First ever ETKF maps using 40-member NCEP ensemble, comprising 10 members from each initialization time 2004051500, 2004051418, 2004051412 (+12h), 2004051406 (+12h).

"Official" initialization time is given as 2004051500.

Summary maps are provided, using a wind velocity norm and a verification region of radius 500km centered on the red hurricane symbol at 96h past the ensemble initialization time 00Z 15 May (i.e. verifying 00Z 19 May).

The summary maps suggest that the typhoon is the best place to fly, with a a little extra emphasis on the steering flow to the east/northeast and the big trough over China. The forecast ensemble spread valid at the targeting time is given for comparison.

Targeting at +24h refers to flying at 00Z 16 May
Targeting at +48h refers to flying at 00Z 17 May
Targeting at +72h refers to flying at 00Z 18 May
Verification time is +96h in all cases (00Z 19 May)

Signal variance maps have been produced for the two projected flight times (12Z 16th, 12Z 17th). Planned dropwindsonde locations are shown in the top left-hand figure, which corresponds to the targeted observing time. The region of maximum signal variance coincides with the typhoon as it evolves over 84h past the targeted observing time.