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TC Watch / 熱帶氣旋 > Selected TC Review / 重要熱帶氣旋回顧 > 201015W (MEGI 鮎魚) [Refresh 更新]

201015W (MEGI 鮎魚) - Profile 檔案

(Issued on November 12, 2010)
(於 2010 年 11 月 12 日發出)

Additional Information 附加資料 : Wind Speed Data for TCs that Have Affected Hong Kong 影響香港氣旋之風速數據

Brief profile of MEGI 鮎魚小檔案:

JTWC number 聯合颱風警報中心 (JTWC) 號碼 15W
International number 國際編號 1013
Period of existence 生存時期 (JTWC) 2010/10/13 08 HKT - 2010/10/23 14 HKT
Lifetime 壽命 (JTWC) 10.25 days 日
Maximum 1-minute wind (JTWC) JTWC 一分鐘平均最高中心風速 160 knots 節 (Category 5 Super Typhoon 五級超級颱風)
Minimum pressure (JTWC) JTWC 最低氣壓 903 hPa 百帕*
Highest TC signal by HKO (if applicable)
香港天文台發出最高熱帶氣旋警告信號
3 (Strong Wind Signal 強風信號)
Closest point of approach by HKO (if applicable)
香港天文台所示之最接近距離 (如適用)
Not available - CPA occurred after cancellation of TC signals.
不適用 - 最接近距離於熱帶氣旋警告信號取消後出現
[During issuance of TC signals 熱帶氣旋警告信號生效時 : ESE 430 km (TC report 熱帶氣旋報告)]
Time of closest approach by HKO (if applicable)
香港天文台所示之最接近時間 (如適用)
Not available - CPA occurred after cancellation of TC signals.
不適用 - 最接近距離於熱帶氣旋警告信號取消後出現
[During issuance of TC signals 熱帶氣旋警告信號生效時 : 2010/10/22 02 HKT (TC report 熱帶氣旋報告)]
Lowest pressure recorded at HKO (if applicable)
香港天文台錄得的最低氣壓 (如適用)
1002.0 hPa 百帕 (2010/10/21 14:34 HKT)

*Aircraft reconnaissance reports minimum pressure below 895 hPa; Minimum pressure reported by the JMA is 885 hPa. 飛機偵察錄得最低氣壓低於 895 百帕,而日本氣象廳熱帶氣旋報告之最低氣壓為 885 百帕。

TC signals for Hong Kong & Track 香港曾經生效的熱帶氣旋警告和路徑圖:

Table 表:

Signal
信號
Date and time
日期和時間
Distance from HK
與香港的距離
Predicted movement
預測移動方向和速度
Max. 10-min winds
中心最高十分鐘平均風速
2010/10/20 (WED) 16:35 HKT
SSE 570 km
N / NNW Slowly
175 km/h (95 knots, CAT. 2 / ST)
2010/10/21 (THU) 05:40 HKT
SE 480 km
N at 10 km/h
175 km/h (95 knots, CAT. 2 / ST)
2010/10/22 (FRI) 18:05 HKT
E 440 km
N at 12 km/h
145 km/h (80 knots, CAT. 1 / T)
2010/10/22 (FRI) 20:40 HKT
E 440 km
N at 12 km/h
130 km/h (70 knots, CAT. 1 / T)

Figure 圖:

(Track courtesy of Lorenzo. Data from HKO. 鳴謝 Lorenzo 提供路徑圖,資料取自天文台)

TC Track

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 track from HKO 天文台的熱帶氣旋路徑圖:

TC Track

Past HKWW Bulletins on MEGI 本站有關鮎魚的發佈

Please click here for bulletins on MEGI. 請按這裡

Storm Formation and Development 氣旋形成和發展

MEGI is the first super typhoon (at maximum strength) to necessitate tropical cyclone signals since the implementation of the new tropical cyclone classification system in 2009. It is also the first storm in this basin in almost 20 years to have a measured minimum pressure of less than 900 hPa.

A tropical disturbance persisted near Guam on October 11. The disturbance acquired spiraling characteristics and a well-defined low-level circulation on October 12, and a tropical cyclone formation alert was promptly issued by the JTWC. It strengthened into the fifteenth tropical depression in this basin in the morning of October 13. At that time, model forecasts had been consistently predicting a fierce intensification leading to a very intense system by the next week, and ECMWF was at that time forecasting an intense typhoon inside the South China Sea a week later. Since the storm was expected to move west with a large body of warm ocean ahead, the JTWC also predicted a continual intensification.

Model guidance was not in good agreement. At that time the subtropical ridge was E-W oriented and anchored north of 15W. All model expected a weakness to appear due to a passing trough, but they disagree on whether or not 15W will be captured into the weakness and recurve. ECMWF had been very consistent, predicting that the ridge would not be weakened that much and MEGI would not be north enough to induce a recurvature, while GFS and NOGAPS indicated recurvature at some point.

