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This report provides an update on the recent evolution and current conditions of the Asian-Australian monsoon system, along with predictions for the upcoming weeks. It includes precipitation patterns for the last 90 days, 30 days, and 7 days, along with atmospheric circulation and forecast models.
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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP April 18, 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 Note: Occasionally when the update date of the land+ocean precip maps are not close enough to the release date of this weekly scheduled monsoon ppt. we use the more recent land -only precip maps. During the past 90 days, precipitation has been generally near normal over much of the monsoon region, except for below normal rainfall over south eastern China, Korea, Japan, and over parts of Papua New Guinea. Over central and northern Australia, the seasonal mean precipitation has been above normal. Some hint of dryness is beginning to develop over southeastern Australia.
Precip Patterns: Last 30 Days Please see Note in Slide three. The 30-day precipitation accumulation is seriously deficient over southeastern China, northern Korea and Japan. Elsewhere the precipitation is at or above normal levels, particularly all along northern Australia.
Precip Patterns: Last 7 Days Please see Note in Slide three. If land only maps are used, this map corresponds to the last seven days. During the last seven days, rainfall continues to be deficient over southeastern China, Elsewhere, the rainfall is at normal or slightly below normal levels.
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 precipitation over the various regions is quite consistent with the spatial maps shown earlier, even though as noted above, the rainfall data sets are from different sources and are processed differently.
Atmospheric Circulation Continued slight ridging over southeast China is associated with below normal rainfall in that 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 will continue to trend downward over the next two weeks. This index is more appropriate for northern summer monsoon. 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 March. 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 at or slightly below normal level 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.
Prediction of Australian Monsoon Upper panel: Australian monsoon index (Hung and Yanai 2004) defined as U850 averaged over 2.5ºS-15ºS, 110-150ºE. Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the Australian monsoon circulation (over northern Australia) indicates at or slightly about normal levels of rainfall. Lower panel: Correlation between rainfall and Australian monsoon index (Hung and Yanai 2004; 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. 11
Summary • During the past 90 days, precipitation has been generally near normal over much of the monsoon region, except for below normal rainfall over south eastern China, Korea, Japan, and over parts of Papua New Guinea. Over central and northern Australia, the seasonal mean precipitation has been above normal. Some hint of dryness is beginning to develop over southeastern Australia. The 30-day precipitation accumulation is seriously deficient over southeastern China, northern Korea and Japan. Elsewhere in the monsoon region the precipitation is at or above normal levels, particularly all along northern Australia. • During the last seven days, rainfall continues to be deficient over southeastern China, Elsewhere, the rainfall is at normal or slightly below normal levels. The NCEP GFS model predicts weak rainfall activity over the south Asia region in the next two weeks.
