WINDSHEAR ALERT RESULTS IN ACR GAR AT ORD; IL.

Narrative

ORD WAS EXPERIENCING LEVEL 3 RAIN SHOWERS IN THE TERMINAL AREA. OUR FLT HAD 1 DEV ON THE KNOX ARR NEAR THE KNOX INTXN. THE REMAINDER OF THE ARR AND THE SUBSEQUENT ATC VECTORING WAS UNEVENTFUL. MAINLY LIGHT RAIN AT THE OM FOR RWY 22R.THE PFD DISPLAYED WINDSHEAR AHEAD AND THE NAV DISPLAY DISPLAYED THE ASSOCIATED WINDSHEAR ICON AT APPROX 3 MI DIRECTLY IN FRONT OF THE ACFT. THIS OCCURRED AT APPROX 1500 FT AGL. I IMMEDIATELY PERFORMED COMPANY SOP; AND PERFORMED A GAR; WITH A R TURN DEV AROUND THE DISPLAYED THREAT. THE FO ANNOUNCED THE GAR AND THE REASON FOR IT. WE TURNED 40 DEGS R TO AN INITIAL HDG OF 260 DEGS; FOLLOWED BY AN ASSIGNED LEVELOFF AT 4000 FT. ORD WAS CONDUCTING SIMULTANEOUS APCHS TO RWY 22L/R ALONG WITH RWY 14R; WHILE DEPARTING RWY 27L AS WELL. WE WERE THEN VECTORED DOWNWIND RWY 14R FOLLOWED BY AN UNEVENTFUL APCH AND LNDG TO RWY 14R. MY PERSPECTIVE; THE TWR DID NOT FULLY COMPREHEND THE NATURE OF THE INFO PROVIDED TO US BY THE ONBOARD PREDICTIVE WINDSHEAR SYS. I BELIEVE THIS WAS BECAUSE THERE WERE NO VISUAL WX THREATS SUCH AS A TSTM; OR LIGHTNING; ONLY LIGHT RAIN. COMPANY SOP IS TO AVOID THE THREAT IF THE DISTANCE IS GREATER THAN 1.5 NM.