ACR X WX DEV HAD LTSS FROM ACR Y. SYS ERROR.

Narrative

ACR X WAS WBOUND JUST S OF J-64 AND W OF LMN. ACR Y WAS 8 MI BEHIND AND SLIGHTLY S OF X. X WAS CLRED TO DEV S. ALL PREVIOUS ACFT HAD PICKED UP ABOUT A 240-230 DEG HDG TO SKIRT THE TSTMS. MOST ACFT HAD GONE TOWARDS SLN; HOWEVER; A FEW HAD GONE N OF LNK J-60/ X AND Y WERE ON APPROX PARALLEL HDGS ABOUT 240 DEGS. SUDDENLY X BEGAN A L TURN TO 135 DEGS. THE CTLR WORKING THE RADIO TRIED TO TURN AND DSND THE Y FLT. STANDARD SEPARATION WAS LOST; AND AT LEAST ONE OF THE ACFT RESPONDED TO A TCASII ALERT. I WAS THE MANUAL CTLR ON THIS INCIDENT AND I THINK THAT IT WOULD HAVE BEEN A GOOD IDEA FOR THE PLT TO SAY SOMETHING BEFORE HE MADE SUCH A DRASTIC TURN; EVEN THOUGH HE HAD BEEN CLRED TO DEV. TSTMS AND BAD FREQS ALSO CONTRIBUTED TO THE PROB. SUPPLEMENTAL INFO FROM ACN 273858: BY THE TIME ACR X RE-ESTABLISHED COM AND RECEIVED CLRNC TO DEV S OF COURSE WE WERE GETTING QUITE CLOSE TO THE STORM. TO REMAIN CLR OF THE STORM WE TURNED CLOSE TO 90 DEGS TO OUR RTE OF FLT. WHEN WE RECEIVED THE CLB RA; WE INITIATED A CLB; NOTIFIED ATC; WHO INSTRUCTED US TO LEVEL AT FL330. THE OTHER ACFT PASSED BELOW AND TO THE L AS WE FOLLOWED THE CLB RA. THE CTLR WAS TRYING TO RESOLVE THE DEVELOPING CONFLICT WHEN WE RECEIVED THE RA. THE CTLR PROBABLY DID NOT EXPECT US TO TURN AS FAR S AS WE DID.