There must be a lot of work to do still between "sliding down the ways" and commissioning.
http://www.history.navy.mil/faqs/faq108.htm
Fitting Out and Commissioning
Christening and launching are the inseparable elements which endow a ship hull with her identity. Yet, just as many developmental milestones must be passed before one takes his place in society, so too must the newly-launched vessel pass such milestones before she is completed and considered ready to be designated a commissioned ship of the United States Navy. The engineering plant, weapon and electronic systems, galley, and multitudinous other equipment required to transform the new hull into an operating and habitable warship are installed and tested. The prospective commanding officer, ship’s officers, the petty officers, and seamen who will form the crew report for training and intensive familiarization with their new ship. Crew and ship must function in total unison if full potential and maximum effectiveness are to be realized. The most modern naval vessel embodying every advantage of advanced technology is only as good as those who man her.
Prior to commissioning, the new ship undergoes sea trials during which deficiencies needing correction are uncovered. The preparation and readiness time between christening-launching and commissioning may be as much as three years for a nuclear-powered aircraft carrier to as brief as twenty days for a World War II landing ship. Monitor, of Civil War fame, was commissioned less than three weeks after launch.
I think that there will be tremendous upgrades in radio, radar, and AAA gunnery between November 1941 and mid-1942.