Asian-Australian Monsoon System: Recent Evolution, Current Status, and Prediction Update

1. The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP August 16, 2010 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml

2. Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology

3. Precip Patterns: Last 90 Days During the past 90 days, precipitation was above average (1979-95 climatology) over Kashmir region, northern Pakistan, Bangladesh, northeast India, much of Burma, the Arabian Sea, the Bay of Bengal, Bangladesh, equatorial Southeast Asia, eastern Indian Ocean, southeastern China, Japan, maritime Indonesia, and the northwestern Pacific storm track region. On the other hand, slightly below-average precipitation occurred over much of India, much below normal rainfall over Indo-China peninsula, the Philippines, and the subtropical western Indian Ocean and western Pacific(consistent with La Nina). It must be noted that there is a discrepancy between this data set and others such as the from the IMD. The discrepancy could also be because of the differing climatologies used as well. The % of normal 90-day accumulated precip map (right) shows the Middle East, northern Pakistan and Indian Kashmir region at over 200-250% of normal, as well as northwestern Australia.

4. Precip Patterns: Last 30 Days During the past 30 days, precipitation was above average over much of tropical south Asia except peninsular India, eastern Indo-China peninsula, the Philippines and southeastern China. Above-average precipitation was also observed over northern India, northern Pakistan, the eastern Arabian Sea, southern and central Bay of Bengal, tropical central eastern Indian Ocean, and the northwestern Pacific storm track region. However, below-average also occurred over portions of India particularly eastern central India, equatorial western Pacific, Indochina peninsula, and northeastern Asia. Excessive precipitation and flooding continued over northern India, Pakistan and near Gujarat, India. Mudslides continued in the Gansu province of China, where moderate rains fell in the generally arid region.

5. Precip Patterns: Last 5 Days Light to moderate rains fell throughout India, Indo China peninsula, and along western central, central and northeast China. Heave precip also occurred in the central and eastern tropical Indian Ocean.

6. Rainfall Time Seriesover 5x5 lat-lon boxes *This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. Upper panel: Southeast China rainfall excess continues. Middle panel:. In spite of the recent rainfall near Cambodia, Vietnam and Laos the seasonal rainfall deficits either continue to stay. Lower panel :Northern Pakistan continues to receive devastating rainfall amounts. The floods in these regions may turn out to be the worst in terms of impact.

7. Atmospheric Circulation This summer monsoon’s anomalous rains over the middle east region, combined with flooding in northern Pakistan will probably merit a detailed study regarding the role of global warming if any, particularly if the associated monsoon circulation has also got something to do with the unusual heat wave in the Moscow area and surrounding regions. These standard 850 mb maps and anomalies do not reveal much anomalous behavior.

8. NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Week-2

9. 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 continues to be at or below normal for 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.

10. Prediction of South Asian Monsoon Circulation 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 the South Asian monsoon index will be near or slightly above normal 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.

11. 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 East Asian WNP Monsoon Index will continue its up and down swing, as it has done in the past several 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 July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

12. Summary • During this immediate past week normal to moderate rain fell over much of south and southeast Asia. However, the rainfall over the generally arid regions of north Pakistan or the Gansu province of Central China, when added to the rains that these regions already received in previous weeks, led to serious flooding, and mudslides in these regions, thus making the monsoon related rainfall and circulation this season one of the most unusual one. The hurricane activity in the western Pacific (and the associated rainfall from the landfalling storms in the south east Asian region) is well below normal this year so far.

13. Onset of the Asian Monsoon

14. Climatology