QTPA Member Alert | Queensland Weather and Climate Forecasts (1/11/2012)

Queensland Weather and Climate Forecasts

Please find below information on the weather and climate forecasts for Queensland for the next few months, including information on what this summer is likely to be like in terms of temperature and rainfall.

In addition there is information on natural climate variability including ENSO, MJO, PDO, STR, IOD and SAM, and their influence on Queensland.

This information has been provided by the Queensland government’s Senior Scientist, Science Delivery, Department of Science, Information Technology, Innovation and the Arts.

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What is this summer going to be like?

For more information see: http://www.bom.gov.au/climate/ahead/

According to the Bureau of Meteorology throughout eastern Queensland, there is a 50% chance of exceeding median rainfall for the next three months (October to December) (Figure 1). Further inland, the chance of exceeding median rainfall is higher at 55 to 65%. As such, for the next three months, Queensland can expect slightly above average rainfall.

Figure 1: Chance of exceeding the median rainfall between October and December 2012.

The Queensland Government’s SOI phase system has been in a rapidly rising phase from Aug-Sept and the probability of above-median rainfall for the next three-month period (Oct to Dec) is near-normal (40 to 60 per cent) for most of Queensland (Figure 2).

Figure 2: Chance of exceeding the median rainfall in Queensland between October and December 2012. http://www.longpaddock.qld.gov.au/seasonalclimateoutlook/index.html

According to the Bureau of Meteorology, for October to December this year, there is a 75% to 80% chance of exceeding the median maximum temperature for Queensland (Figure 3). Similarly, there is projected to be a 65% chance of exceeding median minimum temperatures for southern Queensland and a 70% to 75% chance of exceeding median minimum temperatures for northern Queensland (Figure 4).

Figure 3: Chance of exceeding the median maximum temperature between October and December 2012.

Figure 4: Chance of exceeding the median minimum temperature between October and December 2012.

Current Status and Explanations of Climate Variability

El Niño Southern Oscillation

The El Niño Southern Oscillation (ENSO) occurs in three main phases: Neutral, El Niño and La Niña. The El Niño phase is known as the warm-phase of the ENSO pattern and is associated with warmer temperatures and decreased rainfall particularly over Northern and Eastern Australia. The La Niña, or cold-phase, is associated with cooler temperatures and increased rainfall. ENSO patterns occur due to a difference in sea surface temperatures between the eastern and western Pacific Ocean.

The Southern Oscillation Index (SOI) can be used to determine the current SOI phase and forecast future climate patterns. The SOI is derived from the pressure difference between Darwin and Tahiti. A strongly negative SOI is associated with a strong El Niño phase, while a strongly positive SOI is associated with a strong La Niña phase.

The average SOI for the last 30 days is +2.3 suggesting a neutral phase. Recently, there has been a retreat from El Niño thresholds, which is considered highly unusual as, historically, September-October has been the time when developing El Niño (or La Niña) events consolidate and mature. (Figure 5; www.bom.gov.au).

Figure 5: Variation of SST from the Average for September 2012

Madden Julian Oscillation (40 day wave)

The Madden Julian Oscillation (MJO) is an eastward moving pulse of cloud and rainfall near the equator that recurs every 30 to 60 days. The MJO influences the timing, development and strength of the major global monsoon patterns, including the Australian monsoons.

The MJO has its greatest impact on Australian rainfall during summer and mainly on the northern parts of Australia. The MJO goes through eight phases as it moves along the equator each 30-60 days and the greatest chance of rainfall in Queensland is when the MJO is strong and in phase 4. Visit the website http://www.bom.gov.au/climate/mjo/ to find out what phase the MJO is currently in (each phase takes approximately 5‑6 days).

Recently, the MJO has recently moved east and is currently over the Indian Ocean in phase 2 (Figure 6; http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=mjo).

Figure 6: Current MJO cycle and phases: the blue line is for October; when the line goes inside the circle, the MJO has weakened (http://www.bom.gov.au/climate/mjo/graphics/rmm.phase.Last90days.gif)

Pacific Decadal Oscillation

The Pacific Decadal Oscillation (PDO) is a long-lived (inter-decadal) ENSO-like pattern of Pacific climate variability. The term was first coined by fisheries scientists researching connections between Alaskan salmon production cycles and the Pacific climate. The PDO modulates the ENSO signal by strengthening La Nina conditions when negative and El Nino conditions when positive.

The PDO value is -2.21 as of September 2012, indicating a cool phase (http://jisao.washington.edu/pdo/PDO.latest).

Sub-Tropical Ridge

The Sub-Tropical Ridge (STR) is a belt of high pressure that encircles the globe in the mid-latitudes. The position of the STR influences seasonal weather patterns in Australia. The STR is often located to the south of Australia during the warmer half of the year (November to April) and from autumn begins to move northwards to remain over Australia during the cooler half of the year (May to October).

The STR moves south in spring and summer and is located to the south of the Australian mainland. If its location is further south than normal (e.g. anomalously poleward) more rain is likely in southern Queensland during spring and summer. In the winter the STR is located over central Australia and is associated with areas of high pressure and lower chance of rainfall in southern Queensland.

Indian Ocean Dipole

Rainfall patterns in north-western Australia are impacted by sea surface temperatures (SSTs) in the Indian Ocean. Warmer than average SSTs near Australia often enhance rainfall while cooler SSTs result in reduced rainfall. The Indian Ocean Dipole (IOD) has an influence on central and southern Australia’s climate and very little influence on Queensland rainfall.

A positive IOD is associated with drier conditions over much of southern and central Australia (including Queensland) during winter and spring, especially when combined with an El Niño phase of the ENSO. A negative IOD is associated with wetter conditions over parts of Australia, particularly in the south east, during winter and spring.

The current value of the IOD is +0.6 for the week ending 21 October 2012. The IOD is projected to remain neutral over the next few weeks (http://www.bom.gov.au/climate/enso/).

Southern Annular Mode

The Southern Annular Mode (SAM) refers to the north/south movement of the strong westerly winds that dominate the middle to higher latitudes of the Southern Hemisphere. Each SAM event, both positive and negative, tends to last for around ten days to two weeks. The time frame between positive and negative events however is quite random, but is typically in the range of a week to a few months.

A positive SAM refers to a more poleward location and decreased westerly winds in southern Australia which can result in more rainfall in spring and summer in NSW and southern Queensland.

In southern Australia a positive SAM event results in weaker than normal westerly winds, higher pressure and lower rainfall while a negative SAM event results in more storm systems, lower pressure and more rainfall over southern Australia, particularly in winter.

When SAM is positive the latitude of the STR is poleward which are both associated with increased rainfall in spring and summer in southern Qld and NSW.

Current values of the Antarctic Oscillation Index (an indicator of SAM) are at: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/aao.shtml

The current value of the SAM is +0.562 for September 2012.

Other relevant information

Tropical Climate Note – http://www.bom.gov.au/climate/tropnote/tropnote.shtml

Our Products

http://www.longpaddock.qld.gov.au/

• AussieGRASS environmental calculator – system provides:
  • historical rainfall maps from 1890
  • pasture growth, biomass and grass fire risk maps from 2000
  • pasture growth outlooks

•  FORAGE – a web-based system which generates and distributes information relating to climate and pasture conditions at user-specified locations

•  SILO climate database- Australia-wide patched point and gridded climate datasets from 1889, used for research and modelling