Depending on the installation of tomcat, I have seen instances where catalina.pid is not defined. In this case, shut down tomcat, and define it yourself thusly:
In tomcat/bin/setenv.sh, add this line:
CATALINA_PID="$CATALINA_BASE/bin/catalina.pid"
or for windows (in setenv.bat): set CATALINA_PID=%CATALINA_HOME%/bin/catalina.pid
This will define and create the pid file in the tomcat/bin folder, assuming your CATALINA_HOME is defined as your tomcat folder. However, you may also change the location of the pid file, by just changing the path above.