lightning flash.
- In hydrologic terms, a length of timber, concrete, or steel placed on the crest of a spillway to raise the retention water level but which may be quickly
removed in the event of a flood by a tripping device, or by deliberately designed failure of the flashboard or its supports
- Float Recording Precipitation gage
- In hydrologic terms, a rain gage where the rise of a float within the instrument with increasing rainfall is recorded. Some of these gages must be emptied
manually, while others employ a self-starting siphon to empty old rainfall amounts.
- A cluster of frazil particles
- In hydrologic terms, an accumulation of frazil flocs (also known as a "pan") or a single piece of broken ice
- Any high flow, overflow, or inundation by water which causes or threatens damage.
- Flood Categories
- Terms defined for each forecast point which describe or categorize the severity of flood impacts in the corresponding river/stream reach. Each flood category is bounded by an upper and lower stage (see Example 1). The severity of flooding at a given stage is not necessarily the same at all locations along a river reach due to varying channel/bank characteristics or presence of levees on portions of the reach. Therefore, the upper and lower stages for a given flood category are usually associated with water levels corresponding to the most significant flood impacts somewhere in the reach. The flood categories used in the NWS are:
*Minor Flooding* - minimal or no property damage, but possibly some public threat.
*Moderate Flooding* - some inundation of structures and roads near stream. Some evacuations of people and/or transfer of property to higher elevations.
*Major Flooding* - extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.
*Record Flooding* - flooding which equals or exceeds the highest stage or discharge at a given site during the period of record keeping.
Note: all three of the lower flood categories (minor, moderate, major) do not necessarily exist for a given forecast point. For example, at the level where a river reaches flood stage, it may be considered moderate flooding. However, at least one of these three flood categories must start at flood stage.
- Flood Control Storage
- In hydrologic terms, storage of water in reservoirs to abate flood damage
- Flood Crest
- Maximum height of a flood wave as it passes a certain location.
- Flood Frequency Curve
- In hydrologic terms,
(1) A graph showing the number of times per year on the average, plotted as abscissa, that floods of magnitude, indicated by the
ordinate, are equaled or exceeded.
(2) A similar graph but with recurrence intervals of floods plotted as abscissa.
- Flood Hazard Outlook (FHO)
- A high Level graphical depiction and key messages highlighting the potential threat of inland flood hazards (flash, urban, small stream and riverine) and their associated impacts (catastrophic, considerable, and limited) for the next seven days.
- Flood Inundation Mapping (FIM)
- In the context of the National Water Model (NWM) FIM, the expected maximum inundation extent over a particular period of time derived using the Height Above Nearest Drainage (HAND) method. Stage heights are interpolated from the NWM discharge values using synthetic rating curves, and are rounded to the nearest foot.
- Flood Loss Reduction Measures
- In hydrologic terms, the strategy for reducing flood losses. There are four basic strategies. They are prevention, property protection, emergency
services, and structural projects. Each strategy incorporates different measures that are appropriate for different conditions. In
many communities, a different person may be responsible for each strategy.
- Flood of Record
- In hydrologic terms, the highest observed river stage or discharge at a given location during the period of record keeping. (Not necessarily the highest
- Flood Plain
- In hydrologic terms, the portion of a river valley that has been inundated by the river during historic floods.
- Flood Potential Outlook
- (ESF on AFOS) (FPO for Acronym): In hydrologic terms, An NWS outlook that is issued to alert the public of potentially heavy rainfall that could send area rivers and streams into flood or
aggravate an existing flood.
- Flood Prevention
- In hydrologic terms, measures that are taken in order to keep flood problems from getting worse. Planning, land acquisition, river channel maintenance,
wetlands protection, and other regulations all help modify development on floodplains and watersheds to reduce their susceptibility
to flood damage. Preventive measures are usually administered by the building, zoning, planning and/ or code enforcement offices
of the local government.
- Flood Problems
- In hydrologic terms, problems and damages that occur during a flood as a result of human development and actions. Flood problems are a result from:
1) Inappropriate development in the floodplain (e.g., building too low, too close to the channel, or blocking flood flows);
Development in the watershed that increases flood flows and creates a larger floodplain, or;
3) A combination of the previous two.
- Flood Profile
- In hydrologic terms, a graph of elevation of the water surface of a river in flood, plotted as ordinate, against distance, measured in the downstream
direction, plotted as abscissa. A flood profile may be drawn to show elevation at a given time, crests during a particular flood, or to
show stages of concordant flows
- Flood Routing
- In hydrologic terms, process of determining progressively the timing, shape, and amplitude of a flood wave as it moves downstream to successive points
along the river
- Flood Stage
- An established gage height for a given location above which a rise in water surface level begins to create a hazard to lives, property, or commerce. The issuance of flood (or in some cases flash flood) warnings is linked to flood stage. Not necessarily the same as bankfull stage.
