Improving the prediction and understanding of hurricane rapid intensity change through assimilating TCI and IFEX field campaign data using the hybrid EnVar system

Observations from recent field campaigns such as ONR TCI and NOAA IFEX have provided unprecedented observations to improve the prediction and understanding of hurricane rapid intensification. During ONR TCI field campaign, HDSS dropsondes were released from WB-57 aircraft flying high above the hurricanes to sample the dynamic and thermodynamic fields including the outflow layers. In the mean time, high-altitude Wind and Rain Airborne Profiler (HIRAD) onboard the same WB-57 aircraft sampled surface wind. Tail Doppler radar (TDR) on board NOAA P-3/G-IV aircrafts during IFEX surveyed both the inner core and environment of the hurricanes. Together with the high resolution CIMSS Atmospheric Motion Vectors (AMV), these data provide an un-precedent 3-dimensional sampling of the TCs including the inner cores, its environment, the outflow layer and the surface inflow. The goal of this study is to use hybrid data assimilation system (Lu and Wang 2015) as a tool to a) study the impact of these data on the prediction of intensity change and b) to understand the mechanism that drives the hurricane intensity change.

For the first goal, except the P3 TDR data whose impact has been studied before using the hybrid DA system (Lu et al. 2015), the impacts of other field campaign using the newly developed hybrid EnVar DA system are still unknown. In addition to exploring the impacts of various kinds of field campaign data using the hybrid EnVar DA system, the most efficient way to combine and utilize the field campaign data which sample various aspects of the TCs will be explored.

For the second goal, the following questions will be addressed: 1) what is the impact of outflow on TC intensity change? 2) How is the TC outflow coupled with the inner core convection and therefore affects intensity change? And 3) what is the relationship between upper level outflow and low level wind structure?

The first experiment was conducted for Patricia (2015). Patricia was a Category 5 hurricane which formed in the East Pacific on Oct, 20th and landed along the coast of Mexico on Oct, 24th. Many has claimed that this is the strongest observed TC in East Pacific. Through coordination between ONR TCI and NOAA IFEX, Patricia was successfully sampled by both NOAA P-3 aircrafts with TDR and WB-57 aircrafts with HIRAD and dropsondes. Our experiments assimilating P3 TDR data for Patricia has shown that using our newly developed hybrid DA system, the intensity forecast for Patrica was improved compared to operational HWRF forecast. Specifically, our new hybrid DA system was able to predict the rapid intensification more consistently with the best track than the operational HWRF. At the same time, the trend of the track forecast using the new hybrid DA system were also more consistent with the best track than the operational HWRF. Impact of other field campaign data are being explored. In addition to Patricia, impact of these field campaign data for Jaoquin (2015) will be studied as well. Both the impact of the data and the intensity change mechanism for both Patricia and Jaoquin will be reported in the conference.