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201908W (WIPHA 韋帕) - Profile 檔案

(First draft issued on August 9, 2019)
(初稿於 2019 年 8 月 9 日發出)

Brief profile of WIPHA | 韋帕小檔案:

JTWC number 聯合颱風警報中心 (JTWC) 號碼 08W
International number 國際編號 1907
Period of existence 生存時期 (JTWC) 2019/07/30 20 HKT - 2019/08/03 14 HKT
Lifetime 壽命 (JTWC) 3.75 days 日
Maximum 1-minute wind (JTWC) JTWC 一分鐘平均最高中心風速 40 knots 節 (Tropical Storm 熱帶風暴)
Minimum pressure (JTWC) JTWC 最低氣壓 991 hPa 百帕
Highest TC signal by HKO
香港天文台發出最高熱帶氣旋警告信號
8 (NE) (Gale or Storm Signal 烈風或暴風信號)
Closest point of approach by HKO
香港天文台所示之最接近距離
SSW 310 km (real-time warning 實時報告)
Time of closest approach by HKO
香港天文台所示之最接近時間
2019/07/31 18 HKT (real-time warning 實時報告)
Lowest pressure recorded at HKO
香港天文台錄得的最低氣壓
TBA 稍後公佈

TC signals in Hong Kong* 香港曾經生效的熱帶氣旋警告*:

Signal
信號
Date and time
日期和時間
Distance from HK
與香港的距離
Predicted movement
預測移動趨勢
Max. 10-min winds
中心最高十分鐘平均風速
2019/07/30 (TUE) 15:40 HKT S 490 km NW at 15 km/h 45 km/h (25 knots, TD)
2019/07/30 (TUE) 21:15 HKT S 500 km NW at 12 km/h 55 km/h (30 knots, TD)
2019/07/31 (WED) 13:40 HKT S 340 km NW at 15 km/h 85 km/h (45 knots, TS)
2019/07/31 (WED) 23:40 HKT SW 370 km WNW at 20 km/h 85 km/h (45 knots, TS)
2019/08/01 (THU) 19:20 HKT WSW 400 km NW/NNW at 12 km/h 85 km/h (45 knots, TS)
2019/08/02 (FRI) 08:40 HKT WSW 530 km W Slowly 85 km/h (45 knots, TS)

*Based on the information from real-time tropical cyclone warning bulletins.
*根據實時熱帶氣旋警報資料。

Percentile Ranks 百分等級:

TBA 稍後公佈

IR imagery animation 紅外線雲圖動畫:

TC track from HKWW 本站的熱帶氣旋路徑圖:

TC Track

TC tracks from HKO 天文台的熱帶氣旋路徑圖:

TBA 稍後公佈

Past HKWW Bulletins 本站發佈

Please click here for bulletins on this tropical cyclone. 請按這裡

Storm Development Overview 風暴發展概覽

Unless otherwise stated, all times below are in Hong Kong Standard Time (UTC+8)
除非特別註明,下文時間均為香港標準時間 (協調世界時加 8 小時)

WIPHA originated as tropical disturbance 92W in central South China Sea in late July. The JTWC issued a tropical cyclone formation alert at 2 am July 30. The patch of convections gradually gained spiraling characteristics during the day. The HKO upgraded it into a tropical depression at 4 pm that day, while the JMA issued a gale warning that afternoon.

Being a monsoon depression, 92W's winds were stronger at its periphery. Its convections were also confined to the periphery and appeared loose at the storm's formation. The cyclone was situated in the southwestern periphery of the subtropical ridge, and was expected to move northwest towards the Leizhou Peninsula.

As 92W developed further, the JTWC upgraded it into tropical depression 08W in the small hours of July 31. Meanwhile, both the HKO and JMA upgraded 08W into tropical storm status in the morning, with the JMA naming it WIPHA. WIPHA was initially drifting westwards slowly, but started to pick up speed towards the northwest during the day. WIPHA's eastern circulation was also seen expanding significantly.

WIPHA turned west during the night of July 31 and approached Hainan. According to the NMC, it made landfall at Wenchang in northeastern Hainan just before 2 am August 1, with an estimated strength of 23 m/s (83 km/h). Thereafter, WIPHA made an anticlockwise loop and emerged into the South China Sea again that morning. It moved towards the north during the day, and made landfall again near Zhanjiang, Guangdong at around 6 pm.