15W gathered strength quickly. The JMA upgraded it into a tropical storm at 20 HKT on October 13, naming it MEGI. This name was contributed by South Korea, meaning catfish. In the next 12 hours, MEGI's eastern semicircle expanded in size, while development in its western side was limited, probably due to a disturbance persisting to the southwest of MEGI which impeded inflow channels.

MEGI adopted a WNW track along the southern periphery of the subtropical ridge, with northward component coming from the southward extension of the ridge to MEGI's east. The JMA upgraded MEGI into a severe tropical storm on October 15 as convection expanded outward. By that time the disturbance affecting MEGI was dissipating.

Although still not quite symmetric in shape, it intensified into a typhoon later that day. Difference in strength estimation was wide between the JTWC and JMA, with the former estimating MEGI to have maximum winds of 90 knots when the JMA upgraded MEGI into a typhoon (65 knots) (this difference is still large after accounting for the fact that the JTWC uses 1-minute average wind speeds while JMA uses 10-minute average).

At that time, the subtropical ridge was getting thinner as it interacted with the trough, but it remained intact. Nevertheless, the weakening of the ridge allowed more room for poleward track component and MEGI moved northwest on October 15 as a result. As it neared the southern edge of the ridge, it gradually turned westward.

鮎魚是自香港天文台於 2009 年實施熱帶氣旋新分級制度以來首個曾達超強颱風強度而之後需要發出熱帶氣旋警告信號的熱帶氣旋。它亦是接近 20 年來西北太平洋的首個熱帶氣旋實測氣壓低於 900 百帕斯卡。

一股熱帶擾動於 10 月 11 日在關島一帶出現。該擾動於 12 日發展出一明顯低層環流中心,螺旋性亦轉好,聯合颱風警報中心 (JTWC) 對其發出熱帶氣旋形成警報。它於 10 月 13 日早上增強為西北太平洋本年度第 15 個熱帶低氣壓 (15W)。當時,一些預測模式已經預料 15W 將急速增強,而歐洲中期天氣預報中心 (ECMWF) 更預測 15W 將在一星期後以極高強度出現於南海中。由於預料 15W 向西移動,將經過大片溫暖洋面,JTWC 亦預測 15W 將持續增強。

數值預報結果並不一致。當時副熱帶高壓脊處於 15W 以北並呈東西向。所有模式皆預計西風槽經過將令副高減弱,但減弱幅度分歧較大,部分模式預料 15W 將進入弱點並轉向。ECMWF 連續數天的預測一致認為副高減弱幅度將不會大得令 15W 轉向,但 GFS 和 NOGAPS 則於部分時間持不同意見。

15W 迅速增強。日本氣象廳 (JMA) 於 13 日下午 8 時升格 15W 為熱帶風暴,並把其命名為由南韓提供的名字鮎魚。隨後 12 小時鮎魚的東半圓擴展起來,但西面發展則相對較為遜色,這可能是由於其西南面的一個擾動影響該區的輻合。

鮎魚沿副高南面向西北偏西移動,其向北分量由副高在其東面南伸帶來。隨著對流向外擴展,JMA 於 10 月 15 日將鮎魚升格為強烈熱帶風暴,而在其西南面的擾動則逐漸消散。

雖然鮎魚看起來不太對稱,但它於當日較後時間增強為颱風。JTWC 和 JMA 對鮎魚的強度估計分歧頗大,前者和後者所估計的強度分別為 90 和 65 節 (雖然它們使用不同風速標準,但此分歧仍然屬於偏高)。

當時,由於受西風槽侵擊,副高變得單薄,但仍然完整。然而,其減弱令鮎魚路徑的偏北分量增多,它於 15 日主要向西北移動。隨著鮎魚接近副高南緣,它逐漸轉往西移。

Figure 1 - 15W developed into a tropical depression
圖 1 - 15W 形成初期

Figure 2 - Wind shear chart at 11 HKT, October 14. The almost null shear environment enhanced MEGI's intensification
圖 2 - 10 月 14 日上午 11 時的垂直風切變分佈圖。接近零垂直風切變有利鮎魚增強

Figure 3 - ECMWF's model forecast. MEGI was expected to be an intense system in the South China Sea in late October
圖 3 - ECMWF 數值模式預報圖。當時預料鮎魚將於 10 月下旬在南海大幅增強

Figure 4 - JTWC's initial forecast track
圖 4 - JTWC 的初始預測路徑圖

Figures 5a and 5b - Forecast tracks from different agencies at 20 HKT, October 13 and 14 HKT, October 15
圖 5a 及 5b - 各氣象台於 10 月 13 日下午 8 時和 15 日下午 2 時之預測路徑圖

Attaining Peak Intensity 到達巔峰強度

MEGI intensified steadily on October 16 while still going westward. The central dense overcast was developing quickly, but peripheral convections remained asymmetric. It intensified into an 80-knot (JMA) / 105-knot (JTWC) system by 20 HKT that night. In the next 12 hours, MEGI deepened rapidly, and a clear eye appeared on IR satellite images. The HKO upgraded MEGI into a severe typhoon at 22 HKT on October 16 and then a super typhoon at 06 HKT on October 17. The JMA revised MEGI's intensity upwards to 90 knots at 02 HKT on October 17, and 110 knots at 08 HKT that day. Meanwhile, JTWC's estimate surged to 125 knots and 140 knots (category 5 super typhoon) at 02 HKT and 08 HKT respectively.

