Extreme Rapid Intensification of Typhoon Vicente (2012) in the South China Sea

One of the primary challenges for both tropical cyclone (TC) research and forecasting is the problem of intensity change. Accurately forecasting TC rapid intensification (RI) is particularly important to interests along coastlines and shipping routes, which are vulnerable to storm surge and heavy seas induced by intense tropical cyclones. One particular RI event in the western North Pacific with important scientific implications is the explosive deepening of Typhoon Vicente (2012). Vicente underwent extreme RI in the northern South China Sea just prior to landfall west of Hong Kong, with maximum sustained winds increasing from 50 kts at 0000 UTC 23 July to 115 kts at 1500 UTC 23 July. This increase of 65 kts in 15 hours far exceeds established thresholds for TC RI. Just prior to this RI episode, Vicente exhibited a near-90° poleward track shift. The relationship between the track and intensity change is described, and we speculate that the passage of a subtle upper-tropospheric (UT) “inverted” trough was a significant influence. An analysis of real-time numerical model guidance is provided and discussed from an operational perspective, and high-resolution global model analyses are evaluated. Proper numerical model forecasts of the UT trough interaction with the TC circulation were determined to be a shortcoming that contributed to the intensity prediction errors for Vicente. This case study discusses the importance of considering subtle UT features with regard to TC intensity forecasting and establishes an understanding of current model capabilities for future research. Developments in the use of global numerical model analyses to objectively track upper-tropospheric lows and quantify their interactions with TCs will be discussed.