Slide 4 of 29
This is Riehlís conceptual model and the vertical cross section display of a tropical wave. Note the vertical extent of this wave to the mid levels (500 hPa). This is an ideal wave, since most perturbations across the Tropical Atlantic generally extend vertically no higher than 700 hPa (10,000 ft). Also, Riehl suggested the wave extended from west-to-east with height. The stronger winds east of the axis, one can assume, resulted in low level confluence favoring upward vertical motion and convective development to the east of the axis. Advances in numerical weather prediction and satellite imagery have shown that this is not the rule, since there are variations in axis orientation with height.
Copied from: USAFETAC/TN-89/003, The Caribbean Basin, A Climatological Study, December 1989