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<br />NEXRAD SAA (Snow Accumulation Algorithm) was developed for Level II dala. II was Ihereby
<br />limited in application to past events using Levell! data tapes and to a few real-time operations at
<br />Ihose radar siles using the WDSS (Warning Decision Support System) computer software.
<br />Forecasters who were fortunate to have the use of the SAA appreciated ils help in understanding
<br />regional snowfalls and were reluctant to yield the system to other users. Distribution of the
<br />algorithm 10 all northern (snowy) sites is wailing lor future improvements to the NEXAAD hardware
<br />and software systems everywhere.
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<br />In the interim, Reclamation wanted to study SAA pertormance in the Missouri and Mississippi River
<br />Basins. To do so, the SAA was modified to accept Level III data in near real time from a NIDS
<br />(NEXRAD Inlonnation Dissemination System) vendor. The resolution of Level III dala is only 4
<br />or 5 dBZ, depending on volume coverage pattern, while Level II data are at 0.5 dBZ resolution.
<br />Angular and range resolutions are the same, but no more than the first four tilts are available with
<br />NIDS data. Occultation and hybrid scan adjuslments and the z,-S relation remained the same as
<br />with Level II data. Use of Ihe NIDS data did not seriously degrade Ihe snow accumulation
<br />estimates.
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<br />During the first winter 01 testing. SAA accumulations (S and SO products) were provided lor five
<br />radars (Bismarck. KBIS; Aberdeen. KABR; Grand Forks, KMVX; Minneapolis. KMPX.lhe required
<br />site; and Duluth, KOLH). Accumulation updates were provided hourly for art live radars according
<br />to the approximate 4 km HRAP grid specified by the National Weather Service (NWS) National
<br />Operational Hydrologic Remole Sensing Center (NOHRSC), in Chanhassen, MN. A five-radar
<br />composite was also available. This composite was extended to include five additional radars thai
<br />extended from Duluth, MN to Great Faits. MT for the winter of 1999-2000 which is presented in
<br />real-time on the Internet at our web site (see Fig. 1).
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<br />;\,EXJ.t,.\f) WSR-HRO R.III...- SlIlm f)('pth and Wall'"
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<br />Figure 1. Nortb.'rn Plain... anrJ upper Mississippi compositc
<br />NEXI{Al> Sl't of 10 radars from Duluth. MN In Grcat Falls. MT.
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