* Temperatures are well above El Nino threshholds
* Three of five models also show positive Indian Ocean Dipole
* Conjunction of patterns could spread, intensify drought (Adds details)
By Colin Packham
SYDNEY, Aug 18 (Reuters) - An El Nino weather pattern has strengthened over the last two weeks, the Australian Bureau of Meteorology (BOM) said on Tuesday, with now only a "small chance" the event will be over by the end of this year.
Tropical Pacific Ocean temperatures are well above El Nino thresholds, the Australian weather bureau said, alongside consistently weakened trade winds.
The BOM said three of five models monitored expect a positive Indian Ocean Dipole in addition to the El Nino.
A positive Indian Ocean Dipole indicates warmer sea surface temperatures in the western Indian Ocean relative to the east.
While an El Nino will typically bring dry conditions to Australia's east coast, when associated with an positive Indian Ocean Dipole, drought-like conditions are seen across more of the country, often with greater intensity - data from the Australian Weather Bureau shows.
The last El Nino and positive Indian Ocean Dipole was recorded in 2006. (Editing by Tom Hogue)