Abstract/Summary

We examine the merit of atmosphere‐ocean coupled models for tropical cyclone (TC) predictions in the western North Pacific (WNP), where accurate TC predictions remain challenging. The UK Met Office operational atmospheric global numerical weather prediction (NWP) model is compared with two trial coupled configurations, in which the operational atmospheric model is coupled to a one‐dimensional mixed‐layer ocean model and a three‐dimensional dynamical ocean model. Re‐forecasts for the 2016 TC season show that the coupled models outperform the NWP model for TC location predictions, with a systematic improvement of 50‐100km over the 7‐day forecasts, but the coupled models amplify the underestimation of TC intensity in the NWP model. Nearly identical TC predictions (for both location and intensity) are found in the two coupled models, indicating the dominance of thermodynamic processes at the air‐sea interface for TC predictions on these timescales. The improved prediction of TC position in the coupled models is associated with an enhanced Western North Pacific Subtropical High (WNPSH), which introduces an anti‐cyclonic steering flow anomaly that shifts TC tracks further west in the southern part of the region and further east in the northern part. Based on sensitivity experiments, we show that these improvements in the coupled models are mainly due to colder initial sea surface temperatures (SSTs). Air‐sea feedbacks do not noticeably change the WNPSH or TC tracks. Apart from the effect of the initial SSTs, tropical ocean warming due to air‐sea interaction in the coupled forecasts can also reduce the predicted TC intensity, presumably due to a stronger regional Hadley circulation with increased subtropical subsidence