WIND ATLAS OF THE NORTH PACIFIC 



By 



James W. McGary, Oceanographer 



and 



Thomas M. Naito, Fishery Aid 



Pacific Oceanic Fishery Investigations 



Honolulu, T. H. 



In commercial fishing, as in any other 

 maritime operation, weather must be consi- 

 dered when evaluating the operating potentiali- 

 ties of an area. Regardless of the abundance 

 of fish, if wind and sea prevent a vessel from 

 obtaining pay loads, the area has greatly re- 

 duced value for a commercial fishery. The 

 results of the first three exploratory fishing 

 cruises of vessels of the Pacific Oceanic Fish- 

 ery Investigations {POFI)to the waters north of 

 Hawaii in search of new albacore grounds denn- 

 onstrated this situation quite strikingly. On IZ 

 of the 25 days spent north of 30*N. latitude, on 

 John R. Manning cruise 19 (January- March 

 1954), the seas were considered too rough for 

 longlining. On John R. Manning cruise 22 

 (September-November 1954), on 18 of 41 days, 

 sea conditions were not suitable for fishing, and 

 on JohnR. Manning cruise 23 (January-February 

 1955), fishing was not possible on 9 of 25 days 

 (Shomura and Otsu 1956). Furthermore, the 

 northern limit of the albacore distribution in 

 the central North Pacific during the fall and 

 winter months could not be definitely established 

 because adverse weather forced the vessels to 

 turn south. 



As the result of this experience, work was 

 started on a guide which, it was hoped, would 

 aid in evaluating the operational limitations of 

 small (80 to 130 feet) vessels at different sea- 

 sons of the year in the North Pacific above 30 *N. 

 latitude. The resulting atlas consists of a series 

 of four contour charts for each month, (with a 

 few exceptions) showing the frequency of winds 

 of 20 knots or less, 25 knots or less, 30 knots 

 or less, and 35 knots or less, and a fifth show- 

 ing the maximum wind that has been observed 

 in each 5-degree square of latitude and longi- 

 tude (charts 1-53). 



The existing wind summaries (e.g., 

 McDonald 1938, U. S. Navy 1956) publishedfor 

 the benefit of mariners in the North Pacific pro- 

 vide a wealth of data on average winds, percent- 

 age of winds of gale force or greater, and per- 

 centage of calms. While these data are useful 

 they do not provide the essential information for 

 evaluating operating areas in terms of potential 



operating time for fishing vessels since they do 

 not provide a precise breakdown of data in the 

 20-30 knot range, where experience has shown 

 that most fishing operations must cease. 



Ideally, sea height would be a better indi- 

 cator of operating conditions than wind, but there 

 is not a sufficient nunnber of wave observations 

 available for the North Pacific to permit the prep- 

 aration of reliable charts. The U. S. Weather 

 Bureau and the U. S. Navy Hydrographic Office 

 have been compiling wind data from ships' 

 weather reports and deck logs since the latter 

 part of the 19thcentury, but it was only recently, 

 September 1, 1955, that a concerted effort was 

 made to have all vessels report sea conditions 

 (A. J. Rohlfs, USWB personal connmunication). 

 The relation between wind and sea has long been 

 recognized, and sea characteristics are still 

 used as the basis for estinnating wind speed on 

 vessels not equipped with anemometers 

 (Bowditch 1953, p, 52). 



The validity of using wind as an indicator 

 of sea state has also been demonstrated in the 

 development of wave-forecasting techniques. 

 Sverdrup and Munk (194 7) derived equations for 

 computing wave height and velocity from wind 

 velocity, duration of wind, and fetch. Duration 

 of wind refers to the period of time during which 

 the wind velocity has been approximately uni- 

 form. Fetch is the length of the generating area 

 or the distance over which the wind velocity has 

 been approximately steady. Detailed instruc - 

 tions for connputing these parameter s and wave- 

 forecasting techniques are given in USNHO 

 Miscellaneous Publication 11275. Sverdrup and 

 Munk (1947, p. 31) also found that the British 

 Admiralty's empirical rule that waves lose 

 roughly one -third of their height each tinne they 

 travel a distance in miles equal to their length 

 in feet was in general agreement with theoreti - 

 cal values and could be used to estimate the 

 decay rate of waves after they left the genera- 

 ting area. 



From data in Wave Report No. 73 (unpub- 

 lished), Scripps Institution of Oceanography , 

 table 1 was compiled showing the minimum time 



