Dated 13/12 01
The 30day average of the SOI has dropped from +8.3 at the start of December to +3.6 as of the 13th December. If this drop continues it will be of concern as it may be providing an early indicator to a decrease in rainfall probabilities for early next year.
Despite the rise in the value of the SOI from the end of October to the end of November a mixed outlook in terms of rainfall probabilities currently exists across the Queensland. Regions of the state that have relatively low probabilities (20-40%) of exceeding median rainfall across the next 3 months include a strip running from Broadsound to Townsville shire, parts of the Dalrymple, Flinders and Richmond shires and a large part of north Queensland running from Mareeba to Bourke shires.
A few areas of higher rainfall probabilities exist. These are predominantly in the south west of Queensland where the probability of getting above median rainfall is between 50 to 80%. For most of the rest of Queensland there is currently no strong signal either way as to the next 3 months being excessively wet or dry.
However, if the 30day average of the SOI stays strongly positive through to the end of December rainfall probabilities can be expected to lift especially across southern and central Queensland for the rest of summer.
The 30-50 day oscillation appears to have passed eastern Australia. It will therefore be next expected to influence our atmosphere in mid-January. Although strictly speaking it is a tropical phenomenon, this phenomena can be a useful indicator as to the timing of potential rainfall events (rather than the actual amount of rain) over southern and central parts of Queensland.
This section will be next updated on the 19/12/01.