Diagnosis and prognosis of extreme precipitation events in the Mexico City Basin

The number of severe storms (more than 20 mm hr-1 of rainfall) in the Mexico City basin has increased in recent decades. In some parts of the city there is substantially more precipitation than in the past. These changes in the weather regime have resulted in higher risk to intense precipitation and floods. In disaster preparedness activities, it is necessary to determine when an extreme precipitation event occurs. In the present study, a criterion to determine an extreme precipitation event in the Mexico city basin is defined. Based on continuous records of precipitation from a dense rain gauge network, the spatial and temporal characteristics of precipitation are documented. The western part of the city experiences the strongest precipitation events due to the interaction of easterly winds with orography. Thus, the threshold values for an extreme event are higher in the western than in the eastern part of the basin. The current capability to predict extreme precipitation events in Mexico City using a mesoscale model is analyzed. Potential use of weather information to reduce the vulnerability of Mexico City to intense precipitation is discussed.