An aircraft reconnaissance mission on MEGI was carried at about 08 - 09 HKT on October 17. The aircraft reported maximum flight level winds of 169 knots and estimated maximum surface winds of 143 knots. The minimum sea level pressure dropped to 909 hPa (Full decoded message here).

At that time, MEGI started to turn WSW as it started to be influenced by the continental ridge NW of it. In almost null shear environment MEGI continued to intensify during October 17. Its eye increased in size during the day and convections in its southern periphery expanded.

Another reconnaissance mission was conducted later that day near 20 HKT. The results returned from that mission was astonishing - maximum flight level winds reached 190 knots and the estimated maximum surface wind was 165 knots (Full decoded message here). Perhaps the most surprising measurement was the minimum sea level pressure - at 890 hPa MEGI became the first storm in the northwest Pacific basin in about 20 years to reach a measured sea level pressure of below 900 hPa (it is important to note that there might well be cyclones in these 20 years to reach such a pressure but went unnoticed), and this is the minimum sea level pressure recorded since Hurricane Wilma in the Alantic in 2005 (882 hPa; the most intense cyclone ever recorded in that basin). With such measured information, all official agencies revised MEGI's intensity upward further in their 20 HKT bulletin on October 17 (See table below):

鮎魚於 10 月 16 日穩定增強並繼續向西移動。它的中心密集雲區正快速建立,但周邊對流仍然不對稱。它當晚增強至 80 節 (JMA) / 105 節 (JTWC) 的颱風。在隨後 12 小時,鮎魚急速增強,紅外線衛星雲圖上出現一清晰的風眼。香港天文台於 16 日下午 10 時升格鮎魚為強颱風,翌日上午 6 時為超強颱風。JMA 於 17 日上午 2 時將其強度上調至 90 節,6 小時後更上調至 110 節。同時,JTWC 在上午 2 和 8 時的強度則分別為 125 和 140 節 (後者達五級超級颱風強度)。

在 17 日上午 8 至 9 時所進行的飛機偵察行動測到在鮎魚中心附近航行高度風速最高達 169 節,估計表面風速亦達 143 節。當時的最低海平面氣壓為 909 百帕斯卡 (報告全文)。

隨著鮎魚開始受其西北面大陸高壓的影響,它開始向西南偏西移動。在幾乎零垂直風切變的環境下,鮎魚在 17 日繼續增強。它的風眼稍為擴大,南面對流亦向外擴展。

另一次飛機偵察行動於當晚約 8 時進行,其觀測數據令人驚訝 --- 飛行高度風速達 190 節,換算回地面後的估計仍高達 165 節 (報告全文)。除此以外,該行動錄得鮎魚的中心氣壓只得 890 百帕斯卡,令鮎魚成為約 20 年來西北太平洋上首個實測錄得低於 900 百帕氣壓的熱帶氣旋 (要注意的是在這 20 年來絕對有可能曾出現低於 900 百帕氣壓的颱風,只是它們未被實測數據確認),而這氣壓讀數亦為自 2005 年颶風威爾瑪 (882 百帕,大西洋上錄得的最低氣壓) 以來全球最低的。此數據公佈後,各氣象台於當晚 8 時紛紛調高鮎魚的強度:

Agency
機構
Measurement standard
測量標準
Wind speed at 14 HKT
下午 2 時之風速
Wind speed at 20 HKT
下午 8 時之風速
Hong Kong Observatory (HKO)
香港天文台
Max. 10-minute average
最高 10 分鐘平均
105 knots 節 (08 HKT)**
(195 km/h 公里每小時)
120 knots 節
(222 km/h 公里每小時)
Japan Meteorological Agency (JMA)
日本氣象廳
Max. 10-minute average
最高 10 分鐘平均
115 knots 節
(213 km/h 公里每小時)
120 knots 節
(222 km/h 公里每小時)
China Meteorological Administration (CMA)
中國氣象局
Max. 2-minute average
最高 2 分鐘平均
125 knots 節
(232 km/h 公里每小時)
140 knots 節
(259 km/h 公里每小時)
Central Weather Bureau (CWB, Taiwan)
台灣中央氣象局
Max. 10-minute average
最高 10 分鐘平均
113 knots 節
(209 km/h 公里每小時)
117 knots 節
(217 km/h 公里每小時)
Korea Meteorological Administration (KMA)
韓國氣象局
Max. 10-minute average
最高 10 分鐘平均
110 knots 節
(204 km/h 公里每小時)
117 knots 節
(217 km/h 公里每小時)

