User:Flux55/1990 Pacific typhoon season

The 1990 Pacific typhoon season was a relatively active season, producing 41 depressions, 29 storms, and 19 typhoons. The season ran throughout 1990, although most tropical cyclones typically develop between May and October. The season's first named storm, Koryn, formed on January 12, while its last named storm, Russ, dissipated on December 23.

The scope of this article is limited to the Pacific Ocean to the north of the equator between 100°E and 180th meridian. Within the northwestern Pacific Ocean, there are two agencies which assign names to tropical cyclones which can often result in a cyclone having two names. At the time, the Joint Typhoon Warning Center (JTWC) named tropical cyclones which had 10-minute sustained wind speeds of at least 65 km/h (40 mph) anywhere in the basin, while the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) named tropical cyclones which are active in the Philippine Area of Responsibility (PAR), located between 135°E and 115°E and between 5°N–25°N, regardless of whether or not a tropical cyclone has already been named by the JTWC.

Season summary
This season's ACE index, as calculated by Colorado State University using data from the JTWC, is approximately 170.8 units. This number represents sum of the squares of the maximum sustained wind speed (knots) for all named storms while they are at least tropical storm intensity, divided by 10,000. Therefore, tropical depressions are not included.

Severe Tropical Storm Nathan (Akang)
On June 13, the Joint Typhoon Warning Center (JTWC) began tracking a weak circulation embedded in the monsoon trough. Twelve hours later, the Japan Meteorological Agency (JMA) recognized the system as a tropical depression. The next day, the JTWC issued a TCFA on the system as it had organized significantly, issuing their first advisories on the system on June 15. The nascent depression absorbed a weakening Tropical Depression 04W later that day as the JMA upgraded it into a tropical storm. The JTWC recognized the system as a tropical depression the next day, naming it Nathan.

Nathan gradually intensified, and by 12:00 UTC on June 17, peaked with both 1-minute and 10-minute sustained winds of 65 mph. Weakening soon commenced, and when Nathan made landfall along the China-Vietnam border a day later, it was a minimal tropical storm. The JMA discontinued all advisories around that time, but the JTWC still monitored the system until it dissipated over Northern Vietnam on June 19.

In the Philippines, Nathan (known as Akang) caused 64 fatalities. Additionally, it affected over 227,000 people. In eastern Guangdong, torrential rain associated with Nathan was responsible for 10 deaths. Over 100,000 acres of farmland was affected. In Macau, two men were reported missing. The Hong Kong Observatory issued their Strong Wind Signal No. 3 on 10.00 p.m. Mudslides were reported throughout the area and scaffoldings collapsed in Kowloon. On June 16, the cargo ship, Tien Fu, sank in the South China Sea, killing four.

Typhoon Ofelia (Bising)
On June 15, the Joint Typhoon Warning Center (JTWC) began tracking an area of persistent convection embedded in the monsoon trough. Eighteen hours later, the Japan Meteorological Agency (JMA) upgraded the system into a tropical depression. On June 17, the JTWC issued a Tropical Cyclone Formation Alert (TCFA) for the system, recognizing the system as a tropical depression later that day. On 18:00 UTC that day, the JMA upgraded the depression into a tropical storm, with the JTWC following suit the next day, naming it Ofelia.

Ofelia gradually deepened, and on 00:00 UTC on June 20, was upgraded into a severe tropical storm. Following the development of a central dense overcast, Ofelia was upgraded into a typhoon by the JTWC late on June 20. Two days later, the JMA upgraded Ofelia into a typhoon, stating that it peaked with 10-minute sustained winds of 75 mph and a minimum central barometric pressure of 970 mbar, while the JTWC reported that it peaked with 1-minute sustained winds of 105 mph. Turning northward, Ofelia struck the east coast of Taiwan, rapidly weakening as it tracked inland. The storm then began to turn north, eventually recurving towards the Korean Peninsula. At 00:00 UTC on June 24 the JMA declared Ofelia an extratropical cyclone. with the JTWC following suit the next day as the system merged with a frontal zone.

