TY - JOUR
T1 - A wave-relative framework analysis of AEW-MCS interactions leading to tropical cyclogenesis
AU - Núñez Ocasio, Kelly M.
AU - Evans, Jenni L.
AU - Young, George S.
N1 - Funding Information:
Acknowledgments. The authors thank Chris Thorncroft, Ron McTaggart-Cowan, Zachary Moon, James Russell, and, especially, Angel Adames, for discussions that helped to inform this study. Thanks are given to Alan Brammer for providing the AEW track data. We thank ECMWF for free access to the ERA-Interim reanalysis data. The feedback by scientists and colleagues at the 2019 Cyclone Workshop and the 100th American Meteorological Society Annual Meeting was also very helpful. The analyses developed here were performed on the Penn State Institute for Computational and Data Sciences Advanced Cyber Infrastructure (ICDS-ACI). This project has received funding from National Oceanic and Atmospheric Administration Educational Partnership Program under Agreement NA16SEC4810006-NCAS-M.
Publisher Copyright:
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PY - 2020/10
Y1 - 2020/10
N2 - An African easterly wave (AEW) and associated mesoscale convective systems (MCSs) dataset has been created and used to evaluate the propagation of MCSs, AEWs, and, especially, the propagation of MCSs relative to the AEW with which they are associated (i.e., wave-relative framework). The thermodynamic characteristics of AEW-MCS systems are also analyzed. The analysis is done for both AEW-MCS systems that develop into tropical cyclones and those that do not to quantify significant differences. It is shown that developing AEWs over West Africa are associated with a larger number of convective cloud clusters (CCCs; squall-line-type systems) than nondeveloping AEWs. The MCSs of developing AEWs propagate at the same speed of the AEW trough in addition to being in phase with the trough, whereas convection associated with nondeveloping AEWs over West Africa moves faster than the trough and is positioned south of it. These differences become important for the intensification of the AEW vortex as this slower-moving convection (i.e., moving at the same speed of the AEW trough) spends more time supplying moisture and latent heat to the AEW vortex, supporting its further intensification. An analysis of the rainfall rate (MCS intensity), MCS area, and latent heating rate contribution reveals that there are statistically significant differences between developing AEWs and nondeveloping AEWs, especially over West Africa where the fraction of extremely large MCS areas associated with developing AEWs is larger than for nondeveloping AEWs.
AB - An African easterly wave (AEW) and associated mesoscale convective systems (MCSs) dataset has been created and used to evaluate the propagation of MCSs, AEWs, and, especially, the propagation of MCSs relative to the AEW with which they are associated (i.e., wave-relative framework). The thermodynamic characteristics of AEW-MCS systems are also analyzed. The analysis is done for both AEW-MCS systems that develop into tropical cyclones and those that do not to quantify significant differences. It is shown that developing AEWs over West Africa are associated with a larger number of convective cloud clusters (CCCs; squall-line-type systems) than nondeveloping AEWs. The MCSs of developing AEWs propagate at the same speed of the AEW trough in addition to being in phase with the trough, whereas convection associated with nondeveloping AEWs over West Africa moves faster than the trough and is positioned south of it. These differences become important for the intensification of the AEW vortex as this slower-moving convection (i.e., moving at the same speed of the AEW trough) spends more time supplying moisture and latent heat to the AEW vortex, supporting its further intensification. An analysis of the rainfall rate (MCS intensity), MCS area, and latent heating rate contribution reveals that there are statistically significant differences between developing AEWs and nondeveloping AEWs, especially over West Africa where the fraction of extremely large MCS areas associated with developing AEWs is larger than for nondeveloping AEWs.
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U2 - 10.1175/MWR-D-20-0152.1
DO - 10.1175/MWR-D-20-0152.1
M3 - Article
AN - SCOPUS:85098094927
SN - 0027-0644
VL - 148
SP - 4657
EP - 4671
JO - Monthly Weather Review
JF - Monthly Weather Review
IS - 11
ER -