Midday on May 18 , the JTWC began to monitor an area of persistent disturbed weather associated with a broad low @-@ pressure area southwest of Chuuk . Within highly conductive conditions , the disturbance quickly organized and became classified as a tropical depression at 0000 UTC the following day . In its initial stages , the depression tracked slowly northeastwards . However , a shortwave trough forced a weakness in a nearby ridge , allowing for the storm to take a more streamlined , northward path . At 1200 UTC on May 20 , the JMA upgraded the depression to Tropical Storm Chan @-@ hom . Following the system 's naming , Chan @-@ hom temporarily meandered towards the northwest before resuming its northeasterly track . The next day , the storm began to develop an eye ; this was reflected with an upgrade by the JMA to typhoon status at 0600 UTC on May 23 . Gradual intensification followed , and at 1800 UTC that day Chan @-@ hom reached its peak intensity with maximum sustained winds of 155 km / h ( 100 mph ) and a minimum pressure of 940 mbar ( hPa ; 27 @.@ 76 inHg ) .