Improved CYGNSS Observations of Storm Force Winds and their Impact on TC Forecast Skill

The CYGNSS constellation of eight satellites was successfully launched in December 2016 into a low inclination (tropical) Earth orbit. Each satellite carries a four-channel bistatic radar receiver which measures signals transmitted by Global Positioning System (GPS) satellites and scattered back into space by the Earth surface. Over the ocean, direct measurements of surface roughness are used to estimate the near-surface (10 m referenced) wind speed. The GPS signal is able to penetrate through all levels of precipitation due to the long radio wavelength of operation. The number of satellites in the constellation and their continuous data-taking operation result in a high spatial sampling density and low temporal revisit times. Over ocean, this makes possible the tracking of storm development throughout its life cycle, typically with 2-3 overpasses per day depending on latitude. Level 2 science data products regularly produced over the ocean include wind speed, surface roughness, and sensible and latent heat fluxes. The wind speed product during major storm overpasses is reprocessed into a storm centric gridded Level 3 product and a best-fit parametrized tropical cyclone model from which tropical cyclone intensity (peak sustained winds) size (radius of maximum winds), extent (34, 50 and 64 knot wind radii), storm center location, and integrated kinetic energy can be determined. The Level 2 and Level 3 products can also be assimilated into tropical cyclone forecast models. The status of CYGNSS high wind speed retrieval performance will be presented, together with a description of current related science data products and examples of TC forecast skill impact due to the assimilation of CYGNSS wind speed products.