How to Wipe the Head in Wudu
Question

How is the head wiped in Wudu?
Praise be to Allah.Is there a specific way to wash or wipe the parts of Wudu? 
The way in which parts of the body are washed or wiped over in Wudu is not obligatory. What is obligatory is to wash the parts that are to be washed, and to wipe the parts that are to be wiped, in any manner that it is achieved. But undoubtedly following the way which is narrated from the Prophet (peace and blessings of Allah be upon him) is better and more perfect. (See Al-Mughni, 1/171) 
How to wipe the head in Wudu
Two ways of wiping over the head in Wudu have been narrated: 

After wetting the hands in water, you place them at the front of the head and wipe the head until you reach the back of the head, then you bring them back to the front of the head. 

An-Nawawi (may Allah have mercy on him) said in Sharh Muslim that the scholars unanimously agreed that this is recommended. 
This is proven in a number of Hadiths from the Prophet (peace and blessings of Allah be upon him). 
Al-Bukhaari (185) and Muslim (235) narrated from ‘Abdullah ibn Zayd (may Allah be pleased with him) that he described the Wudu of the Prophet (peace and blessings of Allah be upon him): … Then he wiped his head with his hands , front to back. He started at the front of the head and (wiped) until his hands reached the back of the head, then he brought them back to where he started. 
Abu Dawud (124) narrated that Mu`awiyah (may Allah be pleased with him) did Wudu for the people as he had seen the Messenger of Allah (peace and blessings of Allah be upon him) doing Wudu. When he reached his head, he scooped up some water into his left hand and put his hands onto the middle of his head until the water dripped down or almost dripped down. Then he wiped it from front to back, and from back to front. (Classed as authentic by Al-Albani in Sahih Abu Dawud) 
Abu Dawud (122) narrated that Al-Miqdam ibn Ma’di Yakrib (may Allah be pleased with him) said: I saw the Messenger of Allah (peace and blessings of Allah be upon him) doing Wudu. When he reached the wiping of his head, he put his hands at the front of his head (and wiped) until he reached the back, then he brought them back to the place where he had started. (Classed as authentic by Al-Albani in Sahih Abu Dawud) 
This way of wiping the head suits one whose hair is short and will not be messed up by bringing the hands back to the front of the head. 

Wiping the whole head , but in the direction of the hair only, so that the hair is not changed or messed up. 

This way of wiping suits one whose hair is long – man or woman – lest the hair be messed up by bringing back the hands. 
Ahmad (26484) and Abu Dawud (128) narrated from Ar-Rubayyi` bint Mu`awwidh ibn `Afra’ (may Allah be pleased with her) that the Messenger of Allah (peace and blessings of Allah be upon him) did Wudu in her house, and he wiped his entire head from the top of the head to the end of the hair, but he did not move the hair out of place. (Classed as sound by Al-Albani in Sahih Abu Dawud)  
Al-`Iraqi (may Allah have mercy on him) said: “What is meant is that he used to start wiping at the top of his head and end at the bottom, doing that on all sides of his head.” 
Ibn Raslan (may Allah have mercy on him) said: This method is only for one who has long hair, because if he moves his hands back again to make the water reach the roots of his hair, he will mess up his hair. 
It was narrated from Imam Ahmad (may Allah have mercy on him) that he was asked how a woman or one who has long hair like a woman should wipe their heads ? He said: If he wishes he may wipe it in the manner narrated from Ar-Rubayyi`, then he said, Like this: And he placed his hand at the top of his head and brought it down to the front, then he lifted it up and placed it where he had started (at the top of his head) and brought it down to the back. 
It may be understood that what is meant by Qarn (translated above as “the top of the head”) is the front of the head, i.e., the wiping starts at the front of the head covering all sides of it to the back of the head, i.e., he wipes his head once from front to back, and he does not bring his hands back again, to avoid messing up the hair. Ar-Rubayyi` (may Allah be pleased with her) said: Do not mess up the hair. (See ‘Awn Al-Ma`bud Sharh Sunan Abi Dawud, Nayl Al-Awtar (1/189) and Al-Mughni (1/178) 
The point is that this way is to be used by one who fears that his hair will get messed up, so he wipes his hair in the direction that the hair is growing, so that his hair will not get messed up. 
And Allah knows best.