University of Wisconsin–Madison

Season Ahead Summer Precipitation Forecast for Southern Peru

Forecast Design

Index definition: Southern Peru Rainfall index (SPRidx): January-March(JFM) 29 local stations domain averaged rainfall.

Station Information:

Forecast Models:

1) Simple NIÑO indices model: single regression models based NIÑO 1+2 and NIÑO 3.4 indices

2) Principal Component Regression (PCR): multiple regression model using first four principal components (PCs) of 11 potential season-ahead predictors (as identified via spatial correlation and composite mapping, global wavelet analysis, and literature review)

3) PC tendency Model: single regression model based on the Tropical Pacific Sea Surface Temperature (SST) anomalies’ Principal Component (PC) tendency of August and November:

4) Linear Inverse Model (LIM): Based on PCs of Southern Peru rainfall, Pacific SST and 200 hPa geopotential heights (GHT)

Predictors and Verification:

JFM 2018 Forecast


Mortensen, E., S. Wu, M. Notaro, S. Vavrus, R. Montgomery, J. De Piérola, C. Sánchez, and P. Block. 2017: Regression-based season-ahead drought prediction for southern Peru conditioned on large-scale climate variables, Hydrol. Earth Syst. Sci. Discuss.,, in review.

Wu S., M. Notaro, S.Vavrus, E. Mortensen, P.Block, R. Montgomery, J. Piérola and C. Sanchez. 2017: Statistical season-ahead summertime rainfall forecast for Southern Peru based on Principal Components tendency and Linear Inverse Model  (to be submitted).

Additional Resources:

Standard disclaimer: These forecasts are experimental. We are not responsible for any loss occasioned by the use of these forecasts.

Other available forecasts:





Paul Block:

Shu Wu: 

Eric Mortensen: