After weeks of inactivity, the western Pacific has just spawned four tropical cyclones, two of which will probably become typhoons.

In most years, the Philippine Sea grows clusters of thunderstorms, and the atmosphere above is ideal in forming these into cyclones. In an El Nino year, the nursery for tropical cyclones moves further east.

This year is an El Nino year and because the warmest Pacific water has been drawn east, so has the typhoon growth region.

Added to that, in the atmosphere high above, the Madden-Julian Oscillation has arrived and it very much encourages storm development. 

One of these cyclones, Raquel, unusually, was south of the equator.

It was named on June 30 and, despite never becoming anything more than a tropical storm, blew a gale over the Solomon Islands and dumped 176mm of rain on Honiara, the capital. Most recently Munda, on Kohinggo Island was swamped with 282mm of rain from Raquel’s remnants.

Like giant sea snails seen from space, the three cyclones north of the equator are evenly spaced, from the Philippines to Guam to the Marshall Islands.

Furthest west is Linfa, locally known as Egay, which has been interacting with the hilly north of Luzon for 24 hours. It too has never exceeded tropical storm status, so besides big waves battering the coast, its main effect has been heavy rain.

Tuguegarao, in the Cagayan valley, recorded 104mm of rain in 24 hours until 06:00 GMT on Sunday from Linfa’s thunderstorms. This same area of Luzon was hit by Noul eight weeks ago. Noul reached super-typhoon category on the Saffir-Simpson Scale but weakened by the time it hit the Philippine coast.

The last two storms in the current crop are both in the prime development area and over open ocean. Chan-Hom and Nangka will both become typhoons over the next two days as they track northwest.

Even at their creation they caused damage: Nangka's big waves and storm surge damaged Majuro in the Marshall Islands while it was still a tropical depression. Chan-hom is still meandering, just north of Guam, before it starts its growth spurt.

The next contact with land for Chan-hom, next weekend, seems likely to be in the Ryukyu chain of Japanese Islands, then China, near Shanghai. Nangka is heading for Micronesia and then Iwo Jima, but will take all week to get there.

Source: Al Jazeera