Narrative:

On departure from mdw we were vectored 090 directly towards the heaviest cells in a frontal line with heavy precipitation. I expected ATC to turn us north or south around the worst cells directly in front of us. Instead ATC asked us if we could climb above it. Captain replied that we did not know the extent of the weather ahead. ATC said maintain 5000 ft (but did not offer a heading deviation). Now less than ten miles from the front I asked the captain to request a 150 heading to deviate south of the heavy precipitation. He made the request with no reply from ATC; yet there was no other radio traffic. Captain then repeated the request and said; 'request weather deviation south; right to 150 degrees.' the right deviation was approved and I started my turn; but now we were so close that we entered the weather front with precipitation and turbulence in the turn; so I continued the right turn past the 150 deg heading (as far as 210 deg heading) to get out of the weather; then slowly reversed my turn left toward the 150 heading; intending to work my way back to the southeast as soon as possible as we skirted the storm. The captain tried to inform ATC of our situation and current heading but the radio was now congested with other calls; so ATC called us before we had a chance to explain our situation; 'you were granted 15 degrees right and now you are heading south!' captain replied; 'no; we requested right to 1-5-0 degrees.' ATC said; 'well you're now past that heading to south!' the captain explained we were avoiding weather and were unable to inform him because of the radio congestion. We asked if he could vector us south around the weather. ATC said he could not immediately do that and added a comment that now he had to keep us from being a conflict with other aircraft. He then resumed very positive control keeping us out of the weather by providing us multiple airspeed/heading/altitude instructions back north then west and finally south to a new controller who eventually worked us back eastbound on course. I was glad when the captain told me that he heard on our company frequency that flights behind us were now getting ATC assistance; being re-routed to avoid the weather. With moderate-to-heavy precipitation close to the departure field; I prefer ATC be proactive to provide options/routing around the weather; since we will not have the time/distance to devise our own request. Today we were only offered a climb; and then held at 5000 ft pointing at the storms. (I can only guess that perhaps flights ahead of us climbed through it?) congestion on the radio contributed to the problem; and I hope ATC realizes we did our best to inform them of our weather avoidance requests and actions. I believe ATC said; 'deviation right is approved' but did not say 'deviation up to 15 degrees right approved.' this is the only way we could have known he misunderstood our request. But only 15 degrees right would have driven us into the weather we needed to avoid. I had no intention to fly through that front. We needed to make that immediately clear to ATC when radio traffic allowed it.

Related reports:

Google
 

Original NASA ASRS Text

Title: Air carrier flight crew deviated around weather without clearance to do so; they request ATC to be more proactive during periods of convective weather.

Narrative: On departure from MDW we were vectored 090 directly towards the heaviest cells in a frontal line with heavy precipitation. I expected ATC to turn us north or south around the worst cells directly in front of us. Instead ATC asked us if we could climb above it. Captain replied that we did not know the extent of the weather ahead. ATC said maintain 5000 FT (but did not offer a heading deviation). Now less than ten miles from the front I asked the Captain to request a 150 heading to deviate south of the heavy precipitation. He made the request with no reply from ATC; yet there was no other radio traffic. Captain then repeated the request and said; 'Request weather deviation south; right to 150 degrees.' The right deviation was approved and I started my turn; but now we were so close that we entered the weather front with precipitation and turbulence in the turn; so I continued the right turn past the 150 deg heading (as far as 210 deg heading) to get out of the weather; then slowly reversed my turn left toward the 150 heading; intending to work my way back to the southeast as soon as possible as we skirted the storm. The Captain tried to inform ATC of our situation and current heading but the radio was now congested with other calls; so ATC called us before we had a chance to explain our situation; 'You were granted 15 degrees right and now you are heading south!' Captain replied; 'No; we requested right to 1-5-0 degrees.' ATC said; 'Well you're now past that heading to south!' The Captain explained we were avoiding weather and were unable to inform him because of the radio congestion. We asked if he could vector us south around the weather. ATC said he could not immediately do that and added a comment that now he had to keep us from being a conflict with other aircraft. He then resumed very positive control keeping us out of the weather by providing us multiple airspeed/heading/altitude instructions back north then west and finally south to a new Controller who eventually worked us back eastbound on course. I was glad when the Captain told me that he heard on our Company frequency that flights behind us were now getting ATC assistance; being re-routed to avoid the weather. With moderate-to-heavy precipitation close to the departure field; I prefer ATC be proactive to provide options/routing around the weather; since we will not have the time/distance to devise our own request. Today we were only offered a climb; and then held at 5000 FT pointing at the storms. (I can only guess that perhaps flights ahead of us climbed through it?) Congestion on the radio contributed to the problem; and I hope ATC realizes we did our best to inform them of our weather avoidance requests and actions. I believe ATC said; 'Deviation right is approved' but did not say 'Deviation up to 15 degrees right approved.' This is the only way we could have known he misunderstood our request. But only 15 degrees right would have driven us into the weather we needed to avoid. I had no intention to fly through that front. We needed to make that immediately clear to ATC when radio traffic allowed it.

Data retrieved from NASA's ASRS site as of April 2012 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.