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This report provides an update on the recent evolution and current conditions of the Asian-Australian monsoon system, as well as 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 August 08, 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 central and southern peninsular India, southern and northeast China, but above normal along the Gangetic plains of India, Nepal Burma, parts of Thailand, Philippines and over eastern Indonesia and Papa New Guinea. The dryness over eastern Australia is also continuing.
Precip Patterns: Last 30 Days Please see Note in Slide three. The 30-day precipitation pattern is overall similar to the 90-day pattern. General weakness in the overall strength of the summer monsoon circulation continues.
Precip Patterns: Last 7 Days Over the last seven days summer monsoon continues to be geerally 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 various regions India is relatively consistent with the spatial maps shown earlier.
Atmospheric Circulation The continued weak ridging in the low level westerly flow over near western India has its impact in the low precip amounts over peninsular India. The presence and approach of category 5 super typhoon MUIFA in the east China sea and southwest of Japan will likely impact the rainfall amounts in the nearby regions.
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 generally stay 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 August. 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 or slightly above 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 August. 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 sink to below 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 August 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 central and southern peninsular India, southern and northeast China, but above normal along the Gangetic plains of India, Nepal Burma, parts of Thailand, Philippines and over eastern Indonesia and Papa New Guinea. The dryness over eastern Australia is also continuing. The 30-day precipitation pattern is overall similar to the 90-day pattern. General weakness in the overall strength of the summer monsoon circulation continues. • Over the last seven days summer monsoon continues to be generally weak over the monsoon region as a whole. The continued weak ridging in the low level westerly flow over near western India has its impact in the low precip amounts over peninsular India. The presence and approach of category 5 super typhoon MUIFA in the east China sea and southwest of Japan will likely impact the rainfall amounts in the nearby regions. • The NCEP GFS model in the upcoming weeks is predicting above normal rainfall along India Pakistan border and relative dryness in central and northern India. It is also predicting below normal rainfall over large parts of China.
