Title: The North American Monsoon System: Recent Evolution and Current Status
1The North American Monsoon System Recent
Evolution and Current Status
Update prepared by Climate Prediction Center /
NCEP 31 August 2009
2Outline
- Recent Evolution and Current Conditions
- Summary
- Climatology
3Rainfall Patterns Last 7 Days
During the past 7 days, near-average rainfall was
observed over Southwest U.S. and northwest Mexico.
4Rainfall Patterns Last 30 Days
During the past 30 days, belowaverage
precipitation was observed over most of the NAM
domain.
5Recent Evolution Rainfall
Top over Arizona, US, rainfall was slightly
below normal during the past week. Bottom
Below-normal precipitation over central and
southern Mexico during the past week.
6Atmospheric Circulation OLR Last 7 days
- During the past five days, OLR anomalies were
positive over most of the NAM domain, consistent
with the drier-than-average condition in the
region.
Upper-level anticyclone was not evident over the
NAM domain during the last 7 days, consistent
with below-average precipitation in the NAM
domain during the period.
7NCEP/GFS Model Forecasts Bias-Corrected Precip.
Anom. for Weak 1 Week 2
Week-1
Week-2
8Summary
- Near-average rainfall was observed over Southwest
U.S. and Northwest Mexico during the past 7 days. - Although the NCEP Global Forecast System predicts
near-average precipitation over the southwestern
U.S in the next two weeks, Hurricane Jimena is
expected to bring substantial rainfalls to the
region in the next few days.
9ClimatologyMONSOON ONSET
July 9
July 13
July 14
July 7
July 8
July 13
July 3
July 6
July 11
June 27
June 25
June 29
June 23
June 22
June 21
June 17
June 16
June 14
June 14
June 10
June 11
June 8
June 7
Higgins, R. W., Y. Chen and A. V. Douglas, 1999
Interannual Variability of the North American
Warm Season Precipitation Regime. J. Climate,
17, 653-680
June 6
June 6
June 5
10Precipitation Climatology