omitted from the chart. Another area where, 

 in winter, the percentage of low-speed winds 

 also seems abnormally higher than climatolog- 

 ical data would indicate i s the band between 

 50° and 55 'N. latitude. The primary storm 

 track, i. e. , the path of the maximum concen- 

 tration of individual storm tracks, lies in this 

 band between October and April (U. S. Navy 

 1956), and hence the minimum percentage fre- 

 quency of low winds would be expected. Such 

 an abnornnality in the records may have 

 resulted from vessels taking shelter in the 

 Aleutian Islands during periods of high winds . 

 This tendency of wind data to become skewed 

 towards lower speeds in coastal and insular 

 areas will tend to become oceanwide in the 

 future as more and more vessels tzike advan- 

 tage of the increasing reliability and dissemi - 

 nation of marine weather forecasts in choosing 

 their sailing routes. 



The plots of maximum wind simply show 

 the maximum Beaufort force that has been 

 reported in each unit of area, regardless of the 

 number of observations. Forces of 8 or less 

 have been lumped into a single group, since 

 lower speeds are adequately covered in the 

 contour charts. In the majority of the squares 

 the mJLximum values comprise less than 1 per- 

 cent of the total observations, and in a large 

 number of the areas they represent single 

 observations. Nevertheless, they indicate 

 wrind speeds that have occurred and speeds 

 that a vessel should be able to withstand if it is 

 to operate in the area. 



USE OF THE CHAKTS IN EVALUATING 

 OPERATIONAL POTENTIALITIES 

 IN VARIOUS AREAS 



The most practical method of illustrating 

 the use of the charts is to compare the actual 

 conditions encountered by POFI vessels with the 

 average conditions indicated by the charts. 

 Taking the most adverse season first, during 

 John R. Manning cruise 19, some excellent 

 longline catches of albacore were made in late 

 January 1954 along 160'W. between 30* and 

 35 'N. latitude, but because of rough seas, fish- 

 ing was possible on only 4 of 7 days, or 57 per- 

 cent of the time. The weather log shows that 

 cnly 15 (65 percent) of the 23 wind observations 

 were 20 knots or less and winds up to 50 knots 

 were reported. Charts 1-5 show that the per- 

 centage of winds of 20 knots or less which might 

 be expected in January lies between 60 and 65 

 percent and that the maximunn speed is Beaufort 

 force 1 1 or 56-63 knots. Thus it appears that 

 the charts of winds of 20 knots or less give a 

 fair estimate, although slightly on the high side 



in this case, of the percentage of time the 

 Manning could expect to longline in the area. 



Considering next the summer season, when 

 the best conditions occur, and again using the 

 John R. Manning as the example, on cruise 32 

 of the Manning (July 25 to Septennber 3, 1956) 

 excellent gill-net and troll catches of albacore 

 were made in the area from 145*W. to 175*W. 

 longitude, between 42*N. and48*N. latitude 

 (POFI unpublished data). During the cruise two 

 independent series of wind observations were 

 made, one by the scientists as part of the stand- 

 ard 6-hour weather observations and the other 

 by the ship's officers at the end of each 4-hour 

 watch. The officers also logged additional 

 observations during periods of high winds. Both 

 series indicated that the wind frequencies were 

 about what the August charts (charts 32-34), the 

 midpoint of the cruise period, indicate for the 

 area. Of the 121 observations nnade by the 

 scientists 90 percent were 20 knots or less, 96 

 percent were 25knots or less, and the maximum 

 was 30 knots. Of the 127 reports by the ship's 

 officers, including the special observations, 87 

 percent were 20 knots or less, 94 percent 25 

 knots or less, 99 percent 30 knots or less, and 

 the maxinnum was 32 knots. The observed con- 

 ditions lie within the 85-90 percent range of the 

 frequency of winds of 20 knots or less indicated 

 for the area by the August chart (chart 32). 

 During this cruise the weather conditions per- 

 mitted gill nets to be set at 23 of the 26 planned 

 stations, or 88 percent of the time. Thus, the 

 frequency of winds of 20 knots or less appears 

 to be an excellent index of t h e percentage of 

 time suitable for gill netting. The trolling log 

 showed that conditions were suitable for trolling 

 with all lines (6) on 28-1/2 days and with a 

 reduced number of lines on 2 days, for a total 

 of 92 percent of the 32 days actually spent in the 

 area. Although trolling was performed in winds 

 of up to 27 knots under exceptional sea condi- 

 tions, a comparison of the observed wind fre- 

 quencies and the total trolling time indicates a 

 more reliable index of the probable trolling time 

 for the Manning would be about midway between 

 tlie frequencies of winds of 20 and 25 knots or 

 less. 



The actual working limit of each vessel 

 must be determined in the above manner by ex- 

 perience. Once this has been established, a 

 reliable estimate of the time that it could expect 

 to fish in the North Pacific can be obtained from 

 the charts. It is apparent, however, from the 

 frequency with which forces 10-12 appear in the 

 charts of maximum observed wind for the sum- 

 nner months, that a vessel must be capable of 

 riding out the seas generated by such winds if it 