Joint Typhoon Warning Center (JTWC)
聯合颱風警報中心

Max. 1-minute average
最高 1 分鐘平均
145 knots 節
(269 km/h 公里每小時)
160 knots 節***
(296 km/h 公里每小時)

**The HKO only issues position fixes and intensities once every 12 hours for cyclones east of 125°E. 香港天文台對處於東經 125 度以東的熱帶氣旋只會每 12 小時公佈一次其定位和強度。

***According to here. This may be different from strengths indicated in live bulletins. 根據這裡的強度。此強度或會與當時發佈強度不同。

The sea level pressure indicated in their bulletins were also revised to below 900 hPa, with the JMA assigning 895 hPa which was the lowest in almost two decades (again this is because no measured data could be captured for many strong cyclones since early 1990s). MEGI maintained its intensity in the next 12 hours as it approached northern Luzon. The JMA lowered their pressure estimate to 890 hPa at 02 HKT on October 18, then further to 885 hPa at 08 HKT with maximum winds of 125 knots.

它們發佈中的最低氣壓亦調至低於 900 百帕斯卡,其中 JMA 給予的氣壓讀數為 895 百帕,幾乎是 20 年來最低 (同樣這是由於這段時間內沒有飛機實測)。鮎魚於隨後 12 小時維持強度。JMA 在 18 日上午 2 時再度調低鮎魚的氣壓估計至 890 百帕,6 小時後更調低至 885 百帕,風速亦調高至 125 節。

Figures 6a to 6d - IR satellite image at 20 HKT from October 14 to 17
圖 6a 至 6d - 10 月 14 日至 17 日下午 8 時之紅外線衛星雲圖

Figure 7 - Wind vector plot near 21 HKT, October 17
圖 7 - 10 月 17 日約下午 9 時之風矢量圖

Figure 8 - MEGI near peak intensity. The round eye can be clearly seen
圖 8 - 鮎魚接近巔峰強度。圓渾的風眼清晰可見

Figure 9 - Different images showing MEGI near peak intensity.
圖 9 - 鮎魚接近巔峰強度時之不同影像

Figure 10 - MEGI's central dense overcast is mature and has very low cloud top temperatures
圖 10 - 鮎魚的中心密集雲區成熟,雲頂溫度非常低

Figure 11 - Visible image available after daybreak. MEGI appears symmetric in shape and its eye is very clear
圖 11 - 日出後再次攝到可見光衛星雲圖。鮎魚結構仍然對稱,風眼十分清晰

Figure 12 - Note the very high intensities assigned to MEGI by different agencies
圖 12 - 留意各氣象台均給予鮎魚非常高的強度

Making Landfall at Luzon and Entering South China Sea 登陸呂宋和進入南海

The Philippines braced itself for the strongest typhoon to hit the country in 4 years. Packing winds of category 5 strength, MEGI made landfall at Sierra Madre at about noon on October 18. The Storm signal #4, highest in the country, was issued in some parts of Luzon indicating that winds of above 185 km/h (100 knots) were to be expected. 19 people died in the country as a result of the storm, and damages amounted to 11 billion Philippine peso (about 2 billion HKD).

The clear eye disappeared about an hour after MEGI's landfall. The storm then traversed Luzon in the afternoon that day, and passed across the mountain ridge between Mount Sapocoy and Mount Pulog (both with summit above 2000 metres). As a result its lower structure was severely damaged. Deep convections were lost and MEGI's convections appeared looser than before, but it managed to retain (severe) typhoon strength.

After a relatively fast journey across Luzon, MEGI turned west again and entered South China Sea before midnight, October 19. It started to decelerate during that night. For the past few days, ECMWF consistently predicted that MEGI would continue its westward journey (or turn WNW) towards Hainan, and it would intensify again to super typhoon strength as it travelled in warm seas. Probably as a result of this, agencies had been predicting that MEGI would strike Hainan Island. However, an increasing number of models pointed out in the possibility of the subtropical ridge weakening more heavily than originally predicted, and that the storm would turn north in South China Sea or even recurve. Therefore, agencies have started to retract their westward predictions and indicate a poleward turn since October 18. A eastward correction to their prediction meant that central and eastern Guangdong coastal areas (including Hong Kong) would be under a heightened threat, and due to the severity of the cyclone's destructive power, people in these regions and the media started to monitor the situation closely as soon as MEGI entered South China Sea.

