The 24-year-old, tipped for a Test debut this summer but not included in the line-up for Lord's Test next week, resumed on 57 on day two of the County Championship clash at the Rose Bowl and his eventual 126 helped the hosts reach 375 for five by stumps.
Former England batsman John Crawley anchored Hants' first innings with a measured 106 from 247 balls, while Greg Lamb weighed in with 42. Glamorgan's bowlers toiled and skipper Robert Croft was their most successful with two for 107.
Leaders Nottinghamshire were in trouble after a sterling performance from Kent paceman Simon Cook at Trent Bridge.
The hosts lost four big wickets for 12 runs inside three overs on the second afternoon as they limped to 169 for nine in reply to 301 by the time rain and bad light brought an early close to a day shorn by bad weather.
Cook ended the day with four wickets at the cost of 38 runs while Darren Bicknell, who managed 63 before being run out, was the only Notts man who can have been happy with his day's work.
In Division Two, wicketkeeper Philip Mustard struck a vital 78 to give Durham a first-innings lead against Yorkshire at Chester-le-Street.
In reply to the visitors' 254, Mustard came to the crease with his side struggling on 146 for six before launching an offensive to swing the game in Durham's favour.
Mike Hussey's men established a 62-run lead by the time they were bowled out, then were in the wickets before stumps.
Yorkshire lost Philip Jaques as they finished the day on nine for one in their second innings.