On the Sub‐tropical Jet Stream and its Role in the Development of Large‐scale Convection

摘要: This paper contains mainly the results of a synoptic and climatological study large-scale convection in northern India Pakistan during three months preceding onset southwest monsoon. It has been shown that sea-level lower tropospheric charts give little clue to development latter is overwhelmingly determined by divergence waves sub-tropical jet-stream. further from detailed evidence nor'westers, andhis majority thunderstorms without squalls pre-monsoon period are fundamentally same phenomenon. The role cold-air advection middle upper troposphere also discussed. revealed regions upper-divergence convergence can be qualitatively located identifying certain typical patterns on high-level maps more than 12 hours before usual time commencement that, consequently, these used as effective tools issue area-warnings against thunder general nor'westers particular. A made southeast Australia, Union South Africa, Bechuanaland, Southern Rhodesia, northeast Argentina, Uruguay, Brazil United States similarities between countries Indo-Pakistan have brought out. On basis studies, it suggested jet stream plays very important producing subtropics all over world wherever over-runs its equatorward side, moist air possessing high degree latent instability. DOI: 10.1111/j.2153-3490.1956.tb01194.x