22 



APRIL WEATHER 



Maximum air temperature, 65° F. 



Minimum air temperature, 34° F. 



Average air temperature, 42.3° F. 



Visibility was less than 4 miles 49.1 per cent of the time. Visibility 

 was less than 2 miles 40.8 per cent of the time. The first half of the 

 month was particularly foggy. A glance at the weather diagram will 

 show that there was practically continuous fog from the 4th through 

 the 11th. Then a^ain on the 14th the fog blanketed the entire ice- 

 patrol area for three days. After the 16th there was comparatively 

 little fog, but the continuous fog during the first part of the month 

 brings time with fog for April well above the average of previous years. 

 The weather generally was particularly mild. There were no 12-hour 

 periods in which the wind force averaged 6 on the Beaufort scale. 

 There were only two days in which the vessel actually on patrol 

 experienced wind of force 7. On the morning of the 18th a moderate 

 southerly gale blew for six hours. Again the wind reached a moderate 

 gale on the 25th, but the gale lasted for only two hours. 



The Pontchartrain en route from Boston to the ice-patrol area 

 passed through a southerly gale on April 16. The force of the wind 

 in this disturbance reached that of a strong gale and maintained it 

 for'eight hours. 



APRIL WEATHER DIAGRAM 



Figure 9.— For explanation of symbols, see Figure ! 



