Assessing the Effectiveness of Spectral Nudging in Improving Tropical Cyclone Track Simulations over the Western North Pacific Using the WRF Model

Improving tropical cyclone (TC) track forecasts is critical for enhancing disaster prevention and mitigation efforts. This study evaluates the effectiveness of the spectral nudging (SN) technique in simulating TC tracks with diverse path patterns over the Western North Pacific using the Weather Research and Forecasting (WRF) model. The results show that the SN technique is remarkably effective in improving tropical cyclone track forecasts for all types of regular track patterns, except for irregular tracks. Specifically, spectral nudging reduced simulated mean track position errors by approximately 60%, 67%, and 77% on average for curving, northwestward-, and westward-moving tracks, respectively. Better simulations of large-scale flow dynamics contributed to these improvements, particularly in scenarios where the subtropical high underwent rapid changes in its circulation patterns. For irregular tracks, applying the SN technique showed mixed results, ranging from 75% error reduction to 20% error increase. This implies that the effectiveness of spectral nudging on the simulation of irregular tracks is case dependent. Since the effectiveness of spectral nudging depends on the scales (spectrum) of the underlying processes creating the irregularities of the tracks, when such irregularities were caused by local and regional-scale factors, spectral nudging became ineffective.