northeast and decreased significantly in 

 magnitude. The stress along the Gulf 

 coast has shifted to the westnorthwest 

 but has not changed significantly in 

 magnitude. During the month of May 

 the stress along the east coast is more 

 to the northeast while along the Gulf 

 coast the direction remains to the west- 

 northwest but the gradient has increas- 

 ed producing an increase in the stress 

 values. 



During the summer months (June, 

 July, August) the stress along the east 

 coast has shifted predominately to the 

 northeast and decreased to its 

 minimum magnitude generally in 

 August. However, July shows an in- 

 crease in magnitude from June in all 

 areas except Boston and the Gulf coast. 

 The definite establishment of the 

 southwest U.S. thermal low is the 

 major factor producing the stress 

 direction and magnitudes from the 

 Miami to Corpus Christi areas. 



In September the thermal low is 

 beginning to dissipate and the direc- 

 tion of the stress along the east coast 

 suggests a closed high pressure cell in 

 the mid-U.S. This situation appears to 

 remain through October and Novem- 

 ber. By November the thermal low is 

 completely gone. 



Pacific Coasts 



The west coast areas (figures 13 

 through 36) from Eureka southward 

 show the northern extent of the North 

 Pacific High Pressure System during the 

 winter months of December, January, 

 and February. This high pressure area 

 produces a definite southeasterly stress 

 which is also evident throughout the 

 entire year. The only change that 



occurs in these areas is in the mag- 

 nitude of stress. The formation of the 

 thermal low of the southwest U.S. pro- 

 duces a strong pressure gradient over 

 these areas and reaches a maximum in 

 May and June. During the winter 

 months north of Eureka the areas of 

 Seattle through Attu are influenced 

 very strongly by the Aleutian Low 

 Pressure System while the areas of 

 North Bend to Astoria are a transi- 

 tional zone. In the Gulf of Alaska and 

 the Aleutian chain there are generally 

 two centers of low pressure within the 

 Aleutian Low System. This is evident 

 from the stress vectors in the Sitka to 

 Kodiak areas which show a definite 

 cyclonic stress. The other local low 

 pressure area is northwest of Unimak 

 Island and is illustrated by the stress 

 vectors in the areas around St. Paul. 



During the spring months of March, 

 April and May a ridge of high pressure 

 begins to extend from the center of the 

 North Pacific High in a northeasterly 

 direction which is evident by the stress 

 directions from Queen Charlotte to 

 North Bend. At the same time the 

 thermal low is forming in the southwest 

 U.S., the magnitudes of the stress 

 vectors show a significant increase from 

 Eureka to Baja. The conditions in the 

 Alaskan areas remain mostly the same 

 as the winter conditions, except the 

 lows are becoming weaker. 



The summer months of June, July, 

 and August generally produce the mini- 

 mum in stress values in the Alaskan 

 areas where the Aleutian Low System 

 has degenerated into isolated local areas 

 of weak low pressure. The areas from 

 Seattle to San Diego are reaching a 

 maximum magnitude with the pressure 

 gradient being the greatest in the San 



