B757 FLC ADVISES UNABLE ZJX TURN DUE TO WX. ZJX ADVISES SQUAWK 7700 AND FLC DEVIATES THROUGH WX SYS.

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UNABLE ATC VECTORS DUE TO DEVELOPING CONVECTIVE WX SO WE ADVISED ATC WHAT OUR ONLY SAFE HEADING WOULD BE. THEY SAID THEY COULD NOT APPROVE IT AND ASKED THAT WE SQUAWK 7700. WE NAVIGATED AROUND WX WITHOUT FURTHER INCIDENT AND WERE EVENTUALLY GIVEN ANOTHER CODE. SUPPLEMENTARY INFO FROM ACN 543334: WE KEPT ASKING FOR ALTERNATIVE VECTORS. THEY KEPT SAYING UNABLE AND WE DECIDED WE NEEDED TO GO 090 AND THEY SAID UNABLE AGAIN AND WE SAID WE NEED TO GO 090. THEN CENTER SAID SQUAWK 7700 WHICH WE DID AND GOT AROUND THE STORM TOWARD THE E AND WENT INTO MCO WITHOUT FURTHER PROB. DIDN'T THINK THE GAP THEY WERE TRYING TO FORCE US THRU WAS WIDE ENOUGH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PIC ADVISED HE HAD NO PROB IN CHANGING THE SQUAWK TO 7700; BECAUSE HE DECLARED AN EMER WITH ATC ANYWAY. THE CAPT ADVISED THAT COMPANY POLICY IS TO PROCEED NO CLOSER THAN 20 MILES TO THIS TYPE FRONTAL ACTIVITY. HE HAD GONE AS FAR IN THE 'BOX' AS HE COULD BEFORE EMER ACTIONS WERE REQUIRED; WHICH HE EXERCISED. HE HAS HAD NO FEEDBACK FROM COMPANY OR ATC.