ON APCH TO ORD RWY 22L; A B737 FLC RECEIVE NOTIFICATION OF A LLWAS MICROBURST ALERT AND EXECUTE A MISSED APCH. THE PIC PROCEEDS TO ALTERNATE ARPT WHEN ADVISED MICROBURST RPTS ARE STILL BEING RECEIVED. FLC RETURN TO ORD; RECEIVE ANOTHER ALERT; EXECUTE A MISSED APCH; RETURN LAND; EVEN THOUGH RECEIVING OTHER MICROBURST ALERT.

Narrative

ON APCH TO ORD RWY 22L; MICROBURST ALERT WAS ISSUED FOR SHORT FINAL RWY 22L. A MISSED APCH WAS EXECUTED. DISPATCH WAS CONTACTED TO ADD A SUITABLE ALTERNATE; MKE FOR FUEL. WE DETERMINED WE HAD ADEQUATE FUEL FOR 1 ADDITIONAL APCH ATTEMPT AT ORD AND WOULD THEN BE REQUIRED TO PROCEED TO MKE FOR FUEL. ON DOWNWIND TO ORD RWY 22L; THE FINAL CTLR INFORMED US THAT NO ONE HAD COMPLETED FINAL SINCE WE LAST ATTEMPTED AND THAT THE TWR WAS STILL RECEIVING MICROBURST ALERTS. WE ELECTED TO PROCEED TO THE ALTERNATE AGREED UPON WITH DISPATCH (MKE) WITHOUT MAKING THE SECOND APCH. WE SENT AN ACARS RPT OF OUR DIVERSION AND ETA. WE LANDED AT MKE; REFUELED; AND RETURNED TO ORD. UPON ARR ORD RWY 22R; WE AGAIN RECEIVED A MICROBURST ALERT BELOW 1000 FT. WE EXECUTED A MISSED APCH AND AFTER A DELAY PERIOD RETURNED TO ORD AND LANDED ON RWY 22R. DURING THE FIRST MISSED APCH AT ORD; THE DEP CTLR GAVE US A FREQ CHANGE AT ABOUT THE SAME TIME AS WE RECEIVED THE SELCAL FROM COMMERCIAL RADIO FOR OUR CONNECTION TO DISPATCH. WHEN I FINISHED CONFERRING WITH DISPATCH AND WE DETERMINED OUR 'BINGO' FUEL; I NOTIFIED ATC THAT WE WERE READY FOR OUR RETURN TO ORD. THE CTLR ASKED US TO STATE OUR POS AND ASKED IF WE WERE ON A MISSED APCH. I SAID YES AND HE GAVE US A NEW FREQ FOR OUR RETURN TO ORD. WE DID NOT HAVE ANY INDICATION OF AN ENCOUNTER WITH A 'MICROBURST' AND BELIEVE THE TWR ALERTS WERE GENERATED BY THE STRONG SURFACE WINDS BLOWING ACROSS THE MIDWEST THAT AFTERNOON. IF A 'MICROBURST ALERT' IS BEING GENERATED; OUR COMPANY POLICY AND GOOD OPERATING PRACTICES SAYS GAR. SUPPLEMENTAL INFO FROM ACN 420012: DURING A VMC APCH TO RWY 22L AT ORD; TWR RPTED SURFACE WINDS OF 230 DEGS; 25 KTS; GUSTING TO 39 KTS AND ISSUED A MICROBURST ALERT FOR RWY 22L. NO EVIDENCE OF MICROBURST ACTIVITY WAS ENCOUNTERED IN A MISSED APCH THAT WAS INITIATED AS A RESULT OF THE ALERT. NO MICROBURST ACTIVITY WAS ENCOUNTERED AND CONDITIONS NORMALLY ASSOCIATED WITH MICROBURSTS WERE NOT PRESENT. THERE WAS NO CONVECTIVE ACTIVITY IN THE AREA AND THE SURFACE WIND AND APCH WIND WERE NEARLY THE SAME. THE TWR RPTED THAT THE ALERT HAD PERSISTED FOR OVER 20 MINS AND NO ACFT HAD LANDED. WE MADE AN UNEVENTFUL APCH AND LNDG ENCOUNTERING LIGHT TO MODERATE TURB NORMAL FOR THE GUSTY WIND CONDITIONS; BUT EXPERIENCED NO WINDSHEAR.