nx=120;
ny=31;
nz=29;
nf=4; % covers u, v, w, and theta
h=zeros(nf*nz*ny*nx,1);

vectorsize=nx*ny*nz*nf;
dim=1; % current dimension in loop
obs=0; % observation counter
fid = fopen('hfile.txt','w');

for i=1:nf
   for j=1:nz
      for k=1:ny 
        for l=1:nx
            if ((any(j==[5 10 15 20 25]) & ... % 5 levels...
                 any(i==[1 2]) & ...  % of u and v...
                 k>8 & ...  % that clear the center...
                 mod(l,3)==0 ) | ... % every third "spoke", plus...
                (i==4 & ... % theta...
                 any(k==[9 30]))) % in the vert boundary layers
                 h(dim)=dim;
                 fprintf(fid,'%i\n',dim);
                 obs=obs+1;
            end
            dim=dim+1;
         end
      end
   end
end
fclose(fid);
obs
h3=reshape(h,[nx,ny,nz,nf]);