Three Active Tropical Systems in the Western Pacific
Once again, we see that 20206 continues to bring a large number of tropical systems in the Pacific. This time, we turn our eyes to the western part of our planet’s largest ocean to see a trio of tropical cylones in action. On the morning of 6 October 2026, three separate tropical systems were actively churning in the western Pacific Ocean. These systems included Typhoon Choi-Wan, the continuing Typhoon (former Hurricane) Nolo, and Tropical Storm Koguma. Here’s a large-scale true color view from Himawari-9 showing all three systems. Choi-Wan is the large storm near Japan in the northwest of the animation, Nolo is the more compact system in the east-central part of the animation, and Koguma is the small and not-yet-organized storm in the south central portion of the loop.
While there is a convective mass in the southwest part of the loop that is, in fact, larger than Koguma, the animation shows strong vertical shear with lower level and upper level windows in basically opposite directions. It also doesn’t appear to have any circulation characteristics, so in the end it doesn’t appear to be a typhoon-in-waiting.
A look at the contemporaneous Band 13 infrared animation helps bring a little more definition to these storms. It’s easier to see the circulation around Koguma, for example, and the lack of circulation associated with the convective system in the southwest.
Choi-Wan actually peaked at Category 5 status, joining the notorious list of 20206 Category 5 super typhoons that included Sinlaku, Bavi, and Dolphin. The synthetic aperture radar (SAR) winds from the 4th show an almost perfectly symmetrical wind field with magnitudes well over 100 knots.
The D-MINT time series of Choi-Wan shows a pretty steady intensification rate, peaking at Category 5, and then a consistent weakening after that. There was no obvious eyewall replacement in this storm like we’ve seen with some of the other strong typhoons this year.
By comparison, the D-MINT time series of estimated cyclone strengths for Nolo has been quite fascinating. As reported on the blog, Nolo started out as an eastern Pacific hurricane but crossed the 180 degree longitude line to officially be classified as a typhoon. While it was still in the east, Nolo got very close to Category 5 status, but its northerly trajectory at that time took it into a relatively cooler region of water and so it weakened into a tropical storm. However, it took a westward turn and into fresher waters which reinvigorated it, and it strengthened back to a Category 3.
As far as the weakest of the three systems, Tropical Storm Koguma, while it is over warm water, it’s also experiencing dry air entrainment and is somewhat vertically tilted. Therefore, the Joint Typhoon Warning Center is predicting a marginally favorable environment for continued development.