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December 4, 2008 Meeting Summary

Qingfu Liu presented a summary of the HWRF cycling system and creation of guess fields before describing his work with hurricane initialization in the HWRF. Specifically he discussed the 5 potential changes to be included in the 2009 HWRF. Such changes included changing the minimum surface pressure and making the surface pressure-wind relationship more consistent with the model instead of the observation, redefining the filter domain size based on the observation, setting a radius of maximum wind and radius of outmost isobar limit for small-sized storms, searching for maximum wind position at the 10m height instead of first level height, and finally, increasing the search area of the maximum wind for high latitude storms.

Zhan Zhang described his and Bob Tuleya's work investigating the HWRF surface temperature forecast over land. The direct cause of cold land-surface temperature was found to be sporadic zero-values of the radiative surface fluxes in the nest. Such surface fluxes are used to predict land-surface temperature. The ocean model was not affected because another, equivalent variable was used by the coupler. The sporadic behavior was caused by using an irregular interval between radiation call in the nest. The proposed fix to the problem is to call radiation in the nest at fixed intervals, such as every 9 minutes, which eliminates almost all problems. Small boundary noise in the land-surface temperature remains possibly due to LSM-predicted land-surface temperature along the nest boundary. Zhan and Bob noted that the biggest impact of this correction was that storms would remain more robust over land, and testing to determine impacts on track and intensity skill is to come. Other proposed solutions include inputing a different argument for different situations with more investigation into this to follow.

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