It ran year-round in 1978, but most tropical cyclones tend to form in the northwestern Pacific Ocean between June and December.

These dates conventionally delimit the period of each year when most tropical cyclones form in the northwestern Pacific Ocean.

The scope of this article is limited to the Pacific Ocean, north of the equator and west of the International Date Line.

Tropical storms that formed in the basin were assigned a name by the Joint Typhoon Warning Center while systems that were active in the Philippine area of responsibility were assigned a name by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA).

On 12:00 UTC on April 11, the Joint Typhoon Warning Center (JTWC) began to monitor a surface circulation which had formed within the trough.

Olive would recurve due to a break in the subtropical ridge, peaking with sustained winds of 100 mph (160 km/h) the next day.

It accelerated to the east-northeast, steadily weakening due to intruding cool and dry air, resulting in the system becoming extratropical early on April 26.

[3][4] The MV Leyte, a lengthened ship of the Compania Maritima was caught in it, being wrecked in the southwestern portion of Sibuyan Island as she was on a Manila-Cebu voyage.

Several athletes at the Japan-China Friendship Track and Field Meet in Kitakyushu were injured when a freak gust blew them ten feet in the air.

A Liberian-registered tanker was swept from its moorings off the port of Kure and drifted for nearly 5 kilometers before running aground off a small island in the Inland Sea.

After spending over three consecutive days at that intensity, Rita weakened to a Category 4 and smashed ashore on Luzon.

The typhoon caused considerable damage and loss of life in the Philippines, though exact numbers are unknown.

Tess continued to intensify and reached its peak intensity as a 70 mph (110 km/h) storm; just short of typhoon status.

Increased convective activity in the monsoon trough was first noticed on satellite data on November 14 about 690 mi (1,110 km) southeast of Truk.

Based on an improved satellite signature, TD 33 was upgraded to Tropical Storm Viola at 1200 UTC November 17.

[13] Late on November 19 reconnaissance aircraft confirmed that Viola's surface pressure had fallen to 977 mb; and, that an eye was beginning to form.

Viola then started to rapidly intensify and reached peak intensity on November 21 with winds of 145 mph (233 km/h).

On the 29th, Winnie reached its peak intensity as severe tropical storm with (10-min) winds of 65 mph (105 km/h).

The Philippine Atmospheric, Geophysical and Astronomical Services Administration uses its own naming scheme for tropical cyclones in their area of responsibility.

This table will list all the storms that developed in the northwestern Pacific Ocean west of the International Date Line and north of the equator during 1978.

It will include their intensity, duration, name, areas affected, deaths, missing persons (in parentheses), and damage totals.