TCASII. WHILE ON RADAR VECTORS DURING DEP; CTLR TOLD FLC TO EXPEDITE CLB; BUT THEY WERE ALREADY CLBING AT THE MAX RATE. CONFLICT DEVELOPED WITH ANOTHER ACFT IN DSCNT. RPTR FLC RECEIVED TCASII RA WHICH THEY FOLLOWED. RPTR ACQUIRED TFC VISUALLY; WHICH BY THEN WAS NO THREAT; AND CONTINUED CLB.

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WE PUSHED BACK ON SCHEDULE BUT WERE DELAYED IN DEPARTING BWI DUE TO ATC WX RERTE. THIS WAS DUE TO INDIVIDUAL AND LINES OF TSTMS IN THE LCL AREA AND ENRTE. ALTHOUGH BWI WX WAS GIVEN AS 5000 FT SCATTERED; AND VISIBILITY 10+ MI; WE ENTERED AN AREA; SHORTLY AFTER TKOF DURING INITIAL CLBOUT; OF HAZE WHERE THE VISIBILITY DECREASED SUBSTANTIALLY. WE TOOK OFF FROM RWY 15R WITH A CLRNC TO FLY RWY AND CLB TO 4000 FT. DEP CTL GAVE US A R TURN TO 330 DEGS ON INITIAL CONTACT. I MADE THE TURN USING TKOF FLAPS SO AS TO COMPLETE THE TURN AS QUICKLY AS POSSIBLE AND STAY AWAY FROM SOME WX WE WERE SEEING VISUALLY AND ON THE RADAR. DURING THE LATTER PART OF THE TURN; DEP CTL TOLD US TO EXPEDITE OUR CLB; WHICH WE DID TO THE BEST OF OUR CAPABILITY. WE HAD RETARDED THE PWR FROM TKOF TO CLB PRIOR TO THIS POINT AND OUR CLB RATE WAS APPROX 1000 FPM DURING CLEANUP. DEP CTL ADVISED US OF TFC; GAVE US A TURN TO 360 DEGS AND AGAIN SAID EXPEDITE CLB. OUR TCASII TA INDICATED A TARGET AT 10:30 ABOVE AND DSNDING. THIS WAS FOLLOWED BY AN RA WHICH COMMANDED A DSCNT. I DID NOT HAVE THE TFC IN SIGHT. I STOPPED CLBING AND STARTED DSNDING. TCASII SAID 'INCREASE RATE OF DSCNT;' WHICH I DID. DEP CTL WAS ADVISED OF OUR RESPONDING TO THE RA AS HE TOLD US TO EXPEDITE CLB TO AN ALT OF APPROX 8000 FT TO WHICH WE HAD BEEN CLRED. IT ALL HAPPENED VERY QUICKLY AS ABOUT THIS TIME I SAW THE ACFT TO MY L; LOWER AND DSNDING. ALL WARNINGS STOPPED AND WE STARTED CLBING PER THE CTLR'S INSTRUCTIONS. NO FURTHER PROBS. I SUSPECT THE ACFT WAS BEING VECTORED TO; OR ON A VISUAL APCH TO RWY 10. IF THE CTLR HAD GIVEN US A L TURN FROM TKOF THERE WOULD NOT HAVE BEEN A CONFLICT OR IF HE HAD BEEN MORE AGGRESSIVE IN CHANGING OUR ROLLOUT HDG ONCE HE REALIZED A CONFLICT WAS DEVELOPING THAT WOULD HAVE PREVENTED THE PROB.