Mirror Image Pacific Tropical Storms Straddle the Equator
A somewhat unusual event could be found on the morning of 10 April 2026 when twin tropical cyclones could be found in the western Pacific. Since each storm was on the other side of the equator, the two systems were rotating in opposite directions. To the north was Sinlaku, a developing storm that is projected to intensify into typhoon strength with the potential to bring adverse impacts to Guam on Monday the 13th. To the south is Maila, a storm that is weakening from its peak strength and which was featured in the Blog earlier this week. Here is an animation of both storms from the Himawari-9 True Color product; remember, unlike the GOES series the Advanced Himawari Imager has a true green channel in addition to its red and blue channels, making for a product that looks slightly different when compared to the American satellites (which assume that a channel that has strong vegetation reflectance is a reasonable proxy for green).
NOAA’s satellite-derived seat surface temperatures, courtesy of the Office of Satellite and Product Operations, show sea surface temperatures around 29 C (84 F) for both systems. However, Maila is in a region of stronger shear and moving toward a region of colder sea surface temperatures, and so it is expected to continue to weaken. Here is an inset of the SST map showing the warm waters around the equator.
While the storms look similar on the visible wavelength imagery, Maila and Sinlaku look rather different on the AHI Band 13 (infrared window) satellite loop. This product shows warmer cloud tops for the southern storm, indicative of weaker convection.
However, that weather convection does not necessarily translate to weaker winds. Here is a mosaic of winds observed by the OSCAT-3 scatterometer. Note how Maila still has plenty of winds greater than 50 knots encircling a tight center of rotation. While this storm is weakening, as of this set of images it is still a Category 1 cyclone and still has the potential for negative impacts to the eastern islands of Papua New Guinea.
The CIMSS MIMIC-TPW2 product also show the twinned nature of these two systems, with clear signals of cyclonic, but mirrored, rotation on either side of the Equator. Note the extreme levels of total precipitable water just to the west of New Guinea on the left side of the animation. Also evident at around 30 S are the remains of Vaianu, a former category 3 tropical cyclone that now shows clear signs of extratropcial evolution.