- Flood Statement (FLS)
- In hydrologic terms, a statement issued by the NWS to inform the public of flooding along major streams in which there is not a serious threat to life or
property. It may also follow a flood warning to give later information.
- Flood Warning
- (FLW) In hydrologic terms, a release by the NWS to inform the public of flooding along larger streams in which there is a serious threat to life or property. A
flood warning will usually contain river stage (level) forecasts.
- Flood Watch
- Issued to inform the public and cooperating agencies that current and developing hydrometeorological conditions are such that there is a threat of flooding, but the occurrence is neither certain nor imminent.
- Flood Wave
- In hydrologic terms, a rise in streamflow to a crest and its subsequent recession caused by precipitation, snowmelt, dam failure, or reservoir releases
- Flooded Ice
- In hydrologic terms, ice which has been flooded by melt water or river water and is heavily loaded by water and wet snow.
- In hydrologic terms, the process of protecting a building from flood damage on site. Floodproofing can be divided into wet and dry floodproofing. In
areas subject to slow-moving, shallow flooding, buildings can be elevated, or barriers can be constructed to block the water’s
approach to the building. These techniques have the advantage of being less disruptive to the neighborhood. It must be noted that
during a flood, a floodproofed building may be isolated and without utilities and therefore unusable, even though it has not been
- In hydrologic terms, a long, narrow concrete, or masonry embankment usually built to protect land from flooding. If built of earth the structure is usually
referred to as a levee. Floodwalls and levees confine streamflow within a specified area to prevent flooding. The term "dike" is used
to describe an embankment that blocks an area on a reservoir or lake rim that is lower than the top of the dam.
- In hydrologic terms,
(1) A part of the flood plain, otherwise leveed, reserved for emergency diversion of water during floods. A part of the flood plain
which, to facilitate the passage of floodwater, is kept clear of encumbrances.
(2) The channel of a river or stream and those parts of
the flood plains adjoining the channel, which are reasonably required to carry and discharge the floodwater or floodflow of any
river or stream.
- (abbrev. FLW) Wind. In meteorology, a qualitative reference of an air parcel(s) with respect to its direction of movement, sometimes specified at a certain height or pressure
elevation, e.g. westerly flow at 500 mb. In hydrology, the volumetric flow of water past a given point on a stream or river, usually in cubic feet per second (cfs)
- Flow Duration Curve
- In hydrologic terms, a cumulative frequency curve that shows the percentage of time that specified discharges are equaled or exceeded.
- Flow Separation
- The process by which a separation eddy forms on the windward or leeward sides of bluff objects or steeply rising hillsides.
- Flow Splitting
- The splitting of a stable airflow around a mountain barrier, with branches going around the left and right edges of the barrier, often at accelerated speeds.
- Flowing Well
- In hydrologic terms, a well drilled into a confined aquifer with enough hydraulic pressure for the water to flow to the surface without pumping. Also
called an Artesian well.
- River Flood Statement
- Time integrated flux
- Matter which flows; gas or liquid.
- Snow flurries are an intermittent light snowfall of short duration (generally light snow showers) with no measurable accumulation (trace category).
- The rate of transfer of fluids, particles or energy per unit area across a given surface (amount of flow per unit of time).
- Follow (or) Flow- Wind
- From or Fathom
- In solar-terrestrial terms, the lowest radiowave frequency that can be reflected from the
- A warm, dry wind on the lee side of a mountain range, the warmth and dryness of the air being due to adiabatic compression as the air descends the mountain slopes. In the United States, the term chinook is used for Foehn winds in the Rocky and Sierra mountains.
- Foehn Pause
- A temporary cessation of the foehn at the ground due to the formation or intrusion of a cold air layer which lifts the foehn off the ground.
- In solar-terrestrial terms, the maximum ordinary mode radiowave frequency capable of reflec-
tion from the sporadic E region of the ionosphere.
- In solar-terrestrial terms, the maximum ordinary mode radiowave frequency capable of reflection from the F2 region of the ionosphere.
- (abbrev. F) Fog is water droplets suspended in the air at the Earth's surface. Fog is often hazardous when the visibility is reduced to ¼ mile or less.
- A rainbow that has a white band that appears in fog, and is fringed with red on the outside and blue on the inside.
- Forced Channeling
- Channeling of upper winds along a valley's axis when upper winds are diverted by the underlying topography. Compare pressure-driven channeling.
- In hydrologic terms, the water behind (upstream) of the dam.
