VIL values will change with the seasons and from
location to location. For instance, warm, moist air
masses exhibit higher VIL values during severe
weather occurrences than cooler, dry air masses do.
Therefore, the product must be tailored to the area of
interest. In addition, strongly tilted or fast-moving
storms may produce unrepresentative VIL values.
VAD Wind Profile (VWP) Product
One of the most useful and unique products
generated by the WSR-88D is the VAD Wind Profile
(VWP). VAD stands for velocity/azimuth display, and
this program produces current upper wind information
on a continuous basis. The VAD Wind Profile is like
having real-time rawinsonde data at your disposal
every few minutes. It shows wind velocities at various
altitudes above the earth in l,000-foot increments, up
to 70,000 feet (fig. 2-39).
VWP provides easy-to-read climb winds for pilot
briefings. The wind plots of VWP are similar to the
wind plots on the Skew-T diagram and are updated
each volume scan. VWP depicts environmental flow
around the RDA and provides valuable insight into
general circulation patterns. Be aware that changes in
the vertical wind profile are clues to the location of
turbulence, inversions, boundary layers, and shear.
Theyre also helpful in determining frontal slope,
thermal advection, and the evolution of jet streams.
Different colors are used to indicate the reliability
of the wind data. For instance, green wind barbs
indicate that plenty of scatterers were available at that
particular azimuth and elevation, thus highly accurate
wind values are displayed. VWP is unique in that the
mere absence of data (plotted as ND) can itself be an
indicator. It suggests fewer scatterers, which implies
dryer air (common behind cold fronts). This same
technique also allows operators to view changes in
overall cloud coverage above the radars viewing area.
Products from the WSR-88D are grouped into
what three areas of application?
What is the purpose of the Routine Product Set
What is the purpose of an alert-paired product?
What does the Base Reflectivity product (REF)
A hook echo signature is associated with what
What does the color blue represent on the Base
Velocity product (VEL)?
Velocities from the Base Velocity product (VEL)
are relative to what major component of the
What is the most serious drawback to the
Composite Reflectivity (CR) product?
What is the primary purpose of the Vertical
Integrated Liquid (VIL) product?
What might a lack of data indicate when using
the VAD Wind Profile (VWP) product?
Echo Tops (ET) Product
Echo Tops (ET) is yet another specialty product
derived from base reflectivity. Its simplistic display
makes for easy interpretation, but also limits the
The ET product indicates heights of echoes, in
hundreds of feet above mean sea level (MSL). The ET
product shows only the highest echoes over a given
location and uses different colors to represent heights
(fig. 2-40). Targets returning less than 18.0 dBZ
(clouds) are completely omitted from the display. ET
provides forecasters with a valuable first look tool. It
allows them to monitor the highest echo tops
throughout the radar viewing area. Echo heights paint a
very good picture of current weather and make
excellent indicators of things to come. For this reason,
ET is of particular interest to forecasters and aviators.
For example, rapidly increasing echo tops might warn
of storm intensification, while decreasing tops indicate
weakening. A rapid collapse of echo tops may indicate
the onset of downburst conditions at the surface. Other
products should be used for additional guidance in
understanding the cause of such changes.
The ET algorithm does not tally a columns
reflectivity like VIL, nor does it depict the strongest
returns like CR. ET merely depicts the highest echoes
observed. The ET product can also be deceiving.
Plotted heights are not actual cloud tops, but rather the
tops of precipitation. The clouds themselves are
probably less than 18.0 dBZ, and thus extend well
beyond the ET heights.