what is the frequency of its occurrence?
Pacific typhoons have formed year round, with peak months from August to October. The peak months correspond to that of the Atlantic hurricane seasons.
Typhoon
This makes this basin the most active on Earth. Pacific typhoons have formed year round, with peak months from August to October. The peak months correspond to that of the Atlantic hurricane seasons. 
where do most hurricanes typhoons and cyclones originate Northern Hemisphere how are its intensities classified? "Typhoon", "severe typhoon" and "super typhoon". who are responsible for monitoring and forcasting it? National Meteorological and Hydrological Service
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Typhoon [SEP] Frequency
Nearly one-third of the world's tropical cyclones form within the western Pacific. This makes this basin the most active on Earth. Pacific typhoons have formed year round, with peak months from August to October. The peak months correspond to that of the Atlantic hurricane seasons. Along with a high storm frequency, this basin also features the most globally intense storms on record. One of the most recent busy seasons was 2013. Tropical cyclones form in any month of the year across the northwest Pacific Ocean, and concentrate around June and November in the northern Indian Ocean. The area just northeast of the Philippines is the most active place on Earth for tropical cyclones to exist.