Overview of synoptic conditions over West Africa and North Atlantic before cyclogenesis

• Main Authors: Diedhiou, A., Camara, M., Gaye, A.
• Other Authors: Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Department of Physics Ziguinchor, Université Assane Seck de Ziguinchor Sénégal (UASZ), Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang (LPAO-SF), École Supérieure Polytechnique de Dakar (ESP), Université Cheikh Anta Diop de Dakar Sénégal (UCAD)-Université Cheikh Anta Diop de Dakar Sénégal (UCAD)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: African monsoon; African easterly waves; cyclogenesis; [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology; [SDE.MCG]Environmental Sciences/Global Changes; North Atlantic
• Online Access: https://insu.hal.science/insu-00564386

International audience The objective of this study is to describe the large scale conditions over West Africa and the Atlantic Ocean before the occurrence of a cyclogenesis over the North Atlantic by comparing synoptic conditions of a 3 day average before the genesis days of all cyclones (269 cyclones given by the National Hurricane Center; NHC) with the mean Aug-Oct climatology from 1980 to 2004. Over West Africa, the mean synoptic pattern before cyclogenesis is characterized by the presence of a stronger monsoon layer and lower values of Outgoing Longwave Radiation than the climatology depicting the presence of deeper convection. Moreover, the potential of genesis is stronger before cyclogenesis over the West African coast than the climatology showing that strong low-level cyclonic vortices propagate from land to ocean in an atmosphere characterized by strong upper level support. Generally, before the occurrence of a cyclonic activity, the atmosphere is more unstable and African Easterly Waves are more active over West Africa than the climatology. Over the Atlantic Ocean, large scale conditions before cyclogenesis are characterized by the presence of high cyclogenesis contributors such as warmer waters, lower pressure, stronger mid-level humidity and higher degree of atmospheric instability.