TY - JOUR
T1 - Favorable monsoon environment over Eastern Africa for subsequent tropical cyclogenesis of African Easterly Waves
AU - Ocasio, Kelly M.Núñez
AU - Brammer, Alan
AU - Evans, Jenni L.
AU - Young, George S.
AU - Moon, Zachary L.
N1 - Publisher Copyright:
© 2021 American Meteorological Society.
PY - 2021/9
Y1 - 2021/9
N2 - Eastern Africa is a common region ofAfrican easterly wave (AEW) onset andAEWearly life.How the largescale environment over East Africa relates to the likelihood of an AEW subsequently undergoing tropical cyclogenesis in a climatology has not been documented. This study addresses the following hypothesis:AEWs that undergo tropical cyclogenesis (i.e., developingAEWs) initiate and propagate under a more favorable monsoon large-scale environment over easternAfrica when compared with nondeveloping AEWs. Using a 21-yr August-September (1990-2010) climatology of AEWs, differences in the large-scale environment between developers and nondevelopers are identified and are proposed to be used as key predictors of subsequent tropical cyclone (TC) formation and could inform tropical cyclogenesis prediction. TC precursors when compared with nondevelopingAEWs experience an anomalously activeWestAfricanmonsoon, stronger northerly flow, more intense zonal Somali jet, anomalous convergence over the Marrah Mountains (region of AEW forcing), and a more intense and elongated African easterly jet. These large-scale conditions are linked to near-trough attributes of developing AEWs that favor more moisture ingestion, vertically aligned circulation, a stronger initial 850-hPa vortex, a deeper wave pouch, and arguably more AEW and mesoscale convective systems interactions. AEWs that initiate over eastern Africa and cross the west coast ofAfrica aremore likely to undergo tropical cyclogenesis than those initiating over central orWestAfrica. Developing AEWs are more likely than nondeveloping AEWs to be southern-track AEWs.
AB - Eastern Africa is a common region ofAfrican easterly wave (AEW) onset andAEWearly life.How the largescale environment over East Africa relates to the likelihood of an AEW subsequently undergoing tropical cyclogenesis in a climatology has not been documented. This study addresses the following hypothesis:AEWs that undergo tropical cyclogenesis (i.e., developingAEWs) initiate and propagate under a more favorable monsoon large-scale environment over easternAfrica when compared with nondeveloping AEWs. Using a 21-yr August-September (1990-2010) climatology of AEWs, differences in the large-scale environment between developers and nondevelopers are identified and are proposed to be used as key predictors of subsequent tropical cyclone (TC) formation and could inform tropical cyclogenesis prediction. TC precursors when compared with nondevelopingAEWs experience an anomalously activeWestAfricanmonsoon, stronger northerly flow, more intense zonal Somali jet, anomalous convergence over the Marrah Mountains (region of AEW forcing), and a more intense and elongated African easterly jet. These large-scale conditions are linked to near-trough attributes of developing AEWs that favor more moisture ingestion, vertically aligned circulation, a stronger initial 850-hPa vortex, a deeper wave pouch, and arguably more AEW and mesoscale convective systems interactions. AEWs that initiate over eastern Africa and cross the west coast ofAfrica aremore likely to undergo tropical cyclogenesis than those initiating over central orWestAfrica. Developing AEWs are more likely than nondeveloping AEWs to be southern-track AEWs.
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U2 - 10.1175/JAS-D-20-0339.1
DO - 10.1175/JAS-D-20-0339.1
M3 - Article
AN - SCOPUS:85114112114
SN - 0022-4928
VL - 78
SP - 2911
EP - 2925
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 9
ER -