Attachments
Section 2
TROPICAL CYCLONE OVERVIEW FOR 1993
In 1993, there were 31* tropical cyclones over the western North Pacific and the adjacent seas bounded by the equator, 45°N, 100°E and 180°. Compared with the 30-year annual average (1961-1990) of 31 tropical cyclones, 1993 was generally speaking a year with normal tropical cyclone activity. Also, the number of tropical cyclones attaining typhoon intensity was near-normal - a total of 15 typhoons in 1993 against the 30-year annual average of 15.6. The monthly distributions of the frequency of first occurrence of tropical cyclones and of typhoons for 1993 are shown in Figure 2. The monthly mean frequencies of these two parameters during the years 1961 - 1990 are shown in Figure 3.
While Ed (9319) was the strongest typhoon in 1993, Lola (9326) was the most destructive in terms of the human damage inflicted. More than 270 people were killed in Lola’s fury in the Philippines. The passages of Yancy (9313) over Japan and of Kyle (9325) over Vietnam also led to relatively high casualties figures in those countries. Among the storms that affected China in 1993, Typhoon Tasha (9309) turned out to be the most costly one.
In 1993, the south China coast was hit by six storms. Five of these landed over western Guangdong and the sixth made landfall near Shantou. In contrast, both eastern China and Taiwan were free from the threat of tropical cyclones as storms approaching the region tended to recurve early. Japan was hit by as many as seven tropical cyclones during the year while the Philippines was affected by nine. Amongst those storms that traversed the Philippines, Kyle (9325) and Lola (9326) crossed the South China Sea and affected Indo-China in the late season.
During the year, 14 tropical cyclones occurred within the area of responsibility of Hong Kong (i.e. the area bounded by l0o N, 30°N, 105°E and 125°E). This number was slightly lower than the 30-year (196l90) annual average of 16.4. Of the 14 tropical cyclones, six developed within Hong Kong’s area of responsibility. Altogether, 439 tropical cyclone warnings to ships and vessels were issued by the Royal Observatory in 1993 (Table 2).
Local tropical cyclone warning signals were hoisted for nine storms. The Stand By Signal No. 1 was the highest signal required for Severe Tropical Storm Lewis (9303), Tropical Storm Winona (9312), Typhoon Abe (9315) and a tropical depression in October. The Strong Wind Signal No.3 was the highest signal required for Typhoon Ira (9323), and the Gale or Storm Signal No.8 was that for Typhoon Koryn (9302), Typhoon Tasha (9309), Severe Tropical Storm Becky (9316) and Typhoon Dot (9318). The last time when the No.8 signal was hoisted for four or more tropical cyclones in a year was in 1964.
The total tropical cyclone rainfall (defined as the total rainfall recorded at the Royal Observatory from the time when a tropical cyclone was centred within 600 km of Hong Kong to 72 hours after the tropical cyclone has dissipated or moved outside 600 km of Hong Kong) in 1993 amounted to 1 018.4 mm, 37 per cent above the mean annual value of 741.0 mm (1961-1990). It accounted for 43 per cent of the year’s total rainfall of 2 343.9 mm. The nine tropical cyclones that necessitated the hoisting of tropical cyclone warning signals all came within 600 km of Hong Kong. Rainfall figures associated with these tropical cyclones are given in Table 8(a).
The following is a review of all the tropical cyclones in 1993.
The first tropical cyclone in 1993 originated from an area of disturbance near the Caroline Islands. It developed to a tropical depression named Irma (9301) about 1240 km east-southeast of Truk on the evening of 11 March and deepened to a tropical storm the next day. Moving slowly at first, Irma accelerated northwestwards to a speed of 30 km/h on 13 March. It also intensified to a severe tropical storm about 710 km east of Truk that afternoon. By the next morning, Irma had weakened to a tropical storm. It started recurving towards the north-northeast on 16 March. After weakening to a tropical depression about 760 km east-northeast of Guam that evening, Irma degenerated to an area of low pressure on the morning of 17 March over the Pacific.
