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[2018] 世紀風暴——2018年超強颱風山竹回顧(英文初版)

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发表于 2019-9-16 23:28 | 显示全部楼层 |阅读模式
本帖最后由 Luigi728 于 2019-9-16 23:29 编辑

世紀風暴——2018年超強颱風山竹回顧(英文初版)

Storm of the Century – 2018 Super Typhoon Mangkhut Review (English Beta Version)



簡介

話說我去年進了美國的康乃爾大學(Cornell University)修讀大氣科學!數個月前,一份大學作業要求我寫一篇關於一個天氣事件的論文。於是,我用英文寫了這一個關於山竹的短篇回顧。本來打算在暑假期間寫一篇完整的雙語山竹回顧,不過最後找不到時間......今天是山竹一週年紀念,所以就想先發一下這個暫時只有英文的初版山竹回顧,給大家看一下,未來再寫完整版雙語山竹回顧吧!


Table of Contents

Chapter 1: Journey to Category 5_______________2-3
Chapter 2: Initial Preparation__________________4-5
Chapter 3: Sprinting Towards Hong Kong ________6-8
Chapter 4: Storm of the Century_______________ 9-11
Chapter 5: Conclusion of the Story_____________ 12-13
Figures___________________________________ Separate Documents
Works Cited_______________________________ 14

Note:
1.        The time referred below are primarily in Hong Kong time zone (UTC+8) by default, or according to Zulu time (Z) if otherwise stated.
2.        The distances referred below are primarily in kilometers (km), unless otherwise stated.
3.        The windspeeds referred below are either in kilometers per hour (km/h) or knots (knots), depending on the primary unit of the meteorology agency.
4.        The temperatures referred below are all in degrees Celsius (OC).
5.        In Northwest Pacific Ocean, different meteorology agencies use different sustained windspeeds: Joint Typhoon Warning Center (JTWC) uses 1-minute sustained windspeed, China Meteorology Agency (CMA) uses 2-minute sustained windspeed, Hong Kong Observatory (HKO), Japan Meteorology Agency (JMA), Taiwan Central Weather Bureau (CWB) and Korea Meteorology Agency (KMA) uses 10-minute sustained windspeed.

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参与人数 2威望 +40 贡献值 +15 好评度 +10 收起 理由
g2ming + 10 + 5 很给力!
颱風巨爵 + 30 + 10 + 10 Storm of the Century

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幸福和快樂是結局......一起寫我們的結局......
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 楼主| 发表于 2019-9-16 23:40 | 显示全部楼层
Chapter 1: Journey to Category 5

        On 4th September 2018, Tropical Disturbance 99W formed in Northwest Pacific Ocean, near the international date line. Three days later, it was named as Mangkhut. Mangkhut’s surrounding environment was very excellent – containing warm sea surface temperature (SST) of above 30OC, high ocean heat content (OHC), low vertical wind shear (VWS) of 5-10knots and excellent poleward outflow that provided it with very strong upper level divergence, all factors that are very supportive and crucial to tropical cyclone development. Therefore, most computer models and meteorology agencies were very optimistic on Mangkhut’s development – European Center for Medium Range Weather Forecasts (ECMWF) forecasted Mangkhut to reach 922hpa, Global Forecast System (GFS) even forecasted Mangkhut to reach an insane atmospheric pressure of 889hpa! JTWC forecasted Mangkhut to reach 135knots high end Category 4 in its first warning for Mangkhut, which is an unusually aggressive forecast! As expected, Mangkhut consciously intensified under the excellent environment, reaching Category 1 Typhoon by 9th September.

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Figure 1: New born Tropical Disturbance 99W on 4th September 2018

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Figure 2: Mangkhut was born in an area with SST above 30C

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Figure 3: ECMWF forecasted Mangkhut to reach an atmospheric pressure of 922hpa

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Figure 4: GFS forecasted Mangkhut to reach an insane atmospheric pressure of 889hpa

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Figure 5: JTWC aggressively forecasted Mangkhut to reach 135knots high end Category 4 in its first warning for Mangkhut

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Figure 6: On 9th September, JTWC upgraded Mangkhut to Category 1 Typhoon

