A warm-front triggered nocturnal tornado outbreak near Kiama, NSW, Australia

This paper documents the case of a nocturnal outbreak of tornadoes on the New South Wales (NSW) south coast on 23 February 2013, and provides an analysis of the conditions that led to the outbreak. These tornadoes were associated with the passage of a warm front which had developed on the eastern flank of a mature extratropical cyclone.The damage from the tornadoes is discussed, and an analysis of the synoptic and mesoscale conditions that led to the event is provided. An analysis of radar at the time of the event shows a series of vortices developing within a zone of horizontal shear just prior to the tornadoes developing. The tornadoes were difficult for operational forecasters to predict, partly due to the infrequent occurrence of nocturnal tornadoes of this type in NSW, and in part due to operational demands from the broader scale severe weather event that resulted from the low-pressure system. This paper presents an analysis of the event that may assist forecasters in identifying similar events in the future.

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Cycad killer, qu'est-ce que c'est? Dieback of Macrozamia communis on the south coast of New South Wales

Australian Journal of Botany ◽

10.1071/bt20071 ◽

2021 ◽

Vol 69 (2) ◽

pp. 102

Author(s):

Keith L. McDougall ◽

Penelope J. Gullan ◽

Phil Craven ◽

Genevieve T. Wright ◽

Lyn G. Cook

Keyword(s):

New South ◽

New South Wales ◽

Scale Insect ◽

South Coast ◽

Management Tool ◽

Sufficient Evidence ◽

Cultivated Plants ◽

The South ◽

Extreme Caution ◽

South Wales

The association of an armoured scale insect (a diaspidid) with dieback of a population of a native cycad (Macrozamia communis L.A.S.Johnson) was investigated on the south coast of New South Wales. The diaspidid was found to be undescribed but morphologically similar to oleander scale – here we call it Aspidiotus cf. nerii. It is probably native to Australasia and its current known distribution is within Murramarang National Park (MNP). Aspidiotus cf. nerii has been abundant on symptomatic M. communis at MNP over at least the past decade and has spread to new parts of the park. In population studies of infested and uninfested areas we found that, although both areas had populations with reverse J curves showing dominance of seedlings, mortality of seedlings and caulescent plants was significantly higher in infested sites. Infested areas had been burnt less frequently than uninfested areas. Fire does not appear to eradicate the diaspidid but may reduce its effects enough for plants to recover. We recommend further research into the use of fire as a management tool. Although other factors may be contributing to the severity of the dieback, we suggest there is sufficient evidence for the diaspidid to be regarded as the primary cause of dieback in M. communis in MNP, regardless of its origin. Given the occurrence of similar diaspidids on cultivated plants in botanic gardens, translocation of threatened Macrozamia species using plants grown in nurseries should be undertaken with extreme caution.

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Characterizing severe weather potential in synoptically weakly forced thunderstorm environments

10.5194/nhess-2017-291 ◽

2017 ◽

Author(s):

Paul W. Miller ◽

Thomas L. Mote

Keyword(s):

United States ◽

High Resolution ◽

Numerical Model ◽

Model Error ◽

Severe Weather ◽

Forecasting Model ◽

Weather Event ◽

Southeast United States ◽

Accurate Representation ◽

Severe Weather Event

Abstract. Weakly forced thunderstorms (WFTs), short-lived convection forming in synoptically quiescent regimes, are a contemporary forecasting challenge. The convective environments that support severe WFTs are often similar to those that yield only nonsevere WFTs, and additionally, only a small proportion individual WFTs will ultimately produce severe weather. The purpose of this study is to better characterize the relative severe weather potential in these settings as a function of the convective environment. Thirty near-storm convective parameters for > 200 000 WFTs in the Southeast United States are calculated from a high-resolution numerical forecasting model, the Rapid Refresh (RAP). For each parameter, the relative likelihood of WFT days with at least one severe weather event is assessed along a moving threshold. Parameters (and the values of them) that reliably separate severe-weather-supporting from nonsevere WFT days are highlighted. Only two convective parameters, vertical totals (VT) and total totals (TT), appreciably differentiate severe-wind-supporting and severe-hail-supporting days from nonsevere WFT days. When VTs exceeded values between 24.6–25.1 °C or TTs between 46.5–47.3 °C, severe-wind days were roughly 5 × more likely. Meanwhile, severe-hail days became roughly 10 × more likely when VTs exceeded 24.4–26.0 °C or TTs exceeded 46.3–49.2 °C. The stronger performance of VT and TT is partly attributed to the more accurate representation of these parameters in the numerical model. Under-reporting of severe weather and model error are posited to exacerbate the forecasting challenge by obscuring the subtle convective environmental differences enhancing storm severity.

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