As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TRANSIENT RADAR RETURNS 30-DEGREES LEFT OF NOSE. DISAPPEARS THEN REAPPEARS. HAPPENS IN ALL RADAR MODES. GROUNDED - YES. PERFORMED OPS CHK OF THE WXR IAW B737-800 AMM 34-43-00-710-802-001. OPS CHK PASSED AT THIS TIME. A/C OK FOR SERVICE. COULD NOT DUPLICATE FAULT.