Dear Linda,

Woody Roberts pointed out a mistake in the written summary of our meeting
in Norman.  Could you replace the first paragraph of the section titled
"Why Level II Data" with the following?  Thanks!

By the way, I'll send along a figure that shows these runs so you can put
it on the web page.


Kelvin Droegemeier gave a briefing which depicted the impact on storm-scale
NWP of using NIDS versus wide band data.  Three different experiments were
made using the ARPS model at 2 km resolution over all of Kansas and Oklahoma.
The model was applied to the Lahoma, Oklahoma supercell storm, which began
as a multicell in central Kansas, became a supercell as it moved southward
into Oklahoma, and eventually became a bow echo in north Texas.  Overall it
had a lifetime exceeding 8 hours.

In all experiments, the ARPS was initialized using the RUC analysis to
provide the background fields, to which were assimilated Oklahoma Mesonet, wind
profiler, and SAO surface observations.  A run using this configuration
was compared to an experiment in which NIDS reflectivity data were also
added (including various assumptions about the motion and other water substance fields), and to an experiment in which the same storm was
initialized using full WSR-88D level II data and the Shapiro single-Doppler
velocity retrieval scheme (which provides high-resolution cross-beam and
vertical winds, along with temperature and pressure fields).  All forecasts
were run for 2 hours and 20 minutes:

Expt #1:   RUC analysis + Mesonet + profiler + SAO
Expt #2:   RUC analysis + Mesonet + profiler + SAO + NIDS
Expt #3:   RUC analysis + Mesonet + profiler + SAO + Level II (+ retrieval)

Without any radar data at all, the model never generated a storm. With NIDS data added, the storm died out within 30 minutes. With full level II data used instead of NIDS, the isolated intense storm maintained its structure, as observed, and moved in the correct direction. These runs clearly show that, without full wide band data, storm-scale NWP will, in many cases, simply not be possible (of course, when forcing is strong, e.g., in terrain, along fronts and drylines), the importance of wide band data becomes more problematic.

Prof. Kelvin K. Droegemeier, Director        E-mail: kkd@xxxxxx
Center for Analysis and Prediction of        Phone:  405-325-0453
 Storms                                     FAX:    405-325-7614
University of Oklahoma                       WWW:
Sarkeys Energy Center, Rm 1110             
100 East Boyd Street
Norman, OK  73019  USA