Date: 201606
Local time of day: 0001-0600
Location: ZHU.ARTCC, TX
Light: Night
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZHU
ATC / advisory: Center ZHU
Second aircraft: Widebody; Low Wing; 2 Turbojet Eng
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Distraction; Situational Awareness
Second reporter function: Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: I had come in for the [late night] shift only 15 minutes or so before the event. All Domestic Sectors were combined and the Ocean Sectors were moved to the domestic side of the room (normal ops) for the midnight shift. Aircraft X was at FL400 and I wanted to begin his descent as he got closer to the Houston area so I issued; 'descend now to FL300 then descend via the BAYYY2 Arrival' because I recognized converging traffic at 31000 feet - Aircraft Y.A couple of minutes later I saw that Aircraft X was descending too slowly so I amended his altitude. I meant to say 'amend altitude; maintain FL320'; but instead I amended him to FL300. I also issued Aircraft X a vector to the southwest (Heading 210) to provide room for his descent when he was clear of traffic. There was weather to the north; so I had to vector him to the south. After a couple of minutes I realized I had not updated Aircraft X's data block with the amended altitude and I wanted to confirm it with him so I stated; 'Aircraft X maintain FL320.' At this point he responded that he was through 31700 feet so I told him to expedite to 30000 feet. I recognized that I needed to keep his descent going fast so I told him to expedite through 30000 feet down to 24000 feet and 'report leaving FL300'. I then issued an aggressive vector to Aircraft Y; even stating to 'turn right immediately heading 300.' I realize this was a very sharp turn but I wanted to create as much space as I could as quickly as I could. However; he never seemed to take the heading. I also instructed Aircraft Y to climb and maintain 33000 feet; again to begin speeding up vertical separation between the two aircraft; but he never acknowledged the climb and at that point I had vertical separation. There was an urgency in my voice as I was scrambling to create separation. Aircraft X did report that he was responding to an RA descending. When both aircraft were vertically separated I cleared them both on course. After the event; I had [a CPC] take over the domestics as well and I reported the incident to the mid-watch supervisor. He listened to the audio and watched the falcon. He said that Aircraft X was trying to report leaving 30000 feet at or just before the computer reported a loss of separation; but Aircraft Y was broadcasting during his report.There was not a failure of the system or a procedure that led to this event. I made the classic 'think one thing; say another' mistake. In over 17 years of ATC this is my first event like this. I simply misspoke. I'll be vigilant about saying what I mean going forward.


Second narrative: We were at 31000 feet southbound enroute to KELPP approximately abeam waypoint LAURL when Houston Center (123.82) called and told us to turn right to 330 degrees immediately with an obvious degree of urgency in his transmission. We started the turn and in less than 5 seconds; received a traffic advisory followed almost immediately by a climb RA. The TCAS guidance was followed which was then followed by a 'level off' command. We initially saw traffic on TCAS at -300ft about our 10 O'clock position and I did see the intruder's aircraft lights outside the window. While the 'return' looked very close to us; I do not recall what range I had set on the ND but I would guess the 160nm range (which would make the traffic look very close). Houston was notified of us responding to a RA. There was no explanation offered as to why the conflict.


Synopsis: ZHU Controller reported mistakenly assigning an altitude 2000 feet below intended. This placed the aircraft into confliction with converging traffic. Both aircraft responded to RAs.