Three tropical cyclones, two of which appear destined to be powerhouse storms of near-super typhoon strength, are spinning slowly across the western tropical Pacific Ocean, with a fourth storm about to be born on Monday.  The most dangerous storm of the group —Typhoon Chan-hom — has already made its presence felt, as it dumped more than a foot of rain in Guam over the Fourth of July weekend. The storm struggled to intensify for the first several days of its life, but it is still forecast to deepen into a super typhoon, with maximum sustained winds of 150 miles per hour, by Thursday. It may affect southwestern Japan, including Okinawa, on Thursday, Taiwan on Thursday night, and China on Friday night through Saturday..  Typhoon Chan-hom in the upper left, followed closely by Typhoon Nangke at the lower right.  Typhoon Chan-hom may come close to the island of Okinawa, and brush past the northern part of Taiwan, or possibly make landfall there, on July 10.  The area at greatest risk for a direct landfall from this storm appears to be between Shanghai and Wenzhou, China, on July 11 and 12. This puts a large, urban area at risk of seeing strong winds of greater than 75 miles per hour, as well as heavy rain and storm surge-related flooding.  About 2 million people call Wenzhou home, while Shanghai is far larger, with a population of about 14.3 million. This part of the Chinese coast has a long history of encounters with typhoons, though many of the landfalling storms there have been weakening as they approached land.  Long range storm track and intensity forecasts have a significant amount of uncertainty, but most computer models now agree on the general direction the storm will follow.  Similarly, there is model agreement that the Typhoon Chan-hom will intensify, although the lack of routine aircraft flights into such storms in the Pacific can make intensity forecasts there less reliable than the already uncertain forecasts in the Atlantic, where hurricane hunters routinely investigate storms to obtain information about their intensity, movement and inner workings.  Following about four days behind Chan-hom is Typhoon Nangka, which is forecast to pass across the Northern Mariana Islands while intensifying into the equivalent of a Category 2 or Category 3 hurricane. It too could be an eventual threat to China or Japan.  Then there is Tropical Storm Linfa, which made landfall in the northern Philippines' island of Luzon over the weekend, dumping copious amounts of rainfall in the process.  Linfa is meandering between the Philippines, Taiwan and the Chinese mainland, and is likely to stumble ashore in a rather disorganized state, its center wobbling to and fro, looking like a drunk person stumbling home after a night on the town.  But wait, that's not all. There's likely to be another tropical cyclone forming behind Typhoon Nangka, where the Joint Typhoon Warning Center issued a tropical cyclone formation alert on Monday.  The sudden burst of activity in the central and western Pacific Ocean follows a six-week lull in activity there, after this part of the world had its most active start to the typhoon season on record. Three of the first four typhoons that developed reached the equivalent of a Category 5 hurricane, and the planet has already seen as many Category 5 storms as it typically does in a given year.  There are two primary reasons for the increase in storm activity. The first is a strengthening El Niño event, which is bringing much above average ocean temperatures to a broad area of the tropical Pacific Ocean, roughly from the international dateline eastward to South America.  El Niño events tend to increase the amount of storminess in areas just north and south of the equator, and these tropical thunderstorms, if given the right encouragement from the atmosphere, can start to organize, take on some rotation and intensify into a fledgling tropical cyclone.  But the El Niño does not explain the whole picture. After all, it has been present during the entire spring and summer, yet the tropical Pacific went into sleep mode for six weeks.  The other factor at work is a global weather cycle known as the Madden-Julian Oscillation, or MJO. Named after meteorologists Roland Madden and Paul Julian, who first described the cycle in 1971, the MJO is an eastward-moving disturbance of clouds, rainfall, winds and pressure that circles the globe in between 30 to 60 days or so, according to the National Oceanic and Atmospheric Administration (NOAA).  The MJO has two phases, an enhanced rainfall phase and a suppressed rainfall phase. Recently, the central and western Pacific entered into a particularly strong enhanced rainfall phase, after being in a six-week suppressed phase.  The enhanced rainfall phase favors increased thunderstorm activity across the ocean basin, resulting in more tropical cyclones.  In other words, once the MJO turned favorable over the abnormally mild Pacific, it's as if someone lit a match — and boom! Four tropical cyclones at once.
Typhoon Chan-hom may intensify significantly before making landfall in China near Shanghai, threatening millions. Other storms lurk in the Pacific, too.