Subj : Wx Terms (V)(2)
To   : All
From : Daryl Stout
Date : Mon Oct 23 2017 12:05 am

VIS

1. Visible satellite imagery

2. Visibile or Visibility

Visibility
The distance at which a given standard object can be seen and identified
with the unaided eye.

Visibility Protection Program
The program specified by the Clean Air Act to achieve a national goal of
remedying existing impairments to visibility and preventing future
visibility impairment throughout the United States.

Visible Satellite Imagery
This type of satellite imagery uses reflected sunlight (this is actually
reflected solar radiation) to see things in the atmosphere and on the
Earth's surface. Clouds and fresh snow are excellent reflectors, so they
appear white on the imagery. Clouds can be distinguished from snow,
because clouds move and snow does not move. Meanwhile, the ground
reflects less sunlight, so it appears black on the imagery. The
satellite uses its 0.55 to 0.75 micrometer (um) channel to detect this
reflected sunlight. Since this imagery relies on reflected imagery, it
cannot be used during night.

Visual Spectrum
The portion of the electromagnetic spectrum to which the eye is
sensitive, i.e., light with wavelengths between 0.4 and 0.7
micrometers. Compare shortwave radiation and longwave radiation.

VLCTY
Velocity

VLY
Valley

VMD
Volume median diameter. A statistical measure of the average droplet
size in a spray cloud, such that fifty percent of the volume of
sprayed material is composed of droplets smaller in diameter than the
VMD.

Volcanic Ash
Fine particles of mineral matter from a volcanic eruption which can be
dispersed long distances by winds aloft. The chemical composition and
abrasiveness of the particles can seriously affect aircraft and also
machinery on the ground. If it is blown into the stratosphere and it
is thick enough, it can decrease the global temperature.

Volume Scan
A radar scanning strategy in which sweeps are made at successive antenna
elevations (i.e., a tilt sequence), and then combined to obtain the
three-dimensional structure of the echoes.

Volume Velocity Processing
A way to guess the large-scale 2-dimensional winds, divergence and fall
speeds from one-dimensional radial velocity data. Essentially a
multivariate regression which fits a simple wind model to the observed
radial velocities. Very similar to VAD and EVAD, except it uses different
functions for the fit.

Voluntary Observing Ship Program
(VOS) - An international voluntary marine observation program under the
auspices of the World Meteorological Organization (WMO). Observations
are coded in a special format known as the ships synoptic code, or
"BBXX" format. They are then distributed for use by meteorologists in
weather forecasting, by oceanographers, ship routing services, fishermen,
and many others.

Vort Max
Common slang reference to Vorticity Maximum; a center, or maximum, in
the vorticity field of a fluid.

Vortex
A whirling mass of air in the form of a column or spiral. It need not be
oriented vertically but, for example, could be rotating around a
horizontal axis.

Vorticity
A measure of the rotation of air in a horizontal plane. Positive
(counter-clockwise or cyclonic) vorticity can be correlated with surface
low development and upward vertical motion (in areas of positive
vorticity advection).

VOS
(Voluntary Observing Ship Program) - An international voluntary marine
observation program under the auspices of the World Meteorological
Organization (WMO). Observations are coded in a special format known as
the ships synoptic code, or "BBXX" format. They are then distributed for
use by meteorologists in weather forecasting, by oceanographers, ship
routing services, fishermen, and many others.

VOT
Vorticity

VR
Veer

VRT MOTN
Vertical motion

VSB
Visible Satellite Imagery

VSBY
Visibility

VTEC
(Valid Time Event Code) - The Valid Time Event Code (VTEC) always is used
in conjunction with, and provides supplementary information to, the
Universal Geographic Code (UGC), to further aid in the automated delivery
of National Weather Service text products to users. The VTEC is included
in many event driven or non-routine products and in some routine Marine
forecasts. The VTEC provides information on the event, while the UGC
describes the affected geographic area.

VVP
Volume Velocity Processing - a way to guess the large-scale 2-dimensional
winds, divergence and fall speeds from one-dimensional radial velocity
data. Essentially a multivariate regression which fits a simple wind
model to the observed radial velocities. Very similar to VAD and EVAD,
except it uses different functions for the fit.

VVSTORM
Model-based convection algorithm.

VWP
VAD Wind Profile - a radar plot of horizontal winds, derived from VAD
data, as a function of height above a Doppler Radar. The display is
plotted with height as the vertical axis and time as the horizontal axis
(a so-called time-height display), which then depicts the change in wind
with time at various heights. This display is useful for observing local
changes in vertical wind shear, such as backing of low-level winds,
increases in speed shear, and development or evolution of nearby jet
streams (including low-level jets). This product often is referred to
erroneously as a VAD.


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