Chanthu formed on September 6, according to the Joint Typhoon Warning Center. The storm then underwent one of the most extreme bouts of rapid-intensification ever recorded, by increasing 80 knots in wind speed in just 24 hours on September 7. Rapid intensification is when a storm gains at least 30 knots (35 mph) in wind speed within 24 hours. Chanthu is the second storm of the year to reach super typhoon status, after Surigae in April.
The super typhoon is passing just to the east and north of Luzon in the Philippines early Saturday morning, bringing with it heavy rainfall, severe winds, and coastal inundation. As of 8 a.m. local time Saturday, the Philippine weather bureau said Chanthu -- known locally as Kiko in the Philippines -- was about to make landfall over Batan and Sabtang islands in Batanes with maximum sustained winds of 215 kph (133mph) near the center and gusts of up to 265 kph (164 mph).
Portions of Luzon can expect torrential rainfall, typhoon-force winds of 171 to 220 kph, and a storm surge of 1 to 2 meters through Saturday morning as the typhoon tracks to the north. Throughout the day on Saturday, Chanthu is forecast to track north of Luzon and toward Taiwan while weakening some. The typhoon is forecast to have sustained winds of about 220 kph (135 mph) prior to impacting Taiwan Saturday night into Sunday.
Weather conditions are expected to greatly diminish across Taiwan on Saturday as the storm approaches the southern coast. The island can expect widespread heavy rain of 200 to 300 millimeters with isolated totals of over 300 millimeters possible. This amount of extreme rainfall could lead to flash flooding and mudslides in Taiwan's high terrain.
As Chanthu tracks along the east coast of Taiwan, the land interaction could weaken the system even further. However, the storm is expected to maintain winds of above 180 kph (111 mph) through the weekend.
The official forecast has the system weakening as it tracks north toward China into early next week. Chanthu could stall just off the coast of Shanghai by Monday or Tuesday, which would bring heavy rain to this region as well.
Conson brings flood threat to Vietnam this weekend
At the same time, in the South China Sea, Tropical Storm Conson is due to make landfall near Da Nang, Vietnam, overnight Saturday into Sunday morning. Vietnam has put 500,000 soldiers on standby ahead of its arrival.
The outer bands of the storm are already bringing thunderstorms and gusty winds to the region on Friday and weather conditions will continue to deteriorate across Vietnam on Saturday as the storm approaches the coast.
Although it is a much weaker storm than Super Typhoon Chanthu, Conson is still expected to have sustained winds of 75 kph (45 mph) prior to landfall this weekend. The Vietnamese government has also ordered vessels to stay in port and prepared evacuation plans, Reuters said, quoting state-run media. As many as 800,000 people in Vietnam's northern provinces could be affected by the storm's arrival -- the fifth to make landfall in the country this year.
Conson is forecast to bring widespread rainfall of 100 to 200 millimeters to the region through Monday with isolated totals above 250 millimeters possible. This amount of rain could lead to flash flooding and mudslides across the mountainous terrain.
Earlier this week, Conson brought heavy rain and gusty winds to the Philippines. The storm traversed the central Philippines Monday afternoon through Wednesday before emerging into the South China Sea early Thursday morning. As the storm moved west into the South China Sea, all warnings were lifted for Luzon.