Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the western North Pacific

Abstract

Abstract. Even though the maximum wind radius (R max )is an important parameter in determining the intensity and size of tropical cyclones, it has been overlooked in previous storm surge studies. This study reviews the existing estimation methods for R max based on central pressure or maximum wind speed. These over-or underestimate R max because of substantial variations in the data, although an average radius can be estimated with moderate accuracy. As an alternative, we propose an R max estimation method based on the radius of the 50 kt wind (R 50 ). Data obtained by a meteorological station network in the Japanese archipelago during the passage of strong typhoons, together with the JMA typhoon best track data for 1990-2013, enabled us to derive the following simple equation, R max = 0.23 R 50 . Application to a recent strong typhoon, the 2015 Typhoon Goni, confirms that the equation provides a good estimation of R max , particularly when the central pressure became considerably low. Although this new method substantially improves the estimation of R max compared to the existing models, estimation errors are unavoidable because of fundamental uncertainties regarding the typhoon's structure or insufficient number of available typhoon data. In fact, a numerical simulation for the 2013 Typhoon Haiyan as well as 2015 Typhoon Goni demonstrates a substantial difference in the storm surge height for different R max . Therefore, the variability of R max should be taken into account in storm surge simulations (e.g., R max = 0.15 R 50 -0.35 R 50 ), independently of the model used, to minimize the risk of over-or underestimating storm surges. The proposed method is expected to increase the predictability of major storm surges and to contribute to disaster risk management, particularly in the western North Pacific, including countries such as Japan, China, Taiwan, the Philippines, and Vietnam.

Advancing global storm surge modelling using the new ERA5 climate reanalysis

“…Since ETCs generally have lower wind speeds than TCs (Keller and DeVecchio 2016), we set a threshold of 20 m/s for observed U10 from ASCAT. For TCs we consider the winds within a 100 and 200 km radius from the TC's eye, hereby including the TC eyewall, where maximum U10 values are generally found (Chavas and Emanuel 2010;Carrasco et al 2014;Takagi and Wu 2016).…”

On the Use of Parametric Wind Models for Wind Wave Modeling under Tropical Cyclones

“…It is important to note that HURDAT2 data do not contain information about the radius of maximum wind (R mw ). While this parameter can be calculated using empirical formulas (e.g., [22,24,[49][50][51]), their uncertainty is large. We then considered it more appropriate to use the R mw available in the original HURDAT database [52].…”

1997 Typhoon Linda Storm Surge and People's Awareness 20 Years Later: Uninvestigated Worst Storm Event in the Mekong Delta

“…The reliability of our model was verified for some strong typhoons, such as 2013 Typhoon Haiyan (Takagi et al, 2017) and 2015 Typhoon Goni (Takagi and Wu, 2016).…”

“…That is, the central positions and pressures at every recording period were used as parameters. The maximum wind radius, which was not contained in the best track data, was estimated from the central pressure (Takagi and Wu, 2016). Figure 1 shows the time series of the sea surface pressure and wind speed at Con Dao close to the storm track, as derived from the typhoon model.…”