nearly all the arctic region of North America. The number of 

 days with precipitation in the Canadian archipelago is particularly 

 small in winter. A maximum frequency occurs in the region of 

 the North Sea Low in October and November, while on the Asiatic 

 Russian north coast the maximum appears in September, though 

 the period of heaviest precipitation is more generally July and 

 August. 



FORECASTING AIDS 



The following remarks relative to forecasting the weather in 

 the Canadian archipelago were extracted from reports submitted 

 by naval aerologists who have served with task forces operating 

 in the area. 



The rules of forecasting used in middle latitudes can be con- 

 sidered of consequence, but cannot be completely relied upon for 

 forecasting in the Canadian Arctic. Single station observations, 

 aided by a general circulation pattern, must be the basis of present 

 forecasting in this area. First-hand experience is of prime im- 

 portance as local influences are a major factor and vary widely 

 from place to place within the area. 



Forecasts covering periods of 18 to 24 hours are the maximum 

 lengths found to have a satisfactory degree of reliability, because 

 of the extent to which forecasts depend upon single station analysis 

 and local observations. By use of the few synoptic reports avail- 

 able in the Canadian archipelago, weather can be forecast in a 

 general way, but without experience in the area itself and without 

 greater facilities than are now present, detailed conditions cannot 

 be determined for longer periods in advance. The use of per- 

 sistence forecasting, that is observing the trend of weather toward 

 improving or deteriorating conditions, cannot be relied upon except 

 for a period of a very few hours, and then only in a very general 

 way. 



WEATHER SCHEDULES 



1. Radio Washington cannot normally be copied in most arctic 

 areas, and the best information available comes from Dorval, 

 Canada (VFN), or Westover Field, Mass. (WSO). 



2. One or two radiomen should be assigned the primary respon- 

 sibility for copying weather schedules. A radioman who is fa- 

 miliar with the methods of broadcast peculiar to weather schedules 

 understands what is required of him and obtains a more complete 

 coverage than would an unindoctrinated radioman. 



130 



