The KMA announced at 4:30 PM on Sep 15 that tropical depression No.53 formed. It was at 3 PM on the 15th at 15.1°N, 150.2°E over the sea. Central pressure was 1002 hPa and max wind was 15 m/s. The depression moved west at 18 km/h. The KMA expects it to quickly strengthen into a typhoon. If it becomes a typhoon, the name could be Duji‑an or Surigae. The typhoon may reach max wind of 40 m/s by 3 PM on the 20th. Then the central pressure would be 955 hPa, and it could come near about 740 km southeast of Kagoshima, Japan. This depression formed in the western Pacific before the Chuseok holiday and is expected to move toward the south of Japan. But the track forecast gets more uncertain over time. The 70% probability radius for the 20th position expands to 440 km. Depending on the exact track, Jeju and the east coast could get rain.
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What’s this No.53 anyway, a typhoon before Chuseok?
According to Dong‑A Ilbo, the KMA is watching the 'No.53 tropical depression' that formed in the western Pacific. The number sounds weird, and if it becomes a typhoon it could get names like Duji‑an or Surigae, and this news came right before the Chuseok holiday.
Reading the article raises a lot of questions. Why is the number 'No.53', how scary is a 40 m/s wind, is it common to have a typhoon during Chuseok, and what does '70% probability radius' mean? I’ll explain each.
Sep 15: central pressure 1002hPa, max wind 15 m/s
Sep 20 forecast: max wind up to 40 m/s
70% radius for Sep 20 point: 440 km
'No. 53' isn’t an international number?
The numbers in typhoon articles aren’t just one system. Each agency uses its own numbers.
| Agency | Number format | |
|---|---|---|
| KMA (tropical depression) | No. NN (e.g., No. 53) | |
Meaning The NNth tropical depression confirmed by KMA that year, before it becomes a typhoon. | ||
| RSMC Tokyo (Japan Meteorological Agency) | YYNN format (if this tropical depression becomes a typhoon, it could be 2025 or 2026) | |
| JTWC (US Joint Typhoon Warning Center) | NNW format (e.g., 25W) | |
40 m/s wind, how strong is it really?
Numbers alone are hard to picture, right? KBS’s wind‑speed feel guide makes it clear. (Not the official damage scale, just for news.)
10 m/s
Small trees sway, umbrellas can flip.
15 m/s
Walking against the wind gets hard.
20 m/s
Small branches start to break.
30 m/s
Big trees start to fall completely.
40 m/s — predicted peak wind speed of this typhoon.
Standing outside or driving a car gets dangerous. Damage like broken high‑rise windows can spread to regular buildings.
In Korea, what's the intensity? Same as US hurricane rating?
The KMA will label typhoon intensity with numbers (1~5) starting 2026. Korean "typhoon" covers a wider range than English; even wind over 17 m/s is called a typhoon. If you put 40 m/s (144 km/h) into the US Saffir‑Simpson scale, it falls in Category 1 (119~153 km/h). But Korea uses a 10‑min average wind, while the US uses a 1‑min average, so the ratings aren't directly comparable.
| KMA intensity | Maximum wind speed standard (10‑min average) |
|---|---|
| Intensity 1 | Below 17~25 m/s |
| Intensity 2 | Below 25~33 m/s |
| Intensity 3 (includes this typhoon forecast 40 m/s) | Below 33~44 m/s |
| Intensity 4 | Below 44~54 m/s |
| Intensity 5 (old term 'super‑strong') | 54 m/s or more |
Who names typhoons? Where does '두쥐안' come from?
If this tropical depression becomes a typhoon, it could get the name '두쥐안' or '수리개'. These weird names actually have over 100 years of history.
Early 1900s
Australian meteorologist Clement Rag started putting names of politicians he disliked on typhoons.
1945
After WWII, the US military officially named typhoons, mostly using beloved wives' or girlfriends' names, so they were all female.
1978
After the sexism controversy, they began using both female and male names together.
2000
The "Typhoon Committee" of 14 Asia‑Pacific countries started the current system that uses the 140 names (10 per country) in order. After all 140 are used, it goes back to the start.
Now
South Korea gave small, gentle animal/plant names like ant, rose, roe deer, while North Korea used names like "Suri‑gae" and China used "Du‑jwi‑an". Because North Korea also submitted 10 names, the whole list has 20 Korean names in total.
So why does a different name appear every time?
Actually, typhoon names keep cycling, so the same name usually comes back after a few years. But a name from a very destructive typhoon can be retired completely.
The typhoon committee can permanently drop a name and replace it. 2002's 'Lusa' (over 5 trillion won damage) became 'Nuri'. 2003's 'Maemi' (140 dead/missing) was removed from the list. 2005's 'Nabi' (big damage in Japan) changed to 'Eagle'.
If a typhoon name is permanently taken out, it means the storm caused big damage.
A typhoon on Chuseok? Is that usual?
It wasn't like this before. Lately, September typhoons have gone up a lot.
And why autumn typhoons are especially scary
Huge typhoons in Korean history mostly came in autumn. Because warming keeps the sea warm longer, typhoons don’t lose power in fall.
1959, Typhoon 'Sara'
A typical autumn typhoon that hit the Korean Peninsula in September.
2002, Typhoon 'Lusa'
It landed in September and caused over 5 trillion won in damage.
2003, typhoon 'Maemi'
A famous Korean typhoon that caused 140 deaths/missing, mainly in the Yeongnam region.
2026, the typhoon coming now
It formed in the western Pacific before the Chuseok holiday and is moving north. The sea is still warm, so it likely won't weaken quickly.
What’s a '70% probability radius' and why is it getting so wide?
The KMA’s typhoon track forecasts get a bit more accurate each year. Hover over the dot to see exact numbers.
Does being outside the probability radius mean it's safe?
'70% probability radius' means there's a 70% chance the typhoon center will be inside that circle. The circle grows over time not because the forecast is wrong, but because small errors keep adding up the farther out.
The US uses a similar method. The National Hurricane Center (NHC)'s 'cone of uncertainty' draws a circle so about 67% of the last 5 years' forecast errors fall inside. The Korean agency uses the last 3 years and a 70% standard.
The probability radius is just the predicted location of the typhoon's center.
Strong wind and rain can spread hundreds of km outside the circle.
So what should I prepare for this Chuseok?
In short: The system coming now is still a tropical depression, not a typhoon yet, but it could become typhoon 두쥐안 or 수리개 soon. Around the 20th, it may reach about 40 m/s.
But no one knows the exact path yet. A 440km radius means many variables. As the article said, whether Jeju Island and the East Coast get rain depends on the typhoon's track.
You can check typhoon updates in English on the KMA website (weather.go.kr).
If you have travel plans for the Chuseok holiday, check the forecast again the day before you leave.
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