Latest detailed observed forecast and environmental conditions

Over summer, we monitor the health of the Great Barrier Reef to see how it's faring, as this time brings an increased risk of extreme weather, particularly heat waves, cyclones and flooding.

A detailed overview of the environmental conditions on the Reef is available below, and an overview of current conditions is also available.

Updates on current conditions are provided as part of our Reef Health Incident Response System.

Update 5: 12 April 2017

Environmental condition

Observations

Forecast from the Bureau of Meteorology

Sea surface temperature (°C)

As of 5 April 2017 (latest available information), sea surface temperatures were warmer than average throughout most of the Great Barrier Reef Marine Park (approximately 0.5 to 3 degrees Celsius (°C) above the long-term average for this time of year).


The main exception was an area of the outer shelf (bordering on the Marine Park boundary) offshore from the Mackay/Whitsundays region, where temperatures are average to slightly below average for this time of year.


Between 1 December 2016 and 31 March 2017, most of the Marine Park accumulated between 40 and 100 degree heating days. Some areas in the northern, central and southern Marine Park accumulated up to 160 degree heating days.


Accumulated heat stress, in the form of degree heating days, is calculated by accumulating positive daily sea surface temperature anomalies. This is relative to the appropriate long-term monthly mean, for 1 December to 31 March.

Degree heating day values can represent a broad range of thermal stress; e.g. three days at 1°C above the local long-term average results in the same degree heating day value as one day at 3°C.

The forecast from the Bureau of Meteorology’s seasonal prediction system POAMA (Predictive Ocean Atmosphere Model for Australia) indicates that sea surface temperatures for the majority of the Great Barrier Reef are likely to decrease from significantly above-average to average or slightly below average between April and June.

As of 11 April 2017, the likelihood of an El NiƱo forming in 2017 is 50 per cent.

As at 11 April 2017, the National Oceanic and Atmospheric Administration (NOAA) forecasts that thermal stress levels on the Great Barrier Reef will decrease below coral bleaching thresholds from early-to-mid April onwards.

Tropical cyclones

Tropical Cyclone (TC) Debbie formed as a low in the Coral Sea on 24 March 2017, and was named as a cyclone on 25 March.

The system strengthened as it moved towards the Queensland coast. TC Debbie crossed the coast at Airlie Beach as a Category 4 storm on 28 March 2017.

The eastern region outlook indicates a near-average cyclone season.

The average number of tropical cyclones in the eastern Australian region is four each season, with one or two making landfall (Bureau of Meteorology).

Rainfall levels

Until January, wet season rainfall in the Great Barrier Reef catchment had been below average compared to the long-term average for this time of year. Most areas were between 400-800 mm below average.

January rainfalls were above median in the Normanby, Wet tropics, and the Whitsundays.

February rainfalls were above median in the Normanby and Wet Tropics areas.

In March, ex- tropical Cyclone Debbie brought torrential rainfall and widespread flooding south of the Townsville region to the southern border of Queensland, extending south into New South Wales.

Broad areas of low pressure across northern Australia produced moderate falls in the northern tropics (Bureau of Meteorology).

The national outlook from the Bureau of Meteorology has a 50-75 per cent chance of above median rainfalls for the tropical north between April and June 2017.

The rest of Queensland has a 50 per cent chance of at or below median rainfall.

Flood plumes

Prior to Cyclone Debbie, rivers had been below flood levels.

Soon after 30 March, minor flood level waters discharged from the Burdekin River. Visible plumes from the Burdekin could be seen seaward some 15-20 kilometers and northward along the coast.

The mouth of the Fitzroy had discharge waters starting to emerge from 1 April, with more heavily-laden sediment visible from 3 April.

Rivers also flooded down the remainder of the Queensland coast with flood levels varying from minor to major.

Major flood plumes usually follow above average rainfall conditions, driven by monsoonal activity.

The seasonal stream-flow forecasts near median flows as more likely for most Queensland rivers.