Narrative:

40 mi from final destination when approach controller advised that a level 4-5 thunderstorm was over the destination airport and along the final approach course, and that it was moving to the east/northeast at 20-25 KTS. I was approaching from the east and requested to hold to the nne of my final destination until the widely scattered thunderstorm moved away from final destination. Approach controller gave holding instructions and I proceeded to the holding point (approximately 30 mi from destination airport). 10 mi from holding point the controller advised that the cell was starting to move away from destination airport, and that he could provide vectors to 'sequence' me to the final approach course and around the thunderstorm cell. I accepted and he began vectoring me. After the third vector, he came back on and advised that his radar was now showing a level 2-3 cell, 1 mi in diameter, at my 12 O'clock. It was too late to avoid. I penetrated the cell advising controller of conditions, specifically moderate turbulence. I subsequently gained approximately 300-400 ft of altitude and may have deviated from my assigned altitude of 4000 ft. Having been taught that when encountering significant turbulence it is more important to keep the airplane upright/level, I was not sure of my exact altitude, but I think it indicated 4300 ft at one point in time (a few seconds). A downdraft then took me back down to around 4100 ft and I then corrected to 4000 ft once exiting the cell (total time in cell approximately 20 seconds). After exiting the cell, WX was a lot better (smoother, greater visibility, etc). At the time, the controller was working 2-3 other aircraft, but I believe that they were not in the vicinity of my flight (greater than 15 mi away). In the future, I will request to stay greater than 20 mi away from level 4-5 thunderstorms and greater than 10-15 mi from level 3 thunderstorms. Overall, being my first flight in significant convective activity, it was a definite learning experience!

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Original NASA ASRS Text

Title: A PVT INST RATED PLT FLYING A C210 TO DAY WAS UNABLE TO MAINTAIN ASSIGNED ALT DUE TO WX.

Narrative: 40 MI FROM FINAL DEST WHEN APCH CTLR ADVISED THAT A LEVEL 4-5 TSTM WAS OVER THE DEST ARPT AND ALONG THE FINAL APCH COURSE, AND THAT IT WAS MOVING TO THE E/NE AT 20-25 KTS. I WAS APCHING FROM THE E AND REQUESTED TO HOLD TO THE NNE OF MY FINAL DEST UNTIL THE WIDELY SCATTERED TSTM MOVED AWAY FROM FINAL DEST. APCH CTLR GAVE HOLDING INSTRUCTIONS AND I PROCEEDED TO THE HOLDING POINT (APPROX 30 MI FROM DEST ARPT). 10 MI FROM HOLDING POINT THE CTLR ADVISED THAT THE CELL WAS STARTING TO MOVE AWAY FROM DEST ARPT, AND THAT HE COULD PROVIDE VECTORS TO 'SEQUENCE' ME TO THE FINAL APCH COURSE AND AROUND THE TSTM CELL. I ACCEPTED AND HE BEGAN VECTORING ME. AFTER THE THIRD VECTOR, HE CAME BACK ON AND ADVISED THAT HIS RADAR WAS NOW SHOWING A LEVEL 2-3 CELL, 1 MI IN DIAMETER, AT MY 12 O'CLOCK. IT WAS TOO LATE TO AVOID. I PENETRATED THE CELL ADVISING CTLR OF CONDITIONS, SPECIFICALLY MODERATE TURB. I SUBSEQUENTLY GAINED APPROX 300-400 FT OF ALT AND MAY HAVE DEVIATED FROM MY ASSIGNED ALT OF 4000 FT. HAVING BEEN TAUGHT THAT WHEN ENCOUNTERING SIGNIFICANT TURB IT IS MORE IMPORTANT TO KEEP THE AIRPLANE UPRIGHT/LEVEL, I WAS NOT SURE OF MY EXACT ALT, BUT I THINK IT INDICATED 4300 FT AT ONE POINT IN TIME (A FEW SECONDS). A DOWNDRAFT THEN TOOK ME BACK DOWN TO AROUND 4100 FT AND I THEN CORRECTED TO 4000 FT ONCE EXITING THE CELL (TOTAL TIME IN CELL APPROX 20 SECONDS). AFTER EXITING THE CELL, WX WAS A LOT BETTER (SMOOTHER, GREATER VISIBILITY, ETC). AT THE TIME, THE CTLR WAS WORKING 2-3 OTHER ACFT, BUT I BELIEVE THAT THEY WERE NOT IN THE VICINITY OF MY FLT (GREATER THAN 15 MI AWAY). IN THE FUTURE, I WILL REQUEST TO STAY GREATER THAN 20 MI AWAY FROM LEVEL 4-5 TSTMS AND GREATER THAN 10-15 MI FROM LEVEL 3 TSTMS. OVERALL, BEING MY FIRST FLT IN SIGNIFICANT CONVECTIVE ACTIVITY, IT WAS A DEFINITE LEARNING EXPERIENCE!

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.