        Initially, computer models such as ECMWF and GFS forecasted Mangkhut to head towards Taiwan. However, due to a subtropical ridge that was much stronger than originally expected, Mangkhut’s track was soon significantly adjusted southwards. By 10th September, most models and meteorology agencies reached a consensus that Mangkhut will head towards Guangdong Province, many of which drawing Mangkhut’s track very close to Hong Kong. Considering that Mangkhut is forecasted to be an extremely strong typhoon, and Mangkhut’s size is extremely large, with a circulation radius of more than 700 kilometers, Hong Kong Observatory, the meteorology agency of Hong Kong, was extremely alert about Mangkhut’s threat. Hong Kong Observatory (HKO) forecasted Force 8 gale winds in Hong Kong on 16th and 17th September more than 6 days in advance, such aggressive forecast is almost unprecedented in the history of HKO!

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Figure 7: On 6th September, ECMWF ensemble mean forecasted Mangkhut to head towards Taiwan

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Figure 8: On 9th September, ECMWF ensemble mean forecasted Mangkhut to make landfall in Guangdong Province, a significant southward adjustment compared to 3 days ago

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Figure 9: At 11th September 12Z, Mangkhut’s Dvorak T-Value reached W+WMG, therefore JTWC upgraded Mangkhut to 140knots Category 5 Typhoon

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Figure 10: Category 5 Typhoon Mangkhut on 11th September

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Figure 11: At 12th September 18Z, Mangkhut’s Dvorak T-Value continued increasing up to T7.5, therefore JTWC upgraded Mangkhut to 155knots Category 5 Typhoon

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Figure 12: Category 5 Typhoon Mangkhut on 12th September

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Figure 13: Category 5 Typhoon Mangkhut on 12th September
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 楼主| 发表于 2019-9-16 23:45 | 显示全部楼层
Chapter 2: Initial Preparation

        On 11th September, most meteorology agencies forecasted that Mangkhut will make landfall within 100km range of Hong Kong at a very high intensity. JTWC forecasted Mangkhut to make landfall at 100knots Category 3 intensity, while HKO even forecasted Mangkhut to make landfall at 210km/h Super Typhoon intensity, which would be an unprecedented landfall intensity in Hong Kong’s history! Despite that at the same time, there is another tropical storm Barijat affecting Hong Kong, all eyes were focusing on Mangkhut, a storm that is posing potentially unprecedented threat to the 7 million population of Hong Kong.

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Figure 14: JTWC forecast track for Mangkhut at 11th September 06Z, forecasting Mangkhut to move within 45km range of Hong Kong at 100knots Category 3 intensity

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Figure 15: HKO forecast track for Mangkhut at 11th September 12Z, forecasting Mangkhut to move within 70km range of Hong Kong at 210km/h Super Typhoon intensity

        However, on the next day, as the subtropical ridge became increasingly rigid, Mangkhut continued to take a more southern track than expected. Therefore, meteorology agencies’ forecast track for Mangkhut continued to adjust southwards, instead of forecasting Mangkhut to move within 100km range of Hong Kong, meteorology agencies’ start to forecast that Mangkhut will move through 100-200km south of Hong Kong, and make landfall in western Guangdong. But this doesn’t change the fact that Mangkhut was posing a huge threat to Hong Kong. Therefore, on 12th September, HKO issued a Special Weather Announcement, warning citizens that Mangkhut will lead to very significant bad weather to Hong Kong on 16th September four days in advance.

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Figure 16: On 12th September, the subtropical ridge became increasingly rigid, causing Mangkhut to take a more southern track than expected

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Figure 17: HKO forecast track for Mangkhut at 12th September 12Z, forecasting Mangkhut to move within 170km range of Hong Kong at 210km/h Super Typhoon intensity

        On 13th September midnight, Mangkhut started entering an eyewall replacement cycle. Usually, eyewall replacement cycles would lead to significant weakening of tropical cyclones. However, Mangkhut’s eyewall replacement was very successful, Mangkhut completed its eyewall replacement cycle within one day, and its intensity stayed at Category 5 throughout its whole eyewall replacement cycle, which is very rare. Mangkhut continued to take a more southern track than expected, causing meteorology agencies to continue adjusting Mangkhut’s forecast track more southwards, forecasting Mangkhut to move through 180-250km south of Hong Kong. Despite the increase in forecasted closest point of approach (CPA), as Mangkhut continued moving closer to Hong Kong, confidence that Mangkhut will lead to serious impact to Hong Kong increased, therefore HKO further forecasted Force 10 Storm winds on 16th September.

