Typhoon Sinlaku (2026)

The origins of Typhoon Sinlaku are traced back to an atmospheric circulation center near Majuro that crossed the International Date Line at 4°N on March 29, 2026. No development occurred—contrary to weather forecasting models—as it held weak convection moving southwestward, and merged with another circulation west of Tarawa inside the Intertropical Convergence Zone. The resultant center later developed south of Kosrae by April 4, turning west and slowly organizing over time.^[4] Low vertical wind shear, warm sea surface temperatures of 29–30 °C (84–86 °F), and poleward outflow allowed convection to flare and overcast the center.^[5] Additionally, a powerful westerly wind burst that also spawned Cyclones Maila and Vaianu in the Southern Hemisphere contributed to the disturbance's consolidation.^[4][6] By 06:00 UTC of April 8, the Japan Meteorological Agency (JMA) classified the system as a tropical depression as it drifted northwestward;^[7][4] the Joint Typhoon Warning Center followed suit eighteen hours later on April 9, designating it the numeral identifier 04W. Weakily steering west between a near-equatorial ridge in the Central North Pacific and the eastern edge of a subtropical ridge over the Luzon Strait, the system intensified from an abundance of mid-level moisture.^[8] The embryonic storm consisted of a large, defined, partially-exposed circulation center with nascent convective banding over its northwest quadrant.^[9] The rainbands later improved and expanded to the north and west of the storm, leading to it becoming a tropical storm at 18:00 UTC according to the JMA and JTWC, with the former agency labeling it Sinlaku.^[10][11]

A ragged central dense overcast then emerged, with satellite imagery detecting intense burst of lightning storms despite dry air and vertical shear restricting outflow from the southeast.^[12] By 09:00 UTC of April 10, the JMA classified Sinlaku a severe tropical storm.^[13] The overcast rapidly expanded over the eastern edge of the slow-moving, meandering system, with very cold overshooting tops of −97 °C (−143 °F) and a defined gravity wave propagation indicating further intensification.^[14][15] At 18:00 UTC, the JMA reported that Sinlaku had strengthened into a typhoon,^[16] followed by the JTWC six hours later on the next day.^[17] The addition of high ocean heat content and strong diverging winds aloft amplified by an upper-level trough led to extremely favorable conditions for development, commencing a period of rapid intensification.^[18][19] Despite a ragged eye struggling to form,^[19] it later became well-defined and reached near-perfect symmetry as Sinlaku drifted northwestward towards the Mariana Islands, becoming a super typhoon at 06:00 UTC on April 12. In addition, a vigorous radial outflow structure—which is indicated by cirriform clouds—was exhibited.^[20] Furthermore, the dense overcast became uniform as southern banding elongated,^[21] and six hours later, the JMA and JTWC both reported that Sinlaku had attained peak intensity; the JMA reported 10-minute maximum sustained winds of 215 km/h (130 mph) and a lowest atmospheric pressure of 905 hPa (26.72 inHg), and the JTWC estimated 1-minute winds of 295 km/h (185 mph).^[22][23] Shortly after, an outer eyewall was detected on microwave imagery, suggesting the onset of an eyewall replacement cycle—a process common in very powerful tropical cyclones. Sinlaku slightly weakened as a result, though its inner eyewall remained strong.^[24]

The persistent, extraordinarily favorable environment slowed weakening from the cycle and dry air intrusion, though the size of the central dense overcast decreased on April 13. Initially preserving its nearly axisymmetrical structure,^[25] Sinlaku's northern periphery began to deform as the outer eyewall encircled the smaller inner eyewall, leaving a moat.^[26] As Sinlaku neared the island of Saipan, a scatterometer passing directly over the storm's center revealed winds of gale-force with a diameter of 400 nautical miles (740 km; 460 mi).^[27] At 11:40 UTC on April 14, the western side of the eyewall struck Tinian and Saipan, reporting sustained winds of 209 km/h (130 mph) from Tinian International Airport.^[4] Despite convection remaining strong, the center became more ragged as the inner eyewall further diminished as Sinlaku decelerated significantly, prolonging its effects on the Mariana Islands. At 12:00 UTC, the JTWC reported that Sinlaku was no longer a super typhoon.^[28] By the next day, the eyewall replacement cycle was near completion as a mass of dry air to the west began invading through Sinlaku's southeastern outer bands.^[29] The eye became 30 nautical miles (56 km; 35 mi) wide and Sinlaku had expanded its wind field, maintaining winds of 215 km/h (130 mph), according to the JTWC.^[30] A eyewall replacement cycle then started for a second time, evident by a secondary eyewall formation.^[31] It caused the eye turning cloud-filled while Sinlaku recurved north-northeastward under the influence of the near-equatorial ridge to the southeast.^[32]

Sinlaku continued to steadily weaken from the marginal conditions, losing its defined eye on April 16,^[33] entering an area of lower sea surface temperatures and increased wind shear. The weak inner eyewall then collapsed, moving the deepest convection to the outer eyewall.^[34] Regardless of outflow boosted by the westerlies, convective activity decreased near the core of the system.^[35] By the start of April 18, the JMA downgraded Sinlaku back to a severe tropical storm.^[36] Furthermore, an increasingly exposed circulation center led the JTWC to report that Sinlaku had degraded to a tropical storm at 12:00 UTC.^[37][23] Convection shifted to the east quadrants as low-level stratocumulus clouds advected southward from the subsident dry air mass.^[38] Amidst the very unconducive conditions, Sinlaku began transitioning into an extratropical cyclone during the next day, accelerating while 459 km (285 mi) northwest of Minamitorishima.^[39] At 06:00 UTC, the JMA determined that Sinlaku had weakened into a tropical storm.^[40] The JTWC described the system as a hybrid subtropical storm with frontogenesis occurring to the east.^[41] The final bulletin on the storm from the JTWC was issued at 18:00 UTC,^[42] followed by the JMA six hours later on April 20—which concluded that Sinlaku had become an extratropical low moving east-northeastward under the influence of the mid-latitude westerlies.^[43]

The Guam Power Authority offered help in reinstating power in the Northern Mariana Islands, reaching out to personnel from the Commonwealth Utilities Corporation of the Islands.^[74] All schools within the scope of the Guam Department of Education were kept closed under further notice, with Department spokesperson Michael Borja reporting that the schools will be opened once "all of our schools are ready to go"; none of the schools suffered damage, but operational and health concerns still affect the schools.^[75] As of 09:00 ChST on April 19, 73% of system loads and 86% of feeders and circuits in Guam were reinstated, with every major substation energized and most of its power restored.^[76] Seniors in Guam were provided hot meals by "Grab and Go" as well as home delivery due to the closure of senior centers.^[69]

Wikimedia Commons has media related to Typhoon Sinlaku (2026).

• Weather of 2026
• Tropical cyclones in 2026
• List of typhoons in the Mariana Islands
• List of super typhoons
• List of violent typhoons
• Typhoon Yutu (2018) – Strongest typhoon to strike the Mariana Islands
• Typhoon Surigae (2021) – Another exceptionally intense super typhoon that occurred in April
• Typhoon Mawar (2023) – Another typhoon which affected Guam the same way as Sinlaku, nearly 3 years prior