ON THE NEED FOR VOLUMETRIC RADAR DATA WHEN ISSUING ...

14
National Weather Digest
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Fig. 9. Four reflectivity slices (OS, 1S, 2.4° and 4.3° elevation angles) from the Twin Lakes (near Oklahoma City, Oklahoma) WSR-88D
system 2304 UTC, 26 April 1991. This storm is exhibiting a WER on the south side of the storm.
supercell, even though a hook echo was never apparent with
the storm.
4.3 WSR-88D Strategy for Examining Storms
New observational data and computers to deal with radar,
satellite and environmental conditions will be implemented
gradually into future modernized weather offices. Those
forecasters using the WSR-88D system must take advantage
of the exciting new capabilities the system has to offer. The
combination of the better resolution reflectivity data and the
addition of the mean radial velocity will greatly enhance
forecasters ' abilities to warn for dangerous storms. Also,
forecasters will have more time to scrutinize the data, since
the radar will sample several elevation angles automatically
and create displays for each elevation angle sampled. The
WSR-88D system will collect reflectivity and velocity data
at either 9 or 14 different elevation angles every 5 or 6 min.
(Lemon et al. 1992). The operator can display at the Principal
User Processor (PU P; Alberty 1990) the best elevation angles
to examine the low, middle, and upper regions of a storm
and then interpret the data to determine the storm's potential
severity (as illustrated in Figs. 9 and 10). All of this can be
done easily and repeatedly and in a few seconds through the
use of a User Function (Lemon et aI., 1992).
The three-dimensional evaluation of the storm with four
slices of reflectivity and velocity will be the best radar method
to anticipate the development of mesocyclones before the
detection algorithms indicate their presence, as well as validate
or refute the algorithm output. The same criteria
described by Lemon (1980) for issuing severe thunderstorm
and tornado warnings can be used with the WSR-88D system,
although the three-dimensional storm structure features are
emphasized rather than the specific values. If one is monitoring
the reflectivity structures properly with this system, forecasters
will be able to watch the three-dimensional reflectivity
structure evolve from non-severe to severe storms
before that evolution is evident in the velocity fields (Lemon
and Doswell 1979). The WSR-88D system also will store all
products received at the PUP during the event on an optical