Wednesday, 12 January 2005: 1:45 PM
Numerical simulation of heavy precipitation in northern Baja California and southern California
We used the MM5 mesoscale model to simulate the heavy precipitation events of 6-21 January 1993 of a moderate El Niņo, which produced severe flooding, landfalls, and the lost of many lives near the border of California and Baja California. The synoptic atmospheric condition during this period consisted of a strong upper-level jet located over the US-Mexico western border, which produced intense advection of tropical moisture and convective activity over the region. The model reproduced the mean observed circulation patterns but with less intensity. The MM5 sounding profile in San Diego during the first extreme event (6 Jan) was more unstable and saturated than observed, but the winds were weaker, thus the forecast precipitation was close to observed. We verified the model precipitation with gridded observations of daily precipitation and obtained regional errors; daily time series of observed precipitation in several stations were also used for verification. The forecast showed an improvement when the resolution increased from 90 to 30 km, but there was not a noticeable improvement from 30 to 10 km; moreover, with the finer grid the largest precipitation errors were enclosed near the mountains tops where there are no available data for verification.