Well. this time it seems to be very simple :

yum –releasever=13 upgrade

update 22/April/2010:
The key file will not be there so there are two options for you in this case:

1. Install the following rpms from the downloaded rpms with ”yum –nogpg localinstall”
   a) fedora-release
   b) fedora-release-notes
2. Run the whole upgrade with –nogpg option.

Issue observed after the upgrade:
The new kernel was not added in the grub menu and I had to manually add the below entry in the <a class="zem_slink freebase/en/gnu_grub" title="GNU GRUB" rel="homepage" href="http://www.gnu.org/software/grub/">menu.lst file:

title <a class="zem_slink freebase/en/fedora" title="Fedora" rel="homepage" href="http://fedoraproject.org/">Fedora (2.6.33.1-24.fc13.i686.PAE)
root (hd0,11)
kernel /boot/vmlinuz-2.6.33.1-24.fc13.i686.PAE ro root=UUID=f832d6ce-dad3-4af9-9ef1-aac950f8284c rhgb quiet SYSFONT=latarcyrheb-sun16 LANG=en_US.UTF-8 KEYTABLE=us <a class="zem_slink freebase/en/init" title="Init" rel="wikipedia" href="http://en.wikipedia.org/wiki/Init">init=/sbin/bootchartd

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