ACR LGT ALT DEVIATION OVERSHOT DURING DESCENT WHILE DEVIATING AROUND TSTM ACTIVITY. REPORTERS CLAIM THEY WERE DISTRACTED BY AN AGGRESSIVE ARTCC RADAR CTLR TRYING TO KEEP THEM FROM MAKING THE WX DEVIATION.

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CLRED TO FL230 FROM FL270 DEVIATING TRW WITH TURB AND RAIN. TOLD TO STOP DSCNT AT FL250 DSNDED TO FL242 AND RETURNED TO FL250 IN A MATTER OF SECS. NO CONFLICT WITH OTHER ACFT. A CONTRIBUTING FACTOR WAS A DISCUSSION BY MYSELF AND THE CTLR WHICH WAS INAPPROPRIATE ON THE PART OF THE ATC CTR CTLR WHO INITIATED IT. HE WAS QUESTIONING MY DECISION TO DEVIATE AROUND TRW'S THAT WERE CONTOURING ON MY RADAR; INDICATING INTENSIVE PRECIPITATION WITH ATTENDANT TURB. I HAVE THE ULTIMATE AUTHORITY OVER MY ACFT AND THE SAFETY OF ALL SOULS ON BOARD. THE QUESTIONING BY THE CTLR DISTRACTED ME. SUPPLEMENTAL INFO FROM ACN 91243: ATC SAID THAT ANOTHER ACFT HAD GONE THROUGH THE STORM WITH ONLY MODERATE TURB AT THE MOST. THE STORM APPEARED TO BE A GROWING CB; NOT YET MATURE. ATC THEN ASKED US TO STOP DSCNT AT FL250 AND AGAIN TOLD US THAT 2 OTHER ACFT HAD GONE THROUGH THE AREA WITH OUT PROB. THE CAPT TOLD HIM WE WOULD RETURN TO COURSE WHEN HE FELT IT WAS SAFE. WE COULD HARDLY UNDERSTAND ATC COMS AND WERE CONCENTRATING ON GETTING AROUND THE STORM AND WEAKLY HEARD ATC ASK US ABOUT OUR ALT. ACFT WAS AT APPROX FL242. TIME BELOW FL250 WAS ABOUT 40-60 SECS. THE PRIME CAUSE IS COCKPIT DISTR; AND THE RAPID INCREASE OF WORKLOAD. SUPPLEMENTAL INFO FROM ACN 91162: THE CAPT WANTED TO DEVIATE AROUND THE WX; BUT CTR SAID IT WAS NOTHING BUT RAIN. RADAR SHOWED DEFINITE CELLS AND THE CAPT AGAIN PRESSED TO DEVIATE. CTR THEN SAID THAT A PIREP INDICATED IT WAS ONLY RAIN AND THERE WAS NO NEED TO DEVIATE. CAPT ENTERED 25000 FT IN THE ALT ALERT INDICATOR AND WENT BACK TO THE RADAR. WE HAD NOT YET REACHED FL260 IN THE DSCNT. WHEN MY SCAN WENT FROM THE ENG ANTI-ICE CTLS TO THE INSTRUMENTS TO CHK FOR STABILIZATION; I NOTICED THE RED ALT ALERT LIGHT BLINKING. I NEVER HEARD THE TONE BECAUSE OF THE LOUD RAIN. I SAW THAT WE WERE FL245 AND CALLED OUT 'ALT.' THE FO AND CAPT IMMEDIATELY PULLED THE ACFT UP AND INTO A RAPID CLB TO FL250. I ESTIMATE WE WERE OFF ALT FOR APPROX 5 SECS.