Could someone please explain what exactly the POPs in this morning's NWS forecast mean?
Driving in to the university, in steady light to moderate rain, I heard the following forecast on NPR for the Tucson area.
Today: Mostly cloudy. Numerous showers and thunderstorms early in the morning...then scattered showers and thunderstorms. Highs 87 to 92. West wind 5 to 15 mph. Chance of precipitation 60 percent.
This is still the forecast at 9:30 am for the Tucson metro area, even though it has been raining across the metro area since 1200 UTC. The NPR forecast was followed by news about the roads that are currently closed due to flooding washes. The observations at TUS (verification point for the forecast) since 1200 UTC have been:
Day Time VSBY WX 1hr precip
27 Jul 8:55 am 10.00 -RA 0.02
27 Jul 7:55 am 10.00 -RA 0.04
27 Jul 7:30 am 3.00 RA
27 Jul 6:55 am 10.00 -RA T
27 Jul 5:55 am 10.00 -RA 0.01
27 Jul 5:10 am 10.00 -RA
27 Jul 4:55 am 10.00 -RA 0.07
Perhaps the POPs mean that when the current rain stops, then there will be a 60% chance of more rain later today?
Or, perhaps I just don't understand how the NWS defines and uses POPs anymore.
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