Upon landfall, WIPHA turned west under the influence of a continental ridge and entered the Gulf of Tonkin that night. It moved rather slowly initially; the storm's core developed somewhat, but the coverage of its convections shrank considerably at the same time. After spending almost a day crossing the Gulf, WIPHA made its final landfall in northeastern Vietnam near midnight August 3 and accelerated towards the west-southwest. It gradually weakened into an area of low pressure on August 4.

韋帕形成前為熱帶擾動 92W,於 7 月底在南海中部發展。聯合颱風警報中心於 30 日上午 2 時對其發出熱帶氣旋形成警報。92W 的對流於日間漸現螺旋性,香港天文台於當天下午 4 時將其升格為熱帶低氣壓,而日本氣象廳亦於下午發出烈風警報。

由於 92W 是一季風低壓,其周邊風力較強。92W 的對流集中於其外圍,風暴形成時對流較為稀疏。92W 當時處於副熱帶高壓脊西南部,預料向西北移動,趨向雷州半島一帶。

隨著 92W 進一步發展,聯合颱風警報中心於 31 日凌晨將其升格為熱帶低氣壓 08W。另一邊廂,香港天文台及日本氣象廳均於當日上午將 08W 升格為熱帶風暴,日本氣象廳將風暴命名為韋帕。韋帕初時向西緩慢移動,但日間開始加速向西北移。韋帕東面的對流雲團亦大幅擴展。

韋帕於 31 日晚轉向偏西移動並靠近海南。根據中國中央氣象台資料,韋帕於 8 月 1 日上午 2 時前登陸海南東北部的文昌市,估計強度為每秒 23 米 (每小時 83 公里)。登陸後,韋帕以逆時針方向打轉,早上再度進入南海。它於日間北移,並於下午 6 時左右登陸廣東湛江。

登陸後,韋帕受一大陸高壓脊影響西轉,晚上進入北部灣。韋帕初時移動緩慢,其中心結構稍為發展,但周邊對流覆蓋範圍大幅縮小。韋帕用了大約一天時間橫過北部灣,最後於 3 日午夜時份登陸越南東北部。登陸後,韋帕加速向西南偏西移動,並於 4 日減弱為一低壓區。

Weather in Hong Kong During Approach 風暴影響時香港天氣狀況

Link to relevant HKO weather report bulletins: 30/731/71/82/8
香港天文台相關天氣報告連結30/731/71/82/8

The weather in Hong Kong was unstable in the last week of July. As WIPHA developed into a tropical depression, the HKO issued the #1 Standby Signal at 3:40 pm July 30, when WIPHA was situated about 490 km south of Hong Kong. In its initial tropical cyclone bulletin, the HKO had already indicated the possibility of issuing the #3 Signal later that night. This was largely due to the fact that WIPHA's strongest winds were in its northeastern quadrant and were far away from the centre.

Various places in Hong Kong, mostly offshore and elevated, registered strong easterly winds that afternoon. Examples of such stations include Cheung Chau, Waglan Island and Tate's Cairn. The HKO issued the #3 Strong Wind Signal at 9:15 pm; WIPHA was around 500 km from Hong Kong at that time. It was also indicated that the signal would likely remain in force before sunrise the next day.

Winds throughout the night of July 30 remained at roughly the same level as that during daytime. However, winds started to strengthen near daybreak on July 31. Strong winds were recorded at North Point and Central Pier, both within the Victoria Harbour, in the late morning. A South China Coastal Waters weather report issued by the HKO at 9:30 am indicated the presence of force 9 winds at Huangmaozhou, an island around 50 km south of Hong Kong. This suggested the possibility of gale force winds affecting Hong Kong later on. The HKO mentioned in the 9:45 am tropical cyclone bulletin that the #8 Signal would be considered between noon and 2 pm; it then issued the Pre-No. 8 Special Announcement at 11:40 am, warning that the #8 Signal was expected to be issued by 2 pm the latest.

WIPHA's rainbands started to affect Hong Kong in the early morning of July 31. Rainfall turned incessant later that morning; the Amber Rainstorm Warning was issued at 11:55 am. Cargo handling at major container terminals was suspended at 1 pm, and most workers left their workplace near lunchtime due to the impending #8 Signal. After the 2-hour prewarning period, the HKO issued the #8 Northeast Gale or Storm Signal at 1:40 pm, when WIPHA was 340 km south of Hong Kong. At this distance, WIPHA became the tropical storm farthest away from Hong Kong to necessitate the #8 Signal in decades. Near the time of the signal change, gales were observed at Cheung Chau, Green Island, Tai Mei Tuk, Tap Mun and Tate's Cairn, while storm force winds were briefly observed at Waglan Island prior to the issuance of the #8 Signal. Most other urban stations were registering fresh to strong easterly winds.

