The Development Process of Typhoon "Mesak"

2065438+On March 23rd, 2005, a low pressure area was generated in the southwest of Marshall Islands, and the disturbance number was 98W given by the US Naval Research Laboratory. At 6:5438+00:30 am on March 24th, the Joint Typhoon Warning Center gave a "low" rating to the possibility of tropical cyclone formation within 24 hours, and upgraded its rating to "medium" at 7: 00 am on March 25th. At 8 am on March 26th, Japan Meteorological Agency upgraded it to tropical depression. At 2pm, central weather bureau, Taiwan Province Province upgraded it to a tropical depression. At 6: 30pm, joint typhoon warning center raised the possibility of the system developing into a tropical cyclone within 24 hours to "high" and issued a warning of tropical cyclone formation.

At 8 o'clock on the morning of March 27, the Japan Meteorological Agency issued a gale warning to it; At the same time, joint typhoon warning center upgraded it to tropical depression, and numbered it 04W. At 8 pm, the joint typhoon warning center upgraded it to a tropical storm. Guided by the easterly wind south of the subtropical ridge, the system moves west to northwest. At 2 am on March 28th, Japan Meteorological Agency upgraded the system to a tropical storm and named it Mesak. China Central Meteorological Observatory upgraded it to a tropical storm, while central weather bureau, Taiwan Province Province upgraded it to a mild typhoon. At 2 pm, the Central Meteorological Observatory upgraded it to a severe tropical storm. The Japan Meteorological Agency also upgraded it to a strong tropical storm at 8 o'clock that night. Thanks to the excellent environment in the northwest Pacific, Mesak increased rapidly and significantly due to the weakening of vertical wind shear, good convergence in the lower layer and good divergence in the upper layer. Because the subtropical high is in a strong position and dominates the northwest Pacific Ocean, Mesak flies directly to the Philippines at a speed of more than 20 kilometers per hour.

At 2 am on March 29th, the Japanese Meteorological Agency, the China Central Meteorological Observatory and the Joint Typhoon Warning Center upgraded Mesak to a typhoon at the same time, and central weather bureau, Taiwan Province Province also upgraded it to a moderate typhoon. At 8: 00 am on March 30, the Joint Typhoon Warning Center upgraded its intensity to the equivalent of a second-class typhoon under saffir-simpson hurricane scale; At 2 pm, China Central Meteorological Observatory upgraded it to a strong typhoon. At 2: 00 a.m. on March 3 1, the Joint Typhoon Warning Center directly upgraded its intensity to a typhoon equivalent to Class 4, and then upgraded it to a super typhoon in this department. At 5am, China Central Meteorological Observatory upgraded it to a super typhoon. At 8 am, it was upgraded to a strong typhoon in central weather bureau, Taiwan Province Province. At 2: 00pm, the Joint Typhoon Warning Center further upgraded its intensity to category 5 typhoon, which is the highest level in saffir-simpson hurricane scale. At 9: 45 pm, Mesak entered the scope of responsibility of the Hong Kong Observatory, which rated it as a super typhoon. At this time, Mesak has reached the peak intensity, and all official meteorological departments have assessed that the maximum sustained wind speed near its center is more than 2 10 km per hour. Tropical cyclones in the northern hemisphere usually turn northward in the Philippines or its eastern waters from March to May, but the subtropical ridge is still strong, which makes Mesak continue to move to the west-northwest direction at a speed of about 22 kilometers per hour and move to Luzon Island in the Philippines. Meteorological agencies and most numerical forecasting models predict that Mesak will enter the northern South China Sea after passing through Luzon Island, which is rare for tropical cyclones in the northwest Pacific this season. The continuous westward path made Mesak enter the harsh environment in the waters east of the Philippines, and the strong vertical wind shear weakened Mesak. At 2 pm on April 1 day, the Joint Typhoon Warning Center took the lead in downgrading it to a typhoon. On April 2, influenced by wind shear, Mesak's cloud belt began to break away. Central weather bureau, Taiwan Province Province downgraded it to a moderate typhoon at 8 am, while the Central Meteorological Observatory of China and the Hong Kong Observatory downgraded it to a strong typhoon at 2 pm and 4 pm respectively. On April 3, the overall structure of Mesak was destroyed and the eye of the wind became blurred. China Central Meteorological Observatory and Hong Kong Observatory downgraded it to typhoon at 8 am and 9: 45 am respectively.

