Cyclone Sam

Throughout its existence, Cyclone Sam brought heavy rainfall to a wide swath of northern Australia. Rainfall peaked at 520 mm (20 in) in Shelamar over a 48-hour period ending on 11 December. Upon making landfall, damage was considerable, albeit localized. Most of the destruction wrought by Sam occurred near the coast, particularly in Bidyadanga and Anna Springs Station. Some buildings sustained considerable damage, and trees and power lines were felled, resulting in some power outages. Offshore, 163 illegal immigrants aboard two vessels were feared to have drowned, which would make Sam one of the deadliest cyclones in Australian history. However, these people were later accounted for. After the season, the name Sam was retired from the regional naming list.

Meteorological history

During an active Madden–Julian oscillatory period over Australian longitudes in late November, a broad low-pressure area developed within the monsoon trough in the southeastern Arafura Sea, west of Cape York Peninsula. Due to its potential for development, the Bureau of Meteorology Tropical Cyclone Warning Center in Darwin (TCWC Darwin) began monitoring the system on 28 November. Tracking westward, the low eventually moved into the Timor Sea three days later and became quasi-stationary in forward motion. Situated within a good outflow environment, the Joint Typhoon Warning Center (JTWC) began monitoring the disturbance at 0300 UTC on 1 December, assessing it with a 'poor' likelihood of cyclogenesis; these probabilities as assessed by the JTWC would increase up until eventual formation. Nonetheless, TCWC Darwin began issuing tropical-related products on the disturbance beginning at 0730 UTC the following day. At 0000 UTC on 3 December, the JTWC analyzed that the tropical low had organized into a tropical depression. Due to weak steering currents, the depression drifted southward and moved ashore the Kimberley coast roughly 90 km (55 mi) east of Kalumbaru; this stint over land was short lived, however, and the system tracked back westward, reentering the warm Timor Sea the following day. Positioned within favorable conditions under a subtropical ridge, the depression began to strengthen. At 0400 UTC on 5 December, TCWC Perth, having assumed local area responsibilities for the tracking of the storm, determined the system to have strengthened into a tropical cyclone. As such, the warning center assigned the name Sam to the storm. Although a tropical cyclone warning was issued twelve hours prior, the JTWC followed suit by classifying Sam as a tropical storm at 1200 UTC the same day.

Upon tropical cyclogenesis on 5 December, the surrounding atmospheric conditions were generally favorable for continued development; however, a northeasterly wind flow generated wind shear, somewhat inhibiting development and partially exposing Sam's low level center of circulation as it tracked westward. Over the following two days, however, the tropical cyclone's rainbands were able to fully enclose the center of circulation. During the evening hours of 6 December, however, Sam began to interact with a shortwave trough, causing the cyclone to curve southward and towards the northwestern coast of Australia. Over the following day, an eye started to form and Sam began to rapidly intensify. At 0400 UTC, the storm attained Category 3 cyclone intensity on the Bureau of Meteorology cyclone scale. Ten hours later, Category 4 intensity was achieved. At the time, Sam had featured an eye measuring 30 mi (48 km) in diameter. Objective Dvorak intensity analysis gave the system a rating of 7.7, corresponding to an estimated intensity of 215 km/h (134 mph). Around the same time, Sam briefly became stationary before resuming its southward trek. Continuing to intensify, TCWC Perth upgraded the cyclone to Category 5 intensity at 2000 UTC, with winds of 195 km/h (121 mph) and a minimum pressure of 950 hPa (mbar; 28.06 inHg). However, in post-storm analysis, it was analyzed that Sam had had in fact peaked with winds of 205 km/h (127 mph) and a minimum pressure of 935 hPa (mbar; 27.61 inHg). The JTWC rated the storm as a Category 3 hurricane on the Saffir–Simpson hurricane wind scale. At the same intensity, Sam made landfall near Lagrange, Western Australia at 1300 UTC on 8 December. Upon moving ashore, Sam began to slowly weaken over the Great Sandy Desert. On 9 December, the JTWC ceased the monitoring of the system, as the weakened Sam began to curve eastward. After a brief period of restrengthening over central Australia on 13 December, Sam finally weakened below tropical cyclone intensity the following day before dissipating shortly thereafter.