Abstract：Tropical cyclones (TCs) moving across Luzon from east to west are likely to affect Hong Kong. As such, it is
important for forecasters take into account the likely changes in intensity and movement characteristics of TCs
crossing Luzon. 50 TCs in the period 1980-2014 were examined to determine the effect of Luzon’s terrain on
their intensity and movement.
The results indicated that TCs generally weakened as they passed through the terrain of Luzon. The decrease
in the maximum sustained winds (MSW) for TCs with intensity of severe tropical storms or below was
normally < 10 knot. For typhoons, the decrease in the MSW was usually ≥10 knot. The study also showed that
TCs moving across Luzon were likely to accelerate (decelerate) as they approached (moved away) from Luzon.
Furthermore, while there was a slight bias for TCs to deflect leftwards on leaving Luzon, a significant negative
correlation was found between the deflection tendency before and after crossing Luzon. A TC deflected to the
right (left) before landfall was likely to deflect to the left (right) after leaving Luzon. Also, deflection upon/near
landfalling is found to be related to the intensity, moving speed and the direction of motion of a TC.