Forecasting convection in the northern zone of the Mendoza's Province, Argentina

The main goal of this paper is to obtain a statistical model for the forecasting of convection in northern Mendoza (Argentina). The work was done using data from the daily radiosoundings of the Mendoza Aero (Argentina) and Quintero (Chile) aerological stations, as well as from the field pressure on surface at 12:00 UTC from some surface synoptic stations, covering the area between 30° and 36° south latitude and the 58° and 71° west latitude. The period of study reached from October to March of 1987/88, 1988/89 and 1990/91.

The occurrence of convection was defined when low clouds Cumulunimbus Calvus or Cumulunimbus Capilatus, were codified in the 24 hours after the 12 UTC observation at the Mendoza Aero meteorological station.

The stepwise discriminant analysis was applied to the variables selected from data archives, done with: the results from the thermodynamic analysis of the atmosphere, the shear analysis and the wind hodograph at the Mendoza vertical, also with data obtained from some levels proceeding from the Quintero radiosounding, and from the surface pressure field.

Results obtained for the 24-hour forecasting period starting from 12 UTC and until 12 UTC of the following day achieved high total percentages of success. The same was observed for the forecasting of occurrence or not occurrence of the convective event.

In regards to the best predictors the first would be the Faubush-Miller Index, followed by the pressure gradient between Mendoza and Malargüe and between Mendoza and San Rafael.

Therefore, in order to forecast the occurrence of convection the vertical structure of the atmosphere is a must, likewise is important the meridional gradient of pressure on the surface.

The bettering of the forecasting methods of convection in the zone will permit to forecast more efficiently the probability of convection occurrence at the Mendoza piedmont, and in this way to warn about possible flash flood of the mountain river flow in the lower part.