- A statement of prediction.
- Forecast Crest
- In hydrologic terms, the highest elevation of river level, or stage, expected during a specified storm event.
- Forecast Guidance
- Computer-generated forecast materials used to assist the preparation of a forecast, such as numerical forecast models.
- Forecast Issuance Stage
- The stage which, when reached by a rising stream, represents the level where RFCs need to begin issuing forecasts for a non-routine (flood-only) forecast point. This stage is coordinated between WFO and RFC personnel and is not necessarily the same as action or alert stage. The needs of WFO/RFC partners and other users are considered in determining this stage.
- Forecast Periods
- Official definitions for NWS products:
Today...............................Sunrise to sunset
This afternoon..................noon till 6 p.m.
This evening.....................6 p.m. till sunset
Tonight.............................sunset till sunrise
Tomorrow.........................sunrise to sunset of the following day
- Forecast Point
- A location along a river or stream for which hydrologic forecast and warning services are provided by a WFO. The observed/forecast stage or discharge for a given forecast point can be assumed to represent conditions in a given reach (see /reach/).
- Forecast valid for
- The period of time the forecast is in effect
beginning at a given day, date and time, and ending at a given day, date
- In hydrologic terms, a sighting on a point of unknown elevation from an instrument of known elevation. To determine the elevation of the point in
question, the foresight is subtracted from the height of the instrument.
- Forward Flank Downdraft
- The main region of downdraft in the forward, or leading, part of a supercell, where most of the heavy precipitation is.
- In hydrologic terms, the upper end of a confined-aquifer conduit, where it intersects the land surface.
- Forecast Output United States
- Flood Potential Outlook
- Fujita-Pearson Scale
- A cumulus cloud presenting a ragged, shredded appearance, as if torn.
- A stratus cloud presenting a ragged, shredded appearance, as if torn. It differs from a fractocumulus cloud in having a smaller vertical extent and darker color.
- In hydrologic terms, any break or rupture formed in an ice cover or floe due to deformation.
- Fracture Zone
- In hydrologic terms, an area which has a great number of fractures.
- In hydrologic terms, deformation process whereby ice is permanently deformed, and fracture occurs.
- Ragged, detached cloud fragments; same as scud.
- Frazil Ice
- In hydrologic terms, fine spicules, plates, or discoids of ice suspended in water. In rivers and lakes, frazil is formed in supercooled, turbulent water.
- Frazil Slush
- In hydrologic terms, an agglomerate of loosely packed frazil which floats or accumulates under the ice cover.
- Freak Wave
- A wave of much greater height and steepness than other waves in the prevailing sea or swell system. See Rogue Wave.
- Free Atmosphere
- The part of the atmosphere that lies above the frictional influence of the earth's surface.
- Free Ground Water
- In hydrologic terms, unconfined ground water whose upper boundary is a free water table
- In hydrologic terms, the vertical distance between the normal maximum level of the water surface in a channel, resrvoir, tank, canal, etc., and the top of
the sides of a levee, dam, etc., which is provided so that waves and other movements of the liquid will not overtop the confining
- A freeze is when the surface air temperature is expected to be 32°F or below over a widespread area for a climatologically significant period of time. Use of the term is usually restricted to advective situations or to occasions when wind or other conditions prevent frost. "Killing" may be used during the growing season when the temperature is expected to be low enough for a sufficient duration to kill all but the hardiest herbaceous crops.
- Freeze Warning
- Issued during the growing season when surface temperatures are expected to drop below freezing over a large area for an extended period of time, regardless whether or not frost develops.
- Freezeup date
- In hydrologic terms, the date on which the water body was first observed to be completely frozen over
- Freezing Drizzle
- A drizzle that falls as a liquid but freezes into glaze or rime upon contact with the cold ground or surface structures.
- Freezing Drizzle Advisory
- Issued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected. However, even small amounts of freezing rain or freezing drizzle may cause significant travel problems.
- Freezing Fog
- A fog the droplets of which freeze upon contact with exposed objects and form a coating of rime and/or glaze.
- Freezing Level
- The altitude at which the air temperature first drops below freezing.
- Freezing Rain
- Rain that falls as a liquid but freezes into glaze upon contact with the ground.
- Freezing Rain Advisory
- Issued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected. However, even small amounts of freezing rain or freezing drizzle may cause significant travel problems.
- Freezing Spray
- An accumulation of freezing water droplets on a vessel caused by some appropriate combination of cold water, wind, cold air temperature, and vessel movement.
- Freezing Spray Advisory
- An advisory for an accumulation of freezing water droplets on a vessel at a rate of less than 2 centimeters (cm) per hour caused by some appropriate combination of cold water, wind, cold air temperature, and vessel movement.
