Disastrous Weather Prediction
Analysis
Tendency of Typhoon Soulik in various factors.
[figure 1] Rain, Sea level pressure, and Wind
Typhoon SOULIK had a lot of precipitation on the southeastern coast of Japan (8/21 20:00),
but as it gets closer to Korea, it tends to get less precipitation (8/22 22:00).
And when Typhoon SOULIK actually landed in Korea, the precipitation was very low.
(The Hankyoreh, kyLee, 2018-08-24.)
On the other hand Typhoon CIMARON is landing in Japan with heavy rainfall (8/23 18:00).
And when Typhoon CIMARON actually landed in Japan, heavy rain caused great damage.
(Shinailbo, egLee, 2018-08-24.)
[figure 2] Geopotential height, Temperature, and Wind
Typhoon SOULIK’s Geopotential height is dense on the southeastern coast of Japan (8/19 14:00), and the gap tends to widen as it get closer to Korea (8/22 17:00).
[figure 3] Precipitation and Sea level pressure
Given the change in precipitation and sea level pressure, it is possible to expect that the typhoon will gradually weaken as it approaches Korea.
Typhoon SOULIK is unable to move north due to the low pressure in the west.
However, the low pressure moved north and weakened, and SOULIK moved north.
[figure 4] The sea level pressure of Soulik's center
This graph shows sea level pressure change every hour from August 15, 2018 at 12:00 to August 24, 2018 at 06:00. We used the data recorded when we plotted the path of the Soulik using WRF model.
As the result of the simulation, the lowest pressure appeared on August 18 at 18:00, when the typhoon was located at 139.7°E and 25°N. Since then, SLP has increased to 960hpa. It has decreased and the lowest value appeared on August 20 at 07:00. After that time, the slp increases in broad outlines and this results from weakening of the strength of Soulik.
[table 1] SLP as the result of simulation
The lowest pressure of the real Soulik was 950hpa and Lowest atmospheric pressure during typhoon season was 963.2hpa (observed on August 23 at 01:44 at Ieodo General Marine Science Base). At the time of landing, the sea level pressure was 977.5hpa. Considering that the simulation sea level pressure at the time of landing was 967hpa, the typhoon’s strength of the simulation result was stronger than the actual observation result.
[figure 5] Streamline graphic on August 22, 2018 at 22:00
[figure 6] Streamline graphic on August 23, 2018 at 15:00
The result of streamline plot shows that the flow of fluids near the center of Soulik and the flow of fluids near the center of Cimaron were in opposite directions on August 22, at 22:00.(figure 5) At that time, the two typhoons are far apart.
On August 23, at 17:00, two typhoons are close but weaken.(figure 6) That is why we cannot conclude that the Soulik's strength has increased under the influence of Cimaron.
Comparison of the forecast path of the KMA with the forecast path of the WRF
We compared the path of the final Soulik predicted by the Korea Meteorological Administration with the path predicted by our team with WRF. The black line is the actual path of the typhoon, and the blue line is the path predicted by the WRF.
As you can see in the picture, the typhoon's course is clearly different from 12:00 on the 21st. What could be the reason?
The figures below overlap our team's WRF data with the forecasting routes of the Korea Meteorological Administration (KMA) on the 20, 21, 22, and 23.
This is the expected route of on the 20.
8/20
Considering the distortion caused by Map Projection, we can see that the path of the Korea Meteorological Administration should appear more left-hand compared to our team's. Therefore, the route of the Meteorological Agency and our team is very similar.
The same goes for the expected route on the 21st.
8/21
However, the reversal will take place from the 22nd. Even considering the distortion caused by Map Projection, there is a clear difference between the path predicted by the Korea Meteorological Administration and the path predicted by our team.
8/22
This is more pronounced by the 23rd.
8/23
We wanted to find out what happened on the 21st.
According to the outside geopotential height and precipitation graphics, typhoon Cimaron was under the influence of Soulik between 21st and 22nd.
The reason for the difference in prediction paths was that the Korea Meteorological Administration's prediction model had better prediction performance than the WRF model.
After Cimaron's appearance, the prediction path of the WRF and the Korea Meteorological Administration has changed significantly. This shows that the emergence of Cimaron has a significant impact on prediction.
Both the WRF and the Meteorological Agency predicted the route through interactions between Soulik and Cimaron. However, given that the forecast by the Meteorological Agency is more accurate, there are other factors that are not reflected in the WRF.
Therefore, it can be seen that the Meteorological Agency predicted the interaction between Cimaron and Soulik more accurately.