INFLT ENCOUNTER WX WINDSHEAR.

Narrative

FLT WAS TURNING EXTENDED FINAL AT 6000 FT WITH STL APCH CTL AND HAD JUST RECEIVED CLRNC TO DSND TO 4000 FT. WINDSHEAR WARNING AUDIO AND VISUAL ON THE PFD CAME ON. AFTER INITIAL HESITATION SINCE WE WERE AT 6000 FT IT BECAME CLR THAT WE WERE IN A SERIOUS WINDSHEAR SIT AND I EXECUTED THE WINDSHEAR ESCAPE MANEUVER. DURING THE NEXT 30-90 SECONDS; WE EXPERIENCED A VERT DSCNT OF MINUS 1500- 2000 FPM -- PITCH CHANGE OF PLUS OR MINUS 10-15 DEGS -- AIRSPD OF PLUS 30 TO MINUS 40-60 KTS. ACFT CONFIGN WAS 8 DEGS FLAPS -- 180 KTS -- AUTOPLT ON WHEN WINDSHEAR WAS ENCOUNTERED. BECAUSE OF THE ESCAPE MANEUVER THE ACFT EVENTUALLY CLBED TO 7500 FT AND TURNED ABOUT 60-80 DEGS L. IT WAS NEARLY IMPOSSIBLE TO COMMUNICATE WITH STL APCH DUE TO THE COMBINATION OF APCH TO OTHER ACFT COM AND OUR OWN NEED TO COMMUNICATE IN THE COCKPIT DURING THE WINDSHEAR. A WELL DONE SHOULD GO TO THE FO WHO REACTED SWIFTLY AND CALMLY TO OFFER ADVICE AND CALL OUT ACFT PARAMETERS. THE TRAINING PAYS OFF. AS PF I WAS VERY ENGROSSED IN TRYING TO CTL THE ACFT AND THE VERBAL CALL OUTS BY THE FO WERE VERY IMPORTANT. AFTER WE HAD ACFT UNDER CTL AND WERE ABLE TO COMMUNICATE WITH STL APCH WE EXPLAINED QUICKLY WHAT HAD HAPPENED AND STATED THAT WE WERE DIVERTING TO PIA DUE TO FUEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WX WAS SHOWING ON THE ACFT RADAR AND THE FLC KNEW THERE WAS A POSSIBILITY OF WX PROBS. THE CAPT HAD BRIEFED THE FO BEFORE THE APCH THAT; IF A GAR WAS NECESSARY; THEY WOULD DIVERT IMMEDIATELY TO THEIR ALTERNATE; BECAUSE THEY WERE CONCERNED ABOUT THEIR FUEL STATE. ENCOUNTERING THE WINDSHEAR THE CAPT CONCENTRATED ON THE ATTITUDE INDICATOR WHILE ADDING PWR; ETC. THE FO PROVIDED EXCELLENT INPUT BY COMMUNICATING ALT; AIRSPD; ETC. THE WINDSHEAR RECOVERY CAUSED MAJOR HDG AND ALTDEV WHICH WAS CONTINUED INTO THE GAR. WHILE CLBING AND TURNING TOWARD THEIR ALTERNATE; THEY ATTEMPTED TO CONTACT APCH CTL TO ADVISE THEM OF THEIR ACTIONS; BUT DUE TO FREQ CONGESTION; WERE UNABLE TO COMMUNICATE FOR SEVERAL MINS. RPTR'S COMPANY FOLLOWED UP THE INCIDENT WITH AN FAA TASK FORCE TO IMPROVE FUTURE SIMILAR INCIDENTS AND COM PROBS ASSOCIATED WITH THEM.