Narrative:

I was returning to my home base. I had filed an arrival but was advised by ATC to expect to deviate because of severe weather across the state running in a southwesterly direction across the state and into the ocean on the west coast. I changed to an alternate arrival. I thought I saw a hole in the line but it closed up so I requested ATC to give me a vector to a hole he saw on his radar. My radar showed consistent 'red' with a few 'orange' and 'yellow' areas. He gave me a right turn to 120 degrees and said some airplane had gotten through. My radar showed mostly 'red.' I turned to the 'hole' and as I got there; it closed up. I was at 11000 ft. I encountered severe; maybe extreme turbulence and dropped almost 1000 ft approximately 5 minutes into the penetration. I requested a descent and said I need to descend now. After that; I encountered more turbulence to a lesser degree and the controller gave me a heading of 130 and said try to go to the eastern coastline. I complied and made it through. I requested a descent again and he cleared me to 4000 ft. The altitude was good with just moderate rain and a large amount of lightening. I then broke out and landed VFR at my home airport without further incident. The reason I am submitting this report is for my drop of 1000 ft in the storm. I was in a large amount of turbulence and then all of a sudden; I dropped. It was not an intentional altitude violation and was inadvertent. At that point I was not in control of the airplane and I obviously didn't want to try to maintain altitude when it was so violent. ATC didn't say anything about the conflict but I wanted to report it anyway.

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Original NASA ASRS Text

Title: A BE9L pilot reported penetrating a line of severe thunderstorms and loosing 1;000 FT after experiencing 'extreme' turbulence.

Narrative: I was returning to my home base. I had filed an arrival but was advised by ATC to expect to deviate because of severe weather across the state running in a southwesterly direction across the state and into the ocean on the west coast. I changed to an alternate Arrival. I thought I saw a hole in the line but it closed up so I requested ATC to give me a vector to a hole he saw on his radar. My radar showed consistent 'red' with a few 'orange' and 'yellow' areas. He gave me a right turn to 120 degrees and said some airplane had gotten through. My radar showed mostly 'red.' I turned to the 'hole' and as I got there; it closed up. I was at 11000 FT. I encountered severe; maybe extreme turbulence and dropped almost 1000 FT approximately 5 minutes into the penetration. I requested a descent and said I need to descend now. After that; I encountered more turbulence to a lesser degree and the controller gave me a heading of 130 and said try to go to the eastern coastline. I complied and made it through. I requested a descent again and he cleared me to 4000 FT. The altitude was good with just moderate rain and a large amount of lightening. I then broke out and landed VFR at my home airport without further incident. The reason I am submitting this report is for my drop of 1000 FT in the storm. I was in a large amount of turbulence and then all of a sudden; I dropped. It was not an intentional altitude violation and was inadvertent. At that point I was not in control of the airplane and I obviously didn't want to try to maintain altitude when it was so violent. ATC didn't say anything about the conflict but I wanted to report it anyway.

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.