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Generation and propagation of African squall lines
Author(s) -
Bolton David
Publication year - 1984
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711046509
Subject(s) - squall line , geology , meteorology , front (military) , microburst , leading edge , storm , mechanics , mesoscale meteorology , atmospheric sciences , climatology , physics , wind speed , wind shear
A study of squall lines affecting Minna, Nigeria during 1974–1976 emphasizes two particular aspects of their dynamics: that a strong jet around 650 mb is essential for their development, and that the forward edge of the squall line moves slightly faster than the maximum jet speed. A linear model of the squall line as a superposition of normal modes of an unstably stratified sheared flow sheds light on these observations. If the flow profile has a mid‐level maximum, constructive interference of normal modes gives rise to an expanding circle of convection with an arc front moving slightly faster than the maximum mean flow speed, followed by individual cells. If, however, shear is unidirectional, there is no arc front, and a line of cells is formed moving at the middle level mean flow speed. These two cases are suggested as models for tropical and mid‐latitude squall lines respectively, while a further case provides a possible model for storm‐splitting.