Hindawi Publishing Corporation Advances in Meteorology Volume 2013, Article ID 294956, 16 pages http://dx.doi.org/10.1155/2013/294956 Research Article Modeling the Impacts of the Large-Scale Atmospheric Environment on Inland Flooding during the Landfall of Hurricane Floyd (1999) Qianhong Tang, 1 Lian Xie, 2 Gary M. Lackmann, 2 and Bin Liu 2 1 Public Meteorological Service Center, China Meteorological Administration, 100081 Beijing, China 2 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, NCSU/MEAS, P.O. Box 8208, Raleigh, NC 27695, USA Correspondence should be addressed to Bin Liu; bin liu@ncsu.edu Received 1 March 2013; Accepted 13 May 2013 Academic Editor: John M. Morrison Copyright © 2013 Qianhong Tang et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he contribution of the large-scale atmospheric environment to precipitation and looding during Hurricane Floyd was investigated in this study. hrough the vortex removal technique in the Weather Research and Forecasting (WRF) model, the vortex associated with Hurricane Floyd (1999) was mostly removed in the model initial conditions and subsequent integration. Results show that the environment-induced precipitation can account for as much as 22% of total precipitation in the innermost model domain covering North Carolina coastal area and 7% in the focused hydrological study area. he high-resolution precipitation data from the WRF model was then used for input in a hydrological model to simulate river runof. Hydrological simulation results demonstrate that without the tropical systems and their interactions with the large-scale synoptic environment the synoptic environment would only contribute 10% to the total discharge at the Tarboro gauge station. his suggests that Hurricane Floyd and Hurricane Dennis preceding it, along with the interactions between these tropical systems and the large-scale environment, have contributed to the bulk (90%) of the record amount of lood water in the Tar-Pamlico River Basin. 1. Introduction Hurricane Floyd in September 1999 caused disastrous lood- ing along the US Atlantic Coast from South Carolina to Mas- sachusetts. Flooding was particularly severe and prolonged in eastern portions of the state of North Carolina, where the combined efects of Hurricanes Dennis and Floyd resulted in greater lood-low loadings of water and contaminants to Pamlico Sound, North Carolina, than any previously recorded events [1]. Over 50 cm of rain fell in isolated areas of North Carolina with widespread amounts exceeding 20 cm stretching from the Carolina Piedmont into southeastern New York [2]. Previous studies (e.g., [1, 3, 4]) indicated that this severe looding was not only caused by the combination of Dennis and Floyd, but also due to the enhancement of precipitation ater interaction with a mid-latitude trough during Floyd’s landfall. he efect of the previous rainfall event, Hurricane Dennis, has been studied and quantiied by Tang et al. [5]. However, the quantitative relations between the synoptic-scale environment, such as a trough/ridge sys- tem, and its associated precipitation during Floyd’s landfall are still unclear. he large-scale atmospheric environment hundreds to thousand kilometers away from a tropical cyclone (TC) may play an important role in TC landfall. he intensity of the troughs/ridges can afect the track, speed, intensity, and duration of TCs (e.g., [3, 6–9]). hese features may further afect the rainfall amount and distribution. Many eforts have been devoted to understanding how environmental features afect TC and the resulting precipitation distribution (e.g., [3, 4, 10, 11]). hese studies can be grouped, according to focus, into three primary aspects. he irst one is the inluence of extratropical transition (ET). A signiicant number of TCs move into the mid- latitude and transform into extratropical cyclones (usually occurring in the 30–40 ∘ N latitude band). his process is generally referred to as ET. During ET, a cyclone frequently acquires increased forward motion and sometimes intensiies