| dc.description.abstract | Consecutive Supertyphoons Mangkhut and Yutu in 2018 underwent rapid intensifications (RI) over the western North Pacific (WNP) and made landfall at the northern Philippines. Hurricane Weather Research and Forecasting System (HWRF) was used to investigate the different processes in RI over the WNP and track evolution near the northern Philippines between both typhoons.
Both ocean-coupled (CTL) and uncoupled (UN) experiments were conducted for comparison. The model results show that CTL improves the over-predicted typhoon intensity of UN as a result of typhoon-ocean interactions, particularly for Yutu. Stronger angular momentum (AM) is transported inward by the intensifying radial inflow flow at lower levels and outflow at upper levels for Yutu, which then leads to a stronger RI than Mangkhut, mainly contributed by the larger positive vertical mean AM advection in the troposphere and vertical eddy AM advection at low levels near the eyewall. The simulated RI will not occur if the initial ocean temperature along the Mangkhut track is decreased by 1oC, while Yutu’s RI is much less affected by the same temperature decrease or increase. Environmental weaker deep-layer vertical wind shear associated with the slower-moving Yutu is favorable for the faster development of RI as compared to the faster-moving Mangkhut. The later development after RI onset for both typhoons is more dominated by physics schemes applied in the simulations than the initial ocean temperature change; however, their induced RI onsets and rates are only slightly changed.
For the typhoon approaching the northern Philippines, all coupled and uncoupled, no-terrain, and ocean temperature change experiments obtain good simulated tracks in the first two days (for Mangkhut) or first three days (for Yutu) and then followed by a northward deflection for both typhoons. UN gives a better-simulated track than CTL, particularly for Mangkhut. The Philippines and Luzon terrains do not affect significantly the northward deflection for Mangkhut, but they ease the northward track deflection for Yutu. The northward track deflection for both typhoons decreases when their initial ocean temperature is reduced by 1oC, while it increases when their initial ocean temperature is increased by 1oC. The track deflection near the northern Philippines of both typhoons is much more sensitive to physics schemes and initial time. However, the physics schemes have a more effective control on the track of Yutu, but with a less influence in determining Mangkhut intensity. Diagnostics of potential vorticity (PV) tendency budget shows that the northward deflection for Mangkhut near the northern Philippines can be explained by the northwestward tendency induced by horizontal PV advection and the westward but with slightly northward tendency induced by diabatic heating, while the northward deflection for Yutu near landfall is mainly dominated by the northwestward tendency induced by horizontal PV advection. | en_US |