B747-400 FLT CREW ENCOUNTERS WX MICROBURST ACTIVITY ON FINAL AT RJAA; EXECUTES GAR; DECLARES EMER AND DIVERTS TO ALTERNATE.

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AFTER A 5 1/2 HR FLT FROM BANGKOK TO NARITA (I WAS THE CAPT AND THE FO WAS FLYING THIS LEG); WE WERE ABOUT READY FOR DSCNT FROM FL380 WHEN WE WERE TOLD TO HOLD AT A POINT CALLED 'BINAN' (I THINK THAT WAS THE NAME; STILL HAVEN'T BEEN ABLE TO FIND IT ON ANY CHARTS OR PLATES). TOKYO CTL HAD TO SPELL IT PHONETICALLY; IT WAS IN OUR FMS DATABASE; SO WE STARTED HOLDING AT FL330 AND DSNDED IN HOLDING WHEN TOLD TO DO SO. OUR EFC WAS ABOUT 30 MINS FROM THE TIME WE STARTED HOLDING. WE WERE SLIGHTLY AHEAD ON OUR FUEL PLAN AND EXPECTED TO BE ABLE TO HOLD FOR THAT LONG AND THEN PROCEED WITH THE ARR INTO NRT. WE WERE NOT TOLD THE REASON FOR HOLDING AND DID NOT EXPECT ANY PROB GETTING INTO NRT SINCE ATC GAVE NO INDICATION OF A PROB AND THE ATIS LOOKED GOOD. WE WOULD; HOWEVER; BE CUTTING INTO OUR ALTERNATE FUEL IN ORDER TO DO THIS HOLDING. APCHING OUR EFC; WE WERE CLRED TO HOLD AT ANOTHER POINT ON OUR PLANNED ARR CALLED 'VENUS' WITH AN EFC 40 MINS LATER. I RESPONDED THAT WE WERE 'UNABLE' TO ACCEPT THAT CLRNC BECAUSE WE WERE NOW MINIMUM FUEL AND THAT WE NEEDED VECTORS TO COMMENCE THE APCH. I ESTIMATED OUR FUEL REQUIREMENTS AND TOLD THEM WE MUST LAND BY A CERTAIN TIME. ATC COMPLIED WITH OUR REQUEST AND WE WOULD HAVE LANDED ONLY ABOUT 5 MINS AFTER THE TIME I HAD GIVEN THEM; AND WITH THE AMOUNT OF FUEL. I HAD WANTED TO LAND WITH. ATC HAD NOT INFORMED US 1) THAT WE WOULD BE EXPECTED TO HOLD AGAIN AFTER THE INITIAL HOLDING; 2) THE REASONS FOR HOLDING (WE ASSUMED IT WAS JUST FOR SPACING INTO NRT); AND 3) THAT TSTMS WERE AFFECTING OPS AT THE ARPT. WE DID HEAR ANOTHER ACFT ASK WHY THEY WERE HOLDING AND THEY WERE TOLD THAT IT WAS FOR ARRS BACKING UP. THEY FAILED TO MENTION THAT THEY WERE BACKING UP FOR TSTMS. THERE WERE BUILDUPS IN THE AREA AND WE COULD SEE THEM AND PAINT THEM ON WX RADAR; BUT THEY WERE RELATIVELY WIDELY SCATTERED AND WEREN'T A PROB WHERE WE WERE. ATC WAS ALSO NOT ISSUING EFC TIMES INITIALLY UNTIL WE ALL STARTED DEMANDING THEM. IF WE HAD KNOWN THAT TSTMS AND WINDSHEAR WERE IMPACTING ARRS AND DEPS; WE WOULD HAVE GONE TO THE ALTERNATE IMMEDIATELY. SO THE DANGEROUS SIT HERE IS THAT ATC WAS LEADING EVERYONE DOWN A PATH WHERE THEY WOULD BE LOW ON FUEL AND FORCED TO LAND AT AN ARPT WITH MARGINAL WX. SO WE WERE CLRED FOR THE APCH AND ENCOUNTERED RAIN AND GUSTY WIND CONDITIONS ON THE APCH. AFTER BEING CLRED TO LAND AND DOWN TO ABOUT 1200 FT AGL; WE WERE BREAKING OUT OF THE WX AND THE FIELD WAS COMING INTO VIEW. THE AIRSPD WAS FLUCTUATING AND WE HAD MICROBURST INDICATIONS OFF TO THE R OF THE RWY. WE TOLD TWR THAT WE WERE GOING AROUND AND STARTED TO FLY THE PUBLISHED MISSED APCH. AFTER WE HAD COMPLETED THE INITIAL TURN OF THE MISSED APCH PROC; WE COULD SEE THAT IT WOULD TAKE US INTO A THUNDER SHOWER; SO I SELECTED A HDG THAT WOULD AVOID IT; AND THEN INFORMED ATC THAT WE WERE DECLARING AN EMER FOR FUEL; WHAT HDG WE WERE FLYING; THAT WE WERE CLBING TO THE MISSED APCH ALT (6000 FT); AND THAT WE NEEDED TO LAND IMMEDIATELY AT THE NEAREST ARPT. WE WERE ALREADY HEADING IN THE GENERAL DIRECTION OF HND; OUR FILED ALTERNATE. WE WERE GIVEN VECTORS TO FINAL AT HND; FLEW THE APCH TO RWY 34R AND LANDED WITH ONLY ABOUT 30 MINS OF FUEL REMAINING. AFTER REFUELING AND WAITING FOR THE WX TO CLR (ABOUT 4 HRS); WE FLEW FROM HND TO NRT.