1. The North American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 05 August 2013

2. Outline Recent Evolution and Current Conditions Summary Climatology

3. Rainfall Patterns: Last 7 Days Within the NAM domain, slightly below-average rainfall has been observed over southwestern U.S. and northwestern Mexico during the past week.

4. Rainfall Patterns: Last 30 Days Rainfall accumulations over the past 30 days are above-average for northwestern Mexico as well as for southwestern U.S.

5. Recent Evolution: Rainfall

6. NCEP/GFS Forecast Slightly below-average rainfall over southwest U.S. during the next week; near- average precipitation for the same area during week 2. However, most of Mexico are expected to have drier-than-average condition during the next two weeks.

7. Summary Within the NAM domain, slightly below-average rainfall has been observed over southwestern U.S. and northwestern Mexico during the past week, consistent with GFS week 1 forecast made last week (7/22/2013). Rainfall accumulations over the past 30 days are above- average for northwestern Mexico as well as for southwestern U.S. NCEP GFS forecasts indicate slightly below-average rainfall over southwest U.S. during the next week and near-average precipitation for the same area during week 2. However, most of Mexico are expected to have drier-than-average condition during the next two weeks.

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