Synoptic-Scale Influence of the Saharan Air Layer on Tropical Cyclogenesis over the Eastern Atlantic
Open Access
- 1 December 2002
- journal article
- Published by American Meteorological Society in Monthly Weather Review
- Vol. 130 (12), 3100-3128
- https://doi.org/10.1175/1520-0493(2002)130<3100:ssiots>2.0.co;2
Abstract
The formations of Hurricane Andrew, Tropical Storm Ernesto, and Hurricane Luis, which occurred, respectively, during the 1992, 1994, and 1995 hurricane seasons over the eastern Atlantic, have been investigated by utilizing the European Centre for Medium-Range Weather Forecasts (ECMWF) gridded data analyses. These cases were selected to illustrate the contrasting influences of the Saharan air layer (SAL) on tropical cyclogenesis. Analyses results show that Tropical Storm Ernesto (1994) and Hurricane Luis (1995) formed from the merger of the low-level (925 hPa) and midlevel (700 hPa) vortices over the eastern Atlantic within the monsoon trough enhanced by surges in the trades. Midlevel vortices associated with each case appear to evolve from African wave troughs enhanced by cyclonic shear vorticity of the midtropospheric jet, which existed to the south of an SAL anticyclonic eddy as an elongated wind maximum. Vorticity budget calculations suggest that vortex stretching dominated the enhancement of ... Abstract The formations of Hurricane Andrew, Tropical Storm Ernesto, and Hurricane Luis, which occurred, respectively, during the 1992, 1994, and 1995 hurricane seasons over the eastern Atlantic, have been investigated by utilizing the European Centre for Medium-Range Weather Forecasts (ECMWF) gridded data analyses. These cases were selected to illustrate the contrasting influences of the Saharan air layer (SAL) on tropical cyclogenesis. Analyses results show that Tropical Storm Ernesto (1994) and Hurricane Luis (1995) formed from the merger of the low-level (925 hPa) and midlevel (700 hPa) vortices over the eastern Atlantic within the monsoon trough enhanced by surges in the trades. Midlevel vortices associated with each case appear to evolve from African wave troughs enhanced by cyclonic shear vorticity of the midtropospheric jet, which existed to the south of an SAL anticyclonic eddy as an elongated wind maximum. Vorticity budget calculations suggest that vortex stretching dominated the enhancement of ...Keywords
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