What is the Residual Circulation After a Typhoon Makes Landfall and Weakens? Can It Still Cause Heavy Rainfall?
TyphoonSays·防御问答 · Typhoon knowledge · 更新 at 2026-08-08
The Typhoon That "Refuses to Die": What Is Residual Circulation?
Many people mistakenly believe that once a typhoon makes landfall, with weakening winds and rising central pressure, the danger has passed. In reality, although a typhoon loses its primary supply of moisture and heat from the ocean after landfall, causing its structure to gradually loosen, its vast cloud systems and rotating airflows do not disappear immediately. This weather system, which penetrates inland with intensity weakened to a tropical depression or lower but still retains certain rotational characteristics, is what meteorologists call "typhoon residual circulation."
You can imagine it as a spinning top that lacks power but has immense inertia. Although it no longer possesses the destructive power of gale-force winds capable of damaging buildings, the massive amount of water vapor and energy it carries remains significant. According to the National Standard for Tropical Cyclone Grades issued by the China Meteorological Administration (CMA), when the maximum wind force near the center of a typhoon drops below Force 8, it is no longer classified as a typhoon. However, the weather impacts it triggers are often just beginning, potentially lasting longer and being more insidious than during landfall.
Beware of the "Boiling Frog" Threat of Heavy Rainfall
The greatest hazard posed by residual circulation is not strong winds, but heavy rainfall, even extreme rainstorms. This is because, as the residual circulation moves, it easily interacts with westerly belt systems, cold air, or other weather systems, generating intense convergent upward motion. Combined with the lifting effect of terrestrial terrain (such as mountains), this leads to highly efficient rainfall, creating a "train effect," where rain clouds pass over the same area continuously like train carriages.
This type of rainfall has the following characteristics:
- Long Duration: It may rain continuously for several days, resulting in astonishing cumulative rainfall.
- Wide Range: The affected area can extend hundreds or even thousands of kilometers inland.
- High Suddenness: Localized short-term rainfall intensity can be extremely high, easily causing urban waterlogging.
Therefore, even if the typhoon warning signal has been lifted, one must not let their guard down as long as the meteorological department has issued a heavy rainfall warning. Regarding specific regulations on school and work suspensions, standards may vary by location; please refer to announcements from local governments. In daily life, if you encounter persistent heavy rainfall, it is advisable to minimize non-essential outings and avoid high-risk areas such as mountainous regions and riversides.
Prevent Secondary Disasters: Do Not Lower Your Guard Too Early
Rainfall brought by typhoon residual circulation saturates the soil, significantly increasing the risk of geological disasters. In the 2-3 days following the passage of a typhoon, there is still a high incidence of secondary disasters such as landslides, debris flows, and collapses. Additionally, water levels in rivers, lakes, and reservoirs rise due to continuous rainfall, so the risk of lagging floods should not be ignored.
Residents should closely monitor geological disaster meteorological risk warnings issued by local meteorological and natural resources departments. Check drainage facilities at home and clear clutter from balconies to prevent objects from falling from heights. If you live in low-lying areas or at the foot of mountains, pay close attention to community notifications and be prepared to evacuate at any time. Remember, the impact of a typhoon is a process, not an instant event, and defensive measures should be maintained throughout.
Real-time typhoon tracks can be queried at TaifengSays (taifengshuo.com)
This article is typhoonsay's original copy content, and the local policy standards are based on the local government's latest release.