It has no official bounds; it ran year-round in 1997, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November.
[5] Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed.
It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of 39 miles per hour (63 km/h).
This was due to the El Niño of 1997–1998, which contributed to the record amounts of not only super typhoons but also tropical storms in the Western and Eastern Pacific.
Based on satellite imagery estimates, the Joint Typhoon Warning Center upgraded it to Tropical Storm Hannah six hours after first forming.
The deep convection quickly organized into well-defined cyclonic bands, and early on January 20 Hannah attained its peak intensity of 60 mph near the island of Yap.
Increased southeasterly wind shear weakened the storm, leaving its dwindling convection situated along the northern portion of the circulation.
Interaction with a large and powerful extratropical cyclone left the storm moving erratically, and on January 22 Hannah weakened to tropical depression status.
[9] Jimmy continued northwestward through a break in the subtropical ridge caused by Isa, and it steadily intensified as it tracked through an area of light vertical wind shear.
On August 2, the storm merged with an approaching frontal trough,[26] and the following day JMA considered Scott dissipated while located near the Alaskan island of Gareloi.
Tina brought heavy rainfall, strong winds, and storm surges to the Philippines, causing widespread damage and flooding.
The storm, tracked by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) from July 30 to 31, 1997, caused widespread devastation.
Victor's impact underscores the significant threat posed by tropical cyclones and highlights the importance of preparedness and disaster response measures in affected regions.
On the 18th, a minimal Typhoon Winnie passed north of Taiwan and hit eastern China, where it winded down until degenerating into a remnant low on the 20th.
The tropical depression initially tracked slowly west-northwest between the subtropical ridge and Typhoon Zita and developed at a faster than normal pace.
By August 26, Tropical Storm Cass formed to the west-southwest, which accelerated Amber's forward motion to the northwest due to a Fujiwhara interaction.
[36] On August 25, a low-pressure area developed in the South China Sea, west of the Philippines, associated with the dissipating convection of Tropical Storm Zita.
[9] The storm then crossed northern Japan, and it accelerated over the open Pacific Ocean, where it dissipated on September 19, near the International Date Line to the south of the Aleutian Islands.
JTWC issued its final warning on September 20, as the system transitioned to an extratropical low while en route to the Gulf of Alaska.
It originated as a small, disorganized system east of the International Date Line and gradually intensified into a tropical depression.
At this time, Ginger featured a small, well-defined eye surrounded by a smooth central dense overcast and large convective feeder bands.
Over the next 24 hours, the depression stalled in response to weak steering currents before a subtropical ridge developed to the north and caused the system to move quickly to the west.
Ivan eventually made landfall in northern Luzon with winds of 220 km/h (140 mph) on October 20 before weakening to a tropical storm the next day.
[46] The tenth of eleven tropical cyclones to attain super typhoon intensity in the western North Pacific during 1997, Keith formed at low latitudes in the Marshall Islands.
NEXRAD imagery from Guam indicated the eye wall cloud of Keith never touched land as it threaded the narrow channel between these two islands.
The hardest hit provinces were Kiên Giang, Cà Mau, Bạc Liêu, Sóc Trăng, Trà Vinh, Bến Tre and Vũng Tàu.
[17] The remnants of Tropical Storm Mort brought locally heavy rainfall to areas of northern Luzon, resulting in minor flooding.
After causing major damage across the smaller Western Pacific island groups, Paka rapidly weakened and dissipated on December 22.
Later, it passed just north of Guam, where strong winds destroyed about 1,500 buildings and damaged 10,000 more; 5,000 people were left homeless, and the island experienced a complete power outage following the typhoon.
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) uses its own naming scheme for tropical cyclones in their area of responsibility.