A DC-8 FLC REQUESTED A 20 DEG DEV; BUT REQUIRED A 90 DEG DEV; WHICH WAS TAKEN. ATC INTERVENED AS ACR TRACK BECAME A POTENTIAL CONFLICT.

Narrative

WHILE DSNDING INTO THE SDF AREA WE ENCOUNTERED SEVERAL SMALL TSTM CELLS REQUIRING DEV. I ADVISED CTR THAT WE WOULD NEED A 20 DEG COURSE CHANGE TO THE R FOR THE WX. THE CTLR STATED 'DEV APPROVED; CLRED DIRECT TO KSDF WHEN ABLE.' AS WE TURNED R; IT BECAME OBVIOUS THAT FURTHER DEV WAS IMMINENTLY NECESSARY; SO WE CONTINUED OUR R TURN TO APPROX 90 DEGS R OF COURSE. WHEN WE ROLLED OUT ON THE NEW HDG; ATC ASKED US WHAT OUR HDG WAS -- THEN STATED THAT WE WERE ONLY APPROVED FOR A 20 DEG DEV AND THAT THERE WAS OTHER TFC IN THE AREA WE WERE TURNED TOWARDS. AT THIS TIME WE WERE CLR OF THE WX AND TURNED DIRECT TO SDF AS PREVIOUSLY CLRED. I FEEL WE COULD HAVE BETTER HANDLED THE SIT IF WE HAD KEPT THE CTLR INFORMED OF OUR INTENTIONS TO CONTINUE OUR DEV. WE HAD NO CHOICE BUT TO DEVIATE TO AVOID THE CELLS. SUPPLEMENTAL INFO FROM ACN 303936: AS WE DSNDED THE TSTM GREW IN INTENSITY AND WE ENCOUNTERED RAIN; TURB; AND STATIC ON THE RADIO. WITH SO MUCH STATIC ON THE RADIO WE COULD NOT COM; AND WITH TURB AND RAIN; WE ONLY WANTED OUT OF THE BAD WX. IN THE FUTURE I WILL ENSURE THAT WE ADVISE ATC WELL IN ADVANCE WHEN LARGE DEVS MIGHT BE NECESSARY.