When the Cohort-III was introduced it was decided that the older FireBlossom and ThunderStorm Class Starships would be decommissioned. The Cohort-III outguns the FireBlossom, and the Thunderhead was showing a lot of age. As the ThunderStorm was the SDF's only dedicated carrier it was decided that a specific varient of the Cohort-III would be constructed as a stop-gap until a new dedicated carrier could be designed. It would carry less fighters, but due to it's smaller size and heavier armor it would have a higher survivability. Until the new carriers are produced in significant numbers the ThunderStorm's will remain active, though the FireBlossoms are being decommissioned and sold.

Cohort-IIIA Class Specifications
Production Data
Origin: Republic of Sunset
Class and Type: Cohort-IIIA Class Fleet Carrier
Date Launched: 2310

Hull Data
Structure: 30
Size/Decks: 7/12 Decks
Length/Height/Beam: 478/80/248 Meters
Complement: 420

Operation Data
Transporters: 4 Personal, 4 Cargo
Cargo Units: 50
Shuttle Bay: 20
Shuttle Craft: 23 Size Worth (2 Personal, 1 Cargo, 40 DA-100 Fighters)
Tractor Beams: 1 AV, 2 FV
Separation System: No
Sensor System: Class 3 (C)
Operations System: Class 4 (D)
Life Support: Class 3 (C)

Propulsion Data
Impulse System: Type IV (.5C) (E)
Warp System: Type IIIA (Warp 3/6/6.5) (E)

Tactical Data
Phaser Arrays: Type IX (1F, 1FS, 1FP, 1MD, 1MV, 1AP, 1AS, 1A, x8, D)
Penetration: 6/6/6/0/0
Photon Torpedos: Type V (4F, 2A, 1D, 1V, 1P, 1S, x10, C)
Penetration: 7/7/7/7/7
Deflector Shield: Class 5 (D) / Class 4 (C)
Protection/Threshold: 15/3 / 14/4

All specifications are as per the Star Trek RPG.