Heather Holbach and Kelly Ryan

Estimating tropical cyclone wind hazards can be difficult and operationally often requires assumptions to be made about surface wind characteristics relative to available flight-level observations. Approximations of surface wind using reconnaissance flight level (700 mb or 850 mb) have been routinely supported by symmetric assumptions, but observational and modeling comparisons suggest departures from this framework, occasionally detecting variations in surface winds both radially (distance from center) and azimuthally (around the storm). Data collected will be used to refine assumptions asymmetrically, investigate asymmetries in the boundary layer as they relate to wind and wave hazards, and expose potential boundary layer biases in numerical weather and climate models.

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Sim Aberson, Joe Cione, Jun Zhang

Small features in the eyes and eyewalls of very intense tropical cyclones have been hypothesized to increase the amount of energy available for hurricane intensification, or to be responsible for damaging surface wind at landfall or intense turbulence features impacting flight operations. However, the structures of these features, especially the temperature and humidity structures, have never been documented.

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Jun Zhang (PI) and David Nolan (co-PI)

Tropical cyclone (TC) convection produces gravity waves that propagate both upward and outward. The observational data collected from this module will be analyzed to quantify the characteristics of the gravity waves in mature-stage hurricanes and their relationship with storm intensity and intensity change. These data would also provide valuable information for model evaluation and physics improvement.

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Jun Zhang (PI), Jason Dunion, Joseph Cione, Robert Rogers, Frank Marks, Andrew Hazelton, Jonathan Zawislak, Gregory Foltz (AOML), Daniel Stern (NRL), James Doyle (NRL), Sue Chen (NRL), Yi Jin (NRL), Nick Shay (UM), Benjamin Jaimes (UM), Elizabeth Sanabia (USNA), Ping Zhu (FIU), Xiaomin Chen (UAH), Brian Tang (SUNY Albany), Robert Fovell (SUNY Albany), Zhien Wang (CU), Michael Bell (CSU), Ralph Foster (UW), Joshua Wadler (ERAU), Johna Rudzin (MSU), George Bryan (NCAR), Rosimar Rios-Berrios (NCAR), Falko Judt (NCAR), Cheyenne Stienbarger (GOMO), and Emily A. Smith (GOMO)

The atmospheric boundary layer is a crucial region of a tropical cyclone (TC), because it is the area of the storm in direct contact with the ocean moisture and heat sources which power the storm. This module aims to collect observational data to improve our understanding of physical processes in the boundary layer that control the TC intensity change. These data can be used to evaluate and improve the performance of TC forecast models such as the Hurricane Analysis and Forecast System (HAFS).

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Paul Chang (PI), Zorana Jelenak, Joe Sapp (NOAA/NESDIS/STAR): Ricky Roy (Tomorrow.io), Sim Aberson (NOAA/AOML/HRD)

To improve our understanding of microwave retrievals of the ocean surface and atmospheric wind fields, and to evaluate new remote sensing techniques/technologies. To help validate satellite-based sensors of the ocean surface in extreme conditions and reduce risk for future satellite missions. To provide forecasters with near-real-time hurricane boundary layer profiles, where possible.

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Rob Rogers (PI), Michael Fischer, Anthony Didlake (PSU), Michael Bell (CSU), Anthony Wimmers (UWisc), Jim Doyle (NRL), Dan Stern (NRL)

This module will sample the structure of long, spiral bands of rainfall (rainbands) that often extend outward from the eyewall of strong hurricanes out to very large distances from the center. These rainbands, often containing mixtures of strong thunderstorms and lighter rainfall that can cover huge areas, are thought to affect the structure and intensity of the hurricane within which they are embedded. The data from this module will seek to explore these structures and their potential relationship with hurricane structure and evolution.

