29 Mar Driest QLD Summer since 1989-90 – Really?
Driest QLD Summer since 1989-90 – Really?
It is surprising that with the copious amount of rain we have had in recent weeks brought to us by a so-called weak and short-lived rain-bringing La Niña, that this has been the driest summer since 1989-90 for Queensland. The 2017-18 summer has also been the second warmest on record.
Despite generally dry conditions, severe thunderstorms were reported in various parts of Queensland throughout the summer, bringing large hail, strong winds and flash flooding, and the wettest summer day on record to a few sites.
Brisbane received more than 300 mm of rainfall in February, more than twice the long-term average. Severe thunderstorms and showers developed over Brisbane and resulted in three-day rainfall totals of more than 200 mm at some locations.
- Greenbank had its wettest February on record on 24th of February while a number of locations had their wettest February in several decades.
Climate outlook for April to June
The weak 2017–18 La Niña has been active since December 2017, has ended. El Niño–Southern Oscillation (ENSO) indicators have eased back to neutral levels over the past several weeks. This means the ENSO Outlook has shifted from LA NIÑA to INACTIVE. A neutral ENSO state is forecast to persist through the forecast period.
Although El Niño brings a dryer period, it does not necessarily mean average rainfall and temperature for Australia. Accoring to BOM, it rather indicates a reduced chance of prolonged widespread very wet/dry or very hot/cold conditions. Other climate drivers may have greater influence over the coming months.
What is La Nina and Le Nino?
The term El Niño translates from Spanish as ‘the boy-child’. Peruvian fishermen originally used the term to describe the appearance, around Christmas, of a warm ocean current off the South American coast. It is now the commonly accepted term to describe the warming of the central and eastern tropical Pacific Ocean. La Niña translates as ‘girl-child’ and is the opposite ENSO (El Niño–Southern Oscillation).
La Niña is sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO. These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.
El Niño occurs more often than La Niña and the ENSO cycle loosely operates over timescales from 1 to 8 years.
During the El Niño cycle we generally experience reduced rainfall, warmer temperature, higher risk of bush fire and reduced risk of tropical cyclones. During the peak of El Niño, the ocean surface temperature is higher than normal.
The La Niña cycle, on the other hand brings us heavy rain and increased flood and tropical cyclone risk, and decreased bush fire potential. During its peak, the ocean surface temperature is lower than normal.
For more information about the 3 phases of the El Niño–Southern Oscillation (ENSO): https://www.bom.gov.au/climate/enso/history/ln-2010-12/three-phases-of-ENSO.shtml