Despite remaining offshore northern Luzon, the storm's broad circulation enhanced the southwest monsoon that inundated much of the northern Philippines. Taiwan, on the other hand, took a direct hit from Ofelia, with floodwater levels reaching 1 m in some places. According to media reports, the storm was the worst to impact eastern Taiwan in 30 years, dropping up to 18 in of rain in a 24-hour time span, although damage was slight elsewhere. After battering the Philippines and Taiwan, the typhoon dropped 100 mm of precipitation in parts of central China. Across Wenzhou, 12 people were killed.

Typhoon Percy (Klaring)
Typhoon Percy originated from the eastern end of the Western Pacific monsoon trough, first noted by the Joint Typhoon Warning Center (JTWC) on the morning of June 20. Satellite imagery showed signs of a well-defined low-level circulation and the disturbance was situated in a weakly divergent environment aloft along with persistent convection. Later that day, the Japan Meteorological Agency (JMA) upgraded the system into a tropical depression. The system gradually became more organized, resulting in the JTWC issuing a TCFA on the system at 03:00 UTC on June 21. Following a ship report of 40 mph winds, both the JTWC and JMA upgraded the system into Tropical Storm Percy. As Percy continued to intensify, it began to track west-northwestward around another upper-level anticyclone that formed southeast of Typhoon Ofelia. By June 22, Percy was upgraded into a severe tropical storm by the JMA. The JTWC upgraded Percy into a typhoon on the evening of June 23, with the JMA subsequently following suit in the morning of June 24.

After moving away from the Caroline Islands, the typhoon began to intensify at a faster clip as an outflow channel to its north opened, even though the eye was initially ragged. Early the next day, the JTWC estimated that Percy obtained its peak intensity based on the Dvorak estimate of T6.0/130 mph and a clear eye, while the JMA reported that Percy attained its maximum intensity of 90 mph and a minimum barometric pressure of 960 mbar. Increased vertical wind shear took toll on the storm, and by June 27, Percy steadily weakened as the storm passed over northeastern Luzon. Overland, the storm weakened slightly, but remained a typhoon upon entering the South China Sea. At 00:00 UTC on June 29, the JMA downgraded Percy to a severe tropical storm, although the JTWC suggested that Percy was still a typhoon at the time. Shortly thereafter, Percy moved onshore around 130 km southwest of Xiamen. At 06:00 UTC, the JTWC downgraded Percy into a tropical storm, noting that the storm had become less organized. By June 30, both the JTWC and JMA stopped tracking the system, which had dissipated inland.

During its formative stages, Percy affected several of the Caroline Islands. Airline services in and out Yap were halted. The typhoon posed enough of a threat to Hong Kong to warrant a No 1. hurricane signal briefly, but it was dropped within 24 hours. Some flooding occured, especially in the New Territories, where there was slight damage to crops. In Kwai Chung, floodwaters were 0.6 m deep, sweeping away a ten-year-old boy. Two other villages lost power and eleven people had to be evacuated. In the provinces of Fujian and Guangdong of China, power lines were downed. Farm production was reduced by 400 million catties in Fujian.

Severe Tropical Storm Winona
Tropical Storm Winona originated from an area of enhanced convection developed within the monsoon trough in the East China Sea on August 4. Six hours later, the Joint Typhoon Warning Center (JTWC) started tracking the system as a weak low-pressure area developed. At 18:00 UTC, the Japan Meteorological Agency (JMA) classified the system as a tropical depression. Following a Dvorak classification of T1.0/30 mph, the JTWC issued a TCFA at 11:00 UTC on August 5. A day later, the JTWC started issuing warnings on the system, designating the system as a tropical depression, after the system's convection structure improved and thunderstorm activity increased in coverage. On the evening of August 6, the JMA upgraded the depression into a tropical storm.