Two months later, another disturbance developed to a tropical depression named Jack about 810 km east-northeast of Truk on 16 May. It moved northwards at about 13 km/h initially but turned towards the northeast at a reduced speed of 7 km/h the next day. After intensifying to a tropical storm about 1 030 km east-northeast of Truk early on 18 May, Jack started to take on a westward course. It weakened to a tropical depression that afternoon, but intensified again to a tropical storm on 19 May while picking up speed to 15 km/h. Jack became a tropical depression early on 20 May and dissipated over water soon afterwards.
In June, Koryn (9302) developed from an area of low pressure over the Caroline Islands. It intensified to a tropical depression on 21 June and attained typhoon intensity two days later. Koryn necessitated the hoisting of the No. 8 Gale or Storm Signals in Hong Kong. A detailed report on Typhoon Koryn is presented in Section 3.
There were five tropical cyclones over the western North Pacific and the South China Sea in July.
One of them, Severe Tropical Storm Lewis (9303), necessitated the hoisting of the Stand By Signal No. 1 in Hong Kong.
Lewis formed over the central Philippines on 8 July. After crossing southern Luzon, Lewis entered the South China Sea on 9 July. It intensified to a severe tropical storm while heading towards Hainan.
Lewis then moved westwards across Beibu Wan, landing over northern Vietnam and dissipating in Laos on 12 July. A detailed report on Lewis is present in Section 3.
Two days after the dissipation of Lewis, Tropical Depression Marian formed over the western North Pacific about 1 490 km east-southeast of Manila on 14 July. Throughout its entire lifetime, Marian was poorly organized and its movement was northwestwards at 27 km/h in the general direction of Luzon. Marian dissipated over water on the afternoon of 15 July.
Nathan (9304) formed over the western North Pacific about 750 km east of Guam on 19 July. Moving west-northwestwards at 16 km/h initially, it deepened to a tropical storm the next day. Nathan turned northwestwards and weakened temporarily to a tropical depression on the evening of 21 July. Changing direction towards the north-northwest, Nathan re-gained tropical storm intensity the next day. Nathan intensified further to a severe tropical storm on 24 July when it was about 920 km south-southeast of Osaka. Nathan became extratropical over the coastal waters of Japan early on 25 July.
The fourth tropical cyclone in July was Ofelia (9305). It formed as a tropical depression over the western North Pacific on the afternoon of 25 July about 1 220 km east-southeast of Okinawa. Moving northwestwards at 41 km/h, it intensified to a tropical storm early the next morning: Ofelia took on a north-northwestward course that night and made landfall over Kyushu about 60 km east-southeast of Kagoshima on 27 July. Having swept across southern Japan, Ofelia recurved northeastwards and became extratropical over the Sea of Japan on the early morning of 28 July.
While Ofelia was over the Sea of Japan, a tropical depression named Percy (9306) developed about 500 km south-southeast of Okinawa on the morning of 28 July. After deepening to a tropical storm that afternoon, Percy deepened further to a severe tropical storm early the next morning when it was about 70 km northeast of Okinawa. Heading north-northeastwards, Percy made landfall over Kyushu on the evening of 29 July and entered the Sea of Japan early the next morning. It weakened to a tropical storm about 1 030 km southwest of Sapporo and became extratropical later in the day.
There were seven tropical cyclones occurring over the western North Pacific and the South China Sea in August. Two of them, Typhoon Tasha (9309) and Tropical Storm Winona (9312), necessitated the hoisting of tropical cyclone warning signals in Hong Kong.
