Weather, climate
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- 3 November 2015 - Record hot October, and more heat to come. WA, SA, NSW, VIC and TAS have all recorded their hottest Octobers since reliable records began at the beginning of last century. NSW was outstanding, with the statewide average temperature 4.52°C above the historical average and a remarkable 1.94°C above the previous record, set only last year. The NT and QLD were also above average. Much of the anomaly came from an early season hot period (see report for 14 October).
Although the current stormy days in SE Australia seem to contradict it, the Bureau of Meteorology's current ENSO Wrap-Up shows that a strong El Niño and positive Indian Ocean Dipole persist, with the duration of the El Niño now in record territory. The Bureau says "All NINO indices have now been above +1°C for 11 consecutive weeks, equalling the previous record. Recent bursts of westerly winds in the tropics means some further warming remains possible. All models indicate that the strong El Niño is likely to persist until the end of the year, before a marked decline during the first quarter of 2016."
These two strong climatic influences have also dominated the Bureau's Climate Outlook for the next three months, though it's worth noting that chances of warmer and drier conditions are mostly in coastal and immediate inland areas with those farther from the coast more likely to be wetter and cooler than average. Southern WA in particular bucks the trend with strong chances of above average rainfall from November to January, though temperatures there still have a strong likelihood of being above average.
- 23 October 2015 - 2015 shaping up to be hottest on record globally. The US National Centres for Environmental Information (NOAA) released its monthly report yesterday showing that last month was the hottest September globally in the last 136 years, beating the previous record set last year. It was also the greatest global departure above monthly average temperature on record for any month, beating previous records set in February and March this year. This map, provided by NOAA and compiled from surface and satellite observations, shows departures from average around the globe for September and you can see there are few areas of below average temperature.
2015 has been running well above record levels in year-to-date temperatures as well. This NOAA chart, which shows accumulating departure from normal since the start of the year, paints a remarkable picture. 2015 is shown in black, while the previous six hottest progressive year-to-date figures, all occurring since 1998, are plotted in different colours below. To put it in a broader perspective, this NOAA chart shows the same figures for all years of record since 1880.
- 17 October 2015 - Hot dry summer forecast for much of the continent. The International Research Institute for Climate and Society at the Earth Institute, Columbia University, USA, which has been making experimental long-term forecasts since 1997, is forecasting only a slow decay of dry, hot climatic influences for Australia, with relief not forecast until autumn, 2016. As with the Bureau's outlooks, IRI uses a combination of models to produce its forecasts, the practical difference being that it forecasts further into the future.
Maps showing forecast likelihoods of precipitation and temperature being above normal, normal and below normal are available in 3-monthly "seasons" through to February-April here. Select "Australia" from the drop-down Region menu, "Precipitation" or "Temperature" from the Forecast Type, then any season from the Target Season menu. Click the Show Discussion link above the map to get details on the methods used and, probably of more interest to most, the actual outlook and summary forecasts which begin about half-way down.
IRI's Quick Look ENSO forecast page (El Niño, La Niña, and the Southern Oscillation) shows how 25 global climate models are forecasting it through until the July to August quarter 2016, and presents graphs that show the consensus of these forecasts. They show that ENSO is likely to stay in strong El Niño mode until the March-May quarter, after which a rapid return to neutral conditions begins.
The forecast strength of this El Niño, compared to the super El Niño of 1997-8, was described in this ABC News story published yesterday, 16 October, based on new information from NASA and NOAA.
- 14 October 2015 - Fewer tropical cyclones expected this cyclone season. An average tropical cyclone season (1 November to 30 April) sees 11 cyclones in the Australian region of which 4 cross the coast. 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), the Bureau of Meteorology produces a Tropical Cyclone Season Outlook, the latest of which was published on Monday. The outlook is for fewer than normal cyclones this season, due mainly to the strong El Niño. The chances of an above average year for Australia as a whole is a meagre 9%. See the outlook for regional breakdowns, interpretations and how the outlook is produced.
- 14 October 2015 - Hot start to October across most of the country. Everywhere except the NT and QLD experienced an exceptionally warm start to October, with temperatures at least 12C above average across southern Australia during at least one day. Early season temperature records were set from SA to TAS and followed the third driest September on record nationally. The heat was notable for its duration as well as its intensity, with records for number of consecutive days over 35C set at a number of locations from the WA/SA border to the NSW Riverina. A very detailed Special Climate Statement (pdf) has been issued by the Bureau to cover the event.
- 13 October 2015 - Latest ENSO Wrap-Up confirms drier, warmer shift in models. The Bureau's latest ENSO Wrap-Up and October to February Climate Model Summary issued today confirm that the two major climatic teleconnections operating either side of Australia, an El Niño in the Pacific and the Indian Ocean Dipole, will be working together during the next few months to produce much warmer, drier conditions over a large part of the continent for the next few months. While the 2015 El Niño is the strongest seen since 1997, its equivalent in the Indian Ocean—the positive Indian Ocean Dipole (IOD)—is now at levels not seen since late 2006.
Fortunately, the IOD anomaly is expected to be short-lived, with four out of five of the major climate models indicating that it will decline rapidly from late November as the monsoon trough moves into the northern Indian Ocean. The El Niño is not expected to weaken until the first quarter of 2016.
- 7 October 2015 - Sudden change to long-term forecast. For the first time, the Bureau of Meteorology has issued an amendment to its regular monthly Climate Outlook series. The current outlook covers the period from October to December this year. While a strong El Niño continues, it has been offset until very recently by a neutral Indian Ocean Dipole (IOD), the result of very warm waters across much of the Indian Ocean. Although the Indian Ocean during the winter this year was at its warmest since at least 1950, a sudden cooling of waters to the northwest of Australia has now been detected, pushing the IOD in September to the highest positive values since 2006. As these reinforce the effects of El Niño, a very dry October is now more likely, and there are very high probabilities of October to December being well above average temperature, especially in the southern half.
Full details are in the Bureau's Climate Outlook, and also the fortnightly ENSO Wrapup. Also useful is the Climate Model Summary for the next five months, issued around the middle of each month.
This will come as bad news for those that have been battling bushfires, especially in Victoria and Tasmania. It follows a September that was dry to very dry across much of the continent. It was among the 10 driest Septembers on record for WA, VIC and TAS. Here are a map of September rainfall deciles and the Bureau's October Drought Statement.
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