Super Typhoon Surigae was the strongest ever early season typhoon in the North Pacific, when it formed in April 2021.
12 May 2021
21 April 2021
By Jochen Kerkmann (EUMETSAT), Ivan Smiljanic (CGI) and HansPeter Roesli (Switzerland)
In late April Typhoon Surigae, known in the Philippines as Typhoon Bising, was a powerful tropical cyclone east of the Philippines. It became the strongest Northern Hemisphere tropical cyclone to form before the month of May, and one of the most intense tropical cyclones on record.
Surigae became annular on 19 April, following an eyewall replacement cycle, which created a very large eye that could still be clearly seen in a variety of satellite imagery (Figures 1 and 2).
Surigae strengthened at a pace that was double the rate needed to qualify for rapid intensification (jumping by more than 160 km/h in a day and a half), and its 190-mph peak winds were stronger than Hurricane Dorian, which ravaged the Bahamas at the start of September 2019. The threshold for Category 5 status is 156 mph.
The Tropical Airmass RGB of 21 April (Figure 3) shows the extremely big eye (over 100 km diameter), plus the presence of different airmasses at mid to high levels of the troposphere north and south of Surigae (the red v blue hues).
Figure 4 is zoomed in on different wave formations on top of the convective cloud bands surrounding Surigae’s eye. These wave formations are detected both in the visible and temperature signals of the AHI sensor. These are different types of gravity waves that are a consequence of very dynamic (vertical) processes associated to typhoon’s convection. Some of these waves are very untypical, like the quasi-stationary one stretching from the typhoon’s centre towards (roughly) Taiwan, annotated by the blue arrows in water vapour imagery (Figure 5).
Another sign of intense vertical motions are the radial cirrus bands that emerge from the system at the tropopause level. These are seen better in the looping water vapour (WV) imagery (Figure 5), appearing as outward facing linear structures, around the typhoon’s eye. These also appear far away from the Surigae’s eye, as red linear clouds over South China Sea.
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