Early on August 7, the JTWC upgraded the system into a tropical storm, naming it Winona. Wind shear began to relax; consequently, the storm's low-level center moved under the deep convection. Early on August 8, the JMA reported that Winona strengthened into a severe tropical storm. The next day, the JMA stated that Winona peaked with 10-minute sustained winds of 70 mph, while the JTWC estimated that Winona peaked with 1-minute winds of 75 mph over 330 km east-southeast of Tokyo. Early on August 10, Winona made landfall close to Hamamatsu near peak intensity. After landfall, it began to accelerate northeastward and by 12:00 UTC, Winona was embedded in the mid-latitude westerlies and started transitioning into an extratropical cyclone. Both agencies stopped tracking Winona by August 14.

Tropical Storm Winona brought strong winds and heavy rains to the Japanese archipelago. Tokyo was lashed with strong winds and heavy rain for several hours, with damage estimated at 34.9 million yen ($241,000 USD). Seven reservoirs in Tokyo received more than 20,000,000 ST of water; the reservoirs reached 36% capacity, which prompted officials to lift restrictions on water use that were enacted following a drought. Ten homes were flooded, and damage totaled 128.5 million yen ($886,000 USD) in Kanagawa Prefecture. Seven people were wounded, mostly due to gusty winds. The cyclone forced the first two days of the Karuizawa 72 Tokyu Ladies Open to be shortened.

Typhoon Yancy (Gading)
At 06:00 UTC on August 9, Yancy was first noted by the Joint Typhoon Warning Center (JTWC) as a low-level convective center on the eastern side of a monsoon depression. For the next four days, the system gradually organized, resulting in the JTWC issuibg a total of three TCFAs. Meanwhile, the Japan Meteorological Agency (JMA) began monitoring the system on August 11. On 18:00 UTC on August 13, the JTWC issued its first warning on the system as a tropical depression. The next day, both the JMA and JTWC upgraded the system into a tropical storm, with the latter naming it Yancy. At 12:00 UTC on August 16, the JTWC determined that Yancy had strengthened into a typhoon.

According to the JTWC, Yancy intensified into a Category 2-equivelant typhoon on the Saffir–Simpson scale at 12:00 UTC on August 17 with one-minute sustained winds of 90 knots (165 km/h; 105 mph). However, the JMA data stated that Yancy peaked eighteen hours later, with ten-minute sustained winds of 80 knots (150 km/h; 90 mph) and a minimum barometric pressure of 28.05 inHg (950 mbar). Yancy then proceeded to track across Taiwan a few days later. Yancy's interaction with mountainous terrain on the island, and later the Chinese mainland, caused it to weaken. The JTWC downgraded Yancy to a tropical storm at 00:00 UTC August 20; thirty hours later, the agency downgraded the storm to a tropical depression, simultaneously issuing its final warning as Yancy dissipated. The JMA similarly found that Yancy had weakened to a tropical depression on August 22, and it stopped tracking the system the next day.

In the Philippines where Yancy was known by the PAGASA name "Gading", a monsoon surge triggered by the storm resulted in significant rainfall which flooded areas across northern Luzon. In Taiwan, torrential rainfall was recorded, including 1194 mm in the Alishan Range and 718.5 mm on Yu Shan. In Taipei alone, about 525,000 families lost power. Yancy delivered significant impacts to southeastern China. In Fujian, where the cyclone meandered for days and contributed to more than 24 in, more than 4 million residents were directly affected. Throughout the entirety of southeastern China, 400,000 residents were left homeless.

Tropical Storm Aka
On 15:00 UTC on August 13, a weakening Tropical Storm Aka crossed into the basin from the East Pacific, resulting in the Central Pacific Hurricane Center (CPHC) passing its responsibility to the Joint Typhoon Warning Center (JTWC). The next day, the JTWC downgraded Aka into a tropical depression since it had lost convection due to persistent wind shear caused by a nearby TUTT. On 12:00 UTC on August 15, the JTWC issued the last warning on the system, as it passed south of Wake Island.

