30 



The prevailing northwesterly flow over the coast of 

 California is often strengthened by the coincident existence 

 of the thermal low and a strong lobe of the Pacific High 

 extending eastward, resulting in a steep pressure gradient. 

 Such a condition is quite conservative, and once established, 

 is apt to prevail with little modification for days, especi- 

 ally in September,, Whenever this situation develops, offshore 

 winds blow. 

 S ant anna Winds 



Several times each winter a thick lens of continental 

 polar air moves southwestward toward southern California from 

 the interior of the continent,, Strong isallobaric winds blow 

 from the northeast coming through the passes from the desert 

 when the air mass is dammed behind the mountains . But since 

 these winds, although at times strong, blow from the northeast, 

 they have little generative effect upon the waves in Santa 

 Monica Bay. 



Land and Sea Breeze Regime 



(I 

 Unequal heating of the earth's surface over land and 



over the sea causes the development of the land and sea breeze 



regime, which in southern California is especially well developed 



in the summer months. At the coast, when these conditions exist, 



a southwesterly wind prevails during the afternoon (the sea 



breeze) and a northeasterly one during the early morning (the 



land breeze) (Fig. 8). The sea breeze is stronger and more 



persistent than the land breeze. It starts some miles at sea, 



reaches shore about 0900 local time, and obtains its maximum 



extension of approximately 70 miles inland at about 1300. 