菲律賓為 4 年來最強勁颱風正面侵襲作出準備。鮎魚在 10 月 18 日中午時份以五級超級颱風強度登陸菲國東部馬德雷山脈。菲律賓部分地區發出了最高級別的 4 號風暴信號,表示持續風速可達每小時 185 公里 (100 節)。鮎魚登陸菲律賓共造成 19 人死亡,合計損失接近 110 億披索 (約 20 億港元)。

鮎魚登陸後 1 小時風眼消失。它於 18 日下午橫過呂宋,於 Sapocoy 和 Pulog (兩座高山頂峰均達海拔 2000 米) 之間的山脊通過。呂宋的山脈大幅破壞鮎魚的低層結構;其深層對流消失,結構變得較為鬆散,但仍然維持 (強) 颱風強度。

經過呂宋後,鮎魚轉向西移,19 日午夜前進入南海,並於當晚減速。ECMWF 已多佈預計鮎魚將繼續向西或西北偏西移,趨向海南島並於溫暖海水中再度增強為超級颱風。可能因為此預測,多數機構均曾預計鮎魚會趨向海南一帶。可是,其後越來越多數值模式預測副高將大幅減弱並令鮎魚北移甚至轉向。因此,氣象台於鮎魚登陸菲律賓前後開始改變預測,預計鮎魚將轉北。這意味著鮎魚對廣東中東部沿岸 (包括香港) 的威脅大幅增加。同時,由於鮎魚強度非常高,當地市民和傳媒都於鮎魚進入南海後加緊監測其動態。

Figures 13a and 13b - (left) MEGI just before making landfall at Luzon; (right) MEGI just entered South China Sea
圖 13a 及 13b - (左) 鮎魚即將登陸呂宋;(右) 鮎魚剛進入南海

Figure 14 - The JMA depicting an almost direct hit scenario
圖 14 - JMA 近乎直襲的預測

Figure 15 - Forecast tracks from different agencies at 14 HKT, October 19
圖 15 - 各氣象台於 10 月 19 日下午 2 時之預測路徑圖

Preparations in Hong Kong and MEGI's Turn 香港作出之準備和鮎魚轉向

MEGI strengthened again soon after re-entering ocean. It entered Hong Kong's 800-km circle in the morning of October 19. At that time a number of agencies including the HKO predicted MEGI to turn NW or NNW a day later, with the possibility of landfall in the vicinity of Hong Kong later that week. As the HKO emphasized that MEGI was a severe typhoon packing winds of 175 km/h (95 knots), heightened alert could be seen over the territories. Media coverage on MEGI was immense, and major TV stations in Hong Kong reviewed past super typhoons that brought significant damage to Hong Kong.

MEGI stopped moving west in the morning of October 20. The continental ridge was eroded away by a series of mid-latitude troughs and that the subtropical ridge to the east of MEGI became N-S oriented. Agencies shifted their forecast tracks further east, indicating landfall from just east of Hong Kong to southern Fujian. Due to the sudden northward turn, MEGI would get soon get closer, and the Hong Kong Observatory issued the #1 Standby Signal at 16:35 HKT when MEGI was 570 km SSE of Hong Kong. Coupled with the northeast monsoon, northerly winds in Hong Kong strengthened that night, occasionally reaching strong force in offshore areas and on high grounds.

The Observatory initially stated that the chance of raising the alert to #3 that night was not high, but retracted the statement after a general increase in local winds that night. The HKO explained that it was due to the strengthening northeast monsoon, which was probably supported by the increasing barometric pressure (as opposed to decresing pressure if it was due to the cyclone moving closer). The Observatory finally issued the #3 Strong Wind Signal at 05:40 HKT on October 21, but winds actually subsided as the northeast monsoon moderated.

MEGI's eastward track component increased significantly on October 21, and the storm remained outside of Hong Kong's 400-km circle. For most stations, the strongest winds were actually recorded the night before (October 20), and on October 21 winds were not particularly strong. Although MEGI remained strong (still 175 km/h or 95 knots) and was showing a ragged eye on satellite images, it was situated some 400 km SE of Hong Kong, and topographical features in Hong Kong prevented northerly winds from becoming stronger. Nevertheless, a government press conference was held that afternoon to introduce the various measures that the government would undertake if MEGI approached. Such a government press conference about an impending typhoon was almost nonexistent in the past.

However, as MEGI was then edging closer to Taiwan than expected, the CWB issued the Land and Sea Typhoon Warning on October 21. As the southeasterly airstream from MEGI converged with the northeast monsoon, convection activity was violent on the Island and many locations on Taiwan recorded more than 400 mm of rain in three days from October 21 to 23. Rocks falling down from slopes hit a coach in Suhua highway, presumably sending the coach and all 21 people inside, comprising a driver, a tour guide and 19 tourists from Zhuhai, down the cliff and into the Pacific Ocean. They remained missing as of early November.

