Exploring the Extratropical Transition of Typhoon Nuri with the Weather Research and Forecasting Model

Abstract:

Tropical cyclones frequently move into the higher latitudes and transform into extratropical cyclones, a process known as Extratropical Transition (ET). In this study, the ET process of Typhoon Nuri has been explored with the Weather Research and Forecasting (WRF) model. During October 31^st to November 3^rd of 2014, Typhoon Nuri began its journey as a tropical storm intensifying into a category 5 Typhoon over the Pacific Ocean. The storm then started to weaken on November 4^th, and came to the east of Japan, a prime area for ET, on November 6^th. The WRF model successfully captures the transformation and reintensification of Typhoon Nuri into a super strong Arctic storm over the Bering Sea. The model simulations indicate that, with the subtropical high located on the east side of the storm, a low-level jet formed, which accelerated the storm movement northward. At the same time, the resulting enhancement of warm air advection strengthend thermal contrast between the cold air in the northwest of the storm and the warm air within the storm, deforming the high-level jet streak into an orientation favoring the storm’s transformation into an extratropical cyclone. The interaction between the upper-level jet streak and storm further steered the Nuri-transformed extratropical cyclone to continue its northward journey toward the Bering Sea and intensify into a super strong Arctic storm on the November 8^th, 2014.