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Cold air funnel - A funnel cloud
or (rarely) a small relatively weak
tornado that can develop from a small
shower or thunderstorm when the air
aloft is unusually cold. They are much
less violent than other types of
tornadoes.
Crest - The highest level of a
flood wave as it passes a point.
Degree Day - Gauges the amount
of heating or cooling needed for a
building using 65 °F as a baseline. To
compute degree days, the average
temperature for a day is taken and
referenced to 65 °F. An average
temperature of 50 °F yields 15 heating
degree days, while an average
temperature of 75 °F would yield 10
cooling degree days.
Dew Point - A measure of
atmospheric moisture. It is the
temperature to which air must be cooled
in order to reach saturation (assuming
pressure and moisture content are
constant).
Doppler Radar - Radar that can
measure radial velocity, the
instantaneous component of motion
parallel to the radar beam (i.e., toward
or away from the radar).
Downburst - A strong downdraft
from a thunderstorm resulting in an
outward burst of damaging winds on or
near the ground. Downburst winds are
often 50 to 100 mph (80 to 160 km/h) and
in a few cases, 100 to 150 mph (160 to
240 km/h). They can do as much damage as
a small tornado.
Microburst - a small downburst
affecting an area less than 2 1/2 miles
(4 km) in diameter with peak winds
lasting generally less than five
minutes.
Macroburst - a large downburst
affecting an area greater than 2 1/2
miles (4 km) in diameter with peak winds
generally lasting five minutes or
longer.
Flood Stage - The level or stage
at which a stream overflows its banks or
the stage at which the overflow of a
stream begins to cause damage.
Freezing Rain/Freezing Drizzle -
Rain or drizzle which falls in liquid
form and freezes on impact with cold
surfaces to form a glaze on the ground
and exposed objects.
Funnel Cloud - A rotating column
of air, extending from a towering
cumulus or cumulonimbus cloud, that is
not in contact with the ground.
Gustnado - A gust front tornado.
A small, weak, short-lived tornado that
occurs along a gust front - the leading
edge of a thunderstorm, caused by
rain-cooled air flowing out from the
storm's downdraft. A gustnado is often
visible as a debris cloud or dust whirl.
Hail - Precipitation in the form
of lumps of ice that form during some
thunderstorms.
Heat Index - The apparent
temperature that describes the combined
effect of high temperatures and high
levels of humidity, which reduces the
body's ability to cool itself.
Rain/Showers - Rain is a nearly
steady and uniform fall of precipitation
over an area. Showers are intermittent
and/or scattered convective rainfall of
varying intensity.
Relative Humidity - The ratio of
the amount of water vapor actually
present in the air to the greatest
amount possible at the same temperature.
Sleet - Sleet or ice pellets are
solid grains of ice formed from the
freezing of rain or the refreezing of
melted snow, which bounce off the ground
and other objects.
Squall line - A line of
thunderstorms or squalls which may
extend over several hundred miles.
Tornado - A violently rotating
column of air, from a thunderstorm, in
contact with the ground.
Virga- Precipitation that dries
up in the atmosphere and therefore does
not reach the ground.
Waterspout - In general, a
tornado occurring over water.
Specifically, it refers to a small,
relatively weak rotating column of air
over water beneath a towering cumulus or
cumulonimbus cloud. A waterspout may
rotate counter-clockwise or clockwise.
Wind Chill - An apparent
temperature that describes the combined
effect of wind and low temperature on
exposed skin.
See also
References
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