After the passage of a strong rainband, the Amber Rainstorm Warning was cancelled at 2:35 pm. During the period that the #8 Signal was in force, the strongest winds were generally observed towards the late afternoon. The Amber Rainstorm Warning was issued again at 5:30 pm as rain turned heavy; this was elevated to the Red Rainstorm Warning at 8 pm, which lasted until 9:30 pm. The Special Announcement on Flooding in the Northern New Territories and Landslip Warning were issued at 8:25 pm and 8:40 pm, respectively. The Special Announcement remained in force until midnight August 1.

WIPHA was the closest to Hong Kong near 6 pm July 31, when it was around 310 km south-southwest of the territory. As WIPHA turned west and moved away, the #8 Northeast Signal was replaced by the #3 Strong Wind Signal at 11:40 pm, skipping the #8 Southeast Signal as winds generally remained easterly. However, winds remained rather strong overnight. A strong rainband swept across the territory near 7 am August 1, causing a momentary surge in wind speeds over the territory. Cheung Chau recorded a sustained wind speed of 87 km/h, the upper limit of gale force winds and the strongest during WIPHA's approach. Stanley recorded gale force winds shortly after 7 am, and many more stations recorded the strongest winds during WIPHA's approach.

As rain intensified, the Amber Rainstorm Warning was once again issued at 7:25 am. Although there were periods with relatively light rainfall during the day, the Warning remained in force until 9 pm that night.

Winds weakened gradually on August 1. The #1 Standby Signal was issued at 7:20 pm, replacing the #3 Signal. The weather remained unstable that night, and the Amber Rainstorm Warning was in force briefly during the small hours of August 2. The #1 Signal was eventually cancelled at 8:40 am, and the Landslip Warning was also cancelled shortly after.

During WIPHA's approach on July 31, the government received 14 reports of fallen trees and 3 cases of flooding. 20 people sought help at emergency units of public hospitals for injuries related to WIPHA's approach, while around 700 flights were delayed at the Hong Kong International Airport. The rainfall recorded at the HKO amounted to 121.1 mm on July 31 and 98.3 mm on August 1.

香港天氣於七月下旬較為不穩定。隨著韋帕發展成熱帶低氣壓,香港天文台於 7 月 30 日下午 3 時 40 分發出一號戒備信號,當時韋帕位於香港以南約 490 公里。在其初始熱帶氣旋警報中,天文台已經表示有機會於當晚改發三號信號,這是由於韋帕最強的風區處於其東北象限,與其中心相距甚遠。

本港離岸及高地等多個地方如長洲、橫瀾島及大老山下午已吹強風。天文台於下午 9 時 15 分改發三號強風信號,當時韋帕距港約 500 公里。天文台同時表示三號信號較大機會於翌日日出前維持。

30 日晚間本港風勢大多與當天下午相若,但 31 日破曉時份風勢有所加強。早上較後時段,位處維多利亞港的北角及中環碼頭吹強風。天文台於上午 9 時 30 分發佈的華南海域天氣報告中表示於香港以南約 50 公里的黃茅州吹 9 級風,顯示香港有機會於稍後受烈風影響。其後,天文台於上午 11 時 40 分發出預警八號熱帶氣旋警告信號之特別報告,提醒將最遲於下午 2 時改發八號信號。

韋帕的雨帶於 31 日早上開始影響香港,早上較後時段雨勢漸轉持續,黃色暴雨警告於上午 11 時 55 分發出。多個貨櫃碼頭宣佈會於下午 1 時暫停所有貨櫃交收,而由於八號信號即將發出,大部分僱員於午飯時段提早下班。兩小時預警期過後,天文台於下午 1 時 40 分改發八號東北烈風或暴風信號,當時韋帕位於香港以南約 340 公里;韋帕成為數十年來需要發出八號信號的熱帶風暴中最遠的一個。改發八號信號前後,長洲、青洲、大美督、塔門及大老山等地吹烈風,橫瀾島於改發信號前曾短暫吹暴風,而其他市區氣象站大多吹清勁至強風程度東風。

