Earlier in the week, Southorn produced a solid performance in the 500m Time Trial racing in the C5 division but alongside all the female para-cyclists - claiming silver and setting another personal best time of 41.98. Her efforts during the meet earned her enough points to win the Oceania Championship title.
"It's pretty exciting setting some personal bests ... it's a great start to the season, and hopefully a good omen for the rest of the summer," she said.
Southorn will return to Invercargill again in two weeks time for the Southland Track Championships, where she expects to be racing against another strong field.
Southorn is using these early-season meetings to prepare for the 2012 UCI Para-cycling Track World Championships, in Los Angeles from February 10-12, where the New Zealand team will be up against 230 athletes from 30 countries.
Manawatu sprinter Simon Van Velthooven showed real maturity in his young career with a superb victory in keirin on the third night of finals last night.
The 22-year-old produced a massive effort in the final thrust at the line to edge out Australian champion Scott Sunderland.
It was van Velthooven's third gold medal this week after national records in winning the team sprint and 1000m time trial.
Van Velthooven has been the fourth rider among the burgeoning sprint group but his performances have forced him into real consideration for next year's London Olympics.
Earlier world silver medallist Shane Archbold showed speed and skill to claim the lead after three events of the men's omnium at the ILT Velodrome.
Archbald (Timaru) produced a personal best to win the Flying Lap and disappointed for fifth in the Points race earlier in the day, before bouncing back to win the Elimination race.