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Joseph Cione, Jun Zhang, Josh Wadler (ERAU), George Bryan (NCAR), Ron Dobosy (NOAA/ARL-ret), Xiaomin Chen (UAH), Altug Aksoy, Sim Aberson, Frank Marks, Kelly Ryan, Brittany Dahl, Johna Rudzin-Schwing, (MS State), Josh Alland (NCAR), Rosimar Rios-Berrios (NCAR), Don Lenschow (NCAR), Chris Rozoff (NCAR), Eric Hendricks (NCAR), Falko Judt (NCAR), Jonathan Vigh (NCAR)

This experiment uses small drones, instead of crewed aircraft, to sample the lowest and most dangerous regions of the tropical cyclone (TC).  It is believed that observations from these unique platforms will improve basic understanding and enhance forecaster situational awareness.  Detailed analyses of data collected from these small drones also have the potential to improve the physics of computer models that predict changes in storm intensity.

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Heather Holbach, Ivan PopStefanija (ProSensing Inc.), Mark Bourassa (FSU), and Ralph Foster (UW-APL)

This module will collect data in mature hurricanes to continue improving surface wind speed and rain rate estimates from the Stepped-Frequency Microwave Radiometer (SFMR) and understand how the wind speed observations from the SFMR, flight-level winds, dropsondes, tail-Doppler radar (TDR) and, Imaging Wind and Rain Airborne Profiler (IWRAP) should be averaged and adjusted to statistically consistent 1-minute mean (or sustained) winds. Additionally, surface wave observations will be verified and the extent of 8 ft significant wave height waves will be identified.  Improved measurements from the SFMR and understanding how the various aircraft-based wind observations should be averaged and adjusted to statistically consistent 1-minute mean winds along with improving our knowledge of the surface wave field have numerous implications for forecasting and research efforts, such as providing more accurate observations to estimate tropical cyclone (TC) intensity and size along with improved estimates of marine hazards and comparisons for satellite observations.  These improvements allow for better watches and warnings for a TC’s potential impacts to be provided to emergency managers and the general public and leads to more accurate research results.

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Jason Dunion (PI), Jun Zhang (Co-PI), John Knaff (NESDIS/STAR-CIRA/Colorado State University), Chris Slocum (NESDIS/STAR-CIRA/Colorado State University)

This module aims to collect observations that improve the understanding of how day-night fluctuations in radiation affect the intensity and structure of hurricanes.  One component of these oscillations is a phenomenon called the tropical cyclone diurnal cycle where the cloud fields of storms are seen to expand and contract each day. These daily expansions are associated with a pulse of thunderstorms and rain that travel hundreds of kilometers away from the storm center that affects the flow of air into the storm at the lowest levels above the ocean.

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Paul Reasor and John Gamache

Three-dimensional wind analyses derived from two P-3 aircraft equipped with tail-Doppler radar (TDR) and flying simultaneous, perpendicular transects through the hurricane eyewall are compared in an evaluation of the Doppler-radar wind analysis method. Through this evaluation, we seek to gain a better understanding of how to relate radar-derived peak wind speed and other aspects of hurricane wind structure to similar estimates using conventional observations.

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Paul Reasor and John Gamache

This module aims to collect observations that improve the understanding of how day-night fluctuations in radiation affect the intensity and structure of hurricanes. One component of these oscillations is a phenomenon called the tropical cyclone diurnal cycle where the cloud fields of storms are seen to expand and contract each day. These daily expansions are associated with a pulse of thunderstorms and rain that travel hundreds of kilometers away from the storm center that affects the flow of air into the storm at the lowest levels above the ocean.

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Heather Holbach, John Kaplan, Jun Zhang, Ghassan Alaka, Frank Marks, Lew Gramer, George Alvey, Forrest Masters (University of Florida), Michael Biggerstaff (University of Oklahoma), David Nolan (University of Miami), Xiaomin Chen (University of Alabama in Huntsville), Johna Rudzin (Mississippi State University), John Schroeder (Texas Tech University)

Landfalling tropical cyclones (TCs) often produce a variety of high impact weather over land including tornadoes and damaging winds (particularly gusts) for which there exists limited objective forecast guidance. Thus, our experiment seeks to utilize P-3 aircraft and land-based mobile research team instruments to collect data in landfalling TCs to improve both our understanding and capability to predict the dangerous phenomena often associated with these landfalling systems.

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Sim Aberson

Tropical cyclones can either decay (spin down) or transform into powerful extratropical cyclones when they encounter cold water below or high wind shear in the atmosphere.  The mechanisms by which tropical cyclones become extratropical is not well forecast by numerical models leading to large errors, especially in impacts downstream of the actual transitioning cyclone.  This experiment aims to improve forecasts of these systems.

