Narrative:

En route to sju a large buildup was observed downtrack in the vicinity of owski. Most of the storm was to the left of track and hidden in clouds. The western edge was sharp and well defined. The storm consisted of several cells. I waited until I could check the 120 NM range on radar before making any decisions. I then requested through communication radio a 25 NM deviation to the west. We were approximately 100 mi from the storm and I feel that should have given ATC enough time to act on the request. While we were waiting for a reply and monitoring the HF radio, we heard 2 different aircraft receive clrncs for downtrack waypoint crossing restrictions. Some of these are effective many mi and many mins away while we are rapidly running out of both mi and mins. When I felt I could wait no longer, I called communication radio and was told our clearance would be coming through any min. I could wait no longer, so I initiated a turn to the west and, as I did, communication radio advised that deviation to the east was approved but not to the west. However, it was too late as to try to reverse course at that point would have taken us right into the nearest cell. I requested communication radio to advise ATC that I was exercising captain emergency authority and deviating to the west but that we would keep the deviation to the absolute min. A close traffic watch was maintained and TCASII was closely monitored. The proper VHF transmission on guard was made and, since the cell was so well defined on the west, I was able to visually pass close and the deviation was held to the min.

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Original NASA ASRS Text

Title: EMER AUTHORITY. HDG TRACK POS DEV.

Narrative: ENRTE TO SJU A LARGE BUILDUP WAS OBSERVED DOWNTRACK IN THE VICINITY OF OWSKI. MOST OF THE STORM WAS TO THE L OF TRACK AND HIDDEN IN CLOUDS. THE WESTERN EDGE WAS SHARP AND WELL DEFINED. THE STORM CONSISTED OF SEVERAL CELLS. I WAITED UNTIL I COULD CHK THE 120 NM RANGE ON RADAR BEFORE MAKING ANY DECISIONS. I THEN REQUESTED THROUGH COM RADIO A 25 NM DEV TO THE W. WE WERE APPROX 100 MI FROM THE STORM AND I FEEL THAT SHOULD HAVE GIVEN ATC ENOUGH TIME TO ACT ON THE REQUEST. WHILE WE WERE WAITING FOR A REPLY AND MONITORING THE HF RADIO, WE HEARD 2 DIFFERENT ACFT RECEIVE CLRNCS FOR DOWNTRACK WAYPOINT XING RESTRICTIONS. SOME OF THESE ARE EFFECTIVE MANY MI AND MANY MINS AWAY WHILE WE ARE RAPIDLY RUNNING OUT OF BOTH MI AND MINS. WHEN I FELT I COULD WAIT NO LONGER, I CALLED COM RADIO AND WAS TOLD OUR CLRNC WOULD BE COMING THROUGH ANY MIN. I COULD WAIT NO LONGER, SO I INITIATED A TURN TO THE W AND, AS I DID, COM RADIO ADVISED THAT DEV TO THE E WAS APPROVED BUT NOT TO THE W. HOWEVER, IT WAS TOO LATE AS TO TRY TO REVERSE COURSE AT THAT POINT WOULD HAVE TAKEN US RIGHT INTO THE NEAREST CELL. I REQUESTED COM RADIO TO ADVISE ATC THAT I WAS EXERCISING CAPT EMER AUTHORITY AND DEVIATING TO THE W BUT THAT WE WOULD KEEP THE DEV TO THE ABSOLUTE MIN. A CLOSE TFC WATCH WAS MAINTAINED AND TCASII WAS CLOSELY MONITORED. THE PROPER VHF XMISSION ON GUARD WAS MADE AND, SINCE THE CELL WAS SO WELL DEFINED ON THE W, I WAS ABLE TO VISUALLY PASS CLOSE AND THE DEV WAS HELD TO THE MIN.

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.