ADAPT seminar

Speaker: Dr. Erin Munsell (NASA Goddard Space Flight Center)
Topic: "Next-Generation Geostationary Satellite (GOES-16) Observations of Rapidly-Intensifying Tropical Cyclones: Hurricanes Harvey (2017) and Irma (2017)"

Room: 529 Walker Building (refreshments served)
Time: Monday June 11, 2018 3:00pm - 4:00pm

The dynamics that govern the intensification of tropical cyclones (TCs) are dominated by rapidly evolving moist convective processes in the inner-core region. Remotely sensed satellite observations are typically available but in the past have lacked the necessary resolution to sufficiently examine TC intensification processes. However, as a result of the recent launch of the next-generation of high-resolution satellites (e.g. NOAA/NASA’s GOES-16), the spatial and temporal frequency of remotely-sensed observations of TCs have increased substantially. In particular, rapidly refreshing “mesoscale” domains have the capability of providing imagery with 2-km resolution for high-impact events, such as TCs, as frequently as once every 30 seconds.

This study utilizes brightness temperatures observed by the 16 spectral channels available from the Advanced Baseline Imager (on GOES-16) to examine the structure of Hurricane Harvey (2017) and Hurricane Irma (2017) throughout their respective rapid intensification (RI) events. Detailed inner-core structural evolutions in the times leading up to RI are examined utilizing brightness temperature fields that correspond to channels sensitive to IR longwave radiation and water vapor. Hovmoller diagrams constructed by extracting data at constant radii (50-km and 100-km from the TC surface centers) reveal areas of cold brightness temperatures, likely associated with convective bursts, propagating around the TC on timescales of 2–3 h. In addition, when these brightness temperatures are examined in a deep-layer shear-relative sense, the convective bursts initiate primarily in the downshear-left quadrant of the TC, and begin to advect cyclonically. As RI-onset is approached, the areas of the coldest brightness temperatures are able to propagate into the upshear-left quadrant of the TC, promoting enhanced diabatic heating near the TC center, which helps facilitate the onset of more significant intensification.