Subj : Wx Terms (W)(2)
To : All
From : Daryl Stout
Date : Sun Sep 24 2017 12:09 am
WCM
Warning Coordination Meteorologist
WDIR
On a buoy report, wind direction (the direction the wind is coming from
in degrees clockwise from true N) during the same period used for WSPD.
WDLY
Widely
WDSPRD
Widespread
Weak Echo Region
(Abbrev. WER) - A WSR-88D radar product which displays reflectivity for
up to 8 elevation angles for a radar operator selected location as a set
presentation of a storm. The plains in this product are presented in an
ascending order, lowest plain is lowest elevation angle selected. It is
used to depict storm tilt and to identify Weak Echo Regions (WER) and
Bounded Weak Echo Regions (BWER) in thunderstorms.
Weather
The state of the atmosphere with respect to wind, temperature,
cloudiness, moisture, pressure, etc. Weather refers to these conditions
at a given point in time (e.g., today's high temperature), whereas
Climate refers to the "average" weather conditions for an area over a
long period of time (e.g., the average high temperature for today's date).
Weather Forecast Office
(Abbrev. WFO) - this type of National Weather Service office is
responsible for issuing advisories, warnings, statements, and short term
forecasts for its county warning area.
Weatherfax
See RADIOFACSIMILE
Wedge Tornado
Slang for a large tornado with a condensation funnel that is at least as
wide (horizontally) at the ground as it is tall (vertically) from the
ground to cloud base. The term "wedge" often is used somewhat loosely to
describe any large tornado. However, not every large tornado is a wedge.
A true wedge tornado, with a funnel at least as wide at the ground as it
is tall, is very rare.
Wedges often appear with violent tornadoes (F4 or F5 on the Fujita Scale),
but many documented wedges have been rated lower. And some violent
tornadoes may not appear as wedges (e.g., Xenia, OH on 3 April 1974,
which was rated F5 but appeared only as a series of suction vortices
without a central condensation funnel). Whether or not a tornado achieves
"wedge" status depends on several factors other than intensity - in
particular, the height of the environmental cloud base and the
availability of moisture below cloud base. Therefore, spotters should not
estimate wind speeds or F-scale ratings based on visual appearance alone.
However, it generally is safe to assume that most (if not all) wedges have
the potential to produce strong (F2/F3) or violent (F4/F5) damage.
WEFAX
System for transmitting weather charts and imagery via satellite.
Occasionally used as an abbreviation for radiofacsimile via HF radio.
Weighing-Type Precipitation Gage
A rain gage that weighs the rain or snow which falls into a bucket set on
a platform of a spring or lever balance. The increasing weight of its
contents plus the bucket are recorded on a chart. The record thus shows
the accumulation of precipitation.
Weir
In hydrologic terms,
(a) A low dam built across a stream to raise the upstream water level
(fixed-crest weir when uncontrolled);
(b) A structure built across a stream or channel for the purpose of
measuring flow (measuring or gaging weir).
WER
Weak Echo Region - Radar term for a region of relatively weak reflectivity
at low levels on the inflow side of a thunderstorm echo, topped by
stronger reflectivity in the form of an echo overhang directly above it.
The WER is a sign of a strong updraft on the inflow side of a storm,
within which precipitation is held aloft. When the area of low
reflectivity extends upward into, and is surrounded by, the higher
reflectivity aloft, it becomes a BWER.
West African Disturbance Line
A line of convection about 300 miles long, similar to a squall line. It
forms over west Africa north of the equator and south of 15 degrees
North latitude. It moves faster than an Easterly Wave between 20 and 40
mph. They move off the African coast every 4 to 5 days mainly in the
summer. Some reach the American tropics and a few develop into tropical
cyclones.
West Wall
The coast side boundary of the Gulf Stream, typically south of Cape
Hatteras. See also North Wall.
Westerlies
The prevailing winds that blow from the west in the mid-latitudes.
Wet Bulb Zero
(Abbrev. WBZ) - the height where the wet-bulb temperature goes below 0�C.
It is important because WBZ heights between 7000 ft and 10,500 ft (above
ground level) correlate well with large hail at the surface when storms
develop in an airmass primed for strong convection. Higher values infer
mid and upper level stability and also indicate a large melting area for
falling hail. Lower WBZ heights indicate that the low level atmosphere is
often too cool and stable to support large hail.
Wet Floodproofing
In hydrologic terms, an approach to floodproofing which usually is a last
resort. Flood waters are intentionally allowed into the building to
minimize water pressure on the structure. Wet Floodproofing can include
moving a few valueable items to a higher place or completely rebuilding
the floodable area. Wet floodproofing has an advantage over other
approaches: no matter how little is done, flood damage will be reduced.
Thousands of dollars in damage can be avoided just by moving furniture and
appliances out of the flood-prone area.
Wet Microburst
A microburst accompanied by heavy precipitation at the surface. A rain
foot may be a visible sign of a wet microburst.
Wet-Bulb Temperature
The lowest temperature that can be obtained by evaporting water into the
air.
Wetland
In hydrologic terms, an area that is regularly wet or flooded and has a
water table that stands at or above the land surface for at least part of
the year.
WFO
Weather Forecast Office - this type of National Weather Service office is
responsible for issuing advisories, warnings, statements, and short term
forecasts for its county warning area.
WFP
Warm Front Passage
Whirlwind
A small, rotating column of air; may be visible as a dust devil.
White Light (WL)
Sunlight integrated over the visible portion of the spectrum (4000 to
7000 angstroms) so that all colors are blended to appear white to the
eye.
White Light Flare
In solar-terrestrial terms, a major flare in which small parts become
visible in white light. Such flares are usually strong X-ray, radio, and
particle emitters.
Whitecap
The breaking crest of a wave, usually white and frothy.
Widespread
Areal coverage of non-measurable, non-convective weather and/or
restrictions to visibility affecting more than 50 percent of a forecast
zone(s).
Wildfire
Any free burning uncontainable wildland fire not prescribed for the area
which consumes the natural fuels and spreads in response to its
environment.
Wildlands
Any nonurbanized land not under extensive agricultural cultivation,
e.g., forests, grasslands, rangelands.
Willy-Willy
A tropical cyclone of hurricane strength near Australia.
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.
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