Typhoon Tip

Abstract: The present work examines interdecadal variations of typhoon tracks in the western North Pacific (WNP) during the boreal summer (June–September) for the period 1951–2001. Typhoon tracks are expressed as percentage values of the total number of typhoon passages into a 5° × 5° latitude–longitude grid box with respect to the total number of typhoons formed in the WNP. The analysis period is divided into two interdecadal periods: ID1 (1951–79) and ID2 (1980–2001). From ID1 to ID2, typhoon passage frequency decreased significantly in the East China Sea and Philippine Sea, but increased slightly in the South China Sea. The time series of typhoon passage frequency over the East China Sea and South China Sea further reveal a regime shift in the late 1970s, while those over the Philippine Sea indicate a continuous downward trend of −9% decade−1. The interdecadal changes in typhoon tracks are associated with the westward expansion of the subtropical northwestern Pacific high (SNPH) in the late 1970s. The e...

Abstract: Typhoon Haiyan, which struck the Philippines in November 2013, was an extremely intense tropical cyclone that had a catastrophic impact. The minimum central pressure of Typhoon Haiyan was 895 hPa, making it the strongest typhoon to make landfall on a major island in the western North Pacific Ocean. The characteristics of Typhoon Haiyan and its related storm surge are estimated by numerical experiments using numerical weather prediction models and a storm surge model. Based on the analysis of best hindcast results, the storm surge level was 5–6 m and local amplification of water surface elevation due to seiche was found to be significant inside Leyte Gulf. The numerical experiments show the coherent structure of the storm surge profile due to the specific bathymetry of Leyte Gulf and the Philippines Trench as a major contributor to the disaster in Tacloban. The numerical results also indicated the sensitivity of storm surge forecast.

Abstract: The development of extratropical cyclone structural characteristics that resulted from the extratropical transition of Typhoon (TY) David (1997) and TY Opal (1997) over the western North Pacific is examined. David moved poleward ahead of a midlatitude trough that was moving eastward as the dominant midlatitude circulation feature over the western North Pacific. During the transition, David coupled with the midlatitude trough, which led to the evolution of an intense cyclone that became the primary circulation over the North Pacific. Although Opal also moved poleward ahead of a midlatitude trough, the principal midlatitude feature over the western North Pacific was a preexisting stationary cyclone over the Kamchatka peninsula. During transition, Opal weakened and became a secondary cyclone to the preexisting primary North Pacific cyclone. The structural characteristics of the evolving extratropical cyclone with respect to each case are examined in the context of the interaction between a vortex an...

Abstract: A synoptic model is developed to describe a role of the tropical upper tropospheric trough (TUTT) in early season typhoon development in the western Pacific low-level near-equatorial monsoon trough. The role is threefold: 1) The accompanying sub-equatorial ridge on the south side of the TUTT lies over the low-level trough and decreases the vertical shear; 2) the divergent Row on the south and cast side of a cyclonic cell in the TUTT increases the evacuation aloft to aid in depression development in a low-level trough; 3) a channel to large-scale westerlies is established for efficient outflow of the heat released by increased convection in the developing depression.