Qualitative Verification of the Operational GFS and the Ensemble Mean 12UTC 13 March 2003 Serena Chew

Discussion Topics Initialization GFS control run 144 hour forecast 240 hour forecast 372 hour forecast

GFS Initialization of the 500mb heights and vorticity valid for 12UTC 13 March 2003 Focus on the Eastern Pacific –A trough off the West Coast Notice the zonal jet

Ensemble Mean Spread and Normalized Ensemble Spread Valid for 144h Focus on Eastern Pacific –On the left: A moderate jet off West Coast. –On the right: A stronger jet off West Coast. Notice large spread (blue areas) on the right chart

Spaghetti Plot of all the Ensemble models Valid for 144h Ensemble Mean and GFS are almost in agreement

240 hour Ensemble Spread Notice the spread on both charts Notice the height pattern on the Eastern Pacific –On the left: At 140 o W a trough and a ridge off California Coast. –On the right: At 140 o W a split jet and a weak ridge off West Coast.

Spaghetti plot for 240h forecast Valid for Notice the disagreement for the 522 height contour on all the ensembles. The 564 height contour is somewhat in agreement with the ensembles.

372 hour Ensemble Spread Valid for Notice the height pattern on both charts –On the left: A deep trough off California Coast –On the right: A weak trough off West Coast Notice the spread

Conclusions –Off the West Coast, a trough is verified. –The 144 hour forecast predicted better that the 240 and 372 hour forecasts.

The End