Abstract
Middle America is affected by tropical cyclones (TCs) from the Eastern Pacific and the North Atlantic Oceans. We characterize the regional climatology (1998–2016) of the TC contributions to the atmospheric branch of the hydrological cycle, from May to December. TC contributions to rainfall are quantified using Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) product 3B42 and TC tracks derived from three sources: the International Best Track Archive for Climate Stewardship (IBTrACS), and an objective feature tracking method applied to the Japanese 55-year and ERA-Interim reanalyses. From July to October, TCs contribute 10–30% of rainfall over the west and east coast of Mexico and central Mexico, with the largest monthly contribution during September over the Baja California Peninsula (up to 90%). TCs are associated with 40–60% of daily extreme rainfall (above the 95th percentile) over the coasts of Mexico. IBTrACS and reanalyses agree on TC contributions over the Atlantic Ocean but disagree over the Eastern Pacific Ocean and continent; differences over the continent are mainly attributed to discrepancies in TC tracks in proximity to the coast and TC lifetime. Reanalysis estimates of TC moisture transports show that TCs are an important moisture source for the regional water budget. TC vertically integrated moisture flux (VIMF) convergence can turn regions of weak VIMF divergence by the mean circulation into regions of weak VIMF convergence. We discuss deficiencies in the observed and reanalysis TC tracks, which limit our ability to quantify robustly the contribution of TCs to the regional hydrological cycle.
Highlights
Middle America, a continental region that includes Mexico and Central America, is influenced by various precipitating weather systems that drive the regional hydrology
The simultaneous increase in tropical cyclones (TCs) activity in both basins affects a wide portion of the south and centre of Mexico, mainly during October, when North Atlantic and Eastern Pacific TCs together contribute about 10–20% of the monthly-accumulated rainfall (Fig. 2)
The effect of TCs on the regional rainfall extends along the Gulf Coastal Plain, which reaches from eastern to northeastern Mexico through the Yucatan Peninsula, continues along Tabasco and Veracruz to Tamaulipas, and extends around the Gulf of Mexico in the Southern United States (US)
Summary
Middle America, a continental region that includes Mexico and Central America, is influenced by various precipitating weather systems that drive the regional hydrology. This region is subject to landfalling tropical cyclones (TCs), which include tropical depressions, tropical storms and hurricanes from the Eastern Pacific and the. During September 2013, TCs Ingrid and Manuel simultaneously made landfall in the western coast of Mexico and eastern Mexico, respectively, bringing very heavy rains to a large portion of Mexico and causing deadly mudslides and flash flooding (LeComte 2014). Other weather systems contribute to rainfall, including isolated thunderstorms, synoptic and mesoscale convective systems associated with the activity of easterly waves (EWs) (Serra et al 2016; Vigaud and Robertson 2017). Tropical EWs are synoptic-scale precursors of TCs in both the Northeast Pacific and North Atlantic (Belanger et al 2016). Eastern Pacific and North Atlantic vertical wind shear and sea surface temperatures (SSTs) favour cyclogenesis during boreal summer and early autumn (Molinari et al 2000)
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