DC10 FLC DEVIATES AROUND TSTM DEPARTING EHAM.

Narrative

WE TAXIED INTO POS ON RWY 24 AND HELD FOR ABOUT 1 MIN BEFORE DEPARTING. FROM WHAT WE SAW ON THE WX RADAR A 10-20 DEG L TURN TO A HDG OF ABOUT 220-230 DEGS WOULD AVOID TSTMS. I DISCUSSED THE HDG WE SHOULD FLY WITH THE FO AND SO AND WE ALL AGREED WE WOULD BE ABLE TO AVOID THE STORMS WITH A 10-20 DEG HDG CHANGE. ONCE AIRBORNE; WE ASKED DEP CTL FOR A 20 DEG TURN TO THE L; WHICH HE APPROVED. ABOUT 4 MI FROM THE RWY WE COULD SEE ON THE RADAR THAT IT WAS NOT GOING TO BE ENOUGH OF A TURN. I ASKED THE FO (WHO WAS HANDLING THE RADIO) TO ASK FOR A TURN TO THE S. THE CTLR WAS BUSY TALKING TO OTHER FLTS; SO IT WAS HARD TO ASK HIM FOR A SOUTHERLY HDG. THERE WAS NO WAY I WAS GOING TO FLY INTO THE TSTM THAT LAY DIRECTLY AHEAD OF US; SO I TURNED TO A 190 DEG HDG AND LEVELED OFF AT 4000 FT TO AVOID GOING INTO THE DARK CLOUDS (OUR CLRNC WAS TO 6000 FT). THE CTLR TOLD US HE HAD NOT CLRED US TO MAKE THAT LARGE A HDG CHANGE AND TOLD US TO TURN R. WE TOLD HIM WE COULD NOT; BECAUSE OF THE CELL THAT WAS NOW PASSING OFF OUR R. IN A COUPLE OF MINS WE WERE CLR AND TOLD HIM WE COULD TURN R; WHICH WE DID. THE CTLR NEVER DID MENTION ANY CONFLICT WITH TFC AND WE DID NOT HAVE ANY TFC ON OUR TCASII.