31 August-13 September 2021
Hurricane Larry was the the longest-lived Atlantic major hurricane since Dorian in 2019, lasting from 31 August to 13 September 2021.
21 February 2023
06 October 2021
By Romain Husson and Vinca Rosmorduc (CLS), Alexis Mouche (Ifremer) and Ivan Smiljanic (CGI)
EUMETSAT and ESA satellites contribute to the monitoring and forecasting of hurricanes. This example features measurements of wind speed and significant wave heights caused by hurricane Larry, one of the longest-lived Atlantic hurricanes.
The Atlantic hurricane season peaks in September. The 2021 Atlantic hurricane season has been an active one, with 14 named storms to date, including six hurricanes and three major hurricanes (Category 3, 4 or 5). An average Atlantic hurricane season sees eight named storms and three hurricanes by mid-September. Only four other years, since satellite observations began in 1966, had 14 or more named storms by 12 September — 2005, 2011, 2012, and 2020 (Source: NESDIS)
Larry formed close to Africa on 31 August and the following day developed into a tropical storm, named Larry. Larry moved quickly across the far eastern tropical Atlantic, where it strengthened into a Category 1 hurricane on 2 September. After undergoing a period of rapid intensification, Larry became a major Category 3 hurricane early on 4 September. It has stayed a category 3 tropical cyclone for several days, becoming the longest-lived Atlantic major hurricane since Dorian in 2019. Larry made landfall in Newfoundland on 11 September, as a Category 1 hurricane. Later that day becoming an extratropical cyclone. On 13 September, Larry was absorbed by a larger extratropical cyclone near Greenland. Larry's path and dynamics can be followed in the Meteosat-11 Tropical Airmass imagery (Figure 1). See also Larry's track (Source: Wikipedia)
The Sentinel-3A altimeter measured the Significant Wave Heights in the oceanic basins, with extremes at nearly 12m close to Larry's eye (Figures 2 and 3). Note: L2P data distributed in near-real time by EUMETSAT.
Synthetic Aperture Radars (SAR), such as those onboard Sentinel-1A & B measure sea surface roughness. From this, a high resolution wind field can be computed. With two different polarisations available, those missions are also able to retrieve extreme wind speeds, like those during storms, including tropical cyclones. This technique provides unique high-resolution information within and around the eye of the storm, e.g. its diameter and shape. In Larry’s case, the winds computed from Sentinel-1A & B and Radarsat2 (ESA/CYMS project) could be tracked along its path, starting on 31 August, with a maximum sustained wind around 55m/s on 6 September (Figure 4).
Waves generated by the tropical cyclone can also be visible when looking at the SAR roughness within the eye (Figure 5). The SAR high resolution images of Larry's eye highlight the vortex geometry and structure. Zooming further into the eye, TC-generated waves become more visible in this lower-wind region. Due to the local modification of the radar signal incidence angle caused by the wave slopes, a modulation of the sea surface roughness is induced, which appears as south-north oriented stripes. This corresponds to waves propagating westward, the direction in which the tropical cyclone was moving.
Such satellite measurements, significant wave height (SWH) from altimeters and wind speeds from synthetic aperture radar (SAR) are key information for scientists, meteorologists and modelers to better understand Tropical Cyclones. Moreover, they can be assimilated into forecasting models to better assess the strength and path of such oceanic storms and issue warnings when needed.
On 6 September the GOES-16 ABI instrument captured the rotation (mesovortices) around the distinct eye (Figure 6).
Hurricane Larry makes landfall in Newfoundland, then affects Greenland (CIMSS Satellite Blog)
Hurricane Larry wipes out power, trees and fishing wharves across Newfoundland (CTV News)
CYMS project website
Clément Combot, Yves Quilfen, Alexis Mouche, Jérôme Gourrion, Clément de Boyer Montégut, Bertrand Chapron, Jean Tournadre, 2020: Space-based observations of surface signatures in the wake of the 2018 Eastern Pacific tropical cyclones, In: Copernicus Marine Service Ocean State Report, Issue 4, Journal of Operational Oceanography, 13:sup1, s88–s91; DOI: 10.1080/1755876X.2020.1785097