A typhoon sits in the sea south of Hong Kong, yet the Observatory reports a north-easterly. This is not a contradiction. It follows directly from how a cyclone is built — and once you see it, the wind direction alone tells you where the storm is and where it is heading.
The wind circles the centre
A cyclone is a low. Air should flow straight in from the highs around it — but the Earth's rotation deflects moving air to the right north of the equator. The balance leaves the wind circling the centre, anticlockwise, rather than rushing at it.
So: north of the storm the wind is easterly, south of it westerly, east of it southerly. Hong Kong sits north of the usual western North Pacific tracks — an easterly during a storm to the south is the norm.
As the storm moves, the wind veers
As the storm passes, Hong Kong's bearing from the centre changes, and so does the wind. That sequence is a position fix: a north-easterly puts the centre to the south-east; a south-easterly means it has already moved west of you.
This is why the No. 8 signal comes in four directions. The signal describes where the local gales are blowing from, not where the storm is. During a passage the direction changes while the level may hold.
Two corrections: friction and asymmetry
The wind does not circle exactly. Friction slows it near the surface, weakening the Coriolis deflection, so the air spirals inward as it turns — by roughly 20 degrees over open water and more over land, where friction is stronger. That inward component is what feeds moisture into the core and sustains the storm.
The storm's motion makes the two sides unequal. Forward speed adds to the circulation on the right of the track and subtracts on the left, so a storm heading west blows harder on its northern half — the side Hong Kong is usually on.
Why stations disagree
All of this describes the free atmosphere. Hong Kong is hilly: valleys funnel and accelerate the flow, slopes shelter the ground behind them. In one storm, Ngong Ping and Tsim Sha Tsui can differ twofold in speed, and in direction too.
So there is no single answer to what the wind is doing in Hong Kong. The Observatory's signal describes the territory as a whole, and any one location can depart from it noticeably. For the wind where you are, read the nearest automatic weather station.
