Narrative:

Captain flying. We just finished a round trip (city pairs) and were well aware of the squall line moving through from the north. After gate arrival in bna, we had 30-40 mins before departure with a minimal passenger load. The operations agent asked if we wanted to go early because he had just looked at his WX screen. I told him the storm was still 'a ways' off and that we would be gone before it was a factor. I then looked at his screen and saw that it was 50 mi away, but moving fast. We landed runway 20L, but were initially headed for runway 2R for departure then sent to runway 2L which took a few extra mins to taxi to. Just prior to departure, radar showed echoes 20-25 mi away with normal conditions at the field 5-10 KTS. During the takeoff roll, tower started reporting gusts 20-30 KTS, then 40+ KTS as we got airborne. I kept the nose flat and noticed the gust front kicking things up around the business areas. We were in moderate turbulence immediately, got a quick turn to the south and anticipated climbing through and away from it quickly. After rolling out and climbing through 3500-4000 ft, we got whacked as if the gust front just overran us. I was glad it hit when we were wings level because it shook us so hard twice, it was all I could do to discern what the vertical gyro was telling me. Considering time compression, there was a split second that the entire gauge cluster was a blur. I estimated the event at 3-5 seconds, with 2 separate onsets of severe turbulence. The highest gust report I remember was 46 KTS and that was just after getting airborne. Getting runway 2L took more time and put us a little closer to the approaching echoes, but if we had seen the gust front, received the wind reports or had known it was overrunning the field, we could have re-evaluated the takeoff decision.

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Original NASA ASRS Text

Title: B737-700 CREW TOOK OFF NEAR A SQUALL LINE AND ENCOUNTERED MODERATE TURB AND SEVERE WINDSHEAR.

Narrative: CAPT FLYING. WE JUST FINISHED A ROUND TRIP (CITY PAIRS) AND WERE WELL AWARE OF THE SQUALL LINE MOVING THROUGH FROM THE N. AFTER GATE ARR IN BNA, WE HAD 30-40 MINS BEFORE DEP WITH A MINIMAL PAX LOAD. THE OPS AGENT ASKED IF WE WANTED TO GO EARLY BECAUSE HE HAD JUST LOOKED AT HIS WX SCREEN. I TOLD HIM THE STORM WAS STILL 'A WAYS' OFF AND THAT WE WOULD BE GONE BEFORE IT WAS A FACTOR. I THEN LOOKED AT HIS SCREEN AND SAW THAT IT WAS 50 MI AWAY, BUT MOVING FAST. WE LANDED RWY 20L, BUT WERE INITIALLY HEADED FOR RWY 2R FOR DEP THEN SENT TO RWY 2L WHICH TOOK A FEW EXTRA MINS TO TAXI TO. JUST PRIOR TO DEP, RADAR SHOWED ECHOES 20-25 MI AWAY WITH NORMAL CONDITIONS AT THE FIELD 5-10 KTS. DURING THE TKOF ROLL, TWR STARTED RPTING GUSTS 20-30 KTS, THEN 40+ KTS AS WE GOT AIRBORNE. I KEPT THE NOSE FLAT AND NOTICED THE GUST FRONT KICKING THINGS UP AROUND THE BUSINESS AREAS. WE WERE IN MODERATE TURB IMMEDIATELY, GOT A QUICK TURN TO THE S AND ANTICIPATED CLBING THROUGH AND AWAY FROM IT QUICKLY. AFTER ROLLING OUT AND CLBING THROUGH 3500-4000 FT, WE GOT WHACKED AS IF THE GUST FRONT JUST OVERRAN US. I WAS GLAD IT HIT WHEN WE WERE WINGS LEVEL BECAUSE IT SHOOK US SO HARD TWICE, IT WAS ALL I COULD DO TO DISCERN WHAT THE VERT GYRO WAS TELLING ME. CONSIDERING TIME COMPRESSION, THERE WAS A SPLIT SECOND THAT THE ENTIRE GAUGE CLUSTER WAS A BLUR. I ESTIMATED THE EVENT AT 3-5 SECONDS, WITH 2 SEPARATE ONSETS OF SEVERE TURB. THE HIGHEST GUST RPT I REMEMBER WAS 46 KTS AND THAT WAS JUST AFTER GETTING AIRBORNE. GETTING RWY 2L TOOK MORE TIME AND PUT US A LITTLE CLOSER TO THE APCHING ECHOES, BUT IF WE HAD SEEN THE GUST FRONT, RECEIVED THE WIND RPTS OR HAD KNOWN IT WAS OVERRUNNING THE FIELD, WE COULD HAVE RE-EVALUATED THE TKOF DECISION.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.