Understanding weather and climate
Victorian farming communities and businesses know that we have always had fluctuations from wet seasons to dry. Good old fashioned variability.
So what makes the difference between wet seasons and droughts? And how is the climate changing over time?
An update from the Climatedogs
The 2006 drought had a combination event of El Nino (Enso), Indian Ocean Dipole positive (Indy) and Southern Annular Mode positive (Sam). The bigger droughts are when the dogs team up at the driest end of their range.
In 2011, Ridgy was well behaved for position but did exert a bit more air pressure than normal over Victoria, this seemed to affect northern Victoria in Winter.
Sam spent some of winter 2011 in his wetter negative phase bringing some more rain south of the Great Divide.
Indy was up to his usual tricks in 2011 and despite a La Nina brewing went into his rain reducing positive phase in September reducing rainfall in many parts of the state.
Like 2010, in 2011/12 Enso came back again over summer with a weak La Nina but unlike 2010 he didn't bring excessive summer rain to Victoria.
In June 2016, Eastie was responsible for those two major storm events that caused wide spread damage and flooding in NSW and Tasmania.
The Climatedogs animation series is an award winning series of short animated videos produced by the department. The animations explain what drives the climate in Victoria, and how climate drivers are changing over time.
In the spring of 2010, we saw the start of a much wetter season brought about by a combination of both La Nina (Enso) and the IOD (Indy) being in a negative phase, herding more moisture and big rain in southeast Australia.
More recently in 2015 we had Enso bring us an El Nino which brought about some very dry conditions in parts of Victoria. Also the pressure pattern was very high in 2015 due to Ridgy, who has been delivering stronger pressure patterns over parts of southern Australia over recent decades.
Sam herds up our cold fronts but in the past decade, he has been doing that a little less often which has meant we missed out on a few rainfall events during our cooler season.
In 2016 the winter and spring has been more favourable due to Indy being is it's wetter phase (IOD negative).
Learn more about what drives rainfall in Victoria
To make it rain in Victoria a source of moist air is needed, which mostly comes from the north, followed by local weather conditions to promote rainfall. For example, cold fronts crossing Victoria from the south often trigger rainfall when they meet warm, moist air.
This process is caused by different climate drivers that influence Victoria's wetter or drier years. Climate drivers vary over the months and years to influence our seasonal rainfall. For example, our driest years have been when two or more of these climate drivers have been in their 'dry phase' at the same time.
Click on the following climate drivers to learn more about what drives our wet and dry seasons:
- El Nino Southern Oscillation
- Indian Ocean Dipole
- Southern Annular Mode
- Sub-tropical Ridge
- East Coast Low
Our climate is variable. Listen to the latest climate update to get up-to-date information on the position of climate drivers and the forecast for weather conditions in Victoria.