Sunday, 22 January 2012
An Analysis on the 7-10 November 2011 “Medicane” using the WRF-ARW
Hall E (New Orleans Convention Center )
Tropical cyclones (TC) that develop across the Mediterranean are considered a very rare occurrence with only six such storms being documented over this region since 1947. On 5 November 2011, a mesoscale low developed just east of the Balearic. One day later, the storm began to show characteristics that are generally associated with TCs despite the unfavorable sea surface temperatures of 19 C. The storm later made landfall in southern France on 9 November at 0000 UTC with sustained winds of 45 kts. Most of the global numerical weather models that cover this region of the world, such as the US GFS, CMC and UKMET models, failed to accurately forecast the storm's movement within a day of its actual landfall. This was likely due to the insufficient spatial resolution of the global models needed to accurately resolve the mesoscale features of this storm.
To resolve this issue, a customized high-resolution Advance Research WRF (WRFARW) with a two-way nested domain centered over the Balearic Sea was used simulate the storm. The domains used for this model had 12- and 4-km horizontal resolution with 35 vertical levels. The WRF-ARW analysis revealed that the storm developed a deep warm core on the 7 November at 0000 UTC and maintained it up through its eventual landfall. Weak low-level baroclinicity was also observed with the storm however, it was ultimately concluded that due to the storm's warm core and symmetric wind and pressure fields it was likely a tropical system. For this storm, the WRF-ARW model was much better at forecasting the system's behavior than the other operational model forecasts examined here.