一道強雨帶過後,黃色暴雨警告於下午 2 時 35 分取消。八號信號生效期間,風勢普遍於下午後段最為猛烈。隨著雨勢加大,天文台於下午 5 時 30 分再度發出黃色暴雨警告,並於下午 8 時改發紅色暴雨警告,後者維持至下午 9 時 30 分。此外,新界北部水浸特別報告及山泥傾瀉警告亦分別於下午 8 時 25 分及 8 時 40 分發出,該特別報告至午夜 12 時才取消。

韋帕於 31 日下午 6 時左右最接近香港,於西南偏南方約 310 公里處掠過。隨著韋帕西移並遠離,天文台於下午 11 時 40 分改發三號強風信號,取代八號東北烈風或暴風信號。由於此時本港仍普遍吹東風,因此並未有改發八號東南信號。雖然改發三號信號,但本港凌晨風勢頗強。一道雨帶於 8 月 1 日上午 7 時左右掃過本港,多地風勢短暫急速上揚。長洲曾錄得持續風速達烈風上限的每小時 87 公里,是韋帕靠近以來最強。赤柱於上午 7 時後不久錄得烈風,而不少氣象站亦於此時錄得風暴影響香港時最強的風力。

因應雨勢轉強,天文台於上午 7 時 25 分發出黃色暴雨警告。日間部份時間雨勢減弱,但該信號一直生效至當晚 9 時。

本港風勢於 1 日逐漸減弱。一號戒備信號於下午 7 時 20 分發出,取代三號信號。當晚天氣仍然不穩定,2 日凌晨曾短暫發出黃色暴雨警告。一號戒備信號最終於上午 8 時 40 分取消,而山泥傾瀉警告亦於不久後取消。

韋帕於 7 月 31 日襲港期間,政府接獲 14 宗塌樹報告及三宗水浸報告。20 人因風暴受傷而往公共醫院急症室求醫,而香港國際機場有接近 700 班航班延誤。7 月 31 日及 8 月 1 日天文台分別錄得雨量達 121.1 毫米及 98.3 毫米。

Image Gallery 圖片庫

Figure 1 - Satellite image of WIPHA near its formation
圖 1 - 韋帕初形成時之衛星雲圖

Figure 2 - Numerical model forecasts of the mean wind speed distribution in southern China based on the ECMWF model (left, model run time: 8 pm July 30; forecast time: 5 pm July 31) and the GFS model (right, model run time: 2 am July 31; forecast time: 2 pm July 31). Image from weather.us.
圖 2 - 數值模式預報之華南平均風速分佈圖 (左圖為 ECMWF 模式,其起始時間為 7 月 30 日下午 8 時,預測時間為 7 月 31 日下午 5 時;右圖為 GFS 模式,其起始時間為 7 月 31 日上午 2 時,預測時間為 7 月 31 日下午 2 時)。圖片自 weather.us 擷取。

Figure 3 - Steering flow chart at 8 am July 31
圖 3 - 7 月 31 日上午 8 時之駛流場圖

Figure 4 - JMA's initial forecast track. Note the 270 NM (500 km)-wide estimated 30-knot (56 km/h) wind radius in the eastern semicircle.
圖 4 - 日本氣象廳之首佈路徑預測,留意風暴東半圓的估計 30 節 (每小時 56 公里) 風速半徑達 270 海里 (500 公里)。

Figure 5 - Wind field analysis at 10:32 am July 31
圖 5 - 7 月 31 日上午 10 時 32 分之風場掃描圖

Figure 6 - Forecast tracks from various official agencies at 8 am July 31
圖 6 - 7 月 31 日上午 8 時各官方氣象台之預測路徑

Figure 7 - Wind field analysis at 10:15 pm July 31; strong easterly winds were generally observed in seas near Hong Kong.
圖 7 - 7 月 31 日下午 10 時 15 分之風場掃描圖,當時香港附近海域普遍吹強東風。

Figure 8 - Track forecast and estimated wind radii by the HKO at 8 pm July 31. It was estimated that Hong Kong was at the edge of the gale wind circle.
圖 8 - 7 月 31 日下午 8 時香港天文台之預測路徑及估計風圈,顯示香港位處烈風圈邊緣。

Figure 9 - Satellite image of WIPHA at 7 am August 1. An intense rainband was about to cross Hong Kong at that time.
圖 9 - 8 月 1 日上午 7 時之衛星雲圖,當時一道強雨帶即將橫過香港。

Figure 10 - Radar images at 4-hour intervals from noon July 31 to 8 am August 1
圖 10 - 7 月 31 日正午 12 時至 8 月 1 日上午 8 時每四小時之雷達圖

