Storrie added: "Jerome could have been recalled by Charlton in January under the terms of his loan but that is no longer a factor now his deal has been made permanent."
Thomas made his debut for Pompey in the 4-0 defeat at Chelsea on the opening day of the Premier League season.
The 25-year-old had been at Charlton since January 2004 and would have been out of contract with the Addicks next summer.
Thomas began his career as a schoolboy with Luton before moving to Arsenal in 2001.
The former England Under-21 international also had two loan spells at QPR but failed to land a regular first-team spot with the Gunners.
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