MD80 FLT CREW REACTS TO GPWS TERRAIN WARNING ON DEP FROM BUR AT 3200 FT. HVY RAIN SHOWERS IN VICINITY AND DEP RADAR GND TRACK INDICATED NO TERRAIN CONFLICT.

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LEVEL 3 RAIN SHOWER APPROX 5 NM SSE WAS MOVING TOWARDS THE FIELD. THIS IS AN OLD NON-EFIS MD80; SO WE CHOSE TO SELECT WX RADAR VICE EGPWS DUE TO WX ON DEP. TWR CLRED US FOR TKOF HDG 210 DEGS; 4000 FT MSL; AND THEN CHANGED TKOF CLRNC TO HDG 320 DEGS; 5000 FT MSL DUE TO THE WX ON THE DEP END. AT 200 FT AGL; CAPT SELECTED HDG SELECT OF 320 DEGS; 15 DEGS BANK. AT 1000 FT AGL; CAPT CALLED FOR FLAPS UP AND CLB PWR. THE SLATS REMAINED EXTENDED. TWR HANDED US OFF TO DEP AND FO CHKED IN NORMAL. ABOUT 1 MIN AFTER TKOF; AT APPROX 180 KTS; CLBING R 15 DEG BANK TURN; 3200 FT MSL; THE GPWS SYSTEM ANNOUNCED 'TERRAIN; TERRAIN;' FOLLOWED BY 'PULL UP' AND 'TOO LOW TERRAIN.' WE ACCOMPLISHED THE RED BOX ITEMS EXCEPT USED CLB PWR; AND THEN FO SELECTED MCT. THE RADAR ALTIMETERS WERE BOTH VERY ERRATIC AND INDICATED 1000-800 FT AND GOT AS LOW AS 400 FT. FO WAS CALLING OUT RADAR ALTIMETER ALTS AND THE CAPT WAS FLYING THE FLT DIRECTOR TO ABOUT 20-25 DEGS PITCH; V2 + 20 KTS; ROLLING OUT TO ABOUT 270 DEG HDG AND CLBING TO 5000 FT MSL. THE 'EVENT' WARNING CEASED AFTER ABOUT 15-20 SECONDS. THE MOUNTAINS JUST N AND W OF THE FIELD WERE A CONCERN AND BRIEFED EARLIER. DEP SAID 'TURN R TO 320 DEGS AND CLB TO 13000 FT.' WE ACCOMPLISHED NORMAL CLEAN-UP AND AFTER TKOF CHKLIST ITEMS. DURING THE CLB; THE FO ASKED DEP FOR THE MVA RIGHT BEHIND US AND THEY SAID 3000 FT AND INDICATED NO PROBS. FO TOLD DEP WE JUST HAD A 'POSSIBLE FALSE TERRAIN WARNING.' LATER DURING CLBOUT; FO CALLED BACK TO DEP AND ASKED THEM TO MARK THEIR TAPES AND XCHK OUR GND TRACK DUE TO OUR 'TERRAIN WARNING' ON DEP. AFTER MUCH CONVERSATION ABOUT THIS EVENT; CAPT AND FO BOTH THOUGHT THIS WAS PROBABLY A FALSE WARNING DUE TO THE HVY RAIN SHOWER JUST L OF THE ACFT IN OUR R 15 DEG BANK TURN. BUT; WE HAD TO EXECUTE THE PROPER PROC NO MATER WHAT! UPON LNDG; CAPT CALLED DEP OPS MGR. HE SAID HE REVIEWED OUR DEP WITH HIS SUPVR AND CTLRS AND SAID OUR DEP TRACK WAS NORMAL AND HAD NO ALERTS OF ANY KIND! THE CAPT WROTE UP THE GPWS SYS IN LOG BOOK.