On April 4, the structure of Mesak deteriorated further, and the eye of the wind was completely stuffed. At 2pm, the Japan Meteorological Agency downgraded it to a strong tropical storm, while central weather bureau, Taiwan Province Province downgraded it to a mild typhoon. The Hong Kong Observatory downgraded it to a severe tropical storm at 4: 00 pm15. China Central Meteorological Observatory followed suit and downgraded it to a severe tropical storm at 5 pm. At 8 pm, the joint typhoon warning center downgraded it to a tropical storm. As the subtropical ridge weakened slightly at this time, the track of Mesak began to change at night, and the northern vector gradually increased near midnight. In the early morning of April 5, the moving direction of "Mesak" gradually changed from west-northwest to northwest, and the weakening trend continued, and the structure became more loose and shapeless. The flow direction was cut off to the northeast, and the low-level circulation center began to be exposed. The Japanese Meteorological Agency, the China Central Meteorological Observatory and the Hong Kong Observatory downgraded it to a tropical storm at 2 am, 5 am and 7: 45 am on April 5, respectively. As Mesak landed on Luzon Island around noon, it was downgraded to a tropical depression by the Japan Meteorological Agency at 2 pm, and it was downgraded to a tropical depression by central weather bureau, Taiwan Province Province at the same time. The Hong Kong Observatory immediately downgraded it to a tropical depression at 3: 30 pm. Subsequently, due to the influence of Luzon topography, Mesak experienced circulation reorganization, forming a new center in the sea west of Luzon, replacing the original center of Luzon Island, which led to a great adjustment of its center orientation to the northwest. "Mesak" immediately entered the northeast of the South China Sea. This is the first tropical cyclone to enter the northern South China Sea in seven years after Typhoon Raccoon in 2008. However, at that time, the development conditions in the northern part of the South China Sea were worse than those in the waters east of the Philippines. Except for more severe vertical wind shear, the sea water temperature is generally low, and it does not rise above 26 degrees Celsius, which cannot provide enough energy for tropical cyclones. Coupled with the influence of dry air, various factors mean that Messac is entering a dead end.

Mesak continued to cross the northeastern South China Sea on April 6th, and weakened further. The joint typhoon warning center downgraded it to a tropical depression at 2 am and issued a final warning. The Hong Kong Observatory weakened it into a low pressure area at 9: 45 am. At 1 1 in the morning, China Central Meteorological Observatory stopped numbering it. It can be seen from the infrared satellite cloud picture that the convection of Mesak continued to tangential to the Luzon Strait and Taiwan Province Island in the northeast, leaving a completely exposed low-level circulation center, and continued to move to the northwest that morning; However, on the visible satellite cloud image, the low-level circulation center of Mesak is still basically intact, which makes the Japan Meteorological Agency and central weather bureau, Taiwan Province Province maintain the tropical depression rating of Mesak all day; It was not until 2pm the next day (April 7th) that central weather bureau, Taiwan Province Province downgraded it to a low-pressure area. However, due to the rising air pressure in North China, it began to wrestle with the subtropical ridge. Since the afternoon of April 6th, the moving speed of Mesak has obviously slowed down, from 22km/h to less than 8km/h, and it has been wandering in the northeast of South China Sea, about 400km southeast of Hong Kong. With the arrival of the strong northeast monsoon from the southern part of the North China high pressure area, the Hong Kong Observatory showed on the isobar weather map at 2 am on April 8 that the residual low pressure area of Mesak had dissipated, but the Japan Meteorological Agency still rated Mesak as a tropical low pressure. It was not until 9 am that the weather map showed that Mesak weakened and dissipated. At that time, the residual low-level circulation center of Mesak was no longer clearly visible on infrared or visible satellite cloud images, but was replaced by a broad cloud belt related to the cold front of northeast monsoon.