Program: 81880
Project: 81880
Buggy source:
public void tick(){
  super.tick();
  ticksExisted++;
  posGround=new Vec3(pos.xCoord,pos.yCoord,pos.zCoord);
  posGround.yCoord=currentTopYBlock;
  Side side=FMLCommonHandler.instance().getEffectiveSide();
  if (side == Side.CLIENT) {
    if (!WeatherUtil.isPaused()) {
      ticksSinceLastPacketReceived++;
      tickClient();
      if (isTornadoFormingOrGreater() || isCycloneFormingOrGreater()) {
        tornadoHelper.tick(manager.getWorld());
      }
      if (levelCurIntensityStage >= STATE_HIGHWIND) {
        if (manager.getWorld().isRemote) {
          tornadoHelper.soundUpdates(true,isTornadoFormingOrGreater() || isCycloneFormingOrGreater());
        }
      }
      tickMovementClient();
    }
  }
 else {
    if (isTornadoFormingOrGreater() || isCycloneFormingOrGreater()) {
      tornadoHelper.tick(manager.getWorld());
    }
    if (levelCurIntensityStage >= STATE_HIGHWIND) {
      if (manager.getWorld().isRemote) {
        tornadoHelper.soundUpdates(true,isTornadoFormingOrGreater() || isCycloneFormingOrGreater());
      }
    }
    tickMovement();
    if (layer == 0) {
      if (!isCloudlessStorm()) {
        tickWeatherEvents();
        tickProgression();
        tickSnowFall();
      }
    }
 else {
      size=maxSize;
    }
  }
  if (layer == 0) {
    posBaseFormationPos=new Vec3(pos.xCoord,pos.yCoord,pos.zCoord);
    if (levelCurIntensityStage >= StormObject.levelStormIntensityFormingStartVal) {
      if (levelCurIntensityStage >= StormObject.levelStormIntensityFormingStartVal + 1) {
        formingStrength=1;
        posBaseFormationPos.yCoord=posGround.yCoord;
      }
 else {
        float intensityAdj=Math.min(1F,levelCurStagesIntensity * 2F);
        float val=(levelCurIntensityStage + intensityAdj) - StormObject.levelStormIntensityFormingStartVal;
        formingStrength=val;
        double yDiff=pos.yCoord - posGround.yCoord;
        posBaseFormationPos.yCoord=pos.yCoord - (yDiff * formingStrength);
      }
    }
 else {
      if (levelCurIntensityStage == STATE_HIGHWIND) {
        formingStrength=1;
        posBaseFormationPos.yCoord=posGround.yCoord;
      }
 else {
        formingStrength=0;
        posBaseFormationPos.yCoord=pos.yCoord;
      }
    }
  }
}

Fixed version (ground truth):
public void tick(){
  super.tick();
  posGround=new Vec3(pos.xCoord,pos.yCoord,pos.zCoord);
  posGround.yCoord=currentTopYBlock;
  Side side=FMLCommonHandler.instance().getEffectiveSide();
  if (side == Side.CLIENT) {
    if (!WeatherUtil.isPaused()) {
      ticksSinceLastPacketReceived++;
      tickClient();
      if (isTornadoFormingOrGreater() || isCycloneFormingOrGreater()) {
        tornadoHelper.tick(manager.getWorld());
      }
      if (levelCurIntensityStage >= STATE_HIGHWIND) {
        if (manager.getWorld().isRemote) {
          tornadoHelper.soundUpdates(true,isTornadoFormingOrGreater() || isCycloneFormingOrGreater());
        }
      }
      tickMovementClient();
    }
  }
 else {
    if (isTornadoFormingOrGreater() || isCycloneFormingOrGreater()) {
      tornadoHelper.tick(manager.getWorld());
    }
    if (levelCurIntensityStage >= STATE_HIGHWIND) {
      if (manager.getWorld().isRemote) {
        tornadoHelper.soundUpdates(true,isTornadoFormingOrGreater() || isCycloneFormingOrGreater());
      }
    }
    tickMovement();
    if (layer == 0) {
      if (!isCloudlessStorm()) {
        tickWeatherEvents();
        tickProgression();
        tickSnowFall();
      }
    }
 else {
      size=maxSize;
    }
  }
  if (layer == 0) {
    posBaseFormationPos=new Vec3(pos.xCoord,pos.yCoord,pos.zCoord);
    if (levelCurIntensityStage >= StormObject.levelStormIntensityFormingStartVal) {
      if (levelCurIntensityStage >= StormObject.levelStormIntensityFormingStartVal + 1) {
        formingStrength=1;
        posBaseFormationPos.yCoord=posGround.yCoord;
      }
 else {
        float intensityAdj=Math.min(1F,levelCurStagesIntensity * 2F);
        float val=(levelCurIntensityStage + intensityAdj) - StormObject.levelStormIntensityFormingStartVal;
        formingStrength=val;
        double yDiff=pos.yCoord - posGround.yCoord;
        posBaseFormationPos.yCoord=pos.yCoord - (yDiff * formingStrength);
      }
    }
 else {
      if (levelCurIntensityStage == STATE_HIGHWIND) {
        formingStrength=1;
        posBaseFormationPos.yCoord=posGround.yCoord;
      }
 else {
        formingStrength=0;
        posBaseFormationPos.yCoord=pos.yCoord;
      }
    }
  }
}