- Freezup jam
- In hydrologic terms, ice jam formed as frazil ice accumulates and thickens
- French Drain
- In hydrologic terms, an underground passageway for water through the interstices among stones placed loosely in a trench
- the annual spring rise of streams in cold climates as a result of snow melt; freshet also refers to a flood caused by rain or melting snow.
- The mechanical resistive force of one object on another object's relative movement when in contact with the first object. In meteorology, friction affects the motion of air (wind) at and near the Earth's surface.
- Friction Head
- In hydrologic terms, the decrease in total head caused by friction
- Friction Layer
- Same as Planetary Boundary Layer; the layer within the atmosphere between the earth's surface and 1 km above the surface; this is the layer where friction affects wind speed and wind direction.
- A boundary or transition zone between two air masses of different density, and thus (usually) of different temperature. A moving front is named according to the advancing air mass, e.g., cold front if colder air is advancing.
- Frontal Inversion
- A temperature inversion that develops aloft when warm air overruns the cold air behind a front.
- 1. The initial formation of a front or frontal zone. 2. In general, an increase in the horizontal gradient of an airmass property, principally density, and the development of the accompanying features of the wind field that typify a front.
- Frontal Passage
- Frontal Surface
- (Abbrev. FRST) - Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32°F. As with the term "freeze," this condition is primarily significant during the growing season. If a frost period is sufficiently severe to end the growing season or delay its beginning, it is commonly referred to as a "killing frost." Because frost is primarily an event that occurs as the result of radiational cooling, it frequently occurs with a thermometer level temperature in the mid-30s.
- Frost Advisory
- Issued during the growing season when widespread frost formation is expected over an extensive area. Surface temperatures are usually in the mid 30s Fahrenheit.
- Frost Point
- Dew point below freezing.
- Human tissue damage caused by exposure to intense cold.
- Frozen Dew
- When liquid dew changes into tiny beads of ice. This occurs when dew forms and temperatures later drop below freezing.
- Frost- Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32°F. As with the term "freeze," this condition is primarily significant during the growing season. If a frost period is sufficiently severe to end the growing season or delay its beginning, it is commonly referred to as a "killing frost." Because frost is primarily an event that occurs as the result of radiational cooling, it frequently occurs with a thermometer level temperature in the mid-30s.
- A specific aerial spray dispersion model. The acronym comes from the names of the sponsor and developers (Forest Service, Cramer, Barry, Grim).
- Feet (or foot)
- An Internet server application which provides access to Internet FTP server files via e-mail. The National Weather Service operates an FTPMAIL server which provides e -mail access to any product available on the tgftp.nws.noaa.gov FTP server including marine text and graphic forecasts. For further information see: http://weather.noaa.gov/pub/fax/ftpmail.txt, or send an e-mail to firstname.lastname@example.org with the word "help" in the body.
- Fugitive Dust
- Dust that is not emitted from definable point sources such as industrial smokestacks. Sources include open fields, roadways, storage piles, etc.
- Fujita Scale
- (or F Scale) - A scale of tornado intensity in which wind speeds are inferred from an analysis of wind damage:
|F0 (weak)||40-72 mph, light damage
|F1 (weak)||73-112 mph, moderate damage
|F2 (strong)||113-157 mph, considerable damage
|F3 (strong)||158-206 mph, severe damage
|F4 (violent)||207-260 mph, devestating damage
|F5 (violent)||260-318 mph (rare), incredible damage
All tornadoes, and most other severe local windstorms, are assigned a single number from this scale according to the most intense damage caused by the storm.
- Fujiwhara Effect
- A binary interaction where tropical cyclones within a certain distance (300-750 nm depending on the sizes of the cyclones) of each other begin to rotate about a
- Full-Physics Numerical Model
- A computer model used to calculate air pollution concentrations. A full-physics numerical model uses a full set of equations describing the thermodynamic and dynamic state of the atmosphere and can be used to simulate atmospheric phenomena.
- A pattern of plume dispersion produced when a convective boundary layer grows upward into a plume trapped in a stable layer. The elevated plume is suddenly brought downward to the ground, producing high surface concentrations.
- Funnel Cloud
- A condensation funnel extending from the base of a towering cumulus or Cb, associated with a rotating column of air that is not in contact with the ground (and hence different from a tornado). A condensation funnel is a tornado, not a funnel cloud, if either a) it is in contact with the ground or b) a debris cloud or dust whirl is visible beneath it.
- The process whereby wind is forced to flow through a narrow opening between adjacent land areas, resulting in increased wind speed.
- Forecast Verification Tool
- NGM MOS Guidance
- freezing rain
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