The 1999 Pacific typhoon season was the last Pacific typhoon season to use English names as storm names. It also featured the lowest number of typhoons on record, with only five reaching this intensity. This was mainly due to a strong La Niña which persisted from last year. It also featured the least amount of ACE produced on record. The season was also below-average in named storms, with only 20 of such spawning. This season also featured multiple landfalls in Hong Kong, but it was much more active than the previous season. It had no official bounds; it ran year-round in 1999, but most tropical cyclones tend to form in the northwestern Pacific Ocean between June and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northwestern Pacific Ocean. The first named storm, Hilda, developed on January 6.
Tropical Storms formed in the entire west Pacific basin were assigned a name by the Joint Typhoon Warning Center. Tropical depressions in this basin have the "W" suffix added to their number. Tropical cyclones that enter or form in the Philippine area of responsibility are assigned a name by the Philippine Atmospheric, Geophysical and Astronomical Services Administration or PAGASA. This can often result in the same storm having two names.
The strongest storm and only super typhoon of the season was Typhoon Bart (Oniang), which struck the Philippines, Taiwan, and Southern Japan. In June, Typhoon Maggie struck The Philippines as a category 3 typhoon. In December, Tropical Depression 33W struck southeastern Vietnam, ending the season on December 16.
Systems
Tropical Storm Hilda (Auring)
The JTWC issued a Tropical Cyclone Formation Alert (TCFA) for a developing broad circulation that stretched out from the northwest Borneo coast early on January 4. This developed into a tropical depression and moved slowly to the north away from Borneo, becoming Tropical Storm Hilda early on January 6. Soon after reaching its peak strength of 65 km/h (40 mph) Hilda drifted further north into an area of increased wind shear, which caused the storm to dissipate the next day. Both JMA and PAGASA tracked this system, but considered it a tropical depression. PAGASA named the storm Auring.
Malaysia reported to the World Meteorological Organization (WMO) Typhoon Committee that Tropical Storm Hilda brought heavy rain to Sabah. The rain caused flooding and landslides, and was responsible for five deaths. The mudslides caused about $1.3 million in damage (1999 USD, 15 million 1999 MYR) to roads throughout the country.
Tropical Depression Iris (Bebeng)
A monsoon depression began to develop between Pohnpei and Chuuk on February 10 as it moved west. The JTWC issued a TCFA as the depression formed and passed near Palau on February 13. The storm slowly consolidated as it moved towards the Philippines, becoming Tropical Storm Iris on February 17, but did not intensify any further. As the storm turned northwards under the influence of a subtropical ridge to the east it entered a high shear environment and rapidly degenerated, dissipating on February 19 220 km (140 mi) to the east of Luzon.
PAGASA considered this storm to have been a tropical depression and named it Bebeng.
Tropical Depression Jacob (Karing)
A low pressure area 220 km (140 mi) to the west of Yap developed into a tropical depression on April 6. It gradually developed as it moved to the west, becoming a strong depression with 55 km/h (34 mph) winds. It then began to accelerate to the northwest, becoming a minimal tropical storm as it did so. However, this northwards motion brought it into a region of increased shear, which weakened it back into a tropical depression. The low level circulation became completely exposed and the weakening system made landfall on southern Luzon on April 10. PAGASA named the system Karing and considered it a tropical depression.
The rainfall from Jacob ranged from 80 mm (3.1 in) up to 400 mm (16 in) in some places in the Philippines, but only minor damage was recorded on land.
Severe Tropical Storm Kate (Diding)
On April 22, a tropical disturbance which had developed in the Philippine Sea moved over Mindanao and intensified into a tropical depression whilst it was still overland. The depression soon moved overwater again as it tracked north to the east of the Philippines, becoming Tropical Storm Kate the next day. The JTWC initially forecast that the storm would only intensify slightly, as they predicted it to move north-northeast into an unfavorable environment. However, Kate instead moved on a more northerly route and entered an area with minimal wind shear. On April 26 Kate became a typhoon, the first of the season, and reached its peak strength with 140 km/h (87 mph) soon after. Later that day, the typhoon's motion accelerated to the northeast and it passed 9 km (5.6 mi) to the north of Iwo Jima. Kate then began to lose its convection and became an extratropical on April 28 to the northeast of Iwo Jima.
Both JMA and PAGASA considered Kate to have been a tropical storm at its peak, in both cases considering this the first tropical storm of the season. PAGASA named the depression Diding soon after it formed and upgraded it to a tropical storm before the JTWC. Kate brought torrential rain to the east-central Philippines, with amounts as high as 360 mm (14 in) falling in places. The peak winds recorded on Iwo Jima were 95 km/h (59 mph), with gusts of up to 126 km/h (78 mph).
Typhoon Leo
In late April a circulation began to develop within a monsoon depression in the South China Sea, forming into a tropical depression on April 27 when it was 710 km (440 mi) to the west of Manila. It strengthened as it moved to the west and became Tropical Storm Leo the next day. The storm then performed a cyclonic loop off the Vietnamese coast and began to intensify, becoming a typhoon as it moved to the northeast. As it moved towards China under a high-level ridge Typhoon Leo rapidly intensified to its peak with 205 km/h (127 mph) winds. However, it did not sustain this for long as it then moved northeast into a high shear environment and it weakened as it moved to the north. Leo made landfall on May 2 as a tropical depression. By this time, its convection had become separated from its circulation. Shortly afterwards, Leo dissipated overland.
