Guidance for Operational Forecasting: Validity of Selected TC Parameters Derived from Active and Passive Microwave Remote Sensing Satellites

The radius of maximum wind (RMW) is a critical parameter which helps determine tropical cyclones’ (TCs) intensity and related risks such as storm surge, wave development, watches and warnings. It is defined as the distance from the center of the storm to the location of maximum wind speed. A few methods have been developed to estimate the RMW, some of which directly or indirectly rely on sea surface wind speed inferred from active and passive microwave remote sensors (e.g. the Chavas method, the multi-platform tropical cyclone surface wind analysis method). In recent years, measurements from Synthetic Aperture Radars (SARs) and microwave radiometers have been utilized to estimate, in addition to RMW, TC maximum wind speed, and 34-, 50-, and 64-kt wind radii. These satellite derived TC parameters are currently available through the Automated Tropical Cyclone Forecasting System (ATCF) as operational products. Since resolution and sensitivity to high winds and rain vary between satellites, the correct estimation of the aforementioned TC parameters can be challenging, and will vary from sensor to sensor; mismatches between sensor resolution and resolution of the physical processes within the storm, together with steep wind and rain gradients, cause differences between retrieved parameters from different sensors. This, in turn, makes interpretation of the data difficult. In this presentation, our primary focus is to assess the validity of these satellite based derived TC products in order to provide guidance to operational users and forecasters. In particular, we will focus our attention on the effect of sensor product grid resolution, pertaining to the estimation of TC parameters for different storm size and development stage. This study will exploit wind speed products from multiple satellite sources such as the 25 km wind speed products from the Soil Moisture Active Passive (SMAP) mission, provided by the Jet Propulsion Laboratory (JPL) and by Remote Sensing Systems (REMSS), NOAA’s 10 km all-weather wind speed product derived from the Advanced Microwave Scanning Radiometer 2 (AMSR2), and lastly, NOAA's 12.5 km wind speed product derived from the Advanced Scatterometer (ASCAT). Case studies from multiple TCs will be selected, where the aforementioned sensors’ wind speed fields will be compared with Best-Track reported wind radii, TC maximum wind, and RMW. These case studies will include storm passes with similar reported RMWs but with varied storm sizes and stages.