SR SSD 2001-21

Technical Attachment

Easy PRF Selection with Open RPG

George Phillips
WFO Topeka, KS

The Open RPG (ORPG) was installed at WFO Topeka in mid-August. Overall, suffice it to say, we like it a LOT! By way of example why I say that, the discussion below deals with just one, nice enhancement which this system provides over the old way of doing business.

The capability of manually changing the pulse repetition frequency (PRF), and thus the maximum unambiguous range (MUR), has been there since the WSR-88D was installed. My feeling is this capability has been underutilized at a lot of offices, sometimes including ours. There are some good reasons for this:

The only concern in the above list that is still valid with the ORPG is the fifth one; the others are no longer a worry...

Last night was the first example at our office where this enhancement was really useful - when we were confronted with a tornadic supercell about 100 nm from the radar. Because we also had storms at 20 nm from the radar along the same radial, the velocities within the tornadic supercell were mostly range-folded (AutoPRF had chosen the PRF associated with the 80 nm MUR to minimize the overall total range folded area). The supercell was closest to another office's RDA, but outside of their CWA and not threatening it. The storm was about 85 nm from their RDA and the velocity information was obscured. We couldn't really use their radar for investigation.

I turned AutoPRF off, resized the sector to cover an area that contained the supercell, tried out different PRFs to see which would be best, and then selected it. I checked the other sectors for any concerns, then downloaded the new PRF. All this took less than two minutes, and there were no surprises when the next volume scan started. As the storm moved inside 90 nm from our RDA, I just pulled the MUR out to 94 nm for that sector.

Changing the MUR in certain circumstances can be extremely useful. This information, based on our early experience, is being shared in the hope it will alert others to the potential that comes with ORPG. In the particular case of PRF/MUR adjustments during the heat of battle, I'm sure others will find radar operations significantly enhanced with the new system.