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2013–2014 Australian tropical cyclone season outlook
By: AussieStorm , 2:02 AM GMT on November 02, 2013
Near average cyclone season most likely for Australia
* Near average tropical cyclone activity is most likely for the Australian region this season.
*The tropical Pacific Ocean, which affects tropical cyclone activity in Australia, is currently neutral (neither El Niño nor La Niña), meaning there is no strong shift expected in the average number or location of tropical cyclones.
The typical Australian tropical cyclone season:
*has most tropical cyclones between 1 November and 30 April;
averages around 11 tropical cyclones;
*sees an average of four tropical cyclones cross the coast, though coastal impacts can be felt when tropical cyclones remain well offshore;
*on average has its first cyclone cross the coast in late December
Chance of above average tropical cyclone (TC) activity
The above outlook is based upon the status of the El Niño - Southern Oscillation (ENSO) over the preceding July to September period. In 2013, neutral conditions were present during these months in the Pacific. Neutral conditions are also forecast to continue through the southern Summer. In the absence of El Niño or La Niña (i.e., neutral years), tropical cyclone numbers around Australia are most often close to average, though individual years can be above or below the long term mean.
Before a tropical cyclone forms it is difficult to predict its exact strength and path, including whether it will make landfall. Along the east and west coasts fewer than half of the cyclones impact onshore areas, with the majority staying out to sea. Conversely, along the north coast more than half of the cyclones impact the coast. Tropical cyclones which remain out to sea can still cause storm surges, gales and areas of heavy/flooding rainfall over land.
Even after a tropical cyclone has passed, or has decayed below tropical cyclone strength, significant flooding may occur. The impacts of flooding may be more widespread than the area impacted by the cyclones damaging winds. The Bureau's flood warning services are an integral part of the response to tropical cyclones.
During the cyclone season, ensure you are well informed of any warnings from the Bureau of Meteorology and instructions from local Emergency Services authorities.
About this outlook
This outlook is produced using statistical relationships between tropical cyclone numbers and two indicators: the Southern Oscillation Index (SOI) and the Niño3.4 sea surface temperature index (NINO3.4 SST). These indicators provide a measure of the strength of the atmospheric and oceanic state, respectively.
The July, August and September SOI and NINO3.4 values were used in making the Australian tropical cyclone season outlook.
The current status of ENSO can be viewed via the Bureau's ENSO Wrap-up. Tropical Pacific Ocean temperatures have been neutral since October 2012. This means that the sea surface temperature patterns in the Pacific are neither La Niña nor El Niño and is therefore not driving the Australian Region toward significantly more or fewer tropical cyclones than average. As such, the forecast is suggesting a season closer to average.
Over the entire Australian Region, this statistical relationship has proven to be highly accurate, or a skilful way to forecast tropical cyclone activity. However, across the various sub Regions this relationship, and thus forecast skill, can vary. Some regions have much higher forecast skill than others. The North-western sub-region has good skill, while the Western and Eastern regions both have low skill and the northern region has very low skill. Regardless of the region or the skill of the statistical model, there is currently nothing in the broad climate drivers to suggest anything but a typical tropical cyclone season for Australia and the sub Regions.
Australia's area of responsibility for tropical cyclone services is divided between three Tropical Cyclone Warning Centres: Perth, Darwin and Brisbane. Please note, for statistical reasons, the regions described in the outlook differ slightly from the regional boundaries used by the Tropical Cyclone Warning Centres, below. However outlooks may be considered generally indicative of each area.
This blog is thanks to the Commonwealth of Australia, Bureau of Meteorology. Link
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