In August Atsani transitioned from a Category 5 super typhoon into a powerful extra-tropical storm.
09 March 2021
20 August 2015
By NOAA Ocean Prediction Center, Scott Bachmeier (CIMSS ), Jochen Kerkmann (EUMETSAT) and HansPeter Roesli (Switzerland)
In mid-August there were two powerful typhoons in the Western Pacific — Goni and Atsani. While Typhoon Goni made landfall on the Japanese island of Kyushu on 25 August, Atsani circulated over the ocean and didn't make landfall.
On 19 August Atsani reached super typhoon status, with 1-minute sustained winds of 260 km/h (160 mph), and in the following days it started to weaken.
However, on 24–25 August, instead of dying out as it got caught up in the mid-latitude jet stream winds, it transformed into a powerful extra-tropical storm. It went from a storm that had a warm core, with a centre milder than the surrounding air, into a system with a cold core. The resulting storm reportedly produced hurricane-force winds and extremely high waves across the North Pacific (Credit: Mashable).
The Himwari-8 Airmass imagery, Figure 1 and animation produced by NWSOPC (NOAA's Ocean Prediction Center), clearly shows that on 25 August Atsani started to transition into an intense extra-tropical low. On the animation, a graphic is included that highlights the main differences between a tropical and extra-tropical low.
Surface analysis from the Ocean Prediction Center (Figure 2) indicated that the extra-tropical storm deepened to a minimum central pressure of 957 hPa at 12:00 UTC on 25 August, and was producing hurricane-force winds until 00:00 UTC on 26 August (Credit: CIMSS Blog).
Figure 3 shows the Night Microphysics RGB product, for the same situation as shown in Figure 1. This RGB product is mainly used to identify clouds at different levels, including low-level clouds, which are not as visible in the Airmass RGB (Figure 1).
In Figure 3 two images are shown: one RGB with the SEVIRI standard tuning (green component (IR11.2-IR3.9) is displayed for a range of 0 to 10 K), and the other one with a tuning that is appropriate for the AHI instrument (green component is displayed for a range of –5 to +5 K). This shift of the range of the green component is needed as the AHI band 7 (IR3.9) is not affected by CO2 absorption. In the tuned RGB product, low-level clouds can be easily identified by their green colour.
Figure 4 shows typhoon Atsani at its full strength on 20 August 2015, 00:02 UTC.
On this day, Atsani was close to the Philippines. The image shows Band 3 of the AHI instrument (0.64 µ), which is the only channel that has a high resolution of 0.5 km.
Other typhoon cases
Devastating Typhoon Hagibis
Typhoon Hagibis was the worst storm to hit Japan for half a century, when it made landfall in mid-October 2019.
Typhoon Krosa over Japan
Typhoon Krosa weakened before crossing southern parts of Japan in August 2019.
Super Typhoon Lekima
Super Typhoon Lekima scraped past Krosa, a concurrent typhoon, in the Western Pacific Ocean in August 2019.
Record-breaking Typhoon Wutip
In late February 2019 Typhoon Wutip became the strongest February typhoon on record in the Northwest Pacific basin.
Tropical Cyclone Enawo as seen by Meteosat and Metop
In early March Tropical Cyclone Enawo battered Madagascar with winds in excess of 205 km/h.
Latest case studies
Cumbre Vieja volcano eruption
The Cumbre Vieja volcano on the Canary Island of La Palma erupted on 19 September 2021.
Melting Greenland ice sheet cools North Atlantic Ocean
Observing the cooling of the North Atlantic Ocean during the last decade, using weather satellites.
Smoke and burned areas from Greek fires
Smoke and burned area scars from the Greek wildfires in Aug 2021 seen in satellite imagery.
Large smoke plume from wildfires in Russia
In summer 2021 Russia saw unprecedented widespread wildfires ravage large swathes of Siberia.
Widespread smoke from Turkish fires
In summer 2021 parts of the Mediterranean Sea were shrouded in smoke from wildfires along Turkey's coast.