Typhoon Zola
On August 15, the Joint Typhoon Warning Center (JTWC) started watching a persistent area of disturbed weather west of Guam. The next day, the Japan Meteorological Agency (JMA) upgraded the disturbance into a tropical depression. By the evening of August 16, the JTWC issued a Tropical Cyclone Formation Alert, and the following morning, upgraded the system into a tropical depression. The depression turned west-northwest in response to a shortwave trough that tracked north of the system. At noon on August 17, the JMA upgraded it to a tropical storm, although the JTWC did not follow suit until early on August 18, naming it Zola. Zola continued northwest and tracked through region of divergence aloft, which aided intensification. At 06:00 UTC on August 18, the JMA upgraded Zola into a severe tropical storm. Following the appearance of a ragged 45 km eye on weather satellite imagery and a Dvorak classification of T4.0/75 mph, Zola was classified as a typhoon at 00:00 UTC on August 20 by the JTWC. The JMA followed suit later that same morning.

Further intensification was aided by a tropical upper tropospheric trough that provided an excellent poleward outflow channel. Based an increase in the storm's organization, the JTWC raised the intensity of the storm to 115 mph at 06:00 UTC on August 21, its peak intensity. Around this time, the JMA estimated that Zola peaked in intensity, with winds of 85 mph and a minimum barometric pressure of 975 mbar. Increased southwesterly wind shear took toll on the typhoon, and the storm weakened slightly prior as it passed between Kyushu and Shikoku, with the JTWC and JMA reporting winds of 110 and 80 mph respectively at the time of landfall on western Honshu. After recurving to the northeast over the Sea of Japan, Zola weakened to a tropical storm on August 22 and transitioned into a mid-latitude cyclone while interacting with the westerlies early on August 23. Both agencies ceased tracking the system at this time.

The typhoon dropped heavy rainfall across much of the Japanese archipelago. Six fatalities were reported while twenty-four others sustained injuries. A total of 67 houses were destroyed while 420 others were flooded. Sixteen ships and 1845 ha of farmland were damaged. More than 250 flights were cancelled due to adverse weather. Monetary damage totaled ¥15.1 billion (US$104 million). Zola was the second of six tropical cyclone to directly affect Japan in 1990, which set a record for the most systems to hit the country in a year; it was also the latest typhoon to hit the country, with the previous mark set by Typhoon Agnes of the 1948 Pacific typhoon season.

Typhoon Abe (Ilang)
Abe was first noted by the Joint Typhoon Warning Center (JTWC) as an area of persistent atmospheric convection on August 23 at 01:00 UTC. Following this, the disturbance tracked in a mostly west-northwestward direction, traveling beneath a subtropical ridge, with a Tropical Cyclone Formation Alert being issued at 06:00 UTC based on the improving state of the low. Following an increase in the storm's central convection, on August 24, the JTWC upgraded it into a tropical storm, naming it Abe, with the Japan Meteorological Agency ( JMA ) starting to monitor it six hours later. The JMA upgraded the system to a tropical storm the next day. At 06:00 UTC August 27, the JMA upgraded Abe to a severe tropical storm with winds of 95 km/h (60 mph), and as a ragged eye developed in the storm, the JTWC upgraded Abe to a typhoon six hours later. Late on August 28, the JMA upgraded Abe to a typhoon on its scale, with ten-minute sustained winds of 120 km/h.

