Narrative:

While in cruise at FL390, we encountered severe turbulence. The entire episode lasted less than 1 min from start to finish. The captain determined with radar that we would top the large rain cell ahead. When she determined we had passed the cell, she gave a PIREP to ATC. About 2 mins later, the following things happened: airspeed increased from mach 0.80 to mach 0.86, temperature decreased from its previous reading of -20 degrees C, we encountered moderate icing, and altitude fluctuated from approximately FL396 to FL387. Positive aircraft control was maintained throughout the episode. After this, we reported what had happened to ATC. Our experience may have been avoided if we had altered course to avoid the cell and all of its associated adverse WX conditions.

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Original NASA ASRS Text

Title: FLC OF LTT ACFT ENCOUNTERS TSTM RELATED TURB WHILE AT CRUISE.

Narrative: WHILE IN CRUISE AT FL390, WE ENCOUNTERED SEVERE TURB. THE ENTIRE EPISODE LASTED LESS THAN 1 MIN FROM START TO FINISH. THE CAPT DETERMINED WITH RADAR THAT WE WOULD TOP THE LARGE RAIN CELL AHEAD. WHEN SHE DETERMINED WE HAD PASSED THE CELL, SHE GAVE A PIREP TO ATC. ABOUT 2 MINS LATER, THE FOLLOWING THINGS HAPPENED: AIRSPD INCREASED FROM MACH 0.80 TO MACH 0.86, TEMP DECREASED FROM ITS PREVIOUS READING OF -20 DEGS C, WE ENCOUNTERED MODERATE ICING, AND ALT FLUCTUATED FROM APPROX FL396 TO FL387. POSITIVE ACFT CTL WAS MAINTAINED THROUGHOUT THE EPISODE. AFTER THIS, WE RPTED WHAT HAD HAPPENED TO ATC. OUR EXPERIENCE MAY HAVE BEEN AVOIDED IF WE HAD ALTERED COURSE TO AVOID THE CELL AND ALL OF ITS ASSOCIATED ADVERSE WX CONDITIONS.

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.