"Little but smart" - A detailed account of the present and future of super typhoon "Olu"

1. Typhoon Olu Today: Bringing Storms and Rains to the South China Sea

At present, the typhoon is in the central South China Sea, with its center south of my country's Xisha Islands. Its main outer spiral rain belt is bringing heavy rainfall to Hainan Island.

The typhoon bulletin from the Central Meteorological Observatory at 12:00 on September 27, 2022 is as follows:

time:

12:00 on the 27th

name:

NORU

serial number:

No. 2216

Central Location:

15.3 degrees north latitude, 111.7 degrees east longitude

Strength Level:

Super typhoon level

Maximum wind speed:

Level 17, 58 m/s (about 209 km/h)

Central air pressure:

925 hPa

Reference location:

About 185 kilometers south-west of Sansha City, Hainan Province (Xisha Yongxing Island)

Wind circle radius:

The radius of the level 7 wind circle is 220 kilometers northeast, 200 kilometers southeast, 200 kilometers southwest, and 280 kilometers northwest. The radius of the level 10 wind circle is 100 kilometers northeast, 100 kilometers southeast, 100 kilometers southwest, and 100 kilometers northwest. The radius of the level 12 wind circle is 30 kilometers northeast, 30 kilometers southeast, 30 kilometers southwest, and 30 kilometers northwest.

Forecast conclusion:

"Olu" will move westward at a speed of about 15 kilometers per hour, and its intensity will increase

Visible light image of the Fengyun-4B satellite at 12:42 on September 27, 2022

(National Satellite Meteorological Center)

Multi-channel fusion image of the Fengyun-4B satellite at 12:39 on September 27, 2022

(National Satellite Meteorological Center)

Jigsaw puzzle of the combined reflectivity factor of the national network radar at 12:40 on September 27, 2022

and ground-based observation of strong winds (Atmospheric Observation Center)

The typhoon is currently located on the south side of the subtropical high, but its shape should be closer to the figure "6" rather than the figure "9", but it is heading westward rather than northward (see: "Figure 9 heading westward and Figure 6 heading northward - Typhoon "Xuan Lannuo"'s V-shaped path and interpretation of wind and rain"), why?

Answer: This is a very beautiful case that can be used to reveal the only truth in the meteorological world: "In meteorology, there are exceptions to everything."

Let’s just say this is: One of the “ghost” stories of Olu: 6 words on the journey to the west

2. The Childhood of “Aolu”: Rare Explosive Enhancement

When Olu was first formed, our path forecast was accurate, but the forecast error of its intensity was a bit large. At 17:00 on the afternoon of the 24th, its intensity was monitored as a strong tropical storm. At that time, its strengthening trend was correctly predicted, but its strengthening speed and upper limit were greatly underestimated: it was expected to strengthen to typhoon level in 12 hours (05:00 on the 25th), but it turned out to be a super typhoon level in 9 hours.

The typhoon forecast issued by the Central Meteorological Observatory at 17:00 on September 24

As of 13:00 on September 27, the Central Meteorological Observatory was monitoring the location and intensity of "Aolu".

The intensity of a typhoon can change quickly or slowly, but the situation where a typhoon directly strengthens from a strong tropical storm to Level 3 (strong tropical storm-typhoon-strong typhoon-super typhoon) in 9 hours is still relatively rare. It will lead to large errors in the intensity forecast, and there is currently no good solution to this problem.

This situation usually occurs in typhoons that are small but have dense clouds. This is the second "ghost" thing in Aolu: explosive growth

3. Identification of "Olu" - How is the intensity of a typhoon scientifically determined?

Few people know about this issue, so it is necessary to popularize it.

The intensity of a typhoon is determined by the central air pressure and the maximum central wind speed. Wind speed and air pressure can only be accurately measured by direct instruments. However, there are no instruments for direct observation in the vast ocean except for ships and a few buoys. What should we do?

Of course, satellites are used, but satellites cannot measure wind speed and air pressure directly! Not even indirectly.