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Figure 18: On 13th September midnight, Mangkhut started entering an eyewall replacement cycle

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Figure 19: On 13th September afternoon, Mangkhut successfully completed its eyewall replacement cycle

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Figure 20: HKO forecast track for Mangkhut at 13th September 12Z, forecasting Mangkhut’s CPA to be 190km away from Hong Kong

        On 14th September morning, HKO announced that by tonight, it would consider issuing Typhoon Signal Number 1, which means “a tropical cyclone is centered within 800km of Hong Kong and may affect the territory” – despite the fact that Mangkhut was forecasted to be more than 1000km away from Hong Kong by that night! At the same time, Mangkhut finally started taking moving northwestwards, bringing its forecast track even closer to Hong Kong! By afternoon, most meteorology agencies significantly adjusted Mangkhut’s forecast track more northwards, bringing its CPA to 130-170km away from Hong Kong. Considering Mangkhut’s gigantic size, this distance is enough to bring Force 12 hurricane winds to Hong Kong, which now became HKO’s forecasted windspeed on 16th September!

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Figure 21: HKO forecast track for Mangkhut at 14th September 12Z, forecasting Mangkhut’s CPA to be 150km away from Hong Kong

         Considering Mangkhut’s extreme threat to Hong Kong, and also remembering the severe impacts that Super Typhoon Hato last year brought to Hong Kong, many departments of the Hong Kong government started doing preparation on 14th September, even before HKO issued any typhoon signals. Staff of the Home Affairs Department visited residents at Lei Yue Mun and Tai O, two small villages that are very low lying and extremely prone to storm surge, and convinced them to evacuate into temporary shelters before the storm. Most other Hong Kong citizens also started making preparations for the storm, rushing to buy food, daily necessities and tape that can protect windows, causing shortages for a lot of items.

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Figure 22: Hong Kong citizens started making preparations for the storm, using tape to protect their windows from breaking (this is my parents’ preparation in our apartment)
幸福和快樂是結局......一起寫我們的結局......
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 楼主| 发表于 2019-9-17 00:01 | 显示全部楼层
本帖最后由 Luigi728 于 2019-9-17 00:50 编辑

Chapter 3: Sprinting Towards Hong Kong

        At 10:20pm, Hong Kong Observatory issued Typhoon Signal Number 1 (T1). At this point, Mangkhut was still 1110km away from Hong Kong – this means that HKO has broken the convention that T1 should be issued when a tropical cyclone is within 800km range of Hong Kong! Even though this is not the first time HKO has broken this convention, issuing T1 while a tropical cyclone was more than 1000km away from Hong Kong is definitely unprecedented – this broke the previous record of farthest T1 – 870km of 1987 Lynn – by a stunning 240km farther away! This absolutely demonstrates how Mangkhut is seen as posing an unprecedented threat to Hong Kong.

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Figure 23: At 14th September 10:20pm, Hong Kong Observatory issued Typhoon Signal Number 1

        During midnight, Mangkhut made landfall in the northeastern tip of Luzon Island, Philippines, as a 145knots Category 5 Typhoon. Due to land interaction, Mangkhut finally started to significantly weaken, weakening to a Category 4 Typhoon by 15th September morning. Before that, Mangkhut has sustained Category 5 intensity for 78 hours – the longest lasting Category 5 in 21st Century!

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Figure 24: On 15th September midnight, Mangkhut made landfall in the northeastern tip of Luzon Island as a 145knots Category 5 Typhoon

        While making landfall at Luzon Island, land interaction has caused Mangkhut to briefly move westwards. However, after Mangkhut left Luzon and moved into South China Sea, it continued moving west-northwestwards again, towards just west of Hong Kong.