Robyn (9307) formed as a tropical depression over the Caroline Islands about 1 150 km southeast of Guam on the evening of 1 August. Heading west-northwestwards at 25 km/h initially, it deepened to a tropical storm the next day. Robyn began to turn northwestwards on 4 August and deepened further to a severe tropical storm when it was about 480 km southwest of Guam. Gathering strength over water,
Robyn attained typhoon intensity on 6 August when it was about 970 km west-northwest of Guam. Peak intensity was reached on 7 and 8 July with maximum sustained winds and minimum sea-level pressure near its centre estimated at 165 km/h and 940 hPa respectively. After sweeping across the Ryukyus on 9 August, Robyn accelerated and recurved towards Japan. It skirted past western Kyushu and entered the Sea of Japan on 10 August before evolving into an extratropical cyclone the next day.
Robyn brought torrential rain to southwestern Japan, causing floods and landslides. Nine people were killed and 50 others injured. A total of 564 houses and buildings were destroyed or inundated. Roads were cut at 15 locations and two dikes were ruined. In Kyushu, more than 10 000 people had to flee their homes. Electricity supply to about 215 000 households was cut off. Air, land and sea traffic were disrupted in Kyushu and some other areas in western Japan. Robyn also affected South Korea, leaving six people dead.
While Robyn was making its way towards the Ryukyu Islands on 5 August, an area of disturbance near the Mariana Islands developed to a tropical depression named Steve (9308) about 950 km east-southeast of Guam. It tracked northwestwards at 15 km/h during the first 24 hours and headed westnorthwestwards over the next couple of days. Gathering strength over water, Steve intensified to a tropical storm on 8 August and then to a severe tropical storm two days afterwards when it was about 840 km west-northwest of Guam. However, it failed to maintain its intensity and rapidly weakened to a tropical storm a few hours later. Moving northwestwards at 27 km/h, Steve dissipated over the western North Pacific on 12 August.
Tasha formed over the western North Pacific to the east of the Philippines on 16 August. After traversing the Luzon Strait, it entered the South China Sea on 18 August. Tasha landed over the coast of western Guangdong and inflicted severe damage there. A detailed report on Tasha is presented in Section 3.
While Tasha was affecting Hong Kong, Typhoon Keoni (9310) moved northwestwards at 22 km/h across the International Date Line and entered the western North Pacific on 20 August. Keoni reached peak intensity on 21 August when maximum sustained winds of 165 km/h and minimum sea-level pressure of 940 hPa were estimated near its centre. Keoni weakened to a severe tropical storm about 970 km north-northeast of Wake Island the next day, but re-intensified to a typhoon on 24 August. It slowed down to about 7 km/h and weakened to a severe tropical storm again on 25 August. Recurving into higher latitudes over the next few days, Keoni degenerated to a tropical depression about 2 040 km north-northwest of Wake Island on 28 August. It dissipated over water shortly afterwards.
As Tasha was making landfall over western Guangdong and Kenoi traversing the western North Pacific near the International Data Line, Vernon (9311) formed as a tropical depression on 21 August about 1 060 km east-northeast of Guam. After moving north-northwestwards for the first 18 hours, it made a clockwise loop on 22 August and deepened to a tropical storm. Vernon continued to intensify over the next couple of days and attained typhoon intensity about 570 km east-northeast of Iwo Jima on 25 August while moving northwestwards at 25 km/h. Peak intensity was reached that afternoon when maximum sustained winds and minimum sea-level pressure of 140 km/h and 960 hPa respectively were estimated near its centre. Vernon recurved the following day, weakening to a severe tropical storm when it was about 460 km south of Tokyo. It skirted past eastern Honshu on 27 August while heading northnortheastwards. Vernon became extratropical over the eastern waters of Hokkaido the next day.
Two days after the dissipation of Tasha, Winona formed as a tropical depression near the central Philippines. It moved with a speed of 22 km/h towards the west. After deepening to a tropical storm on the evening of 23 August, Winona moved northwestwards towards the northern part of the South China Sea where it performed a looping motion. It then tracked towards Vietnam and dissipated over water before reaching the land. A detailed report on Winona is presented in Section 3.
