Tropical Wave (Cross)Relative Humidity/Vertical Motion
Vertical cross section of ageostrophic circulation/vertical motion (arrows) and the relative humidity (percent).
The strong upward vertical motions support an upward surge of moisture between 18N 41W and 18N 36W, with the 70% contour extending to and above 500 hPa. Thus the model is forecasting deep convection in association with this perturbation.
West of 18N 41W, note areas of downward vertical motion, resulting in adiabatic compression and drying of the atmosphere.