Updated
The Bureau of Meteorology (BOM) has released a
special climate review, officially calling the rain in north Queensland
"exceptional".
According to the special climate statement this year's event has topped the comparable January 1998 and January 1953 events, in terms of area averaged rainfall within the North Coast-Herbert rainfall division.
It is difficult to oversell the amount of rain that has fallen in north Queensland. Places like Paluma, Woolshed, and Upper Bluewater got over two metres of rain in 12 days. For perspective, two metres is taller than Chris Hemsworth, the god of thunder himself.
Records washed away
Interestingly, only a few daily rainfall totals were broken. But it was the accumulation of many days of heavy rain that made this even extraordinary.The tropical Queensland coast is no stranger to heavy rain but the Townsville region is usually a bit of an exception.
The area from Townsville to Bowen sits in a rain shadow, usually making it drier than areas further north, according to the report.
That was definitely not the case this time around.
"In and around Townsville, the accumulated totals from consecutive days of heavy rainfall were the city's highest on record since records began in 1888," the report said.
The records for both the seven and 10-day rainfall totals were smashed.
"In the seven days to February 4, 2019, the Bureau's site at Townsville Aero recorded 1052.8mm, and 1257.0mm in the 10 days to February 6."
The previous Townsville record for a seven-day rainfall period was 886.2mm (1998) and 952.5mm (1953) for a 10-day period.
Despite the lower totals, the rainfall in western Queensland was also exceptional — with large areas receiving more than 400 per cent of their mean February rainfall.
"In the Gulf Country and North West Queensland, record-breaking rainfall also occurred in previously drought-affected regions, including at Julia Creek and Richmond, resulting in major flooding across large areas," the report said.
"Several sites in north-west Queensland had seven-day rainfall accumulations of more than 600mm."
Was climate change involved?
While the report shied away from saying that climate change was definitely a factor, it said that it was "salient to consider" the role climate change played in record-breaking high-impact weather."Natural variability in extreme rainfall in Australia is inherently very large, making it more difficult to discern climate change influences," the report said.
"Nevertheless, it is expected that a warmer atmosphere and ocean will generally lead to an increased likelihood and severity of heavy rainfall events globally."
As stated in the Bureau of Meteorology and the CSIRO's state of the climate report:
"For heavy rain days, total rainfall is expected to increase by around 7 per cent per degree of warming. For short duration, hourly, extreme rainfall events, observations in Australia generally show a larger than 7 per cent increase."Draw from that what you will.
What is this 'MJO' that is getting all the blame?
With the other climate drivers in neutral the report draws attention to a lesser-known climate driver.
"The intra-seasonal tropical wave known as the Madden-Julian Oscillation (MJO) was active across the Australian region during the second half of January," the report said.
"The favourable environmental conditions associated with this MJO contributed to the development and intensification of the monsoon trough and embedded tropical low, which became the focus for the heavy rainfall across northern Queensland from late January."
The low and the monsoon trough both stalled for more than a week, leading to a "convergence zone" and the prolonged heavy rainfall.
The MJO is the climate driver associated with a pulse of wet and stormy weather that circles around the equator every month or so. It is closely linked with the monsoon and is often associated with bringing the monsoon or the driver behind monsoon breaks.
No comments:
Post a Comment