Subj : Wx Terms (D)(2)
To   : All
From : Daryl Stout
Date : Sun Nov 05 2017 12:04 am

DEP
Departure

Depletion Curve
In hydrologic terms, the part of the hydrograph extending from the point
of termination of the Recession Curve to the subsequent rise or
alternation of inflow due to additional water becomming available for
stream flow.

Depression
A region of low atmospheric pressure that is usually accompanied by low
clouds and precipitation. The term is also sometimes used as a reference
to a Tropical Depression.

Depression Storage
In hydrologic terms, the volume of water contained in natural depressions
in the land surface, such as puddles.

Depth of Runoff
In hydrologic terms, the total runoff from a drainage basin, divided by
its area. For convenience in comparing runoff with precipitation, the
term is usually expressed in inches of depth during a given period of
time over the drainage area or acre-feet per square mile.

Derecho
(Pronounced day-RAY-cho), a widespread and usually fast-moving windstorm
associated with convection. Derechos include any family of downburst
clusters produced by an extratropical MCS, and can produce damaging
straight-line winds over areas hundreds of miles long and more than
100 miles across.

Derived Products
Processed base data on the Doppler radar.

Desertification
A tendency toward more prominent desert conditions in a region.

Design Criteria
In hydrologic terms, the hypothetical flood used in the sizing of the
dam and the associated structures to prevent dam failure by overtopping,
especially for the spillway and outlet works.

Detention Basins
In hydrologic terms, structures which are built upstream from a
populated area so that precipitation flows do not flood and cause the
loss of life or property. They are normally dry, but are designed to
detain surface water temporarily during, and immediately after a runoff
event. Their primary function is to attenuate the storm flows by
releasing flows at a lower flow rate. There are no gates or valves
allowed on the outlet so that water can never be stored on a long-term
basis. Typical detention times in such a basin would be on the order of
24 to 72 hours although some are as long as 5 to 10 days.

Detention Storage
In hydrologic terms, the volume of water, other than depression storage,
existing on the land surface as flowing water which has not yet reached
the channel.

Detritus
In hydrologic terms,

(1) the heavier mineral debris moved by natural watercourses, usually in
bed-load form.

(2) the sand, grit, and other coarse material removed by differential
sedimentation in a relatively short period of detention.

Developing Gale/Storm
In the high seas and offshore forecasts, a headline used in the warnings
section to indicate that gale/storm force winds are not now occurring but
are expected before the end of the forecast period.

Dew
Moisture that has condensed on objects near the ground, whose temperatures
have fallen below the dewpoint temperature.

Dew Point
(Abbrev. DWPT) - A measure of atmospheric moisture. It is the temperature
to which air must be cooled in order to reach saturation (assuming air
pressure and moisture content are constant). A higher dew point indicates
more moisture present in the air. It is sometimes referred to as Dew Point
Temperature, and sometimes written as one word (Dewpoint).

Dew Point Depression
The difference in degrees between the air temperature and the dew point.

Dew Point Front
A narrow zone (mesoscale feature) of extremely sharp moisture gradient
and little temperature gradient. It separates moist air from dry air.
Severe weather can be associated with this front. It is also known as a
"dryline" or "dry front".

DEWP
On a buoy report, the dewpoint temperature taken at the same height as
the air temperature measurement.

DFUS
Diffuse

Diabatic
A process which occurs with the addition or loss of heat. The opposite of
adiabatic. Meteorological examples include air parcels warming due to the
absorption of infrared radiation or release of latent heat.

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.

Diagnostic Model
A computer model used to calculate air pollution concentrations. A
diagnostic model produces a wind field over an area by interpolating
from actual wind observations.

Diamond Dust
A fall of non-branched (snow crystals are branched) ice crystals in the
form of needles, columns, or plates.

Differential Motion
Cloud motion that appears to differ relative to other nearby cloud
elements, e.g. clouds moving from left to right relative to other clouds
in the foreground or background. Cloud rotation is one example of
differential motion, but not all differential motion indicates rotation.
For example, horizontal wind shear along a gust front may result in
differential cloud motion without the presence of rotation.

Differential Rotation
In solar-terrestrial terms, the change in solar rotation rate with
latitude. Low latitudes rotate at a faster angular rate (approx. 14
degrees per day) than do high latitudes (approx. 12 degrees per day).

Diffuse Ice
In hydrologic terms, poorly defined ice edge limiting an area of
dispersed ice; usually on the leeward side of an area of floating ice.

Difluence
(or diffluence) - A pattern of wind flow in which air moves outward
(in a "fan-out" pattern) away from a central axis that is oriented
parallel to the general direction of the flow. It is the opposite of
confluence.

Difluence in an upper level wind field is considered a favorable
condition for severe thunderstorm development (if other parameters are
also favorable). But difluence is not the same as divergence. In a
difluent flow, winds normally decelerate as they move through the region
of difluence, resulting in speed convergence which offsets the apparent
diverging effect of the difluent flow.

DIR

1. Direction

2. On a buoy report, the ten-minute average wind direction measurements
in degrees clockwise from true North.

Direct Flood Damage
In hydrologic terms, the damage done to property, structures, goods, etc.,
by a flood as measured by the cost of replacement and repairs.

Direct Hit
A close approach of a tropical cyclone to a particular location. For
locations on the left-hand side of a tropical cyclone's track (looking in
the direction of motion), a direct hit occurs when the cyclone passes to
within a distance equal to the cyclone's radius of maximum wind. For
locations on the right-hand side of the track, a direct hit occurs when
the cyclone passes to within a distance equal to twice the radius of
maximum wind. Compare indirect hit, strike.

Direct Runoff
In hydrologic terms, the runoff entering stream channels promptly after
rainfall or snowmelt. Superposed on base runoff, it forms the bulk of the
hydrograph of a flood.

Direct Solar Radiation
The component of solar radiation received by the earth's surface only
from the direction of the sun's disk (i.e. it has not been reflected,
refracted or scattered).

Directional Shear
The component of wind shear which is due to a change in wind direction
with height, e.g., southeasterly winds at the surface and southwesterly
winds aloft. A veering wind with height in the lower part of the
atmosphere is a type of directional shear often considered important
for tornado development.

Disappearing Solar Filament (DSF)
In solar-terrestrial terms, the sudden (timescale of minutes to hours)
disappearance of a solar filament (prominence).



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