**1. Introduction**

Tropical cyclones (TCs) are among the most destructive natural phenomena. TCs often bring about strong wind, heavy rainfall, and storm surge to the area along or close to the TCs' track. Among the three, heavy rainfall, which may lead to flash flooding and mudslides, is the most lethal natural disaster [1]. Typhoon Morakot, interacted with the strong southwest monsoon,

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

produced copious amounts of rainfall in Taiwan, with a record of 3031.5 mm during August 6–13, 2009 [2]. Hurricane Katrina, one of the deadliest hurricanes in the history of the United States, brought over 15 inches (381 mm) heavy rainfall to Florida at its landfall. The recorded maximum sustained wind speed reached 175 mph (280 km/h) and wind gusts reached 220 mph (350 km/h) at New Orleans, Louisiana [3]. Typhoon Morakot left 619 people dead and the death toll due to hurricane Katrina was over 1100 [3–5]. In order to alleviate enormous loss of lives and properties in the future, it is important to notice the local population and civil authorities to make appropriate preparation for the cyclones, including evacuation of the vulnerable areas where necessary. Accurate and timely (24 and 12 h before landfall) forecasting the TC track and the potential rainfall and wind induced by TC are vital and essential [6].

Most operational meteorologists rely heavily on numerical weather prediction (NWP) models in forecasting TCs. TC track forecasts have improved significantly over the past several decades [1, 7–9]. By contrast, the improvement in forecasting the TCs intensity has lagged behind the progress of TCs' track forecasting [9–12]. The capability for NWP models to predict short-term rainfall is still very limited [1, 6, 13, 14]. Quantitative forecasting of rainfall remains problematic and lags behind the TC's track forecast, although tropical cyclone forecasting is a successful enterprise with favorable benefit-to-cost returns [1]. Kidder et al. [6] report that because few observations are available while the storm is offshore, initializing numerical weather prediction models with sufficient details of the storm is impossible. Therefore, the rainfall forecasts by NWP models are not so accurate. The research of Xu et al. [15] shows that currently in China, there is no effective operational approach to forecast the heavy rainfall and wind induced by tropical cyclone. The forecast of the rainfall and wind due to TC in China all relies on NWP models and the experience of forecasters. Exploring other ways to predict shortterm rainfall is therefore important and necessary.

When TCs approach the land or move across the coast, the TCs structure and intensity change greatly [16]. Landfalling TCs usually bring about heavy rainfall over land. Regarding the forecasting of rainfall due to a TC in a certain region (at a certain rain gauge), it is reported that the rainfall is associated with the distance from the TC center, TC intensity, TC track, TC moving velocity, and TC residing time, as well as the environmental background. Rainfall induced by a TC generally decreases exponentially with distance from the TC center [6, 17, 18]. With the same environmental background, the stronger the TC intensity, the heavier the precipitation will be [18]. The distribution of precipitation due to landfalling TC is asymmetric. In the Northern Hemisphere, the land on the right-hand side of TC would usually receive more intense and spatial rainfall than the land on the left-hand side [19], since the rain bands on the right would carry more moist oceanic air than those on the left. After landfall, the slower the moving speed of the TC or the longer the residence time for the TC in a certain region, the more opportunities and longer time will be for the TC to interact with other weather systems, which might lead to extreme rainfall accumulation [2].

The previous studies indicate that rainfall induced by a TC at a certain rain gauge is attributable to a variety of factors. However, most of those studies focused on either case studies or investigating a specific factor, and the conclusion is mostly qualitative. In this study, a statistical scheme will be developed to forecast the maximum daily rainfall and 3-day accumulative rainfall at a meteorological station by considering the factor of distance between the station and the TC-landfalling center, the intensity of the TC, and the landfalling direction of the TC. This paper is arranged as follows. An overview of the data and methodology is presented in Section 2. Section 3 contains the description of the statistical boxplot scheme for TCs rainfall. The applications of the boxplot scheme to forecast the rainfall due to TCs in 2012 and 2013 are described in Section 4. Summaries and conclusions are given in the final section.