        Making landfall in Luzon Island not only has caused weakening of Mangkhut and brief changes in its track, it has also led to a change in Mangkhut’s structure – while Mangkhut’s eyewall was significantly damaged by mountains in Luzon Island, its spiral rainband, which largely stayed on water, remained very intense. This led to a very rare situation that could in fact be compared with an eyewall replacement cycle – as momentum transferred from the eyewall to the spiral rainband, the windspeed at Mangkhut’s spiral rainband became stronger than the windspeed at its eyewall. However, Mangkhut did not complete an actual eyewall replacement cycle afterwards, therefore that spiral rainband was still considered a spiral rainband, instead of an outer eyewall, by Hong Kong Observatory. This will have very significant implications for Mangkhut’s effect to Hong Kong and rest of the Guangdong coast.

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Figure 25: Mangkhut’s structure significantly changed after it made landfall in Luzon Island, the windspeed at Mangkhut’s spiral rainband became stronger than the windspeed at its eyewall

       On 15th May, Mangkhut continued to sprint towards Hong Kong at a movement speed of 30km/h. On that morning and afternoon, when Mangkhut was still more than 600km away from Hong Kong, Hong Kong experienced extreme heat due to the sinking airflow outside the storm. HKO recorded a maximum temperature of 35.1OC, the second highest ever in September! Happy Valley even recorded a maximum temperature of 36.4OC! But everyone knew this is just the calmness before the storm.

        Soon, as Mangkhut’s outer rainbands started reaching Hong Kong, Hong Kong’s temperature rapidly dropped, and windspeed started to increase. At 4:20pm, Hong Kong Observatory issued Typhoon Signal Number 3 (T3), which means “strong wind is expected or blowing generally in Hong Kong near sea level, with a sustained speed of 41-62 km/h”, when Mangkhut was 650km away from Hong Kong.

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Figure 26: At 15th September 4:20pm, Hong Kong Observatory issued Typhoon Signal Number 3

        As Mangkhut continued to quickly move towards Hong Kong, Hong Kong’s windspeed gradually increased, with windspeed stations such as Green Island, Tate’s Cairn, Waglan Island and Cheung Chau reaching sustained strong winds during that night. On 15th September, Mangkhut continued to take a track that is slightly more north than expected. This caused meteorology agencies to again slightly adjust Mangkhut’s track more northwards – by that night, most meteorology agencies forecasted Mangkhut’s CPA to Hong Kong to be 80-140km. Considering Mangkhut’s gigantic size, and the fact that Mangkhut’s strongest winds are actually located in its spiral rainband instead of the eyewall, it started to seem inevitable that Mangkhut will lead to extreme impact to Hong Kong.

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Figure 27: HKO forecast track for Mangkhut at 15th September 12Z, forecasting Mangkhut’s CPA to be 100km away from Hong Kong

        Entering midnight, Hong Kong’s windspeed started to significantly increase. As Waglan Island and Tate’s Cairn both reached gale winds, at 16th September 1:10am, Hong Kong Observatory issued Typhoon Signal Number 8 (T8), which means “gale or storm forced wind is expected or blowing generally in Hong Kong near sea level, with a sustained speed of 63-117 km/h”. At this point, Mangkhut was 410km away from Hong Kong – making this one of the farthest Typhoon Signal Number 8 ever issued!

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Figure 28: At 16th September 1:10am, Hong Kong Observatory issued Typhoon Signal Number 8

        While a few windspeed stations have reached gale winds or even storm winds during midnight, most windspeed stations in the urban area still hasn’t recorded any significant windspeeds yet. This is due to the geography of Hong Kong – while tropical cyclones are at the east or east-southeast of Hong Kong, Hong Kong generally blows north wind, which is significantly blocked by the land of Mainland China. However, once the tropical cyclone moves to southeast or south of Hong Kong, Hong Kong’s wind direction will quickly change to northeast wind or east wind – the wind will be blown directly from the sea onto Hong Kong, which leads to very significantly higher windspeeds in most areas of Hong Kong. Considering the strength of this storm, this dramatic rise in windspeed could lead to very dangerous consequences. Therefore, HKO was very closely monitoring the windspeeds of each windspeed station in Hong Kong, and be ready to react by issuing even higher typhoon signals – Typhoon Signal Number 9 and 10 when the windspeeds started dramatically rising.

