Narrative:

On a scheduled flight from las to msp, our takeoff weight was 172200#, the WX at las was VFR, wind 0405, OAT was 100 degrees F, runway 25. There were strong thunderstorms approximately 20 mi east and southeast of the field. To avoid taking off in the direction of the thunderstorm, we elected to depart on runway 25 with a 5 KT tailwind. Since these thunderstorms were in our direction of flight, by climbing out away from these storms before we turned on course, we would have had the added advantage of being at a higher altitude before we had to deviate around the WX. We took off on runway 25. Our takeoff roll took most of the 12636' length. Our takeoff roll was much longer than normal (obviously). Immediately after departure, las tower reported the wind at 040 degrees/16 KTS. That is approximately 6 KTS over our maximum tailwind limit of 10 KTS. No accident or injuries occurred and the flight operated normally. Apparently a gust front from the thunderstorm moved into the area during our takeoff roll. If I had known what the read wind was, I would not have used runway 25. In retrospect, it was probably bad judgement to takeoff with a tailwind on a hot day (100 degrees F) with a heavy aircraft. But, my main concern was to remain clear of the WX. In the future if I can't depart into the wind and remain clear of the thunderstorm, then I won't go.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR MAKES DOWNWIND DEP BUT LEARNS WIND EXCEEDS TAILWIND LIMIT.

Narrative: ON A SCHEDULED FLT FROM LAS TO MSP, OUR TKOF WT WAS 172200#, THE WX AT LAS WAS VFR, WIND 0405, OAT WAS 100 DEGS F, RWY 25. THERE WERE STRONG TSTMS APPROX 20 MI E AND SE OF THE FIELD. TO AVOID TAKING OFF IN THE DIRECTION OF THE TSTM, WE ELECTED TO DEPART ON RWY 25 WITH A 5 KT TAILWIND. SINCE THESE TSTMS WERE IN OUR DIRECTION OF FLT, BY CLBING OUT AWAY FROM THESE STORMS BEFORE WE TURNED ON COURSE, WE WOULD HAVE HAD THE ADDED ADVANTAGE OF BEING AT A HIGHER ALT BEFORE WE HAD TO DEVIATE AROUND THE WX. WE TOOK OFF ON RWY 25. OUR TKOF ROLL TOOK MOST OF THE 12636' LENGTH. OUR TKOF ROLL WAS MUCH LONGER THAN NORMAL (OBVIOUSLY). IMMEDIATELY AFTER DEP, LAS TWR RPTED THE WIND AT 040 DEGS/16 KTS. THAT IS APPROX 6 KTS OVER OUR MAX TAILWIND LIMIT OF 10 KTS. NO ACCIDENT OR INJURIES OCCURRED AND THE FLT OPERATED NORMALLY. APPARENTLY A GUST FRONT FROM THE TSTM MOVED INTO THE AREA DURING OUR TKOF ROLL. IF I HAD KNOWN WHAT THE READ WIND WAS, I WOULD NOT HAVE USED RWY 25. IN RETROSPECT, IT WAS PROBABLY BAD JUDGEMENT TO TKOF WITH A TAILWIND ON A HOT DAY (100 DEGS F) WITH A HVY ACFT. BUT, MY MAIN CONCERN WAS TO REMAIN CLR OF THE WX. IN THE FUTURE IF I CAN'T DEPART INTO THE WIND AND REMAIN CLR OF THE TSTM, THEN I WON'T GO.

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.