Multi-year observations of the complex relationship between sea breezes and rainfall along the western Sierra Madre during the North American Monsoon

The North American Monsoon (NAM) is a major component of the summertime weather over the southwestern United States and northwestern Mexico. Atmospheric general circulation models have difficulty predicting the observed daily cycle of precipitation observed during the NAM, possibly due to the inability of the models to correctly simulate the daily cycle of winds in this region. Multi-year high-resolution observations of lower-tropospheric winds and mountain rainfall were collected under the auspices of the North American Monsoon Experiment (NAME), and previous work has documented mean daily cycles of both quantities and their interannual variations. Here we investigate the relationship between sub-seasonal variations in the sea breezes at Estación Obispo (ETO), Mexico and in rainfall on the western slopes of the Sierra Madre Occidental (SMO) inland from ETO. Preliminary results reveal that the onshore flow during mid-afternoon (14 – 17 LT) was both more frequent and from a broader range of directions than previously understood, and that daily rainfall recorded by the North American Monsoon Event Rain Gauge Network (NERN) was highly variable in both time and space. As a result, simple circular statistics show no significant association between the mid-afternoon wind direction along the west coast of Mexico and the daily rainfall on the SMO. A more complex analysis is underway and will be presented.