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February 26, 2009 Meeting Summary

Vijay Tallapragada gave another status update on the 2009 HWRF T&E. He presented more preliminary results from cases that had been completed thus far in the Atlantic and East Pacific. For all Atlantic storms completed to date, the track and intensity errors were shown. The track error plot showed lower H209 errors compared with H047 (new GFS/GSI) and HWRF (operational model) through 96 hours, after which, there was a slight degradation. The degradation could be attributed to Bertha (02L), whose model issues were detailed in last week's presentation. Without Bertha, there was slight improvement overall. The intensity error plot shows slightly larger error values for H209 compared to HWRF and H047 through 24 hours, then lower H209 errors through 96 hours before degrading. This could be caused by the positive bias seen for storms Hanna (08L) and Fay (06L), which showed larger storm sizes than observed. Error plots for track and intensity were also shown for all storms in the East Pacific completed to date. The track error plot for East Pac storms showed a big improvement in H209 error values compared to HWRF. For intensity error, H209 had lower error values than HWRF through 48 hours before making a slight degradation.

Next, individual storm results were examined. For Hanna, overall track error for H209 was lower than that for HWRF and H047. However, intensity errors (perhaps due to the H209-produced larger storm size) for H209 are larger than those for H047 and HWRF throughout. It was mentioned that cycling could play a role in this issue in that a too-intense storm could be carried throughout the H209 runs and made worse with time. More investigation into this is ongoing by Bob Tuleya. For Ike (09L), H209 showed similar track error values to HWRF and H047 throughout and similar intensity error values through 96h with a slight degradation there. Error plots for Gustav (07L) showed lower H209 track and intensity errors through 96h before slight degradation and no intensity bias. For Norbert (15E), there was a substantial reduction in track error compared to HWRF and again a slight increase in intensity error at 96h. There was consistent reduction in track error for Genevieve (08E) and lower intensity errors compared to HWRF through 48h before error values spiked.

The last slide showed a plot of the pressure-wind relationship for storms for H209 Atlantic, H209 East Pac, H047 (Atlantic), and best track. This plot showed that H209 was over-intensifying storms by deepening them too much with too much wind. Steve Lord suggested running some outlier cases (those with the highest pressure-wind values) in higher resolution. Examining the drag coefficient and its effect on storms was also mentioned.

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