Midterm Colloquium by Daniel Jurlander – Niels Bohr Institutet - Københavns Universitet

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Midterm Colloquium by Daniel Jurlander






An analysis of Medicane M01, based on model output from The Weather and Research Forecasting Model, WRF

Abstract:
In 2011 NOAA, for the first time ever, characterized a weather system in the Mediterranean as being tropical. The cyclone was named M01 and occured from the 7 to 9 November of 2011. K. Emanuel (2005) analyzed a case study of a small scale Mediterranean hurricane, Medicane, that occured in January, 1995. He found that these smallscale cyclones can develop when a deep upper level cut off is located over the Mediterranean. This enables the development of a thermodynamically driven warm core cyclone over sea.

A detailed analysis of the Medicane M01 is provided, from hindcast simulations run in WRF (The Weather and Research Forecast Model). Output from the model are computed on a parent 27km X 27km grid for the parent domain and a smaller 9 X 9km nested domain. It is clear that the life cycle presented by Emanuel among others, is also dominating this case. Once a high level cold trough brakes off as a cut-off low on 5 november and moves over the relatively warm Mediterranean Sea, a convective process is started. This creates a new equvialent barotropic surface low, which intensifies the following days, becoming clearly recognizable on 6 november, from satellite observations.

The cyclone follows a path starting off the northeast coast of Spain moving southeastward, then turning northward just before Sardinia, and from here moving northwestward to the French coast. Finally, the cyclone dies when it makes landfall on the Mediterranean coast of France. This indicates that the cyclone is fueled from the thermal disequilibrium between the relatively warm water and the cold trough at height.

I will present a brief introduction to the WRF model, provided by NCAR, going on to describing the synoptic situation found from model outputs in the period of interest. Finally, focus on the vertical structure of the cyclone is discussed from cross section plots taken through the center of M01.