Hurricane Outflow Jet Features Documented by Global Hawk Dropsondes and Satellite AMVs During HS3 as Targets for Future SHOUT Operations

Dropsondes deployed from High-Altitude, Long-Endurance (HALE) Global Hawk Unmanned Aerial Vehicle (UAV) during the Hurricane and Severe Storms Sentinel (HS3) missions from 2012-2014 have proven useful in obtaining dropsonde vertical profile observations from 20 km altitude of detailed hurricane outflow jet structure. Together with satellite-derived Atmospheric Motion Vectors (AMVs), the horizontal and vertical structure of outflow jets from Hurricanes Leslie (2012), Nadine (2012), pre-Guillermo (2013) and Edouard (2014) are described emphasizing the structure transition from inner-core ‘roots' to environmental synoptic scale features. Inner-core roots are found to be associated with, but not necessarily caused by, inner-core convective bursts. The bursts studied were transitory and appeared driven by a diurnal convective cycle as hypothesized by Dunion. In the case of pre-Guillermo, the AMVs showed that this convective pulsation was associated with an in-phase, rapidly-changing outflow jet evolution during the period of Global Hawk dropsonde deployments. Observations in Leslie (2012), Nadine (2012) and Edouard (2014) showed an alignment of outflow feature development with a hypothesized evolution of outflow jet structures from single equatorward, to dual equatorward/ poleward to single poleward relative to hurricane intensity change.

The link between hurricane intensity change associated with HS3 dropsonde observations of inner-core outflow-generating mechanisms and evolution of environmental outflow features suggests that this linkage be targeted for future Global Hawk HALE and satellite AMV operational observations. The evolution of upper layer features observed by AMVs, especially new rapid-scan hourly AMVs, provide a context for time-dependent HALE dropsonde observations of detailed vertical outflow jet structures, a process largely unexplored in hurricane numerical model simulations and unobserved until HS3. Such coordinated observations will provide a new data source for evaluating new model initialization schemes such as 4D-VAR and EnKF as well as a new data source for model structure validation. The new NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT) program, begun during the slow 2015 El-Nino season, provided a sample data set for continuing the transition of research results from HS3 into operational implementation. SHOUT is poised as a foundation to build on this HALE/ UAV/ AMV concept of operations during 2016 and extending into the future.