How Are Typhoon Numbers Assigned? The Meaning of 202509
Typhoon numbers consist of a 4-digit year and a 2-digit sequence number. For example, 202509 refers to the 9th typhoon of 2025. These numbers are assigned by China's meteorological authorities and are used alongside international names.
Structure of the Numbering System
China uses a 6-digit numbering system (often abbreviated to 4 digits in public communications): the first 4 digits represent the year, and the last 2 digits indicate the sequential order within that year.
- 202509 = The 9th typhoon of 2025
- 202601 = The 1st typhoon of 2026
A tropical cyclone receives a number once it reaches tropical storm intensity (maximum sustained winds of Force 8 near the center). Tropical depressions do not receive numbers.
Who Assigns the Numbers?
Typhoon numbers for the Northwest Pacific and the South China Sea are assigned by the China Meteorological Administration (CMA) in accordance with national operational standards. The Japan Meteorological Agency (JMA), serving as the Regional Specialized Meteorological Centre (RSMC Tokyo) designated by the World Meteorological Organization, is responsible for assigning international numbers and names. In most cases, the two numbering systems align. However, occasional discrepancies arise due to differing judgments on whether a system has reached tropical storm intensity, leading to rare instances where Chinese and Japanese numbers diverge.
Relationship Between Numbers and Names
- Number: 201409 – Precise and unambiguous, ideal for data retrieval.
- Name: Rammasun – Drawn from a rotating list of 140 names, making it easier for public communication.
The same name is reused every few years (unless retired), but numbers are never repeated. Therefore, using the number is the most accurate way to search for historical typhoons. TyphoonSays' historical typhoon database supports searches by number, Chinese name, and English name.
Trivia About Typhoon Numbers
- Typhoon sequence numbers start from 01 each year, synchronized with the calendar year. A typhoon forming in January is designated as No. 01 for that year.
- The peak typhoon season occurs from July to October, with approximately 70% of typhoon numbers assigned during these four months.
- The year with the highest number of typhoons was 1967, with 40 numbered storms, while the lowest was 2010, with only 14.
- Cross-year typhoons (forming in late December and dissipating in January of the following year) are assigned to the year of their formation.
Want to see all typhoons for a specific year? TyphoonSays provides annual typhoon almanac pages from 1945 to the present, allowing you to browse the tracks and intensities of all numbered typhoons by year.