Subj : Wx Terms (F)(1)
To   : All
From : Daryl Stout
Date : Sat Oct 07 2017 12:04 am

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
or

2) Fog- Water droplets suspended in the air at the Earth's surface. Fog
is often hazardous when the visibility is reduced to � 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.

FA
Forecast Area

FAA
Federal Aviation Administration

Face
In hydrologic terms, the external surface of a structure, such as the
surface of a dam.

Facula
In solar-terrestrial terms, a bright region of the photosphere seen in
white light, seldom visible except near the solar limb.

Fahrenheit
(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

Fair
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 conditions.

Fall
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.

Fallstreak
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.

FAN
AVN MOS Guidance (older version)

Fanning
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.

FASTST
Fastest

Fathom
Unit of water depth equal to 6 feet.

FAWS
Flight Advisory Weather Service

FBO
(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.

FCST
Forecast

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.

FEMA
Federal Emergency Management Agency. An agency of the federal government
having responsibilities in hazard mitigation; FEMA also administers the
National Flood Insurance Program.

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.

Fetch
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.

3. The distance of the water or the homogenous type surface over which the
wind blows without appreciable change in direction.

Few
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.

FFG
Flash Flood Guidance

FG
(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
� mile or less.

Fibril
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.

Filament
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 disappeared.

Fill Dam
In hydrologic terms, any dam constructed of excavated natural materials
or of industrial wastes.

Filling
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.

Firebrand
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.


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