Soaking rain will douse east-central Australia, potentially sparking serious flooding Friday into Saturday.
Heaviest rain will fall in the state of New South Wales between Sydney and the Queensland border, an area that suffered major flood late last January.
Leading edge of rain on the Grafton, New South Wales, radar, as of 1300 GMT Thursday. Rain backing westward ahead of off-shore sub-tropical low. (Image credit: Bureau of Meteorology)
Flood Watches have been posted as of Thursday by the Australian Bureau of Meteorology (BoM) for drainage basins of east-central and northeastern New South Wales. Advisories have cautioned minor to major stream flooding in these areas.
The BoM have also hoisted Flood Warnings for some east-flowing streams and rivers, in anticipation of torrential rain.
Rainfall reports from northeastern New South Wales, published on the BoM website, show that isolated falls to at least 12 inches (30 cm) have already happened since Sunday along eastern slopes of the Great Dividing Range.
Latest forecast tools available to AccuWeather.com show highest rainfall striking Friday and Friday night, local time, between Newcastle and the Queensland border. Rainfall up to 25 cm (10 inches) will happen in a few places, and isolated amounts to 50 cm cannot be ruled out along wettest eastern slopes.
Some heavy rain is also forecast to spread southward along the coast to greater Sydney later Friday into Saturday.
Subtropical low pressure, lurking off northeastern New South Wales as of 1230 UTC Thursday, Feb. 21, 2013, has begun to back westward. (Image credit: Bureau of Meteorology)
The instigator of the torrential rain that has fallen since the end of last week has been -- and will continue to be -- subtropical low pressure hovering off eastern Australia as of Thursday. This low had, as of the start of the week, been located near southeastern Queensland, where it unleashed some flooding rain.
The low will turn back to the west, landing on the northern or middle New South Wales coast by early Saturday.
Further bouts of heavy rain will be possible next week, owing to persistent on-shore flow and tropical moisture.
The plum rains are known as "meiyu" in China, the "baiyu" or "tsuyu" in Japan, and the "jangma" in the Koreas. The heart of the plum rain season stretches from early June to mid-July, with a tendency to shift south to north across the affected area.
In the wake of the mid-June cloudbursts, most of Pakistan to northwestern India last week saw a return to dry, hot weather typical of the weeks leading up to the Monsoon onset. It was as if the Monsoon withdrew to its "normal" position for the latter half of June.
The 38.5 degree C (101 degrees F) reading Tuesday in Ajaccio, Corsica, may have been tops in Europe.
Monsoon Onset was June 13th, 2013, in Delhi, almost two weeks earlier than average. The June 15th onset at Karachi and Islamabad was more like three week ahead of schedule.
In Pakistan, hit-or-miss downpours missed the Sindh capital, Karachi. One did hit Pad Idan, where it left 60 mm of rain Wednesday. This was more than 20 times greater than the normal June rainfall.
It is still possible that this scenario is over wrought as to the intensity and spread of rain in Pakistan and northwestern India. However, it is the hunch of the present forecaster that some very unusual weather is going to unfold in the Subcontinent during the next week!