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WPC Day 4-7 QPF for 6-hour Intervals
The Weather Prediction Center (WPC) is experimenting with 6-hourly QPF for Days 6-7.
Currently the WPC issues two 48-hour QPF products which encompass Days 4-5 and Days 6-7.
Methodology
Using the GEneral Meteorological PAcKage (GEMPAK) software,
the 6-hourly experimental product displayed in the web drawer is
derived by taking an average the 6-hourly QPF means from the Global Ensemble Forecast
System (GEFS), the European Center Ensemble System (ECENS), and the Canadian Meteorological Center Ensemble (CMCE) for forecast hours 78-120 hours (or 126-168 hours in the case of the day 6-7 QPF), then checking for multi-ensemble mean 48-h QPF values equal to zero or greater than zero at each grid point.
For grid points equal to zero, the WPC 48-hour QPF is multiplied
by 1/8 (0.125) to get a 6-h accumulation for each projection time
written out to the post-processed grid file.
If Multi-Ensemble_48-hr QPF = 0, then WPC_48-hr x 0.125
For grid points where the ensemble mean 48-h QPF is greater than zero, the
Multi-Ensemble mean 6-hour QPF at that projection time is divided by the Multi-Ensemble mean 48-hour QPF.
Then that quotient is multiplied by the WPC 48-hour QPF.
If Multi-Ensemble_48-hr QPF > 0, then (Multi-Ensemble_6-hr QPF / Multi-Ensemble_48-hr
QPF) x WPC 48-hour QPF
GIF images are then made from the post processed grid data.
The change to using the Mulit-Ensemble Mean (GEFS+ECENS+CMCE) was made on July 28, 2015.
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