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Figure 29: The geography of Hong Kong, Hong Kong faces the land of Mainland China in the north, faces the sea of South China Sea in the east, south and west

        One of the most important windspeed stations to focus on is Waglan Island. Waglan Island is a small island located at southeastern Hong Kong, around 20km southeast of HKO. This means that for tropical cyclones that approach Hong Kong from the east to the west, Waglan Island is closer to the center of the storm than any other windspeed station in Hong Kong. Also, Waglan Island is very prone to northeast winds, as there is nothing but sea in the northeast of it. Therefore, usually Waglan Island will experience a dramatic increase in windspeed one or two hours before other places in Hong Kong experience it, allowing HKO to make decisions based on the windspeed trend in Waglan Island.

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Figure 30: Waglan Island is a small island located at southeastern Hong Kong, its location is shown by the pointer

        Waglan Island’s windspeed has steadily increased during midnight, reaching storm winds by around 6:00am. But the dramatic increase in windspeed started at 7:00am – within one hour, Waglan Island’s 10-minute sustained windspeed insanely increased by 28km/h, from 94km/h rising up to 122km/h, reaching hurricane force winds by around 8:00am! HKO reacted immediately – at 7:40am, Hong Kong Observatory issued Typhoon Signal Number 9 (T9), which means “gale or storm force wind is increasing or expected to increase significantly in strength”. At this point, Mangkhut was still 200km away from HKO, and around 180km away from Waglan Island – yet it is already leading to hurricane force winds in Waglan Island, which means that Mangkhut has a radius of hurricane winds of at least 180km – one of the largest if not the single largest ever seen in South China Sea!

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Figure 31: At 16th September 7:40am, Hong Kong Observatory issued Typhoon Signal Number 9

        At 8:00am, despite windspeeds in Hong Kong dramatically increasing, due to Mangkhut’s reducing structural organization, HKO downgraded Mangkhut from 185km/h Super Typhoon to 175km/h Severe Typhoon. But this doesn’t change the inevitable fact that Mangkhut is going to become the Storm of the Century – by around 9:00am, Waglan Island’s windspeed continued dramatically rising up to 140km/h – and there is no sign of slowing down. Both Cheung Chau and Green Island also started recording storm winds, rapidly approaching hurricane winds. And there is still around 100km of room for Mangkhut to move even closer to Hong Kong. All doubt is gone – Mangkhut will cause Hong Kong to issue Typhoon Signal Number 10, and will become the strongest storm to strike Hong Kong in the 21st Century.
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 楼主| 发表于 2019-9-17 00:10 | 显示全部楼层
Chapter 4: Storm of the Century

        At 16th September 2018 9:40am Hong Kong Time (0140Z), the moment has come – “THE HURRICANE SIGNAL, NO. 10, WAS ISSUED AT 9:40 A.M.” Hong Kong Observatory issued Typhoon Signal Number 10, the highest typhoon signal in Hong Kong!!! The first Typhoon Signal Number 10 since 2017 Hato, the third Typhoon Signal Number 10 in 21st Century, the nineteenth Typhoon Signal Number 10 ever, the farthest Typhoon Signal Number 10 issued ever – 160km from Hong Kong. Mangkhut is destined to be written in the history books.

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Figure 32: At 16th September 2018 9:40am, Hong Kong Observatory issued Typhoon Signal Number 10!

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Figure 33: At 16th September 2018 9:40am, Hong Kong Observatory issued Typhoon Signal Number 10!

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Figure 34: At 16th September 2018 9:40am, Hong Kong Observatory issued Typhoon Signal Number 10!

        But this just the start of the nightmare (or a dream for some typhoon enthusiasts). Waglan Island’s windspeed continued to rise at an astonishing, if not unprecedented rate. By around 10:00am, a mindblowing number appeared in front of our eyes – 180km/h! 10-minute sustained windspeed of one eighty kilometers per hour was recorded at Waglan Island – the highest ever in Waglan Island, the second highest ever at a non-high ground location in the whole of Hong Kong! At this point, Mangkhut was 150km away from Hong Kong Observatory, around 130km away from Waglan Island – crazy enough, this distance isn’t even considered a “direct hit” according to the official definition by Hong Kong Observatory!