鮎魚在進入南海後不久再度增強。它於 10 月 19 日早上進入香港 800 公里範圍。當時包括天文台在內的大部分機構預測鮎魚將於一日後改向西北至西北偏北移動,於該周後期登陸香港附近一帶地區。由於天文台強調鮎魚為一強颱風,中心風力達每小時 175 公里 (95 節),香港市民對鮎魚的警覺普遍提高。傳媒對鮎魚的報導篇幅一天比一天多,各大電視台更重溫過去曾為香港帶來重大破壞的超強颱風。

鮎魚於 20 日上午停止西移。大陸高壓已經被一連串的西風槽徹底擊潰,而東面的副高則變為南北向。各機構繼續把預測東調,登陸點東移至香港以東至福建南部。由於鮎魚突然轉北,它與香港的距離將縮短,天文台於當天下午 4 時 35 分發出一號戒備信號,當時鮎魚在香港東南偏南約 570 公里。受到東北季候風的共同影響,本港北風於當晚增強,離岸和高地間中吹強風。

天文台原先預計當晚改發三號強風信號的機會不高,但隨後由於風勢加強,天文台改為表示可能需要提早考慮發出三號信號。天文台解釋這是因為東北季候風加強,這可能是跟當晚徐徐上升的氣壓讀數有關 (如果是熱帶氣旋移近而帶來,氣壓應會下跌)。天文台最終於 10 月 21 日上午 5 時 40 分發出三號強風信號,但由於東北季候風稍為減弱,當時風速實為下降中。

鮎魚路徑的東向量於 21 日明顯增加,而鮎魚則維持在香港 400 公里外。大部分氣象站於 20 日晚 (即三號信號發出前) 已錄得其最高風速,而 21 日的風勢並不特別強。雖然鮎魚強度仍維持於每小時 175 公里 (95 節) 而不規則風眼仍然可於衛星圖上清晰可見,它仍然在香港東南面 400 公里外,地形影響令香港的北風沒有顯著增強。雖然如此,政府仍於當日下午舉行跨部門記者會來解釋政府的應變措施,而同類的記者會幾乎是前所未見的。

另一方面,由於鮎魚比原先預計更接近台灣,當地在 21 日發出海上陸上颱風警報。由於鮎魚帶來的東南氣流與東北季候風相遇,台灣多處對流活動猛烈,部分地區 21 至 23 日雨量超過 400 毫米。滑下山坡的巨石擊中一架沿蘇花公路行駛的旅遊巴,車上 21 人 (包括司機、導遊和 19 名珠海旅客) 很可能隨旅遊巴被沖落懸崖至太平洋。他們到 11 月初仍然下落不明。

Figure 16 - Steering flow at 14 HKT, October 19
圖 16 - 10 月 19 日下午 2 時的駛流圖

Figure 17 - At that time, HKO was predicting MEGI to re-intensify into a super typhoon
圖 17 - 當時天文台預料鮎魚將再度增強為超強颱風

Figure 18 - Wind vector plot near 21 HKT, October 20
圖 18 - 10 月 20 日約下午 9 時之風矢量圖

Figure 19 - MEGI about to pass 20°N
圖 19 - 鮎魚即將到達北緯 20 度

Figures 20a to 20c - Wind speed at Kai Tak, Waglan Island and Cheung Chau
圖 20a 至 20c - 啟德、橫瀾島和長洲之風速

Figure 21 - Convective activity was violent in Taiwan
圖 21 - 台灣對流活動猛烈

Landfall and Dissipation 登陸及消散

Back to Hong Kong, the Strong Wind Signal remained in force for the rest of October 21. As MEGI reached 20°N, cooler water rushing in from the Taiwan Strait entered its core, lowering the amount of energy that it could capture. MEGI shrank in size and its eye disappeared from IR images. On October 22, MEGI acquire slight westward track component, as if it was tracking along Hong Kong's 400-km circle. Due to the apparent weakening of the storm, the HKO issued the #1 Standby Signal at 18:05 HKT that day, replacing the Strong Wind Signal. The Standby Signal was soon lifted at 20:40 HKT when MEGI reached Hong Kong's latitude. Wind direction gradually turned to northwest, which was also a shielded direction.

MEGI weakened into a minimal typhoon as it made its final landfall at Zhangpu, Fujian at about 13 HKT on October 23. It is worth mentioning that MEGI is the third cyclone this year to make landfall at Zhangpu, after LIONROCK in early September and FANAPI later that month. Luckily, due to the effect of cooler water, the intensity at landfall was much weaker than originally predicted, which helped in reducing damages. The shrinking cyclone also provided better weather for Hong Kong than expected, as October 23 remained a fine day for the territory instead of frequent heavy downpours predicted earlier.

Without moisture and being a small cyclone, MEGI weakened quickly upon landfall, dissipating in Fujian province in less than a day.

