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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction. Update prepared by Climate Prediction Center / NCEP July 11, 2011. For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml. Outline.
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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP July 11, 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, but above normal along the Gangetic plains of India, Nepal Burma, parts of Thailand, and Philippines.
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 general weakness in the summer monsoon circulation, and an indication of the continuing “monsoon break” situation over India.
Precip Patterns: Last 7 Days Over the last seven days, except for the anomalous band of heavy precipitation over western India, the summer monsoon precipitation is below normal in general over much of the monsoon region including Southeast Asia. There is considerable discussion among monsoon meteorologists that the Indian monsoon region is under a “break monsoon” situation.
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 anomalously high precipitation over western and central western India is quite consistent with a weak anomalous trough in the low level easterlies near this region.
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 fluctuating considerably as it has done in the past. 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, but above normal along the Gangetic plains of India, Nepal Burma, parts of Thailand, and Philippines. 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 general weakness in the summer monsoon circulation, and an indication of the continuing “monsoon break” situation over India. • Over the last seven days, except for the anomalous band of heavy precipitation over western India, the summer monsoon precipitation is below normal in general over much of the monsoon region including Southeast Asia. There is considerable discussion among monsoon meteorologists that the Indian monsoon region is under a “break monsoon” situation. The anomalously high precipitation over western and central western India is quite consistent with a weak anomalous trough in the low level easterlies near this region. • The NCEP GFS model continues to predict an overall weakened summer monsoon circulation for the next two weeks thus persisting the “break monsoon” like situation over India. The forecasts do imply some relief for parts of southeast Asia in the second week.
