1. The North American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 24 September 2012

2. Outline Recent Evolution and Current Conditions Summary Climatology

3. Rainfall Patterns: Last 7 Days During the past week, below-average rainfall was observed over much of the western Mexico.

4. Rainfall Patterns: Last 30 Days Much of the NAM core areas have received overall near-average rainfall during the past 30 days.

5. Recent Evolution: Rainfall

6. NCEP/GFS Forecast Near-average precipitations are predicted over southwest U.S. during 24 September – 07 October, 2012. Meanwhile, above-average rainfall during the next week is forecasted over northwestern Mexico and Baja.

7. Summary During the past week, below-average rainfall was observed over much of the western Mexico. Most of the NAM core areas have received overall near-average rainfall during the past 30 days. The GFS bias-corrected forecasts show near- average precipitations over southwest U.S. during 24 September – 07 October, 2012. Meanwhile, above-average rainfall for the next week is predicted over northwestern Mexico and Baja.

8. Climatology MONSOON ONSET June 5 June 6 June 8June 7 June 14 June 17June 16 June 23 June 27June 25June 29 July 3July 6July 11 July 7July 8July 13 July 9July 13July 14 June 10June 11 June 22June 21 Higgins, R. W., Y. Chen and A. V. Douglas, 1999: Interannual Variability of the North American Warm Season Precipitation Regime. J. Clim, 17, 653-680

9. Precipitation Climatology