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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 the 6-hourly QPF from the Global Ensemble Forecast
System (GEFS) Mean for forecast hours 78-120 hours (or 126-168 hours
in the case of the day 6-7 QPF), then checking for GEFS 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 GEFS_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
GEFS 6-hour QPF at that projection time is divided by the GEFS 48-hour QPF.
Then that quotient is multiplied by the WPC 48-hour QPF.
If GEFS_48-hr QPF > 0, then (GEFS_6-hr QPF / GEFS_48-hr
QPF) x WPC 48-hour QPF
GIF images are then made from the post processed grid data.
At this time we are using the GEFS MEAN, but we may
incorporate ensemble QPF from the CMC MEAN and ECMWF MEAN in the near
future.
Return to the Experimental Forecast Page
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