The code below assumes each file ends with an empty line. You could also search for 'Lat:' instead to determine the beginning of a new file.
data=readfile('https://www.mathworks.com/matlabcentral/answers/uploaded_files/351353/Example.txt');
lastlineoffile=find(cellfun('isempty',data));
lastlineoffile=[0;unique([lastlineoffile;numel(data)])];%add last line just to make sure
for n=1:(numel(lastlineoffile)-1)
currentfile=data((lastlineoffile(n)+1):lastlineoffile(n+1));
fid=fopen(sprintf('aa__file%03d.txt',n),'w');
fprintf(fid,'%s\n',currentfile{:});
fclose(fid);
end
