Why Do Different Agencies Publish Slightly Different Typhoon Tracks?
TyphoonSays·防御问答 · Typhoon knowledge · 更新 at 2026-08-01
The “Butterfly Effect” of Initial Data
The most fundamental reason for differences in predicted typhoon tracks lies in the chaotic nature of the atmosphere. Meteorologists often use the “butterfly effect” to describe this phenomenon: tiny differences in initial conditions can produce vastly different outcomes after complex nonlinear calculations. To prepare forecasts, major meteorological agencies around the world—such as the CMA (China Meteorological Administration), the Joint Typhoon Warning Center, and the Japan Meteorological Agency—rely on global observing networks, including satellite imagery, radar echoes, buoy data, and weather balloons.
However, there are far fewer observation stations over the oceans than over land, so the data naturally has gaps and errors. When different agencies feed slightly different initial datasets into their respective supercomputer models, the projected future tracks of a typhoon will naturally diverge. It is like several archers aiming at the same target: although they share the same general direction, each arrow is likely to land in a slightly different place. Therefore, it is normal for track maps from different agencies not to overlap completely in scientific forecasting; it does not mean that one of them has “calculated incorrectly.”
Competing Approaches in Numerical Models
In addition to initial data, the numerical weather prediction (NWP) models used by different agencies are another key source of forecast differences. At their core, numerical models are complex systems of mathematical equations that describe physical processes in the atmosphere. Meteorological agencies develop their own core algorithms, using different parameterization schemes to handle details such as cloud microphysics, air–sea interactions, and terrain friction.
For example, some models may be more sensitive to the movement of the subtropical high, while others place greater emphasis on changes in a typhoon’s internal structure. Moreover, to overcome the limitations of a single model, modern forecasting often uses “ensemble forecasting.” This technique runs dozens or even hundreds of slightly perturbed simulations to produce a probability distribution rather than a single definitive track. This is why weather maps frequently feature a fan-shaped “probability cone”: the larger the cone, the greater the uncertainty. Understanding this helps us interpret forecasts more rationally: focusing on the overall trend is more useful than fixating on a precise number of kilometers.
How to Respond Scientifically to Track Uncertainty
When forecast tracks differ, the public should avoid becoming anxious or selectively trusting one agency. Instead, a “defensive” approach is recommended. Under the national standard for tropical cyclone grades issued by the China Meteorological Administration, typhoon intensity is classified according to clear criteria. However, specific wind-related response measures—such as suspending classes, halting work, or suspending transportation—are determined by local governments according to local conditions. Standards may vary by location, so the warnings issued by local governments should be followed.
Residents are advised to take the following actions:
- Follow official authoritative updates: Prioritize warning signals issued by local meteorological authorities rather than relying solely on track maps circulating online.
- Allow for a safety margin: If forecasts indicate that a typhoon may make landfall near your area or cause severe impacts, stock up on essentials and reinforce doors and windows 24–48 hours in advance. Do not wait until the last moment.
- Adjust plans dynamically: Typhoon tracks usually begin to converge during the final 24 hours before landfall, when forecast accuracy improves substantially. During this period, stay informed and be ready to adjust travel plans at any time.
For real-time typhoon tracks, visit TyphoonSays (taifengshuo.com).
This article is original educational content from TyphoonSays. Please refer to the latest official announcements from local governments for policy standards.