Doctor of Philosophy (PhD)
Geography and Anthropology
Unpreparedness of large and increasing populations to Atlantic tropical cyclones (TCs) in North and Central America often causes a significant percentage of human casualties and economic losses, which results in part from the difficulty of forecasting tropical cyclogenesis (TCG) and changes in TC track and intensity. Although the mechanisms that lead to TCG have been studied extensively, lack of knowledge still exists about the relative importance of the precursor factors responsible for TCG, especially in the Gulf of Mexico/Caribbean basin where no clear genesis mechanism has been identified for TCs. A series of studies in this dissertation examines influences of large-scale atmospheric circulation on TCG and intensity change mechanisms for Tropical Storm Arlene and Hurricanes Cindy, Dennis, and Wilma in 2005 by using various derived and observed data sets. To support the main analyses of the large-scale circulations GOES-12 satellite water vapor imagery and the Weather Research and Forecasting (WRF) model (V.3.2.1) are used. Six-hourly NCEP FNL (final) operational global analysis data and daily “real-time global” (RTG) sea surface temperature (SST) data are used as WRF model inputs. Results show that large-scale, low-level circulations incurred by subtropical high pressure systems in the surrounding ocean basins or triggered by mid-latitude troughs over northeastern North America play critical roles in the TCG process in the western North Atlantic. In particular, the convergence of temporary westerly winds from the eastern North Pacific and the southeasterly/easterly winds from the Atlantic under the orographic effects of Central America creates conditions in the lower atmosphere that favor the development of a meso-scale vortex over the warm sea surface, leading to TCG. WRF model simulation revealed that the interaction between the mid-latitude systems and tropical atmosphere determined the success or failure of the TCG forecast, which suggests that large-scale, low-level circulations heavily affect TCG and that every large-scale vortex and circulation component in the immediately-neighboring region of the storm development is important for TCG forecasting. This study shows that the global WRF has a potential to be used for operational short-range TCG forecasting.
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Yoo, Jinwoong, "Large-scale influences on tropical cyclogenesis for selected storms in the 2005 Atlantic hurricane season" (2011). LSU Doctoral Dissertations. 2927.
Rohli, Robert V.