2019-20 Australian region cyclone season (Cyclone Watchers 435)

The 2019–20 Australian region cyclone season is the period of the year when most tropical cyclones form in the southern Indian and Pacific Oceans between 90°E and 160°E. The season will officially run from 1 November 2019 to 30 April 2020; however, a tropical cyclone could form at any time between 1 July 2019 and 30 June 2020 and would count towards the season total. During the season, tropical cyclones will be officially monitored by the Australian Bureau of Meteorology (BOM), the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG), and the National Weather Service of Papua New Guinea. The United States' Joint Typhoon Warning Center (JTWC), and other national agencies such as the Fiji Meteorological Service (FMS), the Meteorological Service of New Zealand (MetService), and Météo-France at La Réunion, will also monitor parts of the basin during the season.

The first system, Blake, made landfall in Queensland and caused damage $400 million USD.

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Seasonal Forecast
Ahead of the cyclone season formally starting on November 1, the BoM, Fiji Meteorological Service  (FMS), New Zealand's MetService and National Institute of Water and Atmospheric Research  (NIWA)  and various other Pacific Meteorological services, all contributed towards the Island Climate Update tropical cyclone outlook that was released during October 2019.[2] The outlook called for a near-average number of tropical cyclones for the 2019–20 season, with nine to twelve named tropical cyclones, predicted to occur between 135°E and 120°W, compared to an average of just over 10.[2] At least four of the tropical cyclones were expected to intensify further and become severe tropical cyclones, while it was noted that a Category 5 severe tropical cyclone could occur during the season.[2] In addition to contributing towards the Island Climate Update outlook, the BoM issued seven seasonal forecasts for various parts of the Australian region and South Pacific basin.[1][3] For the entire Australian region between 90°E–160°E, the BoM predicted that the season would feature, a below-average amount of systems with only a 35% chance of more tropical cyclones.[1] The BoM also thought that their self defined Western and Eastern regions, would both have a 57% chance of fewer tropical cyclones than normal developing.[1] Their northern region and northwestern subregion would also see fewer tropical cyclones than normal, with only a 36% and 39% chance of more tropical cyclones than average.[1] The BoM also issued two seasonal forecasts for their self-defined eastern and western regions of the South Pacific Ocean.[3] They predicted that the Western region between 142.5°E and 165°E, had a 54% chance of seeing activity above its average of 4 tropical cyclones. The BoM also predicted that the Eastern Region between 165°E and 120°W, had a 41% chance of seeing activity above its average of 7 tropical cyclones.[3]

The outlooks accounted for the effects of various major Australian climate drivers, namely the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The BOM noted that sea surface temperature anomalies across the equatorial Pacific Ocean had been characteristic of a neutral ENSO phase since April. The international climate models utilised by the BOM also indicated that the neutral conditions would likely persist until at least February.[1] A neutral ENSO phase typically has little influence on the Australian climate.[4] Warmer than average sea surface temperatures in the central and western tropical Indian Ocean and cooler waters near Indonesia and northern Australia, indicating a positive IOD phase, had also persisted since May.[5] The temperature difference increased throughout the year, and at the beginning of October, the BOM noted that the sea surface temperature anomaly of +1.76 °C was the highest observed value on record (since 2001).[6] The anomaly continued to increase rapidly after this, with the value reaching +2.15 °C a fortnight later.[4] The record-strength positive IOD contributed to the development of a region of higher than normal atmospheric pressure across northern Australia during September, after having remained near neutral throughout winter. The BOM noted that these factors also contributed to the tropical cyclone season outlook.[1] .

Seasonal Summary
The season started earlier with the formation of Tropical Cyclone Blake. Blake made landfall in Queensland. The activity continued with the formation of Tropical Low 02U.

Tropical Cyclone Blake
A low-pressure area formed in the western Great Barrier Reef. The system intensified into Tropical Low 01U. 01U rapidly organized into Tropical Cyclone Blake. Blake intensified and reached peak intensity. Blake made landfall in Queensland and dissipated on October 31. Blake caused $400 million USD damage in Queensland.

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