PA46 COM PLT ENCOUNTERS TSTMS AND DOWNDRAFTS ON APCH.

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ARRIVING IN ZZZ THERE WERE TSTMS IN THE VICINITY JUST S OF ZZZ. MY ARR PATH WOULD HAVE HAD ME GOING STRAIGHT THROUGH THE STORM SO I DIVERTED E AROUND THE STORM STAYING VMC THE ENTIRE WAY. UPON REACHING A STRAIGHT IN FINAL THERE WERE SHOWERS IN THE IMMEDIATE AREA OF THE ARPT BUT STILL VMC I ELECTED TO CONTINUE THE APCH. I WAS ON SHORT FINAL WHEN TWR LOST SIGHT OF ME AND ASKED IF I STILL HAD THE RWY IN SIGHT. I DID AND CONTINUED THE APCH WHILE NOT 10 SECONDS LATER THE SAME DOWNBURST THAT CAUSED THE TWR TO LOSE SIGHT OF ME STARTED PUSHING ME TO THE GND. I LOST SIGHT OF THE RWY; ADDED FULL PWR AND DROPPED MY FIRST NOTCH OF FLAPS AND ATTEMPTED TO GO AROUND BUT WAS THROWN TO THE GND AND AFTER I BOUNCED WAS AIRBORNE AGAIN. WHEN I GOT TO A SAFE ALT RETRACTED MY GEAR BUT THE HYD PUMP STARTED TO WORK AND QUIT WHILE IT WAS SUCKING UP THE NOSEWHEEL. I TRIED TO CYCLE THE GEAR BUT TO NO AVAIL SO I USED THE EMER EXTENSION AND STILL DID NOT GET A DOWN AND LOCKED FROM MY NOSE GEAR HOWEVER THE MAINS WERE READING DOWN. I DECLARED AN EMER AND SET UP FOR A LNDG. PRIOR TO LNDG I HAD THE 2 PAX SIT IN THE FAR AFT SEATS ALONG WITH THROWING ALL AVAILABLE BAGS/WT INTO THE AFT CARGO AREA. ON LNDG I TOUCHED DOWN MAINS FIRST AND KEPT THE NOSEWHEEL OFF AS LONG AS POSSIBLE. WHEN THE MAINS TOUCHED THE NOSEWHEEL SHOWED DOWN AND WHEN THE NOSE FINALLY TOUCHED THE GEAR HELD AND IT WAS A NON EVENTFUL LNDG. WHAT I BELIEVE CAUSED THE SIT IS THE HARD LNDG MAY HAVE CAUSED HARM TO THE HYD PUMP FOR THE LNDG GEAR CAUSING IT TO FAIL. HOWEVER I'M NOT CERTAIN WHY THE NOSE GEAR DIDN'T GET LOCKED INTO PLACE AFTER THE EMER GEAR EXTENSION. ALSO ULTIMATELY I SHOULD HAVE AVOIDED THE AREA ALL TOGETHER WITH THE TSTMS IN THE VICINITY. HOW CAN IT BE PREVENTED? A DECISION TO GO AROUND PRIOR TO LOSING SIGHT OF THE RWY (UPON TWR LOSING SIGHT). ALSO A DECISION TO HOLD AND WAIT FOR CONDITIONS TO IMPROVE WOULD HAVE BEEN IDEAL.