Guam and Rota are now under a typhoon warning as Tropical Storm Champi strengthens; the forecast takes it close to or over Guam on Sunday morning

Thursday’s story had a Typhoon Watch and Tropical Depression Champi (29W) about 895 miles east of Guam, with winds near 35 mph. At 4:11 p.m. Chamorro Standard Time Friday (2:11 a.m. Eastern), the National Weather Service in Tiyan issued a Typhoon Warning for Guam, Rota, and the nearby waters, and a Tropical Storm Warning for Tinian, Saipan, and their waters. A Typhoon Watch continues for Tinian and Saipan. A Flood Watch covers all of Guam and the Northern Marianas.

What the warnings mean. A Typhoon Warning means typhoon conditions, including winds of 74 mph or more, are expected by Sunday morning, with tropical-storm-force winds arriving Saturday night. For Tinian and Saipan, a Tropical Storm Warning with a Typhoon Watch means winds of 39 to 73 mph are expected by Saturday night, and typhoon-force winds are possible if Champi’s track shifts far enough north.

Where it is. Advisory Number 8, issued at 7:08 p.m. Chamorro Standard Time Friday (5:08 a.m. Eastern), put the center at 7 p.m. near latitude 11.6 north, longitude 152.1 east: about 510 miles east-southeast of Guam, about 495 miles east-southeast of Rota and Tinian, and about 490 miles east-southeast of Saipan. Top winds had increased to 60 mph. Champi was moving west at 13 mph and is expected to turn slightly west-northwest and speed up a little through Saturday. The weather service says that track takes Champi close to, or over, Guam Sunday morning. Tropical-storm-force winds reach up to 100 miles from the center.

How strong. The advisory says Champi should keep strengthening over the next few days and could become a typhoon Saturday morning. The 4:11 p.m. local statement says forecasters expect a period of rapid strengthening, and that wind and rain will come in fast and turn dangerous soon after they start. It tells residents: “Do not let a false sense of normalcy now dictate your actions tomorrow; prepare NOW!” An earlier Guam Homeland Security advisory, from 7:30 a.m. Friday, relayed a weather service forecast of a pass very near or over Guam late Sunday morning as a Category 2 typhoon, and warned that faster strengthening could bring a stronger storm.

What to expect. Guam’s Joint Information Center, citing the weather service, says tropical-storm winds should begin Saturday evening, with typhoon-force winds possible Sunday morning through Sunday afternoon, and the possibility of at least extensive damage somewhere in Guam and the Northern Marianas. Surf could build to a dangerous 15 to 20 feet by Sunday morning. Storm surge could flood low ground by 2 to 3 feet, possibly more near the center, and waves could run up as high as 12 feet. Rain totals of 6 to 12 inches are possible.

Readiness. Governor Lourdes A. Leon Guerrero put Guam in Condition of Readiness 2 at 1 p.m. Friday, and the joint information center is partly activated. Joint Region Marianas, the military command on the islands, declared its own readiness level 2 at about 1 p.m. Officials urge people in metal-roof or container homes, storm-surge zones, or flood-prone areas to find a safer place to stay now, such as a sturdy home of family or friends, and to follow official announcements about shelters and evacuations.