CAMP FOSTER, Okinawa — A new tropical storm, the 21st of the northwest Pacific’s tropical cyclone season, spawned overnight Sunday well to the east of Guam. Forecasters indicated Monday the storm is no immediate threat to the main Northern Marianas islands.

“It could possibly threaten some of the smaller islands way up north,” said lead forecaster Mike Middlebrook of Guam’s National Weather Service office in Barrigada.

Joint Typhoon Warning Center forecasts call for Tropical Storm 21W to pass on Wednesday afternoon near Asuncion, one of the northernmost of the sparsely populated outer Marianas, then continuing west-northwest in the general direction of Iwo Jima and Okinawa.

That would take it well out of the way of Guam; as of Monday evening , the storm’s closest point of approach was forecast to be 432 miles north of Andersen Air Force Base at 11 a.m. Wednesday, packing sustained winds of 58 mph with 75-mph gusts.

“We’re keeping a close eye on it,” Middlebrook said, noting that tropical cyclone tracks can change. “It’s been known to happen. None of these things are set in stone.”

“It’s too early for us to tell anything at this point” whether Tropical Storm 21W will approach or threaten Okinawa, said duty forecaster Senior Airman Brianna Riedell of Kadena Air Base’s 18th Wing weather.

At midnight Monday, Tropical Storm 21W was 776 miles east-northeast of Guam, tracking northwest at 15 mph with sustained winds of 40 mph and 52-mph gusts.

If it remains on its forecast track, Tropical Storm 21W will intensify into a typhoon by Thursday evening and come within 190 miles south Iwo Jima at 10 p.m. Thursday, with sustained winds of 81 mph and 98-mph gusts, equal to a Category 1 hurricane on the Saffir-Simpson scale.

Tropical storm 21W will be named Soulik (pronounced SOW-lick), Micronesian for traditional Pohnpei chief’s title.

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