Advancing spaceborne observations of tropical cyclones by the WIVERN 94 GHz Doppler radar: the case study of the rapid intensification of hurricane Milton

Hurricane rapid intensification (HRI) refers to a phenomenon in which a tropical cyclone undergoes a sudden and significant increase in wind speed over a short period, typically defined as an increase of at least 35 mph (30 knots) in maximum sustained winds within 24 hours. Key factors influencing the rapid intensification phenomenon are the presence of warm sea surface temperatures (SSTs) in combination with significant ocean heat content, a low wind shear, a high atmospheric water vapour content, as well a pre-existing well-organized storm structure. The combination of these factors can lead to disruptive HRI as observed for Hurricane Milton (2024), whose winds increased by 78 knots in the 24-hour period from 00:00 UTC October 7 to 00:00 UTC October 8. Monitoring and predicting HRI is crucial for disaster preparedness: a WRF hindcast study at 1.5 km grid spacing for Milton, which well reproduce the trajectory of the hurricane and its maximum wind intensity is presented.

The simulated Hurricane Milton three dimensional cloud and wind structure has been exploited to assess how the WIVERN 94 GHz radar, currently under study in the ESA Earth Explorer program, could sample the systems in correspondence to successive orbits during the hurricane lifetime. The proposed WIVERN radar has ground-breaking Doppler and scanning capabilities that enable to map very strong winds across a large swath of the order of 800 km (Illingworth et al., 2018; Battaglia et al.,2022, Tridon et al., 2023). Different overpasses simulated before and after the HRI demonstrate that the WIVERN system will be able to provide, for the first time from space, information about the mesoscale vertical structure of clouds and dynamics of the cyclone, particularly in the region above the freezing level (94 GHz are strongly attenuated inside the convective regions and the heavily precipitating rain bands). This suggests that WIVERN observations may have great potential to improve the prediction of hurricane intensification.  

 

 

 

Illingworth, A. J., Battaglia, A. et al., 2018: Wivern: A new satellite concept to provide global in-cloud winds, precipitation and cloud properties. Bull.Amer. Met. Soc., DOI: 10.1175/BAMS-D-16-0047.1, 1669-1687.

 

Battaglia, A., Martire, P., Caubet, E., Phalippou, L., Stesina, F., Kollias, P., and Illingworth, A.: Observation error analysis for the WInd VElocity Radar Nephoscope W-band Doppler conically scanning spaceborne radar via end-to-end simulations, Atmos. Meas. Tech., 15, 3011–3030, https://doi.org/10.5194/amt-15-3011-2022, 2022.

 

Tridon, F., Battaglia, A., Rizik, A., Scarsi, F. E., & Illingworth, A., 2023: Filling the gap of wind observations inside tropical cyclones. Earth and Space Science, 10, e2023EA003099. https://doi.org/10.1029/2023EA003099