ZMP controller described a near separation loss when traffic on a parallel route made an unexpected ...

Narrative:

I was working the departure sector off of msp for both sids; coult and zmbro departures. There was a large area of weather around the rgk area inside msp approach and also outside of approach in my sector. There were two departures that were on each of the sids. A DC9 was on the coult SID and an E170 was on the zmbro SID. They were both deviating for the weather. When the DC9 checked in he said they wanted to deviate further left which would take him farther away from the E170. I still stopped the E190 5;687 at 15;000 ft as a backup in case there were further deviations. The DC9 was climbing reasonably well to FL230 and informed me that they were now 'turning hard right now to a 210 heading'. They were already in the turn towards the E170. I informed him where the other traffic was and asked the E170 if they could turn at all to the right. They said no; and as he said that I saw the hard turn that the DC9 was making on radar and saw it was closing in the E170. I descended the E170 to 12;000 ft and told the DC9 to expedite the climb; but I wasn't sure if I had already lost separation. Later the E170 asked about the other aircraft and if that is why they had to descent. I informed him yes; and they said that they were watching them on TCAS but they didn't have an RA. I was using vertical separation until they were both able to continue on course. Recommendation; both the zmbro and coult sids are not that far apart laterally in the first place. When there is weather that is; or could impact the departures in that sector; it is usually best to have a restriction to have a single stream of departures so that these things don't happen. From my experience; you never know when a plane will turn without informing you or even which direction they want to turn. It's usually not in the direction you would prefer. In this situation; I should have stopped the E170's climb earlier and at a lower altitude; not knowing what either of the aircraft would want to do to get around the weather. Aircraft before the two departures involved here did not deviate as much as the DC9 which made a 90 plus degree turn into the other aircraft.

Original NASA ASRS Text

Title: ZMP Controller described a near separation loss when traffic on a parallel route made an unexpected weather deviation turn; the reporter listing the minimal lateral separation of these routes as a causal factor.

Narrative: I was working the departure sector off of MSP for both SIDs; COULT and ZMBRO departures. There was a large area of weather around the RGK area inside MSP approach and also outside of approach in my sector. There were two departures that were on each of the SIDs. A DC9 was on the COULT SID and an E170 was on the ZMBRO SID. They were both deviating for the weather. When the DC9 checked in he said they wanted to deviate further left which would take him farther away from the E170. I still stopped the E190 5;687 at 15;000 FT as a backup in case there were further deviations. The DC9 was climbing reasonably well to FL230 and informed me that they were now 'turning hard RIGHT now to a 210 heading'. They were already in the turn towards the E170. I informed him where the other traffic was and asked the E170 if they could turn at all to the right. They said no; and as he said that I saw the hard turn that the DC9 was making on RADAR and saw it was closing in the E170. I descended the E170 to 12;000 FT and told the DC9 to expedite the climb; but I wasn't sure if I had already lost separation. Later the E170 asked about the other aircraft and if that is why they had to descent. I informed him yes; and they said that they were watching them on TCAS but they didn't have an RA. I was using vertical separation until they were both able to continue on course. Recommendation; both the ZMBRO and COULT SIDs are not that far apart laterally in the first place. When there is weather that is; or could impact the departures in that sector; it is usually best to have a restriction to have a single stream of departures so that these things don't happen. From my experience; you never know when a plane will turn without informing you or even which direction they want to turn. It's usually not in the direction you would prefer. In this situation; I should have stopped the E170's climb earlier and at a lower altitude; not knowing what either of the aircraft would want to do to get around the weather. Aircraft before the two departures involved here did not deviate as much as the DC9 which made a 90 plus degree turn into the other aircraft.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	942444
Time
Date	201104
Local Time Of Day	1801-2400
Place
Locale Reference	ZMP.ARTCC
State Reference	MN
Aircraft 1
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	SID COULT THREE
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

ZMP controller described a near separation loss when traffic on a parallel route made an unexpected weather deviation turn; the reporter listing the minimal lateral separation of these routes as a causal factor.