Verification of tropical cyclone heat potential for tropical cyclone intensity forecasting in the Western North Pacific

Abstract

Tropical cyclone heat potential (TCHP) is a measurable metric calculated by the summation of ocean heat content from the surface down to the depth of the 26 °C isotherm. TCHP calculated by the Meteorological Research Institute multivariate ocean variational estimation (MOVE) system is verified by using TCHP based on in situ observations by profiling floats during 2002–2012. After the verification, the threshold of MOVE-based TCHP before the passage of a tropical cyclone (TC) favorable for triggering TC deepening is determined by best-track central pressure drops for the nearest 6 hours from 1985 to 2012. The threshold is specified as the minimum range of TCHP when the ratio of the number of records for TC deepening to the total best-track number of records in a TCHP bin is significantly greater than the reference ratio determined for each domain at a significance level of 0.05. The threshold is relatively low (40–60 kJ cm−2) around 5–10°N, west of 120°E and east of 140°E, whereas it is relatively high (80–100 kJ cm−2) around 15–20°N. Around 5–10°N, the ratio for each moving speed shows two peaks: with moving speeds of 3–5 and 7–9 m s−1. The former case is exemplified by Typhoon Mike (1990) under relatively low TCHP ( 120 kJ cm−2).