Small Transport; Low Wing; 2 Turboprop Eng
Air Traffic Control Fully Certified
Air Traffic Control Radar 20; Air Traffic Control Time Certified In Pos 1 (yrs) 3
Training / Qualification; Time Pressure; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors; Weather
Aircraft inbound to UDD IFR. Developmental was busy working numerous IFR arrivals into PSP. Aircraft was cleared down to 7;000 [FT] and assigned vector 110 for descent. Pilot kept asking for lower due to moderate turbulence descending out of 10;000 [FT]. The developmental responded that due to the MVA he could expect lower in 3 miles. The pilot then responded that he would need lower as soon as we could give him a descent. The developmental then issued a vector of 180 heading to get the aircraft out 7;000 MVA. When the aircraft was south of the 7;000 MVA; the developmental gave a descent clearance to 6;000 [FT] anticipating the aircraft would miss the next lower MVA of 6;500 [FT] into the 6;000 MVA 2 miles south of the 6;500 MVA. Unfortunately the aircraft clipped the 6;500 MVA at 6;200 [FT] on the descent. I discussed with the developmental that in the future when aircraft are getting bumped around and having problems holding altitude; to keep in mind that as soon as that descent clearance is issued the pilot will be quick with the descent. Hold off on the descent as long as possible.  As on OJTI; remain a little more aware of the developmental control instructions in adverse IFR conditions to ensure all MVA's are met.
SCT TRACON Controller reported a Developmental Controller issued descent to an aircraft too early; which caused aircraft to violate the MVA rule.