A low that formed over the Top End and moved over the Joseph Bonaparte Gulf and intensified to cyclone intensity on 4 January and recurved towards the Northern Territory coast. Helen reached category two intensity before making landfall south of Darwin late on 4 January. Although not an intense system, Helen is notable for being the first cyclone to produce gales in Darwin since Tropical Cyclone Gretel in April 1985.
The maximum recorded wind gust was 120 km/h at Charles Point Lighthouse, while Darwin experienced a maximum wind gust of 102 km/h at about 2am CST 5 January. Winds in Darwin were enough to uproot or snap many trees. There were a few houses that suffered damage from trees falling on them. Powerlines also came down when trees fell across them. Approximately 15,000 homes lost power on Friday night, and there was widespread communications disruption.
Widespread 100-200 mm rainfall totals over the weekend of 4-6 January caused some rivers across the western Top End to rise. The Adelaide River at Adelaide River Township reached major flood level during the afternoon of Saturday 5 January. Similarly, the Waterhouse River at the community of Beswick to the east of Katherine was at and near major flood level for most of Sunday and into Monday. The Katherine River at Nitmiluk Centre reached minor flood level on the afternoon of Sunday 6 January.
Tides along the west coast of the Top End were neap on the evening that TC Helen made landfall, with tide levels remaining several metres below Highest Astronomical Tide level. This largely contributed to the lack of storm surge damage to coastal areas.
For more details see the TC Helen Report (pdf)
Track and intensity
All times in CST.