function [Ta,sa,ua,va,Tb,sb,ub,vb,Tt,st,ut,vt] = comp_tend(Ta,sa,ua,va, ...
                                   Tb,sb,ub,vb,Tt,st,ut,vt,To,so,uo,vo,f1,f2)

% function [Ta,sa,ua,va,Tb,sb,ub,vb,Tt,st,ut,vt] = comp_tend(Ta,sa,ua,va, ...
%                                   Tb,sb,ub,vb,Tt,st,ut,vt,To,so,uo,vo,f1,f2);
%
% Computes the tendencies in a Runge-Kutta integration
% FS-M, 4/23/09
% 

Tt = Tt + f1 * (Ta-Tb);
st = st + f1 * (sa-sb);
ut = ut + f1 * (ua-ub);
vt = vt + f1 * (va-vb);
Tb = To + f2 * (Ta-Tb);
sb = so + f2 * (sa-sb);
ub = uo + f2 * (ua-ub);
vb = vo + f2 * (va-vb);
Ta = Tb;
sa = sb;
ua = ub;
va = vb;
