The relatively compact storm is tracking at an unusually far south latitude, not far from the equator. Writes Wunderground’s Jeff Masters:
Mindanao rarely gets hit by typhoons, since the island is too close to the Equator, and the infrastructure of Mindanao is not prepared to handle heavy typhoon rains as well as the more typhoon-prone northern islands. Bopha is potentially a catastrophic storm for Mindanao.
Satellite imagery of this typhoon is extraordinarily impressive and ominous.
Describes the Joint Typhoon Warning Center:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A WELL DEVELOPED, INTENSE SYSTEM THAT HAS A 9NM [NAUTICAL MILE] EYE AND HAS RAPIDLY INTENSIFIED IN THE PAST TWELVE HOURS.
Storms this strong do not usually occur this far south because the coriolis force, which helps storms spin up, is weak at such latitudes. Bopha became a typhoon just 3.8 degrees above the equator says the UK Met Office.
Correction: The original version of this blog post said: “Masters writes on his blog that this is farthest south a typhoon has ever been recorded in the Western Pacific.” WeatherBell meteorologist Ryan Maue says Typhoon Vamei formed farther south at 1.5 degrees latitude on December 27, 2001. Link: Data source on Typhoon Vamei