July 9, 2009 Meeting Summary
Janna O'Connor presented results from the recent HWRF Genesis experiments run by Vijay Tallapragada. The genesis HWRF (represented by HWRG) is the operational HWRF run with no initialization (INIT=NO) and GSI=YES. There is no relocation for the HWRG runs. Only invest cases are run using HWRG, and no runs are done on named storms. Results, in the form of track and intensity plots, were shown for INVEST 90L, INVEST 91L (which became ONE 01L), INVEST 92L, INVEST 93L, and INVEST 94E (which became BLANCA 03E). In the track and intensity plots, HWRF (operational HWRF) is represented by the red lines and HWRG (genesis HWRF) is represented by the purple lines.
For INVEST 90L, the HWRF and HWRG tracks are not very different for 2009052218, 2300, or 2306. However, the HWRG intensity is much weaker than HWRF intensity, with HWRF peak intensity reaching 35kt or more for each time level. HWRG intensity peaks at only 25kts through the time levels. For INVEST 91L, which was later named ONE 01L, the HWRG and HWRF tracks are fairly similar, and once again, the HWRG intensity is much weaker than that for HWRF. However, HWRF intensifies 91L into a depression, as shown for the 2009052812 intensity plot, while the HWRG does not. Track and intensity plots for INVEST 92L show a much weaker HWRG intensity than that for HWRF, however, the tracks for HWRF and HWRG are not that similar.
For INVEST 93L, the HWRF intensified this disturbance into a category 2 hurricane just before it took it into Tampa, FL for the 2009062618 and 062700 model runs. While the HWRG track is similar to the HWRF track, it stops short of FL. The intensity for the HWRG is again much weaker than the 85kts HWRF produced for 2618 and the >90kts HWRF produced for 2700. It should be noted that among the models plotted here, only NGPS brings 93L into the Yucatan peninsula where it actually moved. Wind swaths for 93L, at 2700, are shown to contrast the HWRF and HWRG runs. Finally, INVEST 94E was presented, a disturbance that eventually became BLANCA 03E. The HWRF track starts off in a more NW direction early in the forecast for 2009070518 and 070600, however, it then turns in a more W direction. The HWRG track is primarily W throughout its forecast. While the HWRF didn't intensify 94E as much as other models, the HWRG's intensity was again weaker, as expected.
Next, Qingfu Liu presented a few slides on his work with excessive condensation in the SAS scheme. Qingfu looked at Arakawa and Schubert's 1973 paper where they used an approximation to calculate dry static energy and saturated water vapor mixing ratio from moist static energy. Qingfu presented equations from the paper followed by graphs to illustrate that these approximations underestimate temperature and saturated mixing ratio in the rising parcel. The underestimation of the saturated mixing ratio means there is excessive condensation (precipitation). This, in turn, makes it harder for the water vapor to be transported to the mid- and upper levels of the environment.