Following the monsoon surge, Abe returned to its original west-northwestward track, further intensifying to become a Category 2-equivalent typhoon at 12:00 UTC on August 29. A weakness appeared in the subtropical ridge in association with a short-wave trough, and Typhoon Abe recurved through this weakness, taking it along the coast of China. Prior to making landfall near 18:00 UTC that day, Abe attained a minimum atmospheric pressure of 955 millibars (hPa; 28.20 inHg) and ten-minute sustained winds of 140 km/h (85 mph)and on August 29 as determined by the JMA. It was found by the JTWC that Abe's one-minute sustained winds peaked at 165 km/h (105 mph) at 00:00 UTC the next day. As a direct result of this interaction with land, Abe weakened to a tropical storm at 12:00 UTC on August 31, entering the Yellow Sea and crossing South Korea in the 30 hours that followed. It was determined at 18:00 UTC on September 1 that the storm had transitioned into an extratropical cyclone. The JTWC ceased tracking the system at 06:00 UTC September 2, and the JMA followed suit 36 hours later.

In the Philippines where Abe was known by the PAGASA name "Iliang", 85 people died. Rainfall-induced landslides ravaged areas previously damaged by an earthquake a month earlier, with landslide-caused fatalities totaling 32 in the Philippine provinces of Benguet, Nueva Ecija, and Nueva Vizcaya, Parts of the Okinawa Prefecture in Japan experienced high winds and heavy rainfall as Typhoon Abe passed nearby. In Taiwan, one person was killed while six others were injured as Typhoon Abe traveled across the East China Sea. Approximately 70,000 households had their supply of electricity cut off, and floods and landslides occurred as a result of heavy rainfall. Early on August 31, Typhoon Abe made landfall over Zhejiang Province in China approximately 250 – south of Shanghai. In Zhejiang, where Abe was reportedly "the worst typhoon to hit the province in 34 years", casualties of the storm numbered in the hundreds, with 65 people rendered dead, 839 wounded, and an additional 45 reported missing. Altogether, an estimated 108 people were killed in China. Abe brought heavy rain and gales to South Korea prior to transitioning to an extratropical cyclone near the east coast of the peninsula.

Typhoon Flo (Norming)
On 06:00 UTC on September 8, the Joint Typhoon Warning Center (JTWC) started tracking a low-pressure area about 430 km (270 mi) east-southeast of Guam. Throughout the next four days, the storm's convective structure slowly improved, and on September 12, the Japan Meteorological Agency (JMA) classified the system as a tropical depression. Following the disturbance's development, the JTWC issued a Tropical Cyclone Formation Alert at 05:30 UTC that day. At 18:00 UTC on September 12, the JTWC declared the system a tropical depression. Six hours later, the JMA upgraded the depression into a tropical storm, with the JTWC followed suit a few hours later, naming it Flo. On 06:00 UTC on September 14, the JMA upgraded Flo to a severe tropical storm. The next day, both agencies classified Flo as a typhoon.

After becoming a typhoon, Flo began to rapidly intensify. Over the ensuing 36 hours, the JTWC estimated that Flo deepened by 80 mph. Midday on September 16, the JTWC upgraded Flo into a super typhoon. The next day, the JTWC recognized the system having 1-minute sustained winds of 165 mph, a Category-5 equivalent tropical cyclone on the Saffir-Simpson Hurricane Wind Scale (SSHWS. Shortly thereafter, a dropsonde from the aircraft measured a barometric pressure of 891 mbar. Around this time, the JMA estimated the typhoon peaked in intensity with 10-minute winds of 140 mph and a pressure of 890 mbar. Soon after, Flo rapidly weakened, and at 00:00 UTC on September 18, the JTWC estimated that the typhoon weakened back to a tropical storm. Weakening continued due to increased vertical wind shear, although the warm waters of the Kuroshio Current helped Flo maintain some of its intensity. Around 06:00 UTC on September 19, the storm made landfall on southern Honshu. After passing over Japan, Flo began to transition into an extratropical cyclone. At 00:00 UTC on September 20, the JMA declared Flo extratropical, while the JTWC kept monitoring it until September 22.

