WA Seasonal Rainfall Outlook: probabilities for Spring 2003, issued 19th August 2003

Increased spring rainfall favoured in southwest WA

The Bureau's spring rainfall outlook shows a moderate swing towards wetter conditions in southwest WA. However odds are near 50:50 for the remainder of the country with no big swings towards a wetter or drier season across any State or Territory.

For the September to November period, the chances of above median rainfall are between 60 and 70% in the southwest corner of WA (see map) with probabilities near 50% in the remainder. So with climate patterns like the current, about 6 or 7 seasons out of 10 are expected to be wetter than average in southwest WA, with about 3 or 4 out of 10 being drier.

probability of exceeding median rainfall - click on the map for a larger version of the map

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During spring, history shows this influence to be moderate in the southwest and northern parts of the state but weak in the remainder (see background information).

The tropical Indian Ocean is currently warmer than average, whilst the Pacific is showing near normal temperatures. For more detail see the El Niño Wrap-Up. The excess warmth in the Indian Ocean has had the greater influence on the overall pattern of probabilities.

July's value of the Southern Oscillation Index (SOI) was +3, fifteen points above the June value of –12. The approximate SOI for the 30 days ending 16th August was +1.

 

Click on the map above for a larger version of the map. Use the reload/refresh button to ensure the latest forecast map is displayed.

 
More information on this outlook is available from 9.00am to 5.00pm (WST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Perth Office: (08) 9263 2222.
 

THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 16th SEPTEMBER 2003.

July 2003 rainfall in historical perspective

May to July 2003 rainfall in historical perspective

 

Background Information