Narrative:

Departed on a 310 degree vector due to thunderstorms building west of the airport. Initially this vector was good and weather radar showed us just to the east of the heaviest convective activity/echoes. As we cleared the initial cumulonimbus and were switched to departure control we visually identified a building towering cumulus off of the nose of the aircraft on a 310 heading. This towering cumulus was not painting on radar but visually it was building and there was no doubt it would be turbulent. We immediately asked ATC for 10 degrees further to the east to avoid this build up. ATC advised something to the effect; 'it's not going to happen company. I'm not authorizing deviations until I get a moderate report.' at this point we were close to entering the buildup. The cabin was secure so we honored ATC not knowing the traffic situation. As soon as we hit clouds; we experienced moderate turbulence and informed ATC. We were vectored immediately to the east cleared the weather. The flight continued uneventfully. Departure control seemed to demonstrate a great deal of hubris while dealing with our request. Given that our radar did not depict a core; I'm sure that ground based radar did not depict a core. Given that the weather was building and we could visually see that a deviation would be warranted; I do not think ATC should be denying weather deviations. We could have declared an emergency and deviated; however that seemed extreme given what we were painting and the unknown consequence of deviating into arriving traffic. Generally; I think ATC should respect the firsthand knowledge of flight crew and prioritize safety rather than offering a rigid approach to a dynamic situation.

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Original NASA ASRS Text

Title: An Air Carrier pilot reported ATC refused their request for a weather deviation.

Narrative: Departed on a 310 degree vector due to thunderstorms building west of the airport. Initially this vector was good and weather radar showed us just to the east of the heaviest convective activity/echoes. As we cleared the initial cumulonimbus and were switched to Departure Control we visually identified a building Towering Cumulus off of the nose of the aircraft on a 310 heading. This Towering Cumulus was not painting on radar but visually it was building and there was no doubt it would be turbulent. We immediately asked ATC for 10 degrees further to the east to avoid this build up. ATC advised something to the effect; 'It's not going to happen Company. I'm not authorizing deviations until I get a moderate report.' At this point we were close to entering the buildup. The cabin was secure so we honored ATC not knowing the traffic situation. As soon as we hit clouds; we experienced moderate turbulence and informed ATC. We were vectored immediately to the east cleared the weather. The flight continued uneventfully. Departure Control seemed to demonstrate a great deal of hubris while dealing with our request. Given that our radar did not depict a core; I'm sure that ground based radar did not depict a core. Given that the weather was building and we could visually see that a deviation would be warranted; I do not think ATC should be denying weather deviations. We could have declared an emergency and deviated; however that seemed extreme given what we were painting and the unknown consequence of deviating into arriving traffic. Generally; I think ATC should respect the firsthand knowledge of Flight Crew and prioritize safety rather than offering a rigid approach to a dynamic situation.

Data retrieved from NASA's ASRS site 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.