The difference in time of occurrence of the diurnal maxima mean wind speeds at the center of each core location (Fig. 3), shows that there is an acceleration of the wind in the streamwise direction, with the maximum mean wind speed occurring at C1 around 2300 LST and C2 around 0400 LST. In contrast, at C3 and C4, the maxima mean wind speeds start approximately at 0700 LST and 0900 LST. The mean wind speeds are a minimum everywhere in the afternoon (~8 m s-1, 1300–1600 LST). Table 1 summarizes the main characteristics of the OLLJ cores.
Based on the traditional mechanisms for LLJ formation (i.e., the Blackadar and Holton mechanisms), the acceleration of the wind should occur almost simultaneously at all locations once the upper-boundary-layer wind decouples from the surface layer; statically stabilized via radiative cooling, this layer impedes the upward propagation of frictionally retarded air. However, in the hourly 950–800-hPa-layer streamwise-acceleration field [\(\partial V_{s}/\partial t\) in Eq. (1)] (Fig. 4) it can be seen that acceleration is not uniform across the domain; rather, there are distinct areas of acceleration coming from the Atlantic Ocean, the Caribbean Sea, and the Coastal Cordillera. Additionally, even though these mesoscale pockets of acceleration propagate in the streamwise direction, the C1–C4 wind-speed cores do not exhibit any propagation, just diurnal intensification (as shown in Fig. 3); they occur at precise locations (Fig. 2, Table 1).