WPC Day 4-5 QPF for 6-hour Intervals
The Weather Prediction Center (WPC)  is experimenting with 6-hourly QPF for Days 4-5. Currently the WPC issues a 48-hour QPF product which encompasses Days 4-5.
Using the GEMPAK software package, the 6-hourly experimental product displayed in the web drawer is derived by taking the 6-hourly QPF from the GEFS Mean for forecast hours 78-120 hours, then checking for QPF values equal to zero and 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) for each time stamp then written out to the post-processed grid file.

If  GEFS_MEAN = 0,   then  WPC_48-hr x 0.125

For grid points where the ensemble mean QPF is greater than zero, the GEFS 6-hour QPF at that time stamp is divided by the GEFS 48-hour QPF. Then that quotient is multiplied by the WPC 48-hour QPF.

If  GEFS_MEAN  > 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 currently using the GEFS MEAN, but hope to incorporate ensemble QPF from the CMC MEAN and ECMWF MEAN in the near future.
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