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Atms 4320 / 7320 Convergent / Divergent regions associated with jet streaks: Forecasting Applications.
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We have talked about Jet streaks, in terms of convergence / patterns associated with the streak. We’ve examined how these patterns evolve via the process of geostrophic adjustment. We have also examined secondary circulations associated with these streaks.
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. We have mentioned the intimate connection between convergence / divergence patterns, height tendencies, vorticity, tendencies, and omega. We also know that there are certain synoptic considerations associated with jet maxima, in term of development.
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. We can superpose the convergent regions of the low - level jets with upper level jets. This allows us to forecast severe weather in the spring.
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. Off the east coast of North America, it is not infrequent to have a poleward, downstream jet maximum (equatorward entrance region) couple with an upstream equatorward jet maximum (poleward exit region) Rogers and Bosart (1991) shows that this enhances cyclone development as the two divergent regions overlap!
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. This frequently is associated with rapidly developing cyclones. A similar scenario can be described for east coast South American cyclogenesis (Lupo et al., 2001?)
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. See Fig!
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. Jet Streak coupling with lower-level fronts (Shapiro, 1982) Jet streaks can enhance and couple with low-level frontal circulations. When the exit region becomes coupled with the low- level frontal circulations (which are thermally direct in the vertical), this can suppress the development of precipitation.
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. When the entrance region becomes superposed over the front, both circulations are thermally direct. The atmosphere becomes de-stabilized which enhances the development of precipitation. Finally, when jet maxima superpose with low-level forcing that causes similar motions, they can enhance eachother. (Low-level warm advection, under left exit region of the jet (PVA).
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. Picture (S. plains scenario)
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. The picture superposes low-level Warm Air Advection which contributes to upward motion, as well as upper level CVA, which contributes to upward motion as well.
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications. The End
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Convergent / Divergent regions associated with jet streaks: Forecasting Applications.
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