Typhoon Flo was the strongest system to affect Japan since 1959 and was the first typhoon to hit the Kii Peninsula in 11 years. For a period of three days, the typhoon dropped heavy rainfall across much of the Japanese archipelago, which caused damage in 44 of 47 prefectures. A peak rainfall total occurred of 1124 mm at Yanase Station. A wind gust of 151 km/h was recorded on Muroto. A minimum barometric pressure of 971.3 mbar was recorded at Gifu, the fourth lowest pressure observed since observations at the station began in 1883. Nationwide, 40 fatalities were reported, and 131 others sustained injuries. A total 16,541 houses were destroyed while 18,183 others were flooded. Monetary damage totaled ¥132 billion (US$918 million).

Tropical Storm Ira
Ira was first noted by the Joint Typhoon Warning Center (JTWC) on September 29. Two days later, the Japanese Meteorological Agency began monitoring the system as a tropical depression. Later that day, the JTWC issued a TCFA for the system following an increase in convection. By October 2, the JTWC had issued its first advisory on the system. Later that day, both the JMA and JTWC upgraded the system into a tropical storm, with the latter naming it Ira. However, by the next day, landfall in Vietnam caused Ira to weaken, resulting in the JTWC downgrading it into a tropical depression and the JMA ceasing all bulletins on it. The JTWC still issued warnings until Ira dissipated on October 5.

In Thailand, Ira caused torrential rainfall, which killed at least 24 people. In Vietnam, around 7 people died as thousands of homes were submerged due to floodwaters. The Nghe Tinh and Thai Binh provinces suffered significantly, with extreme property loss occurring. In their post-season analysis, the JTWC noted that Ira had tracked so far inland, that it was briefly expected to cross into the North Indian Ocean.

Tropical Storm Lola
Lola was first

Other systems
Many of the tropical depressions of the season failed to intensify into tropical storms, or even be numbered.


 * According to the China Meteorological Administration (CMA), a tropical depression formed near Mindanao on May 20. After tracking through the Southern Philippines, the depression dissipated on May 23.
 * The CMA first noted a tropical depression in the South China Sea on May 24. Gradually intensifying, the depression made landfall in Hainan near 3:00 UTC on May 28. Rapidly weakening, the system was last noted on May 29 east of Vietnam.

International names
During the season, 29 tropical storms developed in the Western Pacific, all of them being named by the JTWC once they had 1-minute sustained winds of 65 km/h (40 mph). These names were used from a revised list in 1989.

Philippines
The Philippine Atmospheric, Geophysical and Astronomical Services Administration uses its own naming scheme for tropical cyclones in their area of responsibility. They assigned names to tropical depressions that were active there. Should the list of names for a given year be exhausted, names are taken from an auxiliary list, the first 10 of which are published each year before the season starts. Names not retired from this list were used again in the 1994 season. This is the same list used for the 1986 season. PAGASA uses its own naming scheme that starts in the Filipino alphabet, with names of Filipino female names ending with "ng" (A, B, K, D, etc.). Names that were not assigned/going to use are marked in.

Retirement
Due to its destructive impact, the name Mike was retired and replaced with Manny. PAGASA also retired the name Ruping, replacing it with Ritang.

Season effects
This table summarizes all the systems that were active in the North Pacific Ocean, west of the International Date Line, during 1990. It also provides an overview of each system's intensity, duration, land areas affected, and any associated deaths or damages.
 * Nathan || June 14-19 || bgcolor=#|Severe tropical storm || bgcolor=#|105 km/h || bgcolor=#|980 hPa || Philippines, China, Macau, Hong Kong, Vietnam || ||
 * Ofelia || June 16-25 || bgcolor=#|Typhoon || bgcolor=#|120 km/h || bgcolor=#|970 hPa || Philippines, Taiwan, China || ||
 * Ofelia || June 16-25 || bgcolor=#|Typhoon || bgcolor=#|120 km/h || bgcolor=#|970 hPa || Philippines, Taiwan, China || ||
 * Ofelia || June 16-25 || bgcolor=#|Typhoon || bgcolor=#|120 km/h || bgcolor=#|970 hPa || Philippines, Taiwan, China || ||