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Figure 35: At around 10:00am, Waglan Island recorded 10-minute sustained windspeed of 180km/h (it was originally said to be 179km/h, but adjusted to 180km/h very soon)

        However, while Mangkhut continued to move closer to Hong Kong, Waglan Island’s windspeed started decreasing after reaching that insane peak windspeed, contrary to some typhoon enthusiasts’ belief. This might be partly due to a change in wind direction – due to geographical reasons, Waglan Island is much more prone to northeast wind than east or southeast wind. As wind direction gradually changes towards east and southeast winds, Waglan Island’s windspeed started to decrease. However, I believe this is more to do with Mangkhut’s special structure – as I have explained before, after making landfall in Luzon, Mangkhut’s spiral rainband actually has stronger windspeeds than its eyewall. Therefore, Waglan Island’s peak windspeed was recorded when it was inside Mangkhut’s spiral rainband that contained the strongest windspeeds within Mangkhut. After Mangkhut moved even closer to Waglan Island, Waglan Island entered the zone between the spiral rainband and the eyewall, therefore did not experience higher windspeeds anymore. And in fact, Waglan Island’s peak windspeed was higher than any other place throughout the whole of Guangdong coast, including Mangkhut’s final landfall location, proving that Mangkhut’s highest windspeeds is actually concentrated in its spiral rainband, which moved through Hong Kong, instead of its eyewall, which did not move through Hong Kong.

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Figure 36: Windspeed at Waglan Island on 16th September

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Figure 37: Radar image at 10:24am, when Mangkhut’s intense spiral rainband was moving through Hong Kong

        But while Waglan Island’s windspeed started decreasing, the rest of Hong Kong, which started to enter Mangkhut’s spiral rainband with the strongest windspeeds, and also started blowing eastern winds, the wind direction which many windspeed stations are most prone to, experienced dramatic increases in windspeed. At 11:00am, Green Island, a small island just northwest of Hong Kong Island, recorded hurricane force windspeed of 144km/h. At 12:00pm, Tai Mei Tuk reached its peak windspeed of 153km/h. At 1:00pm, Mangkhut reached its closest point of approach to Hong Kong – 100km south-southwest of Hong Kong. This is also the point when Hong Kong’s general windspeed reached its maximum – Cheung Chau Beach reached its peak windspeed of 159km/h, Hong Kong International Airport reached its close to peak windspeed of 113km/h (it recorded 114km/h two hours later), even Lau Fau Shan, a windspeed station known to be unprone to east wind, recorded a peak windspeed of 109km/h. Most stunningly, North Point, an urban windspeed station located in the Hong Kong Island side of Victoria Harbour, recorded hurricane force windspeed of 124km/h – this is the first time a windspeed station in Victoria Harbour has recorded hurricane force sustained windspeed since Kai Tak during 1983 Ellen!

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Figure 38: Radar image at 1:00pm, when Mangkhut reached its closest point of approach to Hong Kong

        After that, Mangkhut started gradually moving away from Hong Kong. But a few windspeed stations reached its peak windspeed later on. At 2:00pm, Cheung Chau reached its peak windspeed of 165km/h, Kowloon Star Ferry, an urban windspeed station in Victoria Harbour, recorded storm force windspeed of 90km/h. At 3:00pm, HK International Airport reached its peak windspeed of 114km/h, Kai Tak, another urban windspeed station in the Kowloon side of Victoria Harbour, recorded storm force windspeed of 96km/h. Hong Kong Observatory recorded 60-minute sustained windspeed of 81km/h, the highest since 1983 Ellen!

        The most stunning windspeed data was revealed a month after Mangkhut – in October, HKO revealed in an article that Clear Water Bay, a windspeed station under testing whose data was not released during the storm, recorded an unimaginable 10-minute sustained windspeed of 191km/h – this is even higher than the astonishing 180km/h in Waglan Island! HKO further said that this is “believed to be the highest record (except high grounds) since HKO’s commencement of automatic weather station installation in Hong Kong in the 1980s”! However, HKO also stated that since Clear Water Bay is “located on a complex terrain with the anemometer at an elevation over 70 meters above sea level, the corresponding windspeed near sea level is estimated to be below 185km/h”, therefore this data cannot be used as evidence that Mangkhut was still a Super Typhoon at its CPA to Hong Kong. But no matter what, 191km/h is an unbelievably insane windspeed that will be forever remembered.