Figure 11 - Local wind distribution maps at 4-hour intervals from noon July 31 to 8 am August 1
圖 11 - 7 月 31 日正午 12 時至 8 月 1 日上午 8 時每四小時之本港風勢分布圖

Figure 12 - Wind speed time series at Stanley, Cheung Chau, Chek Lap Kok and Waglan Island (top to bottom) between July 31 and August 1
圖 12 - 赤柱、長洲、赤鱲角及橫瀾島 (上至下) 於 7 月 31 日至 8 月 1 日之風速時間序列圖

Figure 13 - Rainfall distribution maps for July 31 (left) and August 1 (right)
圖 13 - 7 月 31 日 (左) 及 8 月 1 日 (右) 之雨量分佈圖

Winds Recorded at Reference Stations 參考站所錄得的風速

Station
風速站
Max. 10-min avg. wind speed
最高十分鐘平均風速
Beaufort classification
蒲福氏風級分類
Chek Lap Kok 赤鱲角 60 km/h* STRONG 強風
Cheung Chau 長洲 87 km/h* GALE 烈風
Kai Tak 啟德 47 km/h STRONG 強風
Lau Fau Shan 流浮山 53 km/h* STRONG 強風
Sai Kung 西貢 56 km/h STRONG 強風
Sha Tin 沙田 31 km/h* Fresh 清勁
Ta Kwu Ling 打鼓嶺 29 km/h Moderate 和緩
Tsing Yi (SHL) 青衣蜆殼油庫 43 km/h* STRONG 強風

*Recorded outside the period when the highest signal was in force. 於最高信號生效時間外錄得。

Number of stations recording at least STRONG force (force 6 - 7) winds: 6
Number of stations recording at least GALE force (force 8 - 9) winds: 1
Number of stations recording at least STORM force (force 10 - 11) winds: 0
Number of stations recording HURRICANE force (force 12) winds: 0

錄得 強風 (6 - 7 級) 或更高風速的站數: 6
錄得 烈風 (8 - 9 級) 或更高風速的站數: 1
錄得 暴風 (10 - 11 級) 或更高風速的站數: 0
錄得 颶風 (12 級) 風速的站數: 0

Charts and Figures 各項數據

Table 1: Track data from HKWW:
表一 : 香港天氣觀測站之路徑資料

YYMMDDZZ Lat Long Wind
18102112 083N1580E 025
18102118 087N1569E 030
18102200 091N1557E 035
18102206 099N1551E 040
18102212 109N1540E 045
18102218 112N1528E 055
18102300 116N1516E 065
18102306 120N1507E 075
18102312 120N1498E 085
18102318 128N1489E 110
18102400 133N1480E 130
18102406 140N1471E 145
18102412 147N1462E 155
18102418 153N1453E 150
18102500 158N1442E 145
18102506 160N1431E 140
18102512 163N1422E 135
18102518 166N1414E 130
18102600 169N1403E 125
18102606 170N1390E 125
18102612 172N1376E 125
18102618 176N1361E 130
18102700 178N1347E 135
18102706 179N1332E 135
18102712 180N1322E 130
18102718 180N1312E 130
18102800 180N1301E 130
18102806 180N1290E 125
18102812 178N1280E 115
18102818 175N1270E 110
18102900 170N1262E 100
18102906 168N1253E 100
18102912 168N1242E 100
18102918 168N1230E 100
18103000 167N1216E 090
18103006 167N1201E 075
18103012 165N1192E 060
18103018 169N1188E 060
18103100 174N1180E 060
18103106 180N1176E 060
18103112 183N1172E 060
18103118 189N1170E 060
18110100 196N1169E 060
18110106 200N1165E 055
18110112 204N1164E 050
18110118 206N1164E 045
18110200 207N1163E 040
18110206 207N1163E 035
18110212 207N1162E 030
18110218 203N1160E 025

Table 2: Maximum gust and hourly average wind speed recorded in Hong Kong from HKO:
表二 : 香港天文台公佈的各站最高每小時平均風力和陣風數據 (英文)

TBA 稍後公佈

Table 3: Rainfall (in millimetres) contributed by WIPHA from HKO (figures in brackets are based on incomplete hourly data):
表三 : 香港天文台公佈的各站雨量資料 (英文) (方括號內之數據由不完整之每小時資料擷取)

TBA 稍後公佈

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