Open AccessTropical Transition of the 2001 Australian Duck
Author(s) -
Luke Andrew Garde,
Alexandre Bernardes Pezza,
John A. T. Bye
Publication year - 2010
Publication title -
monthly weather review
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.862
H-Index - 179
eISSN - 1520-0493
pISSN - 0027-0644
DOI - 10.1175/2009mwr3220.1
Subject(s) - extratropical cyclone , climatology , tropical cyclone , landfall , environmental science , low pressure area , cyclogenesis , middle latitudes , meteorology , cyclone (programming language) , geology , atmospheric sciences , oceanography , geography , atmospheric pressure , field programmable gate array , computer science , computer hardware
In March 2001, a hybrid low pressure system, unofficially referred to as Donald (or the Duck), developed in the Tasman Sea under tropical–extratropical influence, making landfall on the southeastern Australian coast. Here, it is shown that atmospheric blocking in the Tasman Sea produced a split in the subtropical jet, allowing persistent weak vertical wind shear to manifest in the vicinity of the developing low. It is hypothesized that this occurred through sustained injections of potential vorticity originating from higher latitudes. Hours before landfall near Byron Bay, the system developed an eye with a short-lived warm core at 500 hPa. Cyclone tracking revealed an erratic track before the system decayed and produced heavy rains and flash flooding. A three-dimensional air parcel backward-trajectory scheme showed that the air parcels arriving in the vicinity of the mature cyclone originated from tropical sources at lower levels and from the far extratropics at higher levels, confirming the hybrid characteristics of this cyclone. A high-resolution (0.15°) nested simulation showed that recent improvements in the assimilation scheme used by the Australian models allowed for accurately simulating the system’s trajectory and landfall, which was not possible at the time of the event. Compared to the first South Atlantic hurricane of March 2004, the large-scale precursors were similar; however, the Duck was exposed to injections of upper-level potential vorticity and favorable surface heat fluxes for a shorter period of time, resulting in it achieving partial tropical transition only hours prior to landfall.