        In general, the windspeeds over Hong Kong during Mangkhut significantly exceeded any other typhoon in the 21st Century, including 2012 Vicente and 2017 Hato, the two other 21st Century typhoons that caused HKO to issue T10. That is despite Hato’s CPA to Hong Kong was only 60km, much closer than Mangkhut, and Hato was also stronger than Mangkhut when it was closest to Hong Kong, reaching its peak of 185km/h Super Typhoon right at its CPA to Hong Kong. Mangkhut is no doubt the strongest typhoon to strike Hong Kong since 1983 Ellen. But interestingly, due to Mangkhut’s special structure as explained above, Macau, a nearby city which was even closer to Mangkhut’s center, experienced significantly lower windspeeds than Hong Kong. Macau’s windspeeds during Mangkhut was also significantly lower than 2017 Hato, contrary to what happened in Hong Kong.

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Figure 39: 10-Minute Sustained Windspeed of All Windspeed Stations During Mangkhut

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Figure 40: 10-Minute Sustained Windspeed of Selected Windspeed Stations During Mangkhut

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Figure 41: 10-Minute Sustained Windspeed of Urban Windspeed Stations During Mangkhut

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Figure 42: 10-Minute Sustained Windspeed of 8 Reference Windspeed Stations During Mangkhut
(Note that data is only provided for windspeeds above 40km/h)

        Mangkhut not only led to extremely high windspeeds throughout the whole of Hong Kong, it also led to unprecedented storms surges in Hong Kong. Despite that Mangkhut’s CPA to Hong Kong was not as close as other storms that led to significant impact to Hong Kong, its gigantic circulation size “drove a more extensive area of the ocean which in turn raised the water level further”, allowing it to lead to record breaking storm surges at every single working tide gauge in Hong Kong! In Quarry Bay, a tide gauge within the urban Victoria Harbour, Mangkhut’s storm surge was 2.35m above astronomical tide – this broke the record of 1962 Wanda, the deadliest storm to strike Hong Kong since World War II, by 0.58m more, or 32.8% above the previous record! In Tai Po Kau, Mangkhut’s storm surge was an astonishing 3.40m above astronomical tide – this once again broke the record of 1979 Hope!

        Fortunately, unlike 1962 Wanda or 2017 Hato, Mangkhut did not appear during astronomical high tide. Therefore, Mangkhut’s maximum sea level (above chart datum) was just below Wanda – 3.88m at Quarry Bay and 4.71m at Tai Po Kau, both second highest on record. But even though Mangkhut appeared during astronomical low tide, its maximum sea level exceeded that of 2017 Hato, which appeared during astronomical high tide, demonstrating the insanity of Mangkhut’s storm surge! HKO said in an article, “should Mangkhut have hit Hong Kong during the spring tide like what happened during the passage of Hato in 2017, the maximum water level inside the Victoria Harbour and Tolo Harbour would be close to 4.9 metres and 5.9 metres respectively, or about one metre higher than the current record and would definitely lead to more substantial damages”! Therefore, Hong Kong should consider ourselves very fortunate to not have experienced the worst possible outcome.

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Figure 43: Maximum sea level and storm surge recorded at Quarry Bay/North Point during the passage of tropical cyclones (since 1962)

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Figure 44: Maximum sea level and storm surge recorded at Tai Po Kau during the passage of tropical cyclones (since 1962)
幸福和快樂是結局......一起寫我們的結局......
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 楼主| 发表于 2019-9-17 00:21 | 显示全部楼层
Chapter 5: Conclusion of the Story
        As Mangkhut started to gradually move away from Hong Kong, starting from 4:00pm, the windspeed at most windspeed stations in Hong Kong started to decrease. At 5:00pm, Mangkhut made landfall in Taishan, Guangdong Province, around 130km west of Hong Kong. By 7:40pm, as the windspeed at all windspeed stations have dropped below hurricane force, Hong Kong Observatory issued T8 to replace T10. This Typhoon Signal Number 10 lasted for ten hours – the second longest lasting T10 ever!

