When the storm reaches a certain strength, forecasters can easily work out the interaction between the typhoon's own dynamics and the effect of the steering winds. On the other hand, if the typhoon is weak, sometimes you can't even locate the eye, so naturally it is more difficult to judge its movement.
當颱風強度夠強，預報人員就很容易找到颱風偏向力及導引氣流的交互影響；反之颱風若很弱，有時連颱風眼都無法定位清楚，當然很難判斷它的運動方向。