The condominium market is about to get worse as many cities brace for a flood of new supply this year

More than 4,000 new units will be completed in both Atlanta and Phoenix by the end of the year. Developers in Miami and Fort Lauderdale, Fla., are readying nearly 10,000 total new units in a market already struggling with canyons of unsold condos. San Diego, another hard-hit region, will add 2,500 units, according to estimates provided by Reis Inc., a New York-based real-estate-research firm.