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5 January, 2021

QLD weather: What to expect this week

Here is this week's opinion and review of relevant weather and seasonal forecast systems produced by major global agencies with Centre for Applied Climate Sciences' Roger Stone.

By Roger Stone USQ

Fast facts:

  • The 30-day average of the SOI is a healthy +18.0 (plus 18.0).  
  • La Niña is established in the central and eastern Pacific and the sea-surface temperatures in the Coral Sea are now above normal (an almost ‘classic La Nina’ pattern).
  • The MJO is next likely to indirectly impact our weather again around mid-January.  
  • In terms of individual daily forecasts, please refer to BoM for more up-to-date forecasts on a day to day basis.

Weather forecasts:

The model outputs below are obtained from a variety of sources without further comment, except that they are based purely on my opinion on the capability of various weather and climate models and based on the initiating agencies verification outputs and published manuscripts and as explained at our regional workshops.

1st week weather forecasts – higher confidence (all values approximate) – an opinion and summary/review of a number of national and international weather (as opposed to seasonal climate) models:

Values in mm – all values approximate.

Weekly rainfall forecast  totals - review of the US COLA system:

4/1-12/1          10-20 mm E and NE of a line approx. Walgett/Blackall/Broome, increasing to 50-70 mm over NE NSW, SE Qld, parts of the Burnett, southern Gulf, Barkly, and the Top End. Similar falls over the Gascoyne/Murchison. Falls increasing to 100 mm to over 250 mm over NE Qld/southern Cape York, approx. NE of a line from St Lawrence to Normanton. Falls increasing to 90 mm to over 110 mm over the NW Top End. Nil significant remainder.

12/1-20/1       (much less confidence for this period): 5-15 mm NE and N of a line from approx. Bourke/Birdsville to the Pilbara and into the Gascoyne/Murchison, increasing to 20-40 mm over the Central Highlands and parts of NE NSW. Falls increasing to 100 mm to over 240 mm over the Top End, and Western Cape York (plus the coastal fringe of the Gulf of Carpentaria). Nil significant remainder.   

Weekly temperature forecast anomalies:

4/1-12/1         below normal mean temperatures over eastern Qld, the top of the Top End and NE NSW (under the cloud and rain) (-2 to -7degC). Above normal mean temperatures (+2 to +8C) over the remainder .  

Seasonal forecasts:

For the longer period, the seasonal climate forecast models are indicating the following (to be updated when new information confirmed):

  • For the January to March period, the BoM ‘ACCESS-S’  coupled GCM is continuing to indicate high probability of ‘above average’ rainfall probability values (~80% probability of exceeding the median) for most regions, especially for NE and eastern Queensland, and the NSW coast to ranges (close to climatology for the remainder).  
  • The USQ/Qld Govt SOI phase statistically-based model for the end of December suggests the SOI phase as “consistently positive”. For this January to March  period, 2021, this equates to a ~70% probability of exceeding of the long-term median rainfall for most of eastern Queensland (especially central Qld/Central Highlands), coastal and central inland NSW, and most areas of Western Australia, especially the Gascoyne/Murchison and the Pilbara. Close to climatology for remaining regions.    
  • The UKMetOffice GCM is similarly forecasting a 60% to 80% probability of exceeding the long-term median through, at this stage, to at least April 2021 for most of Australia, especially for eastern Australia.
  • The US CPC ocean-atmosphere model is now starting to suggest a continuation of this La Niña climate pattern into the rest of 2021.
  • The European ECMWF GCM is similar to BoM ACSESS indicating 70%-80% probability of exceeding median rainfall through to at least the end of March, 2021, although with the highest probability values over eastern Australia. However, for the period between March and May, 2021 the ECMWF system is indicating above normal rainfall probability values for much of WA,  especially NW WA (with closer to normal rainfall probability values (‘climatological normals’) for the east of the continent).  
  • The Florida State University (FSU) model is showing only slightly positive SOI values for the remainder of 2020 and into 2021 (and, hence, closer to ‘average’ rainfall most likely and a weak La Niña but extending into the southern hemisphere autumn of 2021). The SOI 30-day average is now plus 18.0 (+18.0)
  • MJO information (also courtesy of BoM): the MJO is due to indirectly influence our rainfall patterns around mid-January.  

We are very grateful to Meat and Livestock Australia and the MLA Donor Company for funding key research projects in this area of seasonal and shorter-term forecasting and to which this output belongs.    

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