Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) .4
Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Human Factors; Procedure
Aircraft Y departed 28R; special request.  I had to get him out in an arrival gap.  Aircraft X was in position on 28C.  I waited until I had 5 miles with both aircraft before launching Aircraft X for the wake.  Then before Aircraft X started rolling another controller said 'You know you need 3 minutes'.  I forgot that this operation was considered an intersection departure from the same runway.Aircraft X did not start departure roll.  I cancelled his takeoff clearance; but I got no response and Aircraft X started their departure.  I figured since it was not safety critical and we had a 35-40 kt wind out of the south.  I decided not to reiterate instructions to stop Aircraft X.  I did not want a brake fire or anything of the sort.  I believe wake turbulence was not a factor due to the high winds.  I had about 7 miles between aircraft after Aircraft X got airborne.  I decided that safety was not an issue.  I felt stopping the Aircraft X on the runway would of been the lesser desired scenario.I forgot about the 3 min rule.  I think this was my second time as [a] Full Performance Level (FPL) departing 28C.  The winds were very strong out of the south which made us use rarely used runway configurations.No recommendations - I just needed to remember the 3 min rule.
An ORD Local Controller reported of departing an aircraft and not having the required 3 minute separation. The reporter did attempt to stop the departing aircraft but aircraft did not stop. The Controller thought it was ok to let the departure continue due to the winds at the airport. The Controller forgot the operation was considered an intersection departure.