The forecast is based on the weather map for the North 

 Atlantic of November 7 at 139^0, G.M.T. (fig. 12) and on preced- 

 ing maps. The weather mar) of November 6 showed an elongated 

 low-pressure area to the south of Greenland from which a cold 

 front extended south In longitude 32° W, bending tovmrd SW In 

 latitude /+0° N. Behind the cold front the wind was WW with an 

 average speed of about 30 knots. To the east of the front, to- 

 ward the coast of Spain, the wind was nearly W and the average 

 speed about 20 knots. 



On November 7 the low-pressure area and the cold front had 

 advanced toward SSE and a well-defined generating area was pre- 

 sent to the northeast of the Azores (fig. 12). The isobars, 

 drawn at intervals of 5 xnb, were nearly straight and in ^0° N 

 they were 1.6 degrees of latitude apart. The corresponding geo- 

 stroDhlc wind was 50 knots and, with a reduction factor of 0.65, 

 the wind at the sea surface was 32.5 knots. Ships reported wind 

 velocities of 8 Beaufort (30-35 knots according to the scale ad- 

 opted by the International Meteorological Committee) . The aver- 

 age wind velocity during the past 24 hours is found to be 29 

 knots, according to the rule given when the determination of the 

 wind velocity was discussed. 



In selecting the boundaries of the generating area the front 

 boundary was placed somewhat behind the cold front because of the 

 curving of the Isobars, and the rear boundary was placed where 

 the isobars fanned out. This selection gave a fetch of 800 naut - 

 ical miles . 



52 



