[1] European Ctr Medium Range Weather Forecasts, Reading RG2 9AX, Berks, England
[2] Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA
[3] Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA
[4] Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA