THE big wet has begun, as far western parts of New South Wales and Queensland were soaked overnight, and the Top End continues its wet winter.
The rain started to fall over western parts of NSW on Sunday evening with falls becoming heavy early on Monday morning. Rain at Tibooburra became heavy with thunderstorms around midnight picking up 10 millimetres in just 30 minutes.
In the 24 hours to 9am this morning, Tibooburra picked up 26mm, its heaviest June rain since 2008. Nearby, Wilcannia recorded 31mm, its heaviest since August last year and heaviest June rain since 2000.
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Across the border in Queensland, Birdsville picked up 22mm, the wettest day since January and wettest June day since 2012.
The reason for all of this rain is a moist low pressure trough. It has been lingering over central parts of Australia over the past few days, triggering thunderstorms and rain areas.
This same trough is set to deepen over the coming days and bring widespread areas of 15-30mm of rain across western NSW and southwestern Queensland.
Thundery hail in Alice Springs
The normally red interior turned white yesterday afternoon when small hail fell in Alice Springs, Northern Territory.
Alice Springs had been on track for another warm day yesterday. Temperatures topped at nearly 24 degrees before 3pm, over four degrees above the average for this time of year.
A shortwave low-pressure trough then triggered an unusual storm event for the region. Temperatures begun to plummet, dropping four degrees in an hour as thunderstorms began. As showers began to fall, rain turned to small hail of diameters less than 2cm.
A sudden drop in pressure along with above average temperatures triggered this event. The atmosphere was already quite unstable, primed for isolated thunderstorms. However, hail formed due to a relatively cool pool of air aloft along with a dry socket of air.
Additionally, the presence of vertical wind shear aided in supporting the hail as it formed in the atmosphere. As the hail became bigger, the updraft was no longer able to support it size and hail fell.
Showers are likely to continue in Alice Springs today and into the beginning of next week as a series of troughs slowly move east. Rain-free days are looking to return by Wednesday, with a mostly sunny top of 20 degrees.
Widespread rain coming to Vic, NSW and southern Queensland
Desperate farmers in need of rain have a good reason to smile, with widespread rain set to drench Victoria, the ACT, New South Wales and southern Queensland over the next few days.
After a dry start to June, in which El Nino threatened to prevent rain, a stray low pressure trough over the nation's eastern inland has gradually been deepening over the past few days after being fed by a humid easterly flow.
As the system interacts with the well-timed movement of a strong upper trough from Monday, a complex low pressure system will develop and bring widespread soaking rain and thunderstorms until mid-week, with potential for heavy falls.
NSW, the ACT and southern Queensland will be in the thick of it, mainly in areas on and west of the ranges, with widespread falls of 15-30mm expected across the region. The drought-hit areas of northern NSW (including the Walgett area) and southern Queensland should see the best falls, with potential for 30-80mm, particularly under any thunderstorms.
For Victoria, the amount of rain remains a bit more uncertain and will be determined by the track of the low, however there is potential for similarly heavy falls, particularly over eastern and northern parts of the State.
Showers should clear most areas by Thursday, although they are likely to persist over eastern Victoria and southern NSW as a trough lingers over the region, but will clear by Friday.
Looking further ahead, it is looking increasingly likely a few cold fronts later in June could bring potential follow up rain to Victoria and southern NSW, although falls are unlikely to be as heavy or as widespread at this stage.
Wet start to June for Top End
June has already been unseasonably wet for the Northern Territory's Arnhem region.
Milingimbi kicked the month off with over 35mm in one day, more than has been recorded for the entire month of June in at least 11 years.
When Nhulunbuy picked up an additional 3.6mm to 9am last week, the June total approached the wettest since 2007, which was the wettest on record.
A number of low pressure troughs moving over the region have brought unseasonably heavy falls for the month of June. This has been enhanced by some strong ridges of high pressure directing moist onshore winds to eastern parts.
One such trough triggered rain over the Arnhem region last weekend. By the end of Monday, the trough will have moved further east and a weak ridge of high pressure will set up over the region, bringing mostly clear skies and dry conditions.