WxSIM Chart Errors

I upgraded my OS and my version of PHP to 5.6.12 and my WxSIM Chart is no longer working. I have had a bit of trouble getting some of the scripts on my site working and I think I’m down to the last one needing fixed.

I get a flood of the following when I try to run this script:

PHP Notice: Undefined variable: offest in C:\inetpub\weathercat\wxsimchart\meteogram\highchart.wxsim.php on line 109 PHP
http://www.weathercat.net/wxsimchart/

Here is what the page looked like.
https://web.archive.org/web/20140305085035/http://www.weathercat.net/wxsimchart/

I know this is an older script and may not be compatible with my version of PHP but when looking for a new version I keep running into broken download links.

Can someone help me fix this or point me to something similar that may work for me?