"Marsupial" tracking is a real-time, experimental forecast product to track the wave "pouch" and predict the tropical cyclogenesis location using global model operational data.
Cartoon of the marsupial pouch of tropical cyclogenesis associated with African easterly waves. The dashed green contours depict the horizontal wind currents of the easterly wave in the earth-based reference frame in the lower atmosphere, which is usually open with an inverted V pattern. The solid black curves delineate the approximate boundary of the marsupial wave pouch as viewed moving with the easterly wave. The pouch tends to protect the moist air motions inside from the generally hostile environment, such as dry air associated with the Sahara Air Layer (SAL) that flows westward from the African Sahel. Once the “joey” has attained sufficient spin within the pouch they can exist on their own and leave the mother pouch usually moving northward relative to the mother wave. The thick purple line (CL) and black line represent the critical latitude and the trough axis, respectively. The intersection of the critical line and the trough axis pinpoints the center of the pouch, which is the preferred location for tropical cyclogenesis.(Wang, Montgomery and Dunkerton 2009).
The product is based on the marsupial paradigm for tropical cyclogenesis presented in a recent study by Dunkerton, Montgomery and Wang 2008 (EGU's Atmospheric Chemistry and Physics, hereafter DMW08). The marsupial paradigm indicates that the critical layer of a tropical easterly wave is important to tropical storm formation because (see the schematic on the right)
It has been shown in DMW08 and Wang, Montgomery and Dunkerton (2009, GLR) that genesis tends to occur near the intersection of the critical surface and the trough axis of the precursor parent wave, which is the center of the pouch.
The objective of marsupial tracking is to track the wave pouch (rather than the diabatic vortices inside the pouch), estimate its propagation speed and predict the genesis location, which can be used to provide useful guidance for flight planning during the NOAA hurricane field campaign as part of NOAA/IFEX and the upcoming field experiments NSF-PREDICT and NASA-GRIP in summer of 2010.
USA Today recently published an article on the research being done on the new paradigm of marsupial theory. A copy of the article that appeared in the print version is available for download as a PDF file.