A PA31 PLT ON SHORT FINAL TO 1R7; IMPACTED A TREE TOP; CAUSING HIM TO GO AROUND.

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I LEFT DYERSBURG; TN (DYR) AT XA15 LCL FOR JACKSON; MS (JAN) TO PICK UP A PAX AND FLY THEM BACK TO DYERSBURG. THE FLT WAS UNEVENTFUL UNTIL APCHING THE JACKSON AREA. THERE WAS A BROKEN LINE OF TSTMS JUST N OF JACKSON. I MADE IT THROUGH THIS LINE WITHOUT ANY TROUBLE AND WAS GIVEN CLRNC FOR THE APCH TO RWY 34L AT JAN. WHILE ON THE APCH THE TSTMS CAME OVER THE FIELD AND I BROKE OFF THE APCH. I HELD FOR ABOUT 45 MINS AND THEN STARTED THE APCH AGAIN. JACKSON APCH SAID THE AREA HAD CLOSED UP COMPLETELY AND SUGGESTED THAT I PROCEED S TO BROOKHAVEN; MS (1R7) SINCE IT WAS CLOSE AND HAD A GOOD 5000 FT RWY; AND THE TSTMS WERE STILL N OF THIS AREA. I WAS TURNED OVER TO MEMPHIS CTR AND PROCEEDED TO BROOKHAVEN IFR. WITH THE ARPT IN SIGHT I CANCELLED MY IFR; ACTIVATED THE RWY LIGHTS AND ENTERED DOWNWIND FOR RWY 22. I NOTICED THE DISPLACED THRESHOLD FOR RWY 22 AND ENTERED BASE AT 1500 FT. I WAS NOT ABLE TO SEE A WIND SOCK BUT KNEW THAT THE WINDS WERE FAIRLY STRONG OUT OF THE SW. AS HAS BEEN MY CUSTOM SINCE I HAVE HAD GPS GND SPD DATA; I MONITOR MY GND SPD ON APCH; ESPECIALLY AT NIGHT OR IN ADVERSE WX. MY BASE LEG GND SPD WAS 132 KTS AND AS I TURNED FINAL IT DROPPED TO 98 KTS. THEN AS I CAME CLOSE TO THE THRESHOLD; THE SPD DROPPED RAPIDLY FROM 98 KTS. THEN AS I CAME CLOSE TO THE THRESHOLD; THE SPD DROPPED RAPIDLY FROM 98 KTS TO 77 KTS. IMMEDIATELY ADDED PWR AND BEGAN A CLB. AT THAT POINT; MY LNDG LIGHTS SHOWED THE TOP OF A TREE JUST AHEAD WHICH I HIT WITH THE R ENG. I IMMEDIATELY ADDED PWR; RETRACTED GEAR AND FLAPS; AND MADE A GAR. I ENTERED DOWNWIND AND CAME BACK IN AND LANDED WITHOUT INCIDENT. I HAD INCURRED DAMAGE TO THE R PROP; COWLING; GEAR DOOR AND FLAPS ALONG WITH AN INDENTION IN THE R WING. THE NEXT DAY I SURVEYED THE SITE WITH THE MGR AND ASSISTANT MGR OF THE BROOKHAVEN ARPT. THE TREES ON RWY 22 DO NOT MEET REQUIREMENTS EVEN FOR THE DISPLACED THRESHOLD AND A PROGRAM IS IN PLACE TO CLR THIS AREA OF TREES BEGINNING IN AUGUST. IF I HAD NOT ADDED PWR WHEN I DID; AFTER SEEING THE WINDSHEAR; I DO NOT BELIEVE I WOULD HAVE MADE IT THROUGH THE TREES. THE TREE NEXT TO THE ONE I HIT HAD A LARGE TV ANTENNA ON IT AND I DO NOT KNOW HOW I MISSED IT. THE USE OF GPS FOR WIND PROBS; ETC; IS NOT CURRENTLY DISCUSSED IN ANY PLT TRAINING AREAS THAT I KNOW; BUT THINK IT SHOULD BE.