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This report provides an update on the recent evolution and current conditions of the Asian-Australian monsoon system and offers predictions for its future behavior. It includes information on precipitation patterns over the past 90, 30, and 7 days, as well as atmospheric circulation and model forecasts.
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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP July 25, 2011 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml
Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology
Precip Patterns: Last 90 Days During the past 90 days, rainfall is below normal in general over southern peninsular India, eastern central and northeast China, but above normal over northern central India and along the Gangetic plains of India, Nepal Burma, parts of Thailand, Philippines and over the maritime Indonesian continent. Some dryness over eastern Australia is also developing.
Precip Patterns: Last 30 Days Please see Note in Slide three. The 30-day precipitation pattern is overall similar to the 90-day pattern. The distinct difference in the rainfall anomaly patterns between northeastern and the southern peninsular parts of India is a sign of the continued general weakness in the summer monsoon circulation.
Precip Patterns: Last 7 Days Over the last seven days summer monsoon continues to be weak over the monsoon region as a whole.
Rainfall Time Seriesover 5x5 lat-lon boxes Note: This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. The time series of anomalous precipitation over the various regions India is relatively consistent with the spatial maps shown earlier.
Atmospheric Circulation The weak ridging in the low level westerly flow over near western India and the passage of Typhoon MA_ON near southern Japan led respectively to the dryness over southern India and the excessive precipitation over Japan.
NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Week-2
Prediction of Large-Scale Monsoon Circulation Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as U850 (0-20ºN, 40-110ºE) – U200 (0-20ºN, 40-110ºE).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the Webster-Yang monsoon index (even though the precipitation associated with this index over the India region is not much) will continue to be mostly below normal in the next two weeks. Lower panel: Correlation between rainfall and Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds on the monsoon index (vectors) for July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.
Prediction of South Asian Monsoon Index Upper panel: South Asian monsoon index (Goswami et al. 1999) ) defined as v850 (10-30ºN, 70-110ºE) – v200 (10-30ºN, 70-110ºE).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the Southeast Asian and northwestern Pacific monsoon index (even though the precipitation associated with this index over the India region is not much) will be at near normal level in the next two weeks. Lower panel: Correlation between rainfall and South Asian monsoon index (Goswami et al., 1999; shading) and regression of 850-mb winds on the monsoon index (vectors) for July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.
Prediction of East Asia – NW Pacific Monsoon Upper panel: East Asia – Western North Pacific (EAWNP) monsoon index (Wang et al. 2008) defined as U850 (5-15ºN, 40-80ºE) – U850 (20-30ºN, 70-90ºE). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the Southeast Asian and northwestern Pacific monsoon index will be above normal in the next two weeks. Lower panel: Correlation between rainfall and East Asia – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds on the monsoon index (vectors) for March Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.
Summary • During the past 90 days, rainfall is below normal in general over southern peninsular India, eastern central and northeast China, but above normal over northern central India and along the Gangetic plains of India, Nepal Burma, parts of Thailand, Philippines and over the maritime Indonesian continent. Some dryness over eastern Australia is also developing. The 30-day precipitation pattern is overall similar to the 90-day pattern. The distinct difference in the rainfall anomaly patterns between northeastern and the southern peninsular parts of India is a sign of the continued general weakness in the summer monsoon circulation. • Over the last seven days summer monsoon continues to be weak over the monsoon region as a whole. The weak ridging in the low level westerly flow over near western India and the passage of Typhoon MA_ON near southern Japan led respectively to the dryness over southern India and the excessive precipitation over Japan. • The NCEP GFS model, after several weeks of continued and correctly predicting dryness over southern peninsular India, is finally predicting some (above) rainfall in the upcoming two weeks.