The last tropical cyclone in August was Yancy (9313). It developed over the western North Pacific as a tropical depression about 1 030 km northwest of Guam on 29 August. Yancy deepened to a tropical storm the next day. It intensified further to a severe tropical storm on the evening of 31 August while moving northwestwards at 15 km/h. Yancy attained typhoon strength about 500 km south-southwest of Okinawa on 1 September and then recurved northeastwards towards Japan the following day. Peak intensity was also reached on 2 September when maximum sustained winds of 185 km/h and minimum sea-level pressure of 930 hPa were estimated near its centre. Moving at about 40 km/h, Yancy landed over Kyushu on 3 September and wreaked havoc on southern Japan. It became extratropical over Honshu on 4 September.
In Japan, torrential rain associated with Yancy caused severe flooding and landslides. About 48 people were killed and 266 were injured. A total of 285 houses were destroyed and 1 607 houses were inundated. Roads, dams and bridges were also damaged. Over the coastal waters, two vessels were damaged and 13 others capsized. Electricity supply to about 410 000 households were cut off. Most transport in southern and western Japan were paralysed, affecting more than 250 000 people.
A total of six tropical cyclones formed in September. Amongst them, Zola (9314) affected Japan while Abe (9315), Becky (9316) and Dot (9318) hit the south China coast in quick succession and necessitated the hoisting of tropical cyclone warning signals in Hong Kong.
Zola formed as a tropical depression about 880 km south-southeast of Okinawa on 5 September, just two days after Yancy had rampaged through Japan. Moving west-northeastwards at 15 km/h initially,
Zola intensified to a tropical storm the next morning and recurved north-northeastwards that evening.
Moving steadily towards Japan, Zola intensified to a severe tropical storm about 960 km southwest of Tokyo on 8 September. It made landfall over Honshu on the morning of 9 September and weakened to a tropical storm about 350 km west-southwest of Tokyo a few hours later. Zola then quickly dissipated over land.
Abe formed as a tropical depression over the western North Pacific about 580 km northeast of Manila on 9 September. Moving slowly over water, it deepened to a tropical storm the following day. After traversing the Luzon Strait, Abe entered the South China Sea and became a typhoon on 12 September. It made landfall in the vicinity of Shantou and then dissipated over land two days later.
Following the dissipation of Abe, Becky formed as a tropical depression over the waters to the northeast of Luzon about 530 km north-northeast of Manila on 15 September. It traversed westwards over the Luzon Strait and intensified to a tropical storm the next day. After entering the South China Sea, Becky took on a northwestward course at 30 km/h towards the south China coast. It intensified to a severe tropical storm on the morning of 17 September and then landed over the coast of western Guangdong. Detailed report on Abe and Becky are presented in Section 3.
After a lull of a few days, another low pressure area over the western North Pacific developed to a tropical depression named Cecil (9317) about 800 km east-southeast of Guam on 22 September. Moving northwestwards at 20 km/h initially, Cecil deepened to a tropical storm on the morning of 23 September.
Cecil also started making an anticlockwise loop that afternoon before tracking north-northwestwards and intensifying to a severe tropical storm the next day. It attained typhoon intensity about 1 040 km north of Guam early on 26 September and started recurving northeastwards. Peak intensity was also attained that day when maximum sustained winds and minimum sea-level pressure of 130 km/h and 965 hPa were estimated near its centre. Accelerating towards the northeast, Cecil gradually lost its strength and became extratropical early on 28 September.
Dot was the third tropical cyclone to affect the South China Sea in September. It began as a tropical depression about 320 km southeast of Haikou on 23 September. Moving slowly over water, it deepened to a tropical storm the next day. Dot became a typhoon on 25 September while heading towards the coast of western Guangdong. It made landfall about 180 km west-southwest of Hong Kong on 26 September.
Heavy rain associated with Dot brought widespread flooding to Hong Kong. A detailed report on Dot is presented in Section 3.