Figure 3: (a) Objective analysis of geopotential height and potential temperature at 850 hpa at 12:00 UTC on 25 March 1992. Geopotential contours: every 30 gpm, isentropes: every 2 K, (b) 700 hpa and (c) 500 hpa at the same time and date. Contours are drawn every 60 gpm and isotherms every 2 C. Wind speed above 30 ms-1 is stippled and more than this is shaded with shading increasing every 5 ms-1.