Observations of a subtropical cold front in a region of complex terrain

At the northern extent of the TAMEX network the cold front was shallow (1-2 km deep) and moderately baroclinic with 5°-7°C temperature contrasts at the surface. A Doppler radar cross section of radial velocity reveals a structure similar to that of a density current at the leading edge of the shallow front. The postfrontal air mass was substantially modified by oceanic heat fluxes as it moved southward over the warm ocean waters. This led to a 60%-70% decrease in the temperature contrast across the front between ocean stations at the northern and southern ends of the island, a distance of ~400 km. The inhomogeneous distribution of precipitation attending the frontal passage is related to strong regional variations in thermodynamic stability across the island. These variations in stability are linked to the mesoscale effects of terrain, and to the larger-scale influence of advection of an unstable tropical air mass into the region by a low-level wind maximum. -from Authors