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Table  4-4.Breaker  Angle  Modification
TIDES - 14270_97

Aerographers Mate, Module 02-Miscellaneous Observations and Codes
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Table 4-6.—Relative Wind Modification RELATIVE  WIND  MODIFICATION WIND  MODIFICATION W 36-40KT +2.0 3.0 4.0 1.5 2.0 4.0 I 31-35KT 1.5 2.0 3.0 1.0 1.5 3.0 N 26-30KT 1.0 1.5 2.0 0.5 1.0 2.0 D 21-25KT 0.5 1.0 1.5 0.0 0.5 1.5 16-20KT 0.0 0.5 1.0 0.0 0.0 1.0 S 11-15KT 0.0 0.5 1.0 0.0 0.0 1.0 P 06-10KT 0.0 0.0 0.5 0.0 0.0 0.5 E 0-05KT 0.0 0.0 0.0 0.0 0.0 0.0 E 00-30° 30-60° 60-90° 00-30° 30-60° 60-90° D ONSHORE OFFSHORE WIND DIRECTION RELATIVE TO BEACH FACE The operation go/no-go decision is usually made by SUROB  REPORTING comparing   the   MSI   (6.5   in   the   example)   to   the maximum, safe operating limits for each type of craft provided  in  the  Joint  Surf  Manual.  The  SUROB observer   should   not   be   expected   to   make   any recommendations, but may be expected to provide the modified  surf  index  calculation.  Recommendations  will be  made  by  the  forecaster.  The  MSI  can  also  be computed from the SURF program in TESS and MOSS by using input from the surf observation. In addition to MSI  calculations,  the  SURF  program  produces  a  surf forecast based on forecasted sea/swell, wind, and tide information.  Beach  profiles  can  be  created  by  manually entering  distance  versus  depth  information  obtained from  beach  survey  charts.  This  is  usually  accomplished by the observer. REVIEW  QUESTIONS Q22. What is the purpose of the Modified Surf index? Q23. When calculating the MSI what will be the value for a surf zone with 60% surging breakers and a significant breaker height of 3 feet? Q24. When calculating the MSI, what will be the value for  a  surf  zone  with  an  offshore  wind  at  70° relative at 23 knots? Q25. What  program  in  TESS/MOSS  can  be  used  to compute MSI? LEARNING  OBJECTIVES:  Explain when surf observations are reported. Explain the purpose of the SUROB Brevity Code. Depending  on  conditions  of  the  seas,  tides,  and winds, SUROBS may show significant changes every hour.  No  standard  reporting  times  or  reporting  intervals have   been   established.   The   Joint   Surf   Manual recommends at least one SUROB every 12 hours, 2 to 3 days before an operation, and then increasing to hourly within  6  hours  of  the  landing.  Normally,  operation planners  will  establish  minimum  reporting  intervals  and assign  a  time  to  commence  observations  and  reports. The  observer  should  routinely  monitor  the  surf conditions  and  submit  intermediate  or  supplemental reports  whenever  conditions  change  significantly. Nighttime surf observations are not nearly as reliable as daytime  observations.  Trends  noted  in  the  Modified Surf Index in combination with current meteorological parameters, such as wind and sea state, may provide the best estimate of actual surf conditions at night. 4-14







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