回到香港,三號強風信號於 10 月 21 日餘下時間生效。隨著鮎魚到達北緯 20 度,台灣海峽中較冷的海水開始進入鮎魚的中心,令其可以吸納的能量降低。鮎魚逐漸縮小,風眼於紅外線雲圖上消失。鮎魚路徑的向西分量於 22 日增加,路徑看上去儼如鮎魚繞著距離香港 400 公里的距離圈外行走那樣。由於鮎魚明顯減弱,天文台於 22 日下午 6 時 05 分改發一號戒備信號,而此信號亦於當晚 8 時 40 分鮎魚到達香港的緯度時取消。本港風向轉為西北,屏障仍然較大。

鮎魚減弱至颱風下限強度,於 23 日下午約 1 時在福建漳浦登陸。繼九月獅子山和凡亞比後,鮎魚成為本年第三個登陸漳浦的熱帶氣旋。可幸的是受到較冷海水的影響,鮎魚登陸時的強度比原先估計弱得多,破壞亦得以減低。同時,由於鮎魚在北進時尺度縮小,香港於 23 日的天氣亦比預期好,由預測狂風大雨變為大致天晴。

隨著濕氣供應被切斷,鮎魚登陸後快速減弱,並在少於一天後在福建內陸消散

Figure 22 - MEGI about to make landfall at Fujian
圖 22 - 鮎魚即將登陸福建

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 39 km/h Fresh 清勁
Cheung Chau 長洲 52 km/h STRONG 強風
Kai Tak 啟德 37 km/h Fresh 清勁
Sai Kung 西貢 43 km/h STRONG 強風
Sha Tin 沙田 24 km/h Moderate 和緩
Ta Kwu Ling 打鼓嶺 30 km/h Moderate 和緩
Tsing Yi (SHL) 青衣蜆殼油庫 35 km/h Fresh 清勁
Wetland Park 濕地公園 27 km/h Moderate 和緩

Number of stations recording at least STRONG force (force 6 - 7) winds: 2

Number of stations recording at least GALE force (force 8 - 9) winds:

0
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: 2
錄得 烈風 (8 - 9 級) 或更高風速的站數:

0
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
10101218 120N1417E 020
10101300 120N1413E 025
10101306 119N1410E 035
10101312 119N1408E 040
10101318 119N1406E 040
10101400 120N1405E 045
10101406 126N1394E 050
10101412 131N1385E 055
10101418 135N1377E 060
10101500 145N1371E 065
10101506 149N1366E 075
10101512 157N1355E 085
10101518 169N1343E 090
10101600 174N1330E 090
10101606 181N1315E 095
10101612 183N1303E 105
10101618 187N1288E 125
10101700 187N1275E 140
10101706 185N1262E 145
10101712 181N1251E 155
10101718 176N1242E 160
10101800 175N1233E 150
10101806 172N1218E 130
10101812 167N1205E 105
10101818 167N1195E 100
10101900 163N1190E 100
10101906 167N1185E 105
10101912 167N1180E 105
10101918 170N1176E 110
10102000 172N1173E 115
10102006 178N1172E 115
10102012 184N1172E 110
10102018 188N1174E 110
10102100 195N1174E 110
10102106 199N1175E 110
10102112 202N1178E 110
10102118 206N1180E 105
10102200 210N1182E 100
10102206 217N1183E 090
10102212 223N1183E 085
10102218 227N1182E 080
10102300 234N1180E 075
10102306 240N1177E 065
10102312 244N1178E 055

Table 2: Data collected by reconnaissance aircraft (20 HKT, October 17)
表二 : 偵察飛機所得資料 (10 月 17 日下午 8 時)

URPA12 PGUA 171223
VORTEX DATA MESSAGE
A. 17/12:06:00Z
B. 18 deg 01 min N
125 deg 05 min E
C. 700 mb 2151 m
D. 152 kt
E. 178 deg 7 nm
F. 266 deg 152 kt
G. 178 deg 7 nm
H. 893 mb
I. 9 C / 3048 m
J. 18 C / 3041 m
K. 16 C / NA
L. CLOSED WALL
M. C16
N. 12345 / 7
O. 0.02 / 1 nm
P. AF304 0830W MEGI OB 15
MAX OUTBOUND AND MAX FL WIND 190 KT NW QUAD 12:09:10Z
MAX FL TEMP 19 C 325 / 5 NM FROM FL CNTR
FREQUENT LIGHTNING IN THE EYEWALL
;

Table 3: Maximum gust and 60-minute average wind speed recorded in Hong Kong from HKO:
表三 : 香港天文台公佈的各站最高 60 分鐘平均風力和陣風數據

