the average swell wave height, use the height of all of the swell waves, not just the highest 1/3, as used for sea waves.  Similarly,  when  determining  average  period, count and time all of the rounded swell wave crests passing the fixed reference pointed. Make swell wave observations from the side of the ship the waves are approaching from to see the wave pattern better. The swell wave direction should be determined from a relatively high position on the ship so that a larger area of the sea may be observed. Frequently  more  than  one  group  of  swell  waves may  be  observed,  each  coming  from  a  different direction. When this happens, you should attempt to determine  average  height,  average  period,  and  direction for each swell wave group. Swell wave groups should differ in direction from each other or from the sea waves by 30° or more to be considered and reported in an observation. Further  information  on  sea  and  swell  wave observations  is  contained  in  NAVMETOCCOMINST 3144.1, as well as H.O. Pub 603, Practical Methods for Observing and Forecasting Ocean Waves. ROMEO CORPIN Shipboard Aerographer’s Mates are occasionally tasked to recommend Romeo Corpin for underway replenishment   (UNREP)   operations,   including connected  replenishment  (CONREP)  and  vertical replenishment (VERTREP). Romeo Corpin is the best course and speed a ship should "come to" to minimize the effects of the seas and swell on the ship. Wind is also an important consideration. The most desirable course gives the ship the most stable passage to minimize roll, pitch, and yaw of the ship, while limiting the apparent winds across the deck to a safe working level for personnel.  During  VERTREP  operations,  Romeo Corpin   may   be   limited   by   the   relative   wind requirements  for  the  helicopters  involved. General guidance for determination of Romeo Corpin is found in  Underway  Replenishment,  NWP  4-01.4.  Much  of  the necessary guidance for the best replenishment course depends on how each individual ship type handles in different sea conditions. This information may be obtained from a qualified Underway Officer of the Deck.  All  requests  for  Romeo  Corpin  should  be referred to the Forecaster. REVIEW  QUESTIONS Q68. Define wave height. Q69. What factors will determine the maximum height of sea waves for any location? Q70. Q71. Q72. Q73. Q74. Q7.5. What would be the average wave height with a sea state of 5? Define  wave  period. How is wave direction determined? What is meant by the term "significant wave height"? How do swell waves differ from sea waves? How is swell wave height determined? ICE ACCRETION LEARNING  OBJECTIVES:  Define  ice accretion. Describe the characteristics of ice accretion. List elements to be included in the observation of ice accretion. Ice observations are conducted as part of general shipboard weather observations. Ice accretion is the accumulation of clear ice (glaze) or rime ice on the outside structures of a ship. Ice may form on a ship when  the  air  temperature  is  below  freezing  and hydrometeors are present. Glaze commonly forms when the air temperature is between 32°F and 25°F (0°C and -4°C) with dense fog, freezing rain or drizzle, or blowing spray. Below 25°F the probability of freezing  precipitation  drops  sharply.  As  the temperature  approaches  14°F,  (-10°C),  fog  and  blowing spray form rime ice rather than clear ice, because the freezing occurs too fast for the trapped air bubbles to escape. Ice tends to accumulate first on wires, railings, masts and exposed fittings, and then on flat surfaces receiving little heating from the interior of the ship.  Ice accumulates last on decks and bulkheads heated from within the ship. Ice accretion is dangerous not only to personnel who must walk across or work on the weather decks, but to the ship as well. Ice accumulations may break  wires  and  antennas.  If  the  accumulation  is  heavy enough, the added weight on the superstructure may cause the ship to roll excessively or capsize. Observations   of   ice   accretion   include   a determination of the source of the moisture, such as fog, blowing spray, or freezing precipitation, as well as an average  measurement  of  the  thickness  of  the accumulated ice, in centimeters. The observation also requires a determination of the rate of accumulation or melt-off. 1-49