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Jun Zhang (CIMAS/HRD), Joshua Wadler (Embry Riddle Aeronautical University), Johna Rudzin (Mississippi State), Joe Cione (NOAA AOML/HRD), Nick Shay (UMiami), Chidong Zhang (NOAA PMEL), Gregory Foltz (NOAA AOML), Stephan Howden (USM), Kevin Martin (USM), Travis Miles (Rutgers), Gustavo Goni (NOAA AOML), Kathy Bailey (U.S. IOOS), Steven Jayne (WHOI), Alex Gonzalez (WHOI), Pelle Robbins (WHOI), Paul Chang (NOAA NESDIS), Zorana Jelenak (NOAA NESDIS), Joe Sapp (NOAA NESDIS), Luca Centurioni (Scripps), Martha Schonau (Scripps), Hyun-Sook Kim (NOAA AOML), Matthieu Le Henaff (CIMAS/PhOD), HeeSook Kang (CIMAS/PhOD), Lew Gramer (CIMAS/HRD), Cheyenne Stienbarger (NOAA GOMO)

CHAOS focuses on the coordination of diverse new observing platforms (i.e., autonomous, uncrewed, expendable) and conventional ones (e.g., aircraft) to support:

• Sustained monitoring of key ocean features of the Gulf of Mexico, tropical Atlantic, and/or the Caribbean Sea – e.g., Loop Current, Gulf Stream, eddies and rings, and freshwater barrier layers from the Mississippi & Amazon-Orinoco River Plumes

• Targeted observing of the air-sea transition zone to improve the understanding of air-sea interactions for improved prediction of TC intensification, and/or

• A combination of sustained and targeted observing approaches.

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Jun Zhang (PI), Nick Shay (UM), Joseph Cione, Frank Marks, Sue Chen (NRL), Benjamin Jaimes (UM), Joshua Wadler (ERAU), Elizabeth Sanabia (USNA), Johna Rudzin (MSU), Lew Gramer, Heather Holbach, Rick Lumpkin (AOML), Gregory Foltz (AOML), Gustavo Goni (AOML), Hyun-Sook Kim (AOML), Matthieu Le Henaff (CIMAS), James Doyle (NRL), James Cummings (NRL), Luca Centurioni (SIO), Theresa Paluszkiewicz (OOC, LLC), Steven Jayne (WHOI), Chidong Zhang (PMEL), Dongxiao Zhang (PMEL), Christian Meinig (PMEL), Cheyenne Stienbarger (GOMO), and Emily A. Smith (GOMO)

Physical representation of how the atmosphere and ocean interact in numerical forecast models of tropical cyclones (TCs) have not been fully evaluated against observations. Near collocated and simultaneous measurements of the ocean and the atmosphere just above the ocean surface, the energy exchanges that occur between them, and how they change over time have been lacking and require close coordinations across a wide array of ocean and atmosphere observing platforms. This experiment will provide a unique opportunity to evaluate how well forecast models represent these lowest regions of storms. The observations that are collected should help improve how forecast models represent interactions between the ocean and atmosphere in hurricanes.

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Jason Dunion (PI), Rebekah Esmaili (Co-PI, STC/JPSS), Michael Folmer (NWS/OPC)

This module will collocate radiosondes with real-time satellite sounding products to understand the near and surrounding environment of pre-Tropical Cyclones and/or Tropical Cyclones. The focus of this year’s flights is extratropical transition, tropical transitions, and invests, if useful cases arise. This module will also explore the value of satellite soundings for Tropical Cyclone monitoring and forecasting using newly developed web-based and local software tools.

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Brittany Dahl (co-PI), Jason Dunion (co-PI), Rob Rogers (co-PI), Trey Alvey, William Blackwell (MIT, Lincoln Laboratory)

This experiment is designed to calibrate and validate temperature, moisture, and precipitation measurements obtained from the new TROPICS satellites. These profiles will be compared to NOAA P-3 and NOAA G-IV aircraft observations, whose flight patterns will be coordinated in space and time with overpasses from the satellite.

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