Analysis of High Temporal and Spatial Observations of Hurricane Joaquin during TCI-15

The Office of Naval Research Tropical Cyclone Intensity (TCI-15) field experiment during 2015 collected a unique set of high temporal and spatial resolution observations in four hurricanes in the Atlantic and eastern North Pacific using the NASA WB57 in conjunction with the NOAA P-3 and the Air Force Reserve WC-130 J aircraft. In addition to the High Density Sounding System (HDSS) dropwindsondes from 60,000 feet, the NASA Hurricane Imaging Radiometer (HIRAD) provides surface wind speeds across a swath along the WB57 flight path. Special high spatial resolution Atmospheric Motion Vectors (AMVs) from GOES rapid-scans (as frequently as 7.5 minutes) will be provided by the CIMSS. The focus of this study is the TCI mission in Hurricane Joaquin on 4 October when Joaquin was approaching Bermuda. At this time, Joaquin was weakening due to environmental vertical wind shear and the structure was becoming asymmetric. Thus, the objective is to analyze the three-dimensional structure in the inner-core of Joaquin using the HDSS soundings in conjunction with the rapid-scan AMVs to tie-down the outflow structure and the HIRAD surface wind swaths to anchor the low-level wind structure. Since a primary objective of TCI-15 is to observe, analyze, and model the role of the outflow in tropical cyclone intensity change, the high-density soundings are used to search for the “roots” of the outflow in Joaquin as it is undergoing vertical wind shear. Preliminary analyses suggest that the vortex begins to tilt downshear above 400 mb. A second objective of this analysis is to serve as the “ground truth” for the new SAMURAI/COAMPS-TC dynamic initialization (SCDI) technique for producing an analysis for diagnostic studies and for initial conditions for numerical modeling studies. Key questions include: (i) Whether the SCDI can replicate the 3-D structure in the inner core (including the vortex tilt magnitude as revealed by the HDSS soundings; (ii) Will the vertical structure of the outflow be correctly resolved by the SCDI when the input AMVs are only at the cirrus tops; (iii) Will the surface wind speeds from the HIRAD be properly coupled to the above-boundary circulation from the HDSS; and (iv) Will the “roots” of the outflow layer from SCDI be the same as in the HDSS?