Super Typhoon In-fa Is Passing the Northern Mariana Islands With 145 mph Winds

A super typhoon is brushing the top of the Mariana chain today. In the National Weather Service Guam advisory issued at 4 p.m. Chamorro Standard Time on Friday, October 30, Typhoon In-fa was centred at 18.7°N, 146.2°E — about 35 miles east of Agrihan, 50 miles northeast of Pagan and 80 miles north-northeast of Alamagan — moving west-northwest at 22 mph with maximum sustained winds of 145 mph. Typhoon warnings remain in effect for Agrihan, Pagan and Alamagan, the three northernmost inhabited islands of the Commonwealth of the Northern Mariana Islands, where typhoon conditions are occurring.

The Joint Typhoon Warning Center, which designates the storm 30W, put In-fa at 17.8°N, 147.8°E at midnight UTC — roughly 194 nautical miles northeast of Saipan — with sustained winds of 125 knots gusting to 150 knots. By any agency's measure, this is one of the strongest storms on Earth right now, and today is its closest pass to the Marianas.

In-fa has taken on what meteorologists call annular characteristics: a remarkably symmetrical ring of intense thunderstorms wrapped around a large, nearly cloud-free eye, with few of the outer spiral bands a typical typhoon carries. The JTWC measured that eye at roughly 40 nautical miles — about 46 miles — wide on October 29, when the storm was packing sustained winds of 150 mph.

The ocean underneath matches the satellite picture. The JTWC reported a significant wave height of 60 feet in its October 29 analysis — that is the average height of the highest third of waves in the open ocean beneath the storm, not surf breaking on a beach. Even so, it describes a sea state few ships would choose to be anywhere near.

The islands in the warning area face the storm's core winds, but In-fa's reach extends well south of its centre. In its October 29 forecast discussion, the National Weather Service in Tiyan, Guam warned that large, long-period northeast swell from In-fa would build seas up to 14 feet in Tinian and Saipan waters and around 10 feet near Rota and Guam, with surf building as high as 18 feet along the north- and east-facing reefs of Tinian and Saipan and up to 14 feet for Rota and Guam. A high surf warning is in effect for Friday for parts of the chain, with a dangerous rip current risk running through Saturday afternoon and minor coastal inundation possible on exposed reefs.

For Guam, Rota, Tinian and Saipan themselves, the same discussion is reassuring on wind: direct impacts remain highly unlikely, because the storm's tight wind field is passing north of them. The hazard there is the water, not the wind — a distinction worth keeping, because an 18-foot reef break under a calm sky still closes beaches.

Forecast guidance takes In-fa northwestward, away from the Marianas, over the next day, still at typhoon strength. Japan's Meteorological Agency then brings it toward waters near the Ogasawara Islands over the weekend, and expects it to remain a very strong typhoon through at least November 4.

Beyond that, forecasters are unusually honest about the uncertainty. The JTWC's track discussion describes confidence in the forecast beyond roughly the first day or two as very low: In-fa's path hinges on a passing trough over Japan, a rebuilding ridge, and possibly a sharp westward turn, a stall, and a second attempt to recurve — a loop more than a line. Anyone with interests south of Japan should treat the five-day track as a sketch, and re-check it against each new advisory rather than planning around today's version.

WorldEye's hurricane tracker follows active tropical cyclones — hurricanes, typhoons and cyclones are the same phenomenon in different ocean basins — with their forecast tracks, so you can watch In-fa's northwest turn (or its failure to turn) advisory by advisory. Pair it with the surf webcams page for Pacific-facing coasts as the long-period swell arrives: swell from a storm this size travels for days, and the surf it produces far from the Marianas is part of this story too.

One caution we apply to every storm: satellite imagery on WorldEye is dated Esri World Imagery, never a live satellite feed, and the authoritative word on warnings always belongs to the agencies — the National Weather Service Guam and the Joint Typhoon Warning Center for this storm. Follow their advisories, and local emergency instructions if you are in the warning area, over anything a map shows you.