As Typhoon Leo was developing, its outer rainbands brought up to 130 mm (5.1 in) to regions of Vietnam. High waves caused by the typhoon sank a ship to the south of Hong Kong and only 7 of the 21 people on board were rescued. Peak sustained winds of 90 km/h (56 mph) were recorded on Waglan Island as Typhoon Leo passed to the south of Hong Kong and the storm dropped over 100 mm (3.9 in) of rain on the territory. There was only light damage in Hong Kong as a result of Typhoon Leo, but the rainfall was responsible for 14 injuries, mostly in traffic accidents.
Typhoon Maggie (Etang)
The sixth tropical depression of the season formed in the monsoon trough to the east of the Philippines on June 1. The system intensified as it moved to the north, becoming Typhoon Maggie 36 hours after it had formed. The typhoon intensified further as it began to head to the northwest into the Luzon Strait and it reached its peak with 195 km/h (121 mph) winds on June 5. The typhoon turned further to the west as it began to interact with Taiwan and started to weaken slowly. Maggie made landfall as a 150 km/h (93 mph) typhoon in southeastern China, to the east of Hong Kong on June 6. The storm then moved along the Chinese coast weakening as it did so. Maggie passed just to the north of Hong Kong before it turned into the mouth of the Pearl River and dissipated inland on June 8. Both the JMA and PAGASA considered Maggie a typhoon, and PAGASA named this storm Etang.
The rainfall from Typhoon Maggie caused landslides in the Philippines that killed three people. The storm killed at least two people, with another five reported missing on Taiwan. The electricity supply to over 100,000 homes was cut off and there was over $18 million of agricultural damage on the island. Maggie brought sustained winds of up to 80 km/h (50 mph) and 85 mm (3.3 in) of rain to Hong Kong. Two oil barges docked in the territory sank, one fully laden with oil which polluted a nearby beach. There were five injuries resulting from Maggie in the territory and the total damages were approximately $100,000. The typhoon killed four people and damaged over 3000 homes in Guangdong. At least 120 vessels were also damaged and there was more than $150 million of direct economic damage in the province. Maggie also brought rain of up to 100 mm (3.9 in) to northern Vietnam, causing some localised flooding.
Tropical Storm 07W
An area of disturbed weather to the northeast of Guam slowly developed as it moved to the west, becoming a tropical depression on July 14. Soon after it formed the depression reached its peak strength with 10-minute winds of 65 km/h (40 mph), which it maintained for two days as it moved towards Honshū. Although the JMA classified the depression as a tropical storm, the JTWC did not follow suit. Not long after peak intensity, increased wind shear began to expose the low level circulation and the depression began to weaken as it turned to the northeast. The depression dissipated on July 18 to the southeast of Honshū.
Tropical Depression 08W
A tropical disturbance moving north to the east of Okinawa, Japan gradually developed as it moved to the north towards the Japanese mainland. On July 21 it began to intensify, becoming Tropical Depression 08W to the northeast of Okinawa. The depression strengthened slightly in the East China Sea before it made landfall near Changhung, South Korea on July 22. The storm became extratropical as it moved over the Korean Peninsula and it entered the Sea of Japan, where it dissipated.
Severe Tropical Storm Neil (Helming)
On July 23, a disturbance began to form in the Philippine Sea within the monsoon trough. The convection gradually consolidated as the disturbance moved north and the ninth tropical depression of the season formed on July 25 south of Okinawa. The depression passed near to the Japanese island and soon strengthened into Tropical Storm Neil. The storm turned slightly westward towards the Korean peninsula and reached its peak strength with 75 km/h (47 mph) winds on July 26. Neil made landfall to the southwest of Suncheon the next day as a minimal tropical storm and soon reemerged over the Yellow Sea as a tropical depression. There it interacted with a mid-latitude trough, that redirected back towards South Korea and it made a second landfall 35 km (22 mi) southwest of Seoul on July 28. Neil then quickly dissipated overland.
Both the JMA and PAGASA considered Neil a tropical storm, with PAGASA naming it Helming. Unusually, PAGASA assessed the storm as having reached a peak on July 22, when the JTWC still considered it a developing disturbance. This difference was due to a difference in opinion between the two centers as to where the storm's center was. There were reports of damage from flooding and winds gusts from Tropical Storm Neil in Japan, with a ferry running aground near Kannoura. Neil caused a fishing boat off the Korean coast to capsize, killing its crew of eight. There were wind gusts of up to 95 km/h (59 mph) on Cheju Island and the peak rainfall reported from the storm was over 200 mm (7.9 in). Agricultural damage in Niigata prefecture totaled to ¥693 million (US$6.09 million). As the storm dissipated over Korea, it caused flash floods that killed at least seven and left 7,000 homeless.
Tropical Storm 10W
A tropical disturbance began to develop in the South China Sea on July 23. It formed the same monsoon trough that Tropical Storm Neil developed from to the east. The disturbance became a tropical depression late on July 25 as it turned to the north towards the Chinese coast. It did not strengthen any further and made landfall near Shanwei as a minimal tropical depression on July 27. The depression then moved inland and dissipated. The JMA considered Tropical Depression 10W to be a tropical storm, with peak 10-minute winds of 75 km/h (47 mph), making 10W the second storm in 1999 that the JMA considered a tropical storm but the JTWC considered a depression.
As the depression passed near Hong Kong, it dropped 31 mm (1.2 in) of rain on the territory and sustained winds of 72 km/h (45 mph) were recorded on Waglan Island. There was no significant damage over land in the territory, though 18 swimmers were injured in the strong seas associated with the storm.