What should we do? Do we just make a decision based on our own ideas? How can we scientifically determine the intensity of a typhoon?

The answer is a method of determining the intensity of a typhoon based on research into statistics and physical mechanisms. The intensity of a typhoon is determined by monitoring its shape and cloud top temperature using multi-channel satellite data.

This question is too technical, to put it simply:

Satellite observations can directly obtain the shape of typhoon clouds and indirectly measure the cloud top temperature of typhoon clouds. After a lot of research, some rules have been discovered: the degree of confinement of the typhoon's central cloud area, the development height of the closed cloud area (calculated based on the cloud top temperature estimated by satellite telemetry), the width and length of the spiral arc of the closed cloud area, the presence or absence of a typhoon eye, the size of the typhoon eye, the eyewall of the typhoon eye, and many other characteristics are related to the intensity of the typhoon, so the intensity can be quantitatively determined based on these characteristics.

The content is very complicated, so I will just pick out the simplest part to explain: having eyes is better than having no eyes, and small and clear eyes are better than large and blurry eyes.

The research content to obtain this method is much more complex and huge than the application of this method itself, and I know only a little about it. But there are several key points: the first is the statistical analysis of cloud types of historical typhoons observed by a large number of satellites; the second is the determination of the intensity corresponding to the cloud type, which relies on various ground and sea surface observation methods, such as ground observations before and after landing, ground observations of passing islands, observations of approaching ship buoys, and observations of aircraft flying through typhoons, etc.; the third is to combine the physical mechanism of typhoons.

This work is mainly done in the United States, and the literal translation of this method is called the Dvorak method.

Let's compare the strong tropical storm at 17:00 on the 24th and the strong typhoon at 02:00 on the 25th:

Fengyun-4A infrared enhanced image (left: 17:00, September 24; right: 02:00, September 25)

4. The future of “Olu”: the strongest in history to land in Vietnam

In fact, since the 25th, CCTV has been predicting that "Olu" is likely to land in central Vietnam as a strong typhoon to a super typhoon. Today, it seems that the path and intensity forecast are basically accurate, especially the intensity fluctuation process of weakening first and then strengthening back to a super typhoon after entering the South China Sea, which is very accurate.

At present, everything is developing as expected. From this morning till now, the center of "Aolu" has passed by a little south of the Xisha Islands. It has not entered the 12-level wind circle near the center of the typhoon and the 10-level wind circle a little outside the inhabited Yongxing Island, as shown in the following figure:

The Central Meteorological Observatory's monitoring of "Aolu" at 08:00 on September 27, 2022

The maximum wind speed currently observed in the Xisha Islands was a force 11 wind (29.7 m/s) at the Sansha Beijiao station at 8:48 a.m. on the 27th.

This typhoon has little impact on our country, but it has a huge impact on Vietnam: it is currently expected to land in central Vietnam in the early morning or morning of the 28th as a strong typhoon to super typhoon level. If it is a super typhoon, then "Olu" may become the strongest typhoon to land in Vietnam in recorded history.

This is the third "ghost" story of Aolu: the strongest in Vietnamese history

The typhoon forecast issued by the Central Meteorological Observatory at 11:00 on September 27

5. The afterlife of the “Olu” – “reincarnation” arrives in India

Based on the analysis of various current data, there is a possibility: after landing in Vietnam, Olu will continue to move westward, and then rapidly weaken due to the friction between the mountains and jungles of the Indochina Peninsula. However, due to the continuous water vapor transport of the monsoon, its closed circulation will continue to be maintained, and it should still be maintained after crossing the Indochina Peninsula and entering the Bay of Bengal in the Indian Ocean. The low-pressure circulation that is re-nourished by the tropical ocean is very likely to strengthen again to a level above a tropical storm, and then land on the Indian Peninsula.

Speculations on the future trend of Typhoon Olu (Tao Tao Fengyun)

This is the fourth "ghost story" of Austria: Crossing two oceans and coming back to life

This time is a bit far away and there is a lot of uncertainty. I will keep an eye on it.