A. INTRODUCTION 



The Hydrographic Office Wave Charts are an attempt to present ocean 

 wave conditions synoptically over a large ocean area. Wave charts were 

 first drawn on an experimental basis in December 1952, and their develop- 

 ment has continued on a part-time basis since then. The charts are now 

 being drawn daily* 



The need for such a chart became apparent in planning the activities 

 of the Hydrographic Office Acoustic, Meteorological, Oceanographic Survey 

 (AMOS) cruises, and for special area surveys. With such forecasts, survey 

 work could be scheduled according to expected wave conditions, and locations 

 chosen in the most favorable areas for operating, thereby making survey time 

 most productive. 



Requests for forecasts of wave conditions for specific projects by 

 Fleet Commanders have increased during tne past years. The wave charts be- 

 came particularly valuable when the number of wave forecasts issued began 

 to increase, since the charts made possible immediate evaluation of wave 

 conditions for a large ocean area. 



This study includes a one-week series of synoptic wave charts and 

 2lt-hour prognostic wave charts. This particular series of charts was selected 

 for presentation because of the high wave activity, making the relationships 

 between the predominant wave trains and the synoptic systems generating them 

 stand out much more clearly. Other than this, there are no features of this 

 series which differentiate its charts from those drawn daily at the Hydro- 

 graphic Office. 



B. SYNOPTIC WAVE CHART 



The synoptic wave charts presented in this study are based primarily 

 upon ship observations. A small percentage of plots consists of calculated 

 values, which are used only in -sreas where ship observations are sparse or 

 nonexistent. The plots consist of wind speed and direction, wave direction, 

 height, and period; if the ship observation contains no wave group, wind 

 velocity and direction are plotted. The frontal systems and pressure centers 

 are drawn in. The plotter enters all values reported irrespective of whether 

 cr not they appear reasonable. The rejection or retention of data is de- 

 termined by the analyzer. 



The synoptic wave charts are drawn on the basis of the 1200Z ship ob- 

 servations. However, the 0600Z ship observations are also included to com- 

 pensate for missing or garbled 1200Z reports and to provide an indication 

 of trend. When many ship observations, are available for the same general 

 location, the most representative observations are plotted and the rest 

 rejected. The 0600Z and 12007, ship observations -ire normally plotted in 

 different colors for ei Lysis; this series, however, was plotted in 



one color, according to the c< led in ',"■. ] 1 ., Tor easier repro- 

 duction. 



