A DEP B737 FLC IS ENTRAPPED DURING THEIR DEP PROC BY SEVERE WX 6 MI NW OF FLL; FL.

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WE WERE LATE INBOUND TO DEST DUE TO WX; AND THUS WE WOULD ALSO BE LATE DEPARTING. WX (FRONTAL TSTMS) EXTENDED THROUGH MID-STATE FROM NW TO SE. WE PUSHED FROM GATE AND ON TAXI OUT WERE TOLD THAT NBOUND DEPS WERE STOPPED FOR FLOW CTL BECAUSE OF WX. WE SHUT DOWN ENGS ON TXWY; WAITED FOR APPROX 20-30 MINS; THEN TAXIED BACK TO GATE TO DEPLANE A SICK PAX. AGAIN PUSHED FROM GATE AND AWAITED WORD FROM GND ON DEPS BEING RELEASED. WAITED WITH ENGS SHUT DOWN FOR 1 HR; THEN TOLD TO START ENGS. WE WERE #1 FOR DEP AND TOLD TO EXPECT IMMEDIATE TKOF RWY 27R. WE STARTED ENGS; WENT THROUGH CHKLISTS AND WERE TOLD 'CLRED FOR IMMEDIATE TKOF RWY 27R; AFTER DEP TURN R TO 040 DEGS.' WE HAD WX RADAR ON; 20 MI RANGE; 5-7 DEGS TILT UP. NOTICED A LINE OF WX 5-7 MI NW OF DEP END OF FIELD; BUT DETERMINED WE COULD MAKE THE TURN EBOUND PRIOR TO WX. WE AND ATC MUST HAVE MISJUDGED THE SPD AND DISTANCE OF THE WX; AS SHORTLY AFTER TKOF WE INADVERTENTLY PENETRATED THE WX. AT THIS POINT WE HAD ALREADY STARTED THE TURN; WERE PASSING THROUGH 1500 FT AGL WITH GOOD CLB PERFORMANCE AND INCREASING AIRSPD. PASSING ABOUT A 360 DEG HDG AND 2500 FT AGL; EXPERIENCED SUDDEN MODERATE TO SEVERE TURB WITH A SUDDEN DROP IN AIRSPD FROM ABOUT 220 KIAS TO 185 KIAS. VERT SPD DROPPED FROM 1500-2000 FPM TO ZERO. THE CAPT ROLLED WINGS LEVEL; MAINTAINED CLB PWR AND ALLOWED THE PLANE TO CONTINUE CLBING PAST 3000 FT TO 4000 FT AGL. I ANNOUNCED OUR HDG AND ALT TO DEP CTL. HE GAVE US A CLB TO 7000 FT AND A NORTHERLY HDG; ASSURING US WE WOULD BE CLR OF WX IN 2-3 MI; WHICH WE WERE. ALTHOUGH THE TURB WAS VIOLENT; IT WAS ALSO SHORT-LIVED WITH NO STALL WARNINGS OR WINDSHEAR INDICATIONS IN THE COCKPIT. WE DID A CTL CHK ON CLBOUT AND DETERMINED THERE WAS NO CTL DAMAGE AND THUS PROCEEDED TO DEST. UPON ENG SHUTDOWN AND AFTER DEPLANING PAX; I DID A THOROUGH WALKAROUND AND SAW NO SIGNS OF DAMAGE TO THE ACFT. CONTRIBUTING FACTORS: DELAYED THEN RUSHED; FATIGUE; DUTY DAY; COM; STRESS; WORKLOAD; WX.