On the Relationship Between Horizontal Organization of Precipitating Systems, Easterly Waves and Gulf Surges

Despite the fact that some recent studies have pointed to a relationship between easterly wave troughs and the occurrence of Gulf surges (Stensrud et al., 1997), this relationship has not yet been quantified. A conceptual model for the initiation of Gulf Surges was proposed by Rogers (2005), where convective evaporative cooling near the south-central part of the Gulf of California (GOC) induces a northward propagating linear Kelvin wave-like disturbance along the west facing slopes of the Sierra Madre Occidental. We are interested in examining possible relationships between the size and structure of the convective systems and their ability to drive this dynamical mechanism. It is hypothesized that easterly waves play a major role in organizing convective activity near the south central part of the GOC. Hence, understanding the organization of convection during different phases of the easterly wave and its relationship to Gulf surge initiation is of paramount importance for operational forecasting and cloud modeling. The horizontal organization of precipitating systems during NAME (North American Monsoon Experiment) is examined in this study using composite data from three radars located near the GOC. This study focuses on the relationship between the horizontal organization modes of precipitating systems in south-central part of the GOC, easterly wave troughs and gulf surges. There were approximately 15 easterly waves and two gulf surges during the NAME Extensive Observation Period. One Gulf surge initiated in the central part of the GOC, while the other initiated further south and coincident with the passage of Tropical Storm Blas near the mouth of the GOC.