Saturday, June 18, 2016

Tomorrow And Monday As Forecast By WRF-NAM

Have taken a quick look at the 06 UTC WRF-NAM forecasts from Atmo for tomorrow and Monday (June 19 and 20). Forecast above is 2-m temperature valid at 3:00 pm MST on Sunday - certainly not a good afternoon for anything outside, with deadly heat levels.

On Monday afternoon the WRF-NAM forecasts thunderstorms in Pima County - above forecast of composite radar echoes is valid at 6:00 pm. That model even puts down 1/10 inch of rain at airport. However, the GFS version is now much less active for Monday.

The forecast 2:00 PM skewT from the WRF-NAM is shown below. The well-mixed boundary layer is very deep , extending up to above 600 mb. The model computes CAPE of over 800 J/kg; however that number is an over-estimate and my eyeball says actual CAPE of about half that. Very hard to get much except wind and dust at low elevations with a sounding like this.

To see what NWS is actually forecasting for the airport, I had to dig around on their web page to find the hourly time-series of the grid point forecasts. Below is a snip from those plots showing Monday the 20th - blue is sky cover (%); green is RH (%); and brown is POPs (%). So the official forecast is for 5% POPs for a number of hours during Monday afternoon and evening.

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