linux - Fail to redirect log to /var/log/syslog

I have an upstart script that does the following

start on runlevel [2345]
stop on runlevel [06]

respawn

pre-start script
    exec >/dev/kmsg 2>&1
    REPO=git@github.com:blabla/bli
    mkdir -p /var/log
    mkdir -p /var/www
    echo "Fetching app from $REPO"
    girror $REPO /var/www
    if [ -f /var/www/package.json ]; then
        echo "Installing npm modules"
        cd /var/www
        npm install
    fi
end script

post-stop script
    exec >/dev/kmsg 2>&1
    echo "stopped"
end script

script
    exec >/dev/kmsg 2>&1
    export NODE_ENV=production
    export port=80
    echo "Starting app.js on port 80"
    cd /var/www
    node app.js
end script

I am running the script as root. The log files of the application suppose to go to /var/log/syslog but they don't go there.

However, I do see the app log when running dmesg | tail -f

Using kernel 3.5.0-46

Anyone know why it doesn't work ?