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Mixed outlook for summer rains

WELCOME WEATHER: This photo, called Rainy Day, was taken by William Choice on the outskirts of Toowoomba.
WELCOME WEATHER: This photo, called Rainy Day, was taken by William Choice on the outskirts of Toowoomba. William Choice

MONTHLY values of the SOI rose from minus 2.1 for October to minus plus 10.1 for November.

Rather than indicating a potential La Nina climate pattern or significant improvement in the seasonal outlook, the rise in SOI value can be at least in part attributed to the recent passage of Tropical Cyclone Alessia.

Alessia was a small category 1 cyclone that tracked across the Northern Territory near Darwin and into the Gulf of Carpentaria during the second half of November.

It then dissipated over northern Queensland where it brought some welcome relief rain to drought-affected areas.

Based on this shift in monthly values the SOI is now in a rapidly rising phase.

A rapidly rising SOI phase at this time of year gives a mixed seasonal outlook for Queensland.

Throughout the south-west quarter of the state there is a 50 to 70% chance of getting at least median rainfall for December through to the end of February.

This is somewhat in comparison to the rest of the state where there is a lower 30 to 50% chance of getting at least median rainfall for December to February.

However if the SOI is a consistently positive phase at the end of December, the seasonal outlook for the rest of summer would be expected to improve.

The last time there was a rapidly rising SOI phase at the end of November was in 2006.

Other years since 1950 that have had the same SOI phase at the end of October include: 1959, 1960, 1969, 1973, 1976, 1981, 1984, 1993 and 2001.

It may be useful to find out what rainfall and seasonal conditions where like in your area for November to January in those years.

More information can be found at http://www.longpaddock.qld.gov.au or in the Rainman package.

Topics:  climate watch dave mcrae soi weather