What Do Probability Cones and Error Circles on Typhoon Track Maps Actually Mean?
TyphoonSays·防御问答 · Typhoon knowledge · 更新 at 2026-08-08
Probability Cone: All Possible Areas the Typhoon Might Visit
When you open a typhoon track map, you will see a colored area extending forward from the typhoon center, flaring out like a trumpet. This is the "probability cone." Many residents mistakenly believe that the typhoon will only follow the black line in the middle. This is a common misconception. In reality, that black line represents the "most likely path" calculated by meteorological experts based on current data, while the cone represents the collection of all areas where the typhoon center might pass in the coming days.
The width of the cone gradually increases as the forecast time extends. This is because the atmospheric environment is complex and variable; the longer the forecast period, the greater the uncertainty. Generally, the cone covers approximately 70% of the predicted positional error for the typhoon center. This means that while there is a high probability that the typhoon center will fall within the cone, there is still a small chance it could move outside this range. Therefore, if your city lies within the area covered by the cone, you should remain vigilant regardless of whether you are on the "most likely path." The outer cloud bands and wind circles of a typhoon often extend far beyond the influence range of its central movement path.
Error Circle: The Range of Forecast Uncertainty
Inside the probability cone or at specific points along the path, you may sometimes see a circular or elliptical marker. This is the "error circle." It intuitively displays the confidence level of meteorological departments in their prediction of the typhoon center's position. A smaller error circle indicates that current meteorological data is sufficient and model calculations are consistent, resulting in higher forecast reliability. Conversely, a large error circle suggests significant divergence among various predictions, indicating multiple possibilities for the typhoon's path.
It is crucial to note that the error circle does not represent the typhoon's area of impact. Even if the typhoon center remains within the error circle, the accompanying gales and heavy rain may already cover surrounding areas spanning hundreds of kilometers. According to the National Standard for Tropical Cyclone Grades issued by the China Meteorological Administration (CMA), a typhoon's destructive power depends not only on the central wind speed but also on its vast circulation system. Therefore, do not let your guard down just because you are not at the center of the error circle; the areas affected by strong winds and heavy rain are often much larger than the error circle itself.
How to Respond Scientifically and Check Information
Faced with dynamically changing track maps, the public should adopt a defensive strategy of "better safe than sorry." When your location enters the probability cone, especially when approaching the edge of the error circle, you should begin checking windows and doors, stockpiling supplies, and monitoring the latest warning signals.
Regarding concerns about school and work suspensions, these are typically linked to the color of the local typhoon warning signals (such as Yellow, Orange, or Red warnings). However, please note that standards may vary by region, so you should refer to announcements from local authorities. For example, some coastal cities may recommend stopping outdoor operations during an Orange warning, while inland areas may have slightly different criteria. Do not judge risks solely based on the lines on the track map; instead, take action based on real-time warning information released by local meteorological departments.
Real-time typhoon tracks can be queried at TyphoonSays (taifengshuo.com)
This article is typhoonsay's original copy content, and the local policy standards are based on the local government's latest release.