# Presentation: 077568

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

**Update prepared by**
**Climate Prediction Center / NCEP**
**   ****23 May 2008**

**For more information, visit:****  **_[http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml](http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml)_

## Outline

** **
** ****Recent Evolution and Current Conditions**
** ****Monsoon Prediction**
** ****Summary**
** ****Climatology**

## Rainfall Patterns: Last 90 Days

**During the past 90 days, heavy precipitation occurred over much of the maritime continent, tropical eastern Indian Ocean, tropical western and southwestern Pacific, and the North Pacific storm-track region. Precipitation was above normal over most of the tropics except the below-normal rainfall over the western Indian Ocean, Papua New Guinea, and the equatorial Pacific east of 145E. Above-normal precipitation also appeared over the storm-track region. Below-normal precipitation was found over the subtropical Southern Hemisphere including Madagascar, the Indian Ocean, and Australia. Precipitation was also below normal over the Middle East, western Asia, the coastal regions of East Asia, and the subtropical North Pacific high area.**

## Rainfall Patterns: Last 30 Days

**Heavy precipitation occurred over the tropics and the North Pacific storm-track region. Precipitation was above normal over the Bay of Bengal, the South China Sea, the maritime continent (except the dry conditions over western Indonesia and Papua New Guinea), tropical western Pacific (except the equatorial region east of 150E), and the storm-track region. Below-normal precipitation was found over much of the Southern Hemisphere including Madagascar, the Indian Ocean, and Australia. Precipitation was also below normal over the Middle East, western Asia, southeastern India, Bangladesh, the coastal regions of East Asia, and the subtropical northwestern Pacific high area.**

## Rainfall Patterns: Last 5 Days

**The precipitation pattern during the last 5 days was characterized by the large rainfall over the northern tropics and subtropics east of 90E and over the northwestern Indian Ocean.  Above-normal precipitation was over the central South China Sea and the subtropical northwestern Pacific. However, below-normal precipitation appeared over much of the tropical Indian Ocean, southern maritime continent, the northeast coast of Australia, and eastern China.**

## Recent Evolution: Rainfall

**Upper right: The rainfall over southwestern China including Sichuan Province has been continuously over normal during this rainy season in spite of a decrease in the recent days.**
**Central right: The monsoonal rainfall over the Indo-China peninsula, central South China Sea, and the Philippines has been mostly near normal or above normal.  **
**Bottom right: The rainfall over southern India had been below normal; however, the recent increase in the local rainfall should be further monitored.**

**For other boxes, see: http://www.cpc.ncep.noaa.gov/products/**
**Global_Monsoons/Asian_Monsoons/90d-precip_click_map.shtml**

## Convection has been weakening over the Indo-China peninsula, the South China Sea, and the Philippine Sea but was still above normal.
Over southern China, normal convection returned and the influence of monsoon should be monitored.
While convection remained weak over the tropical Indian Ocean and Australia, it intensified over the western Arabian Sea.
Convection has become active over the western South Indian Ocean after the long-lasting dry conditions.

**Convection has been weakening over the Indo-China peninsula, the South China Sea, and the Philippine Sea but was still above normal.**
**Over southern China, normal convection returned and the influence of monsoon should be monitored.**
**While convection remained weak over the tropical Indian Ocean and Australia, it intensified over the western Arabian Sea.**
**Convection has become active over the western South Indian Ocean after the long-lasting dry conditions.**

## Atmospheric Circulation

** ****Left: The upper-level westerlies over the tropical western South Indian Ocean (IO) have intensified significantly, and weak easterly anomalies still remained over the northern tropics. **
** ****Right: The southeasterly trade wind over the tropical IO, the cross-equatorial flow over western IO, and the low-level westerlies extending from the Arabian Sea, the Bay of Bengal, the South China Sea, and the western Pacific remained stronger than normal.**
** ****Right: The anomalous low-level northeasterly wind over southern China has become weaker compared to last week, accompanied by increasing rainfall.**

## W-Y Monsoon Prediction

_**Upper panel:**_** Webster-Yang monsoon index (Webster and Yang 1992) defined as the mean U850-U200 over 0-20N, 40-110E. The NCEP GFS predicts that, in the next two weeks, the large-scale monsoon circulation will be near normal, implying near normal precipitation and lower-level westerlies over tropical Asia including the Indo-China peninsula and the South China Sea.  **

_** **__**Lower panel:**_** Correlation between precipitation and the Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds against the monsoon index (vectors) for May.**

## SA Monsoon Prediction

_**Upper panel:**_** South Asian monsoon index (Goswami et al. 1999) defined as the mean V850-V200 over 10-30N, 70-110E. The NCEP GFS predicts that the South Asian monsoon circulation will continue to be near normal in the next week and tend to be stronger afterwards.  **

_** **__**Lower panel:**_** Correlation between precipitation and the South Asian monsoon index (Goswami et al. 1999; shading) and regression of 850-mb winds against the monsoon index (vectors) for May.**

## EA-WNP Monsoon Prediction

_**Upper panel:**_** East Asian – Western North Pacific monsoon index (Wang et al. 2008) defined as the mean difference of U850(5-15N/90-130E) – U850(20-30N/110-140E). The NCEP GFS predicts that, in the next two weeks, the monsoon circulation over East Asia and the western North Pacific will be normal or weaker than normal, meaning normal or below normal precipitation over the northern maritime continent and tropical northwestern Pacific.  **

_** **__**Lower panel:**_** Correlation between precipitation and the East Asian – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds against the monsoon index (vectors) for May.**

## Summary

**Above-normal precipitation occurred over most of the tropical Asian-Australian region during the past months except over the equatorial western Pacific (east of 145E) and the tropical western Indian Ocean. Above-normal precipitation was also found over the subtropical western Pacific storm-track region. **
**Below-normal precipitation appeared over the subtropical southern Indian Ocean, Madagascar, Australia, and the subtropical northwestern Pacific high region. The Middle East and western Asia were also drier than normal during the past months.**
**While major rain belt had shifted to the northern tropics, the precipitation over the southern tropics appeared below normal. Below-normal precipitation was also observed over some East Asia regions. **
**The low-level westerlies over tropical Asia have been stronger than normal and monsoon rain band has further extended northward to northern South China Sea. Rainfall tends to increase over southern China.**
**The NCEP Global Forecast System predicts that the Asian monsoon will be largely near normal in the coming two weeks. **

## Onset Dates of ASM 

**Onset Dates of ASM**_ _

## Climatology