ALTDEV ALT UNDERSHOT. ALT XING RESTR.

Narrative

WE WERE GIVEN A RESTR TO CROSS THE VIBES INTXN AT 13000 FT. WE BEGAN A VNAV DSCNT AT THE FMGC COMPUTED TOP OF DSCNT POINT TO MAKE THE RESTR. AFTER LEAVING THE CTR FREQ TO LISTEN TO THE ATIS FOR LGA AND THEN RETURNING BACK; I NOTICED THAT ALTHOUGH THE VNAV INDICATIONS SHOWED THAT WE WERE ON THE CORRECT PROFILE TO CROSS VIBES AT 13000 FT; IT APPEARED TO ME THAT WE WOULD CROSS VIBES CLOSER TO 16000 FT THAN 13000 FT. I INFORMED THE CAPT (WHO WAS THE PF) THAT IT APPEARED WE WERE WELL ABOVE THE PATH REQUIRED TO MAKE OUR XING RESTR. THE CAPT RESPONDED BY INCREASING OUR DSCNT RATE AND USING FULL SPD BRAKES. ALTHOUGH WE THOUGHT WE COULD STILL MAKE THE RESTR; WE ACTUALLY CROSSED VIBES AT 13700 FT (700 FT HIGH). CTR NEVER SAID ANYTHING TO US AND THERE WAS NO TFC CONFLICT. WE WERE UNSURE AS TO WHY THE VNAV SYS DID NOT KEEP US ON THE PROPER PATH TO MAKE THE XING RESTR AT VIBES. WE RECHKED TO BE SURE THAT THE PROPER ALT RESTR WAS SHOWN ON THE FMGC AT VIBES AND IT WAS SET AT 13000 FT JUST LIKE IT WAS SUPPOSED TO BE. I FEEL THAT A CONTRIBUTING FACTOR WAS THE FACT THAT I WAS 'OUT OF THE LOOP' FOR ABOUT 1-2 MINS WHILE LISTENING TO THE ATIS. HAD I NOTICED THAT THE DSCNT PROFILE WAS NOT CORRECT A MOMENT EARLIER; I FEEL CONFIDENT THAT THE RESTR STILL WOULD HAVE BEEN MET. I ALWAYS MAKE IT A POINT TO COMPUTE A TOP OF DSCNT POINT MYSELF AND TO TRY TO CLOSELY FOLLOW THE DSCNT PATH AS IT PROGRESSES; HOWEVER; IN THIS CASE LISTENING TO THE ATIS INTERRUPTED THAT PROCESS. FROM NOW ON; I'M GOING TO ALWAYS TRY AND GET THE ATIS DURING CRUISE FLT IN ORDER TO KEEP MY ATTN WHERE IT SHOULD BE.