C210 PLT HAS AN ALTDEV IN ZJX AIRSPACE.

Narrative

FLT WAS CONDUCTED UNDER IMC. TKOF UNEVENTFUL. DURING CLB ENCOUNTERED BUILDING TSTM CELL AND EXCEEDED CRUISE ALT BY 1000 FT DUE TO STRONG UPDRAFT. DURING CLBOUT FROM DESTIN A LINE OF SMALL BUILDUPS WERE STARTING TO FORM INTO TSTMS. USING VISUAL REF AND A SUGGESTED HDG FROM ZJX; PIC TRIED TO NAV AROUND AND OVER BUILDUPS. AS THE ACFT WAS NEAR GROSS WT AND A VERY HOT DAY; CLB RATE WAS DOWN TO 500 FPM PASSING THROUGH 9500 FT. BASED ON A SUGGESTED HDG FROM ATC WE ENTERED A BUILDING CLOUD. FROM VISUAL OBSERVATION THE AREA LOOKED LIGHT IN COLOR WITH NO LIGHTNING OBSERVED. UPON ENTERING THE SMALL BUILDUP; THE ACFT ENTERED A STRONG UPDRAFT EXCEEDING APPROX 3000 FPM. PIC ATTEMPTED TO SLOW CLB RATE BY LOWERING NOSE AND REDUCING PWR. AIRSPD INCREASED TO THE YELLOW ARC AND PWR WAS REDUCED FURTHER. HVY RAIN AND MODERATE TURB WERE ENCOUNTERED. PIC ASKED ME TO LOOK FOR A LIGHTER OR CLEAR AREA TO FLY TO. I SUGGESTED A SLIGHT TURN BASED ON LIGHTING CONDITIONS. WE SHORTLY FLEW OUT THE SIDE AND BEGAN AN IMMEDIATE DSCNT. ABOUT THIS TIME ZJX ASKED OUR INTENTIONS SINCE WE HAD CLBED TO 12000 FT. WE SAID WE WERE IN A DSCNT TO 11000 FT. ZJX HAD ADVISED HE JUST STARTED PICKING UP A STRONG RADAR RETURN FOR WX IN OUR AREA. INCIDENT CAUSED BY POOR ASSUMPTION THAT CTR RADAR COULD GIVE A GOOD PICTURE OF THE WX AND USING VISUAL CUES TO FLY THROUGH A BUILDING LINE OF STORMS. GROSS UNDERESTIMATE OF THE UPDRAFT STRENGTH AND HOW FAST IT COULD CLB THE AIRPLANE.