MARIANA ISLANDS — Typhoon Choi-wan continues to strengthen as it moves northeast and away from the Mariana Islands, but the storm’s effects are far from over.

As of Saturday afternoon, October 3, Choi-wan had maximum sustained winds of 100 mph, making it a Category 2 typhoon. The National Weather Service in Guam expects the storm to reach Category 3 strength, with forecasts indicating winds could approach 120 mph on October 4 as it moves farther north and northeast of the islands. National Weather Service

Choi-wan was upgraded from a tropical storm to a typhoon late Friday night, October 2, Marianas time, as it began turning north and its typhoon-force wind field expanded across the northern Mariana Islands. National Weather Service

The center of the storm is moving away, but residents from Guam through the Northern Mariana Islands continue to experience hazardous weather.

Guam, Rota, Tinian and Saipan remain under a Flood Watch through late Sunday night. NWS warns that excessive rainfall could cause flash flooding in low-lying, poorly drained and urban areas. An additional 3–5 inches of rain is forecast for Guam and Rota and 4–6 inches for Tinian and Saipan during the watch period. National Weather Service

Saipan and Tinian are also under a High Surf Advisory and Coastal Flood Statement through Monday afternoon. Breaking waves of 9–12 feet are expected along north-, south- and west-facing reefs, with isolated minor coastal flooding, water reaching some low-lying roads and property, and localized beach erosion possible. National Weather Service

The Typhoon Is Leaving. Why Is the Weather Still So Bad?

Part of the answer is the monsoon surge that has been an important part of Micronesia’s weather pattern over the past several weeks.

NWS specifically attributes the continuing strong winds south of Choi-wan to an enhanced southwesterly monsoon surge. Very strong to gale-force southwesterly winds were continuing around Tinian and Saipan Saturday evening, while Guam and Rota were experiencing somewhat weaker but still strong winds. Combined seas across the region were running 13–16 feet. National Weather Service

Earlier Saturday, bands of heavy rain embedded in that monsoon flow produced gusts of up to 75 mph on Saipan and 60 mph on Guam. National Weather Service

This means Choi-wan does not have to remain directly over the islands for dangerous conditions to continue. Its large circulation is interacting with and strengthening the broader monsoon flow to its south, producing strong winds, rain and large waves well away from the typhoon’s center.

The Third Major Typhoon to Affect Micronesia This Year

For residents of Micronesia and the Marianas, Choi-wan comes after two exceptionally powerful storms earlier in 2026.

Super Typhoon Sinlaku developed immediately north of Chuuk in April and moved very little for several days. The developing cyclone was only about 50 miles northwest of Chuuk Lagoon on April 10 and became a typhoon the following morning before finally beginning to move north. An FSM disaster assessment describes Sinlaku as having stalled north of Chuuk Lagoon for three days, bringing destructive winds, heavy rainfall, storm surge and saltwater intrusion. NASA Scientific Visualization Studio

Sinlaku eventually intensified dramatically, reaching estimated peak sustained winds of about 175 mph before reaching the Marianas. NASA Scientific Visualization Studio

It crossed Saipan and Tinian as a Category 4 storm with winds around 150 mph. The eye and eyewall moved so slowly across the islands that NWS says an Extreme Wind Warning remained in effect for more than 22 hours. Buildings and infrastructure were damaged or destroyed, trees were snapped or uprooted, heavy rain caused widespread flooding and destructive waves battered the coastline. National Weather Service

Then came Super Typhoon Bavi in July.

Bavi reached 180 mph sustained winds before making a direct Category 5-equivalent strike on Rota on July 6. The storm’s center passed along Rota’s northern coast while still carrying those 180-mph winds. Saipan International Airport, about 70 miles away, recorded a gust of 111 mph, while Guam received nearly 16 inches of rain over July 4–5. NASA Scientific Visualization Studio

Rota suffered widespread destruction. The island lost power and running water, and its mayor reported that the majority of homes were damaged or destroyed. Stars and Stripes

Unlike Sinlaku, however, Bavi did not linger over the islands for days. It was the storm’s extraordinary intensity and direct passage over Rota that made it so destructive.

Marshall Islands: West-Wind Swell Eases, but the Monsoon Trough Remains

Farther east, the recent west-wind swell episode at Kwajalein Atoll is easing.

The local RTS Weather Station has dropped its West Wind Swell Warning as winds have rotated away from the persistent westerly direction that generated waves across Kwajalein Lagoon. There are currently no new NWS high-surf or coastal-inundation advisories for Ebeye or Kwajalein and no authoritative reports of damaging surf or flooding from the latest episode.

But the broader weather pattern has not disappeared.

NWS Guam is now tracking Invest 94W just east of Kwajalein, embedded in the monsoon trough. As of Saturday evening, the circulation remained poorly organized and was expected to meander near the Marshall Islands before eventually moving north toward Wake Island. National Weather Service

That circulation and the monsoon trough help explain the unusual winds experienced recently around Kwajalein.

Normally, Kwajalein’s trade winds blow predominantly from the east. When the monsoon pattern puts Kwajalein on the opposite side of the trough, winds can instead come from the west. Those winds have enough distance across the enormous Kwajalein Lagoon to build waves that approach normally sheltered lagoon-facing shorelines.

This provides important context for the unusual lagoon-side waves reported at Ebeye in September. It does not establish that every recent west-wind event had precisely the same cause, but it provides a much stronger explanation for why lagoon-facing shorelines can experience significant waves when the regional wind pattern reverses.

One Monsoon Pattern, Different Effects Across Thousands of Miles

A monsoon trough is not itself a typhoon. It is a long zone across the tropical Pacific where winds from different directions meet. Air rises along this zone, helping produce clouds, heavy showers, thunderstorms and sometimes the disturbances that eventually become tropical cyclones.

As the trough moves north or south, an island can suddenly find itself on a different side of that circulation. Wind direction changes, rainfall patterns shift, and waves can begin arriving from directions that are unusual during the normal trade-wind season.

That broader pattern has connected much of the recent weather across Micronesia: westerly winds and lagoon waves in the Marshall Islands, unsettled weather across parts of the FSM, and the powerful southwesterly monsoon surge now continuing behind Choi-wan in the Marianas.

The strengthening 2026 El Niño provides another layer of background conditions. El Niño can alter rainfall, winds, tropical cyclone activity and sea levels across the Pacific. Reports of unusually exposed coral in Yap and parts of the Marshall Islands, for example, are consistent with the temporary lowering of western Pacific sea levels that can occur during strong El Niño conditions.

That does not mean El Niño caused Choi-wan, Sinlaku, Bavi or any individual episode of high waves. Instead, it changes the larger atmospheric and oceanic environment in which all of these events are occurring.

For communities across Micronesia, the events of 2026 are also demonstrating why the effects of a tropical cyclone can extend far beyond the storm’s eye. Choi-wan may be moving away from the populated southern Marianas, but its interaction with the monsoon continues to produce hazardous winds, rain, seas and surf hundreds of miles from its center.