Friday, April 08, 2016

Widespread, But Mostly Light Rains During Night

The first phase of our April wet period ended during the early morning hours, after widespread rainfall covered all of the ALERT network area of Pima County. Coverage was at 100% (as the models had been forecasting for days), but amounts were generally light. The exceptions were up high in the Catalinas and over southern portions of the ALERT network where there were thunderstorms. The situation is well depicted by the three ALERT sectors shown here - the Catalinas, the metro-west area, and the southwest area (top to bottom of the first three graphics). The airport had 0.22", DM had 0.21", and we had 0.19" here at the house.

The humidity, smell of rain, and then the actual rainfall were very much appreciated here; some light sprinkles along with the fragrant smell of rain began here about 7:30 pm MST last evening. Generally the GEFS and WRF model runs at Atmo were quite good, especially with forecasting the 100% coverage across Pima County. The WRF-GFS forecasts of amounts were fairly accurate as the event approached, but amounts were heavier than forecast down south where the thunderstorm activity was embedded. The GEFS members were generally close or a bit conservative for the amounts forecast at the airport. But, all-in-all this was an excellent example of how good the model forecasts can be in many situations these days.

The graphic above, from Atmo and Vaisala, shows detected cloud-to-ground flashes during past 24-hours ending at 4:00 am this early morning. The WRF models from 06 UTC this morning are forecasting some showers and thunderstorms along the northeastern edges of Pima County this afternoon, but with the bulk of rainfall staying mostly north and a bit east of our area.

However, the models are now emphasizing the next phase of the wet period to be more active on Sunday, with some strong storms possible. The QPF plumes for the airport (below) from 06 UTC are much more optimistic for the airport (TUS) this afternoon than are the WRF forecasts. Note that 100% of the ensemble members are again forecasting rainfall Sunday afternoon and night at TUS, but still with a fairly large spread in amounts (ranging from a bit more than 0.20" (red) to about 0.80" (blue). The operational member (blue) has gone very wet and is a serious outlier,with its forecast of heaviest rains at airport on Sunday.

All said, nice to finally have some rain, after such a long dry spell.

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