Estimating Tropical and Extratropical Storm Intensity and Structure from JPSS Microwave Temperature Retrievals - Current and Future Products

The National Hurricane Center (NHC) and Joint Typhoon Warning Center (JTWC) official forecasts include the location of tropical cyclone (TC) center, the maximum sustained surface wind (intensity) and the maximum radial extent of 34, 50 and 64 kt in four quadrants relative to the TC center. These forecasts also include the storm type (e.g., tropical, subtropical, extratropical), which has implications for hazards since the transition between storm types has associated changes in storm structure. For example, Hurricane Sandy (2012) was transitioning to an extratropical cyclone as it approached the U.S. east coast with an expanding wind field that resulted in a very large storm surge.

To accurately forecast these parameters, it is important to have reliable estimates of their initial values. The majority of global TCs occur in remote areas, making satellite data the primary source for TC analysis. In situ data, such as aircraft reconnaissance, conventional surface observations, and emerging technologies such as small Uncrewed Aircraft Systems (sUAS) and Saildrones, are usually limited to storms approaching landfall in the Atlantic and eastern North Pacific basins. While the geostationary satellite data are routinely available (every 10-15 minutes globally) and have low latency (less than 10 minutes), the microwave sounders and imagers that are only available on low-earth-orbiting (LEO) satellites can see through clouds and provide TC intensity and structure information not available from Visible and IR imagery. Currently, there are three JPSS satellites carrying the Advanced Technology Microwave Sounder (ATMS), and several NOAA and MetOP satellites carrying the Advanced Microwave Sounding Unit (AMSU) instruments. Thus, despite much higher latencies of polar-orbiting data (typically 1 - 1.5 hours) there is an increasing amount of information about TC structure that microwave sounders provide in near real-time. Further, instruments similar to ATMS are now becoming available on smallsats (e.g. TROPICS) that have the potential to further improve temporal and spatial coverage.

In this presentation, recent improvements to methods to estimate TC intensity, wind radii and storm type from JPSS and other microwave sounders will be discussed. Specifically, we will focus on two applications.

The first application, the CIRA Hurricane Intensity and Structure Algorithm (HISA), originally developed in 2001, provides global objective and Dvorak-independent TC intensity, wind radii estimates, and two-dimensional wind fields at standard pressure levels estimated from microwave temperature retrievals. The original version of HISA is operational at NCEP for NOAA-15/16/18/19 satellites, and an updated version of HISA is being transitioned to NESDIS operations for SNPP, NOAA-20, MetOp-B, and MetOp-C satellites.

The second application, the JPSS Extratropical Transition (JET), is a new JPSS-TC product that uses ATMS-MiRS temperature retrievals, the two-dimensional wind and geopotential height fields from HISA, and VIIRS imagery to diagnose storm type. Results show that the JPSS data provides information that is independent of the Global Forecast System (GFS) model, suggesting that storm diagnostics can be improved with JPSS input. JET includes a new objective algorithm for classification for storm type (JETClass) that builds on the operational ETClass method, which is part of the NHC’s Statistical Hurricane Intensity Prediction Scheme (SHIPS) model. ETClass uses a linear discrimination method with predictors from IR imagery and GFS. JETClass will utilize new JPSS predictors and a machine learning model for the storm type classification. JET also includes image displays of JPSS data and derived quantities such as temperature anomalies and temperature advection for qualitative storm type diagnostics and situational awareness.

The presentation will discuss the updates to HISA, including verification statistics for TC intensity and wind radii estimates and application to TROPICS data, and present examples of JETClass predictors and JET image displays. We will also discuss future directions for HISA and JET, including improving HISA performance for small storms and developing JETClass model, additional JETClass predictors and image displays. Current and possible future use of HISA and JET at NHC and JTWC will also be discussed.

Disclaimer: The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect those of NOAA or the Department of Commerce.