What Do the Grade 7 and Grade 10 Wind Circles of a Typhoon Mean?
TyphoonSays·防御问答 · Typhoon knowledge · 更新 at 2026-10-11
Understanding Wind Circles: The "Damage Radius" of a Typhoon
In typhoon track maps, the Grade 7 and Grade 10 wind circles are not simple geometric circles but core indicators measuring the scope of a typhoon's destructive power. According to the national standard "Tropical Cyclone Grades," these two concepts define the boundaries covered by winds of different intensities. The Grade 7 wind circle refers to the area where the maximum average wind speed at the surface is ≥13.9 m/s (wind force Grade 7 and above); the Grade 10 wind circle refers to the area where wind speed is ≥24.5 m/s (wind force Grade 10 and above).
Figuratively speaking, if a typhoon is compared to a rapidly spinning top, the Grade 10 wind circle is the "core devastation zone" near the center, where winds are strong enough to destroy simple structures and uproot large trees; while the Grade 7 wind circle is the wider "outer warning zone." Although less intense than the center, it is still strong enough to make it difficult for pedestrians to stand steady and cause tree branches to break. It is worth noting that the shape of wind circles is influenced by terrain, movement speed, and monsoons, often appearing elliptical or irregular. Typically, the wind circle on the迎风 side (right side relative to the direction of movement) is larger and more dangerous than on the leeward side.
Risk Levels: From "Inconvenience" to "Life-Threatening"
Understanding the actual risks associated with wind circles is a prerequisite for scientific avoidance:
- Entering the Grade 7 Wind Circle (Defense Initiation Phase): Wind speeds increase significantly, outdoor billboards sway, and the risk of falling objects from heights rises, hindering maritime navigation. This marks the beginning of the typhoon's substantial impact and is the last window for preparing wind defenses.
- Entering the Grade 10 Wind Circle (Emergency Shelter Phase): Winds are extremely destructive; glass windows may shatter, and outdoor activities become extremely dangerous or even impossible. Being in this area means you must stay inside a sturdy building, strictly avoid going outside, and stay away from windows.
It is particularly important to be vigilant that even at the edge of the Grade 7 wind circle, gusts may instantly reach higher levels. Therefore, do not let your guard down because you are on the edge of the wind circle; always prepare protection according to higher standards.
Action Guide: Precise Prevention, Safety First
When forecasts indicate that your residence may be affected by wind circles, you should adopt a tiered response strategy:
- Before Grade 7 Wind Circle Coverage: Immediately check the sealing of doors and windows, reinforce or bring in items prone to falling such as potted plants and clothes racks on balconies; reserve at least 3 days' worth of drinking water, food, and emergency lighting equipment; fully charge power banks to prepare for potential power outages.
- Before Grade 10 Wind Circle Coverage: Complete all outdoor reinforcement work, and ensure all personnel evacuate to safe indoor locations. If you live in low-lying areas or dilapidated houses, cooperate with government arrangements in advance to transfer to shelters.
Regarding public concerns about school suspensions, work stoppages, and traffic control measures, these are usually linked to the typhoon warning signals issued by local meteorological departments (such as Yellow, Orange, and Red warnings). Due to differences in geographical environments and disaster prevention standards across regions, please refer to the latest announcements issued by local governments and emergency management departments for specific implementation standards. Do not judge risks based solely on perceived wind strength; closely monitor official authoritative information.
Stay vigilant and prevent disasters scientifically to minimize losses to the greatest extent. Real-time typhoon tracks and wind circle dynamics can be queried at TyphoonSays (taifengshuo.com)
This article is original educational content from TyphoonSays. Please refer to the latest official announcements from local governments for policy standards.