The relationship between sea breezes and rainfall along western Mexico during the North American Monsoon

The North American Monsoon (NAM) is an annual phenomenon that influences the southwestern United States and northwest Mexico during the summer months. Atmospheric general circulation models have had difficulty forecasting precipitation events during the NAM season. The cause of this predicament has been linked to models' insufficiency in simulating the daily cycle of winds within this region. Previous studies examined the daily cycle of winds measured by a 915-MHz wind profiler stationed at Estación Obispo (ETO), Mexico in an attempt to characterize the sea breeze events during the 2005 NAM season. This research extends their work by investigating the relationship between variations in the sea breezes over ETO and variations in the precipitation that fell on the western slopes of the Sierra Madre Occidental (SMO) in Mexico during the 2005 NAM season.

Examination of the mid-afternoon (14 – 17 LT) wind directions at ETO revealed that onshore flow was present from a broad range of directions but within the south to west sector. Sea breezes occurred almost every day at ETO, more frequently than previous studies indicated. Daily rainfall from the North American Monsoon Event Rain Gauge Network (NERN) showed high variability throughout the season as well as between NERN stations. There was no significant association between the mid-afternoon wind direction along the west coast of Mexico and the daily rainfall on the SMO. These results may guide NAM scientists as they seek better methods to relate onshore flow with convective activity across the SMO.