Numerical simulation of tropical island thunderstorms (Hectors) during the ACTIVE campaign

During 2005-2006, ACTIVE and two other joint field campaigns were conducted near the Tiwi Islands, north of Darwin, Australia where a local thunderstorm, known as Hector, was very well observed. The dataset collected during the campaign are used to validate a meso-scale model using different set-ups. Four cases of the Hector storm were simulated by running the WRF model in two modes: with or without incorporating local enhanced observations. In the 'operational forecast mode' (OP) the model was run in triply nested domains, with model initial and lateral boundary conditions provided solely by operational global analyses, and the finest domain having a horizontal resolution of 1 km. In the 'observed data incorporation mode' (DI) the model used a single domain at 1 km horizontal resolution, with either radiosonde or aircraft data incorporated during the run. All runs were validated against available observational data. The results showed that only one in four Hector cases was well simulated by the OP mode run, while three other Hector cases were simulated well in the DI mode. For all Hector-produced runs the general evolution and microphysical structure of the storm were reasonably simulated with some notable differences. A large deficiency in all the simulated storms was their smaller size and weaker intensity in comparison with the observed storms. © 2012 Royal Meteorological Society.