Friday, February 16, 2018

Friday Morning Rainfall Amounts

Ghostly telescope structures in the cloud at Kitt Peak this morning. Total event rainfall amounts to 7:00 am MST this morning across the ALERT network (below) show that the event has produced generally over an inch of rain - much higher amounts in the Catalinas and Rincons. The 0.23" at Rincon Creek and X-9 Ranch appears very low, and there may be problems at that site. The subtropical moisture plume did a direct hit to our area, resulting in rainfall amounts that considerably exceeded the forecasts.

This afternoon poses another dilemma. The 06 UTC plumes for QPF at TUS (above) indicates 100% chances for measurable rain at the airport this afternoon - timing is very consistent but amounts range from less than 0.10" to 0.80" - a very large spread at a very short lead time. The 06 UTC WRF-GFS forecast of composite radar echoes below is valid at 3:00 pm this afternoon and indicates another band of light showers across eastern Pima County. I expect that the amount at airport will be lower than both operational GFS (blue) and the mean GEFS amounts (heavy black). The moisture remains high, but a layer of middle-level dry air has moved across the area early this morning. That will tend to suppress shower activity unless more moist air replaces it, or sunshine breaks out and triggers deeper convective showers. Will be interesting to watch how the day evolves.

NOTE - my previous post about the GEFS and its grid point interpolations has some serious errors that I have uncovered, and I will report on latest findings this afternoon.

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