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On 30 June 2013, 19 Granite Mountain Hotshots firefighters were killed fighting a wildfire near Yarnell in the mountains of Central Arizona. They succumbed when the wildfire, driven by erratic winds, blocked their escape route and overran their location. A previous study is extended to simulate and analyze the downscale organization of convective circulations that redirected the wildfire, which started from the scale of the Rossby Wave Breaking over North America to a convective gust front that redirected the wildfire, trapping the firefighters. Five stages are found: Stage I, the initial deep prolonged gust front; Stage II, a front-to-rear jet and its ascending motions that organized high-based convection; Stage III, high-based dry microburst-induced downdrafts organized initially by ascending flow in Stage II that transported mass and entropy to the surface; Stage IV; multiple meso-γ-scale high centers and confluence zones formed that encompassed the firefighters’ location, which established a favorable environment leading to Stage V, canyon-scale circulations formed surrounding the fire. The atmosphere thus transitioned from supporting a deep and long-lived convective density current to elevated dry microbursts with mass and wind outflow into a canyon, redirecting the ongoing wildfire. 

In this study, the Advanced Research Weather Research and Forecasting (WRF) model was adopted to investigate the mechanical and thermal forcing effects associated with the New Guinea Highland (NGH) on Madden-Julian Oscillation (MJO) propagation and rainfall formation and enhancement mechanisms over the island of New Guinea. Our results show that both forces affect the propagation of the MJO07-08, resulting in orographic rainfall production. Even though each forcing helps produce orographic rainfall, the mechanical forcing of the NGH plays a much larger role in the orographic blocking than the thermal forcing. We also found two flow regimes associated with the propagation of MJO07-08 over the NGH. First, in the flow-around regime, the MJO and its associated convective system split around the NGH due to the strong orographic blocking. We can observe this splitting when looking at the splitting stage. Second, the flow-over regime could occur when the mountain is lower than its original height or the flow has a smaller Froude number. A series of numerical experiments indicate that the maximum orographic rainfall increases with increased mountain height; however, the maximum orographic rain decreases when the flow transitions to the flow-around regime. Finally, some common ingredients for orographic rainfall associated with the MJO07-08 passing over the NGH are consistent with those found for tropical cyclones passing over mountains.