Analysis of the structure and genesis of tropical easterly waves in the Caribbean Sea and eastern North Pacific using the WRF model

Tropical easterly waves are known to exist in the Caribbean and Eastern Pacific however their origin and forcing mechanisms remain unclear. The main uncertainty with respect to the origin of these waves is whether they are an extension of existing waves propagating from the Atlantic or if there is wave genesis within the Caribbean and East Pacific region. The present study considers two main aspects: firstly the ability of the WRF model to adequately simulate the structure and location of easterly waves in the region and secondly the relative role of background intra-seasonal variability (such as zonal wind anomalies, horizontal shear, SST, MJO phase etc.), orography and wave accumulation on the wave forcing, energy conversions and genesis mechanisms specific to the East Pacific. Simulations using the WRF model were run for eight consecutive summer seasons (June –September from 2002 to 2009) with a domain spanning the northern hemisphere tropics from longitudes 133W to 61W and a horizontal grid resolution of 22.5km. Low-level and mid-level dynamical fields (eg. meridional wind anomaly and vorticity) and outgoing long-wave radiation are used as the primary means to track the wave propagation and structure.