Abstract This study investigates the development of an east Pacific easterly wave (EW) event in August 2019 and the effect of the Papagayo jet on its evolution. Convective‐permitting numerical simulations were conducted. These included a control experiment and a Gap‐Filled experiment with a closed mountain gap near the Gulf of Papagayo, to test the effect of a weaker Papagayo jet on this EW event. The initial disturbance developed into a mesoscale convective system in the Panama Bight and transitioned into an EW in the Papagayo jet exit region, both of which are reasonably captured in the control experiment. The weakened Papagayo jet in the Gap‐Filled experiment reduces the meridional shear of the zonal wind and the associated barotropic energy extraction from the mean flow. This results in significantly weakened upward motion and vertical stretching near the center of the disturbance, thus weakening vorticity particularly at low levels below 700‐hPa in the jet region. The weaker Papagayo jet and diminished low‐level vorticity in the Gap‐Filled experiment can further limit the subsequent EW vorticity intensity as it travels northwest along the Mexican coast. However, the Papagayo jet appears to have a limited impact on the horizontal vorticity structure and propagation of the EW disturbance. These results suggest that the broad‐scale monsoonal westerlies south of the Papagayo jet may help maintain the low‐level horizontal wind shear, even when the Papagayo jet is weakened, thereby contributing to the formation of the EW's tilted vorticity structure.
Zhou et al. (Sat,) studied this question.