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Figure 45: At 5:00pm, Mangkhut made landfall in Taishan, Guangdong Province

        After that, Mangkhut continued to move further in land while rapidly weakening. At 17th September 5:20am, as the windspeed at most windspeed stations except for Cheung Chau have dropped down to strong wind or below, Hong Kong Observatory issued T3 to replace T8. In usual situations, this means that Hong Kong students will have to go to school the next day. But considering that Mangkhut led to extremely significant impact to most parts of Hong Kong, making it unsafe for students to go to school, therefore the Hong Kong Educational Bureau announced that all Hong Kong schools will be suspended on 17th September. Later, it was announced that schools will be continued suspended on 18th September, until it was safe enough for schools to reopen on 19th September. However, most adults still had to go to work in extremely horrifying circumstances, causing many people to be furious at the Hong Kong government for its ignorance.

        As Hong Kong’s windspeed continued decreasing, Hong Kong Observatory issued T1 to replace T3 at 2:30pm. At 7:10pm, all typhoon signals were cancelled. That night, Hong Kong Observatory downgraded Mangkhut to a low pressure area, other meteorology agencies also determined than Mangkhut has dissipated, finally writing a full stop (period) to the 10 day journey of this storm of the century.

20180917.0140.hm8.x.vis1km.26WMANGKHUT.45kts-989mb-230N-1083E.100pc.jpg
Figure 46: On 17th September, Mangkhut dissipated inland over Guangxi Province

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Figure 47: Track of Mangkhut throughout its 10 day journey

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Figure 48: Track of Mangkhut when it was close to Hong Kong

        The ferocious winds and unprecedented storm surge of Mangkhut led to extremely widespread damage that is unseen since 1983 Ellen. More than 60,000 trees have fallen during Mangkhut, the highest number on record. There were more than 500 reports of smashed windows or glass curtain walls. Many objects such as cranes, rooftops and even walls have been blown down. Storm surge and high waves caused unprecedently serious flooding in various coastal areas of Hong Kong, producing damages to coastal structures such as sports grounds and waterfront promenades. Electricity supply to over 40,000 households in Hong Kong was interrupted, not only in rural areas, but also in urban residential estates such as Heng Fa Chuen, the first time this has ever happened in the 21st Century.

1920px-Yee_Wo_Street_in_Hong_Kong_-_Fallen_Trees_due_to_Typhoon_Mangkhut_2018.jpg
Figure 49: Fallen trees blocked a road in Causeway Bay

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Figure 50: Citizens had to climb through fallen trees to get to work on 17th September

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Figure 51: Many glass curtain walls in an office building in Hong Hum were smashed, blowing paper documents onto the streets

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Figure 52: The interior of that office building with smashed glass curtain walls was completely destroyed

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Figure 53: A large crane in Tai Kok Tsui was blown down, and landed on top of another building

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Figure 54: The outer wall of a building in Tai Kok Tsui was blown down

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Figure 55: The rooftop of Aberdeen Sports Ground was blown off

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Figure 56: High waves surging onto residential buildings in Heng Fa Chuen

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Figure 57: Storm surge led to unprecedented flooding in Heng Fa Chuen

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Figure 58: After the storm, a trail of rubbish remained in Heng Fa Chuen

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Figure 59: A waterfront promenade in Heng Fa Chuen was destroyed

IMG_3756.PNG
Figure 60: Siu Sai Wan Sports Ground was completed flooded by the storm surge

        Despite Mangkhut’s serious damage to most parts of Hong Kong, very fortunately, not a single fatality occurred in Hong Kong. Considering the scale of this storm, this can almost be said as a miracle. This miracle happened because of Hong Kong Observatory – if Hong Kong Observatory had not warned citizens about this storm very early on, allowing Hong Kong citizens and the government to have enough time to make all the preparation required, it is difficult to imagine how much worse this disaster could be. Just last year, Macau’s meteorology agency SMG produced a counterexample of what meteorology agencies should do – due to unpreparedness and delayed warnings of SMG, 10 people in Macau have died from 2017 Hato. Therefore, Hong Kong citizens should consider ourselves very fortunate to have such a great meteorology agency in our city. I hope that one day I can join Hong Kong Observatory, be a part of this great meteorology agency, in order to continue protecting my hometown Hong Kong!
幸福和快樂是結局......一起寫我們的結局......
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发表于 2019-9-17 17:38 | 显示全部楼层
Excellent work! Mangkhut is really an unprecedented disaster to Guangdong, Hong Kong, Macau and Philippine
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