Maximum Gust
Maximum Hourly Mean Wind
Station
Direction
Speed (km/h)
Date/Month
Time
Direction
Speed (km/h)
Date/Month
Time
Bluff Head (Stanley)
N
49
20/10
20:50
NNW
13
21/10
00:00
NNW
13
21/10
01:00
Central Pier
NE
43
20/10
20:14
WNW
30
22/10
13:00
NW
43
22/10
03:43
Cheung Chau
NNE
72
21/10
01:43
NNE
47
21/10
01:00
Cheung Chau Beach
NE
72
21/10
01:44
NE
38
21/10
01:00
Cheung Sha Wan
N
51
21/10
08:28
N
16
21/10
01:00
Green Island
N
76
21/10
00:00
N
51
21/10
10:00
Hong Kong International Airport
N
52
21/10
04:57
N
36
21/10
05:00
Kai Tak
N
67
21/10
04:00
N
31
20/10
20:00
King's Park
NNE
56
21/10
00:11
N
23
20/10
19:00
Lau Fau Shan
N
58
20/10
21:45
N
34
21/10
18:00
Ngong Ping
NE
72
21/10
20:16
ENE
45
20/10
23:00
North Point
NNE
52
20/10
23:44
NNE
25
21/10
00:00
Peng Chau
NNE
63
21/10
00:27
N
38
20/10
22:00
N
38
21/10
01:00
Ping Chau
NNE
49
21/10
06:36
NNE
12
20/10
20:00
NNW
49
21/10
23:51
N
12
21/10
04:00
NNE
12
21/10
05:00
N
12
21/10
07:00
Sai Kung
N
72
20/10
23:52
N
36
20/10
21:00
Sha Chau
N
65
20/10
22:02
N
49
21/10
05:00
N
65
21/10
05:22
Sha Lo Wan
NE
40
20/10
21:47
NNE
20
20/10
22:00
NNE
40
20/10
22:37
Sha Tin
N
56
21/10
04:45
N
20
21/10
05:00
Shek Kong
NE
45
21/10
11:09
NNE
20
21/10
11:00
Star Ferry (Kowloon)
WNW
43
21/10
18:02
WNW
20
22/10
14:00
Ta Kwu Ling
NNE
54
21/10
02:02
N
25
21/10
01:00
Tai Mei Tuk
NNE
68
21/10
21:33
NE
31
21/10
00:00
NNE
31
21/10
22:00
Tai Mo Shan
NNE
81
21/10
04:05
NNE
59
21/10
05:00
NNE
81
21/10
21:12
Tap Mun
N
58
21/10
20:47
N
22
21/10
00:00
N
22
21/10
17:00
N
22
22/10
04:00
Tate's Cairn
N
85
21/10
19:46
N
62
21/10
20:00
Tsak Yue Wu
NE
63
21/10
09:45
NNE
30
22/10
03:00
Tseung Kwan O
ENE
47
21/10
10:00
N
19
21/10
20:00
Tsing Yi Shell Oil Depot
NNW
62
21/10
01:47
NNW
30
21/10
02:00
Tuen Mun Government Offices
N
49
20/10
22:23
N
14
21/10
11:00
N
14
21/10
17:00
Waglan Island
NNE
65
20/10
20:07
NNE
51
20/10
20:00
NNE
51
20/10
21:00
Wetland Park
NNE
49
20/10
21:51
NNE
20
20/10
22:00
Wong Chuk Hang
NW
52
21/10
09:10
NNW
20
21/10
10:00
N
52
21/10
09:38

Table 4: Rainfall (in millimetres) contributed by MEGI from HKO (figures in brackets are based on incomplete hourly data):
表四 : 香港天文台公佈的各站雨量資料 (方括號內之數據由不完整之每小時資料擷取)

Station
20 Oct
21 Oct
22 Oct
Total (mm)
Hong Kong Observatory
0.0
Trace
0.2
0.2
Cheung Chau (CCH)
[0.0]
[0.0]
[0.0]
[0.0]
Hong Kong International Airport (HKA)
0.0
Trace
0.3
0.3
N05 Fanling
0.0
0.5
3.0
3.5
N13 High Island
0.0
0.0
1.0
1.0
K04 Jordan Valley
0.0
0.0
2.5
2.5
N06 Kwai Chung
0.0
0.0
0.0
0.0
H12 Mid Levels
0.0

0.0

0.0
0.0
H21 Repulse Bay
0.0

0.0

0.5
0.5
N09 Sha Tin
0.0
0.0
2.5
2.5
H19 Shau Kei Wan
0.0

0.0

1.5
1.5
SEK Shek Kong
0.0

[0.0]

0.0

[0.0]

K06 So Uk Estate
0.0

0.0

0.0
0.0
R31 Tai Mei Tuk
0.0

0.5

4.0
4.5
R21 Tap Shek Kok
0.0

0.0

0.0
0.0
N17 Tung Chung
0.0

0.0

0.0
0.0
R27 Yuen Long
0.0

0.0

0.0
0.0

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