Typhoon season | Tropical threats stretch from Shanghai to Hawaii as storms develop

Dark clouds above the city of Sanya, south China’s Hainan Province

The tropical Pacific has come alive, and the threats extend from China to Hawaii.
Typhoon Chan-hom is forecast to sweep China’s coast south of Shanghai on Saturday as a Category 1 storm on the five-step Saffir-Simpson scale, according to the Joint Typhoon Warning Center, run by the U.S. Air Force and Navy in Hawaii. That would place its top sustained winds around 120 kilometers per hour.
The biggest danger from Chan-hom may be the water, or storm surge, that it pushes against land, said Jeff Masters, co- founder of Weather Underground in Ann Arbor, Michigan. While China’s largest city is vulnerable, a direct strike wasn’t likely as of yesterday.
“More than half of Shanghai is less than six feet above sea level,” Masters said. “Someday, their number is going to come up, and they are going to get a bad storm surge there.”
Before Chan-hom reaches the coast, its winds may grow to almost 230kph as it threads its way north of Taiwan and through Japan’s Ryukyu Islands, the Joint Typhoon Warning Center said. That would make it a Category 4 system on the U.S. scale.
To the east, Typhoon Nangka also is forecast to become a major storm as it passes north of Guam. Its winds may peak at 260 mph, which would put it at the top of the Saffir-Simpson rankings as a Category 5 cyclone.
“Nangka is going to recurve east of Japan,” said Dan Kottlowski, expert senior meteorologist at AccuWeather Inc. in State College, Pennsylvania.
The C-shaped track could be a threat to Iwo To, also known as Iwo Jima, where the World War II battle was fought.
Also churning in the western Pacific is Tropical Storm Linfa, which may go ashore in China north and east of Hong Kong today.
In the eastern Pacific, a tropical depression is about 1,650 miles east-southeast of Hilo, Hawaii, according to the National Hurricane Center. If the forecast holds and it grows into a tropical storm, it would be the fourth named system to menace the state since last August.
“Three storms passing within 200 miles (320 km) last year was unprecedented, and to get a fourth one, that just piles on,” said Masters.
Tropical Storm Iselle caused about USD66 million in damage, mainly to the Hawaii’s papaya crop, when it struck the Big Island in August. Hurricane Julio came close to the island chain, also in August, and Hurricane Ana threatened again in October.
The current track forecast calls for the new system to sweep north of the island chain through Sunday. If that holds, the size of the storm will determine its threat to Hawaii: The bigger it is, the more likely the island chain will feel its impact, Kottlowski said.
An El Nino is currently under way across the equatorial Pacific, which means water there is warmer than normal. The warm water and low wind shear are making conditions across the basin ripe for storm growth.
“Whenever an El Nino pattern sets up, the odds of Hawaii being impacted by tropical storms and hurricanes is much higher,” Kottlowski said. Brian K. Sullivan,  Bloomberg