Question on WPC QPF graphics.

[Ed Lizard]

This is sort of a met question, but is less about meteorology, per se, how the atmosphere works, as to how a product is generated.

 

 

The rainfall graphics have too many significant figures to be hand generated.  QPF maxes of several inches to the second decimal point.

 

Thus, I am assuming it it is a composite or weighted average of several computer models.  When one reads a WPC disco, and they talk about a weighted blend between one model's op output and another model's ensembles, or some such, is there a computer program that can weight the various models rainfall predictions for a specific small area on the map, and thus generate a map that clearly looks computer generated?

 

 

One other point, about the rainfall maps and possible tropical systems, when one sees mention in the disco of a conference call with NHC, is that/can that be used to influence the rainfall predictions?

 

Thanks.

[Cory]

They probably use something similar (or perhaps the same thing) as WFOs to produce their forecasts. The Graphical Forecast Editor that is used at WFOs to produce all forecasts contains tools to average and weight different models, and the forecaster can also hand-edit the fields. For instance, you can use the model blend tool to incorporate 70% of the ECMWF QPF and 30% GFS, and the grid changes to match that, and you can also use manual tools such as the pencil tool to drag small areas around. It is also possible to only select certain areas and apply different changes to it, then add smoothing to incorporate it into surrounding areas. So what you're seeing is a computer generated graphic that may have substantial human thought and editing applied to it. 

 

The WPC and NHC coordinate on incoming tropical systems and discuss different model scenarios regarding track, etc, so WPC can have QPF forecasts consistent with NHC's thinking. They wouldn't want to put a heavy rainfall track down that doesn't make sense with respect to NHC's ideas. 

[ohleary]

http://www.hpc.ncep.noaa.gov/html/fam2.shtml#qpf