Relative humidity data at Portland and Eastport exhibit the greatest variation 

 among all the climate statistics for the two cities. Ranges shown in figures 

 2-8 and 2-9 represent the average span between afternoon humidities and 

 overnight humidities. The lower bound is determined by the afternoon values, 

 while the upper bound generally is determined by either the midnight or early 

 morning (0700) values. Since the Eastport record contains no midnight 

 observations, peak summer humidities there appear lower than those at 

 Portland. It is expected that these values otherwise would be nearly equal. 

 Significant differences in minimum humidity levels between Portland and 

 Eastport do occur reflecting small differences in distance from the coast. 

 Throughout the year aveage minimum humidity is higher at Eastport than at 

 Portland by 5% to 15% relative humidity. 



Surface winds . Seasonal and annual wind patterns at five stations 

 throughout the region have been analyzed through wind roses. Data for four 

 of the recording stations (Portland, Brunswick, Augusta, and Old Town) were 

 obtained directly from the National Climate Center in Asheville, North 

 Carolina. Data for St. John's, New Brunswick, Canada, were obtained from the 

 Canadian Climate Center to represent the eastern coastal region. The latter 

 data differ from those of the other stations in that the wind speed was 

 recorded in miles per hour, rather than in knots. As a result, wind rose 

 categories at St. John are approximate. Qualitative analysis of the wind rose 

 data should not be hampered by this difference. 



Wind roses for the four seasons and annual average statistics are given in 

 appendix C for Portland, Brunswick, Augusta, Old Town, and St. John. (Wind 

 records were obtained at a few additional sites but, because of their limited 

 period of record, were not included.) Annual average wind statistics are 

 similar at most stations along the Maine coast. Winds from the west dominate. 

 The true west wind is weakest at Brunswick and Augusta, where local topography 

 affects wind direction. Wind channeling along the major inlets from the sea 

 produces a north-south trend at Brunswick, while a weak northeast-southwest 

 alignment with local hills is seen in the Augusta record. A subtle wind-speed 

 distribution shift is seen also, with the lower wind-speed frequencies 

 decreasing with eastward progression along the coast and the higher wind speed 

 frequencies increasing. 



Seasonal statistics provide further insight into the consequences of the 

 observed wind patterns. In winter most winds emanate from the northwest and 

 are associated with the frequent inflows of polar air from the interior land 

 masses of the United States and Canada. These winds are frequently strong and 

 usually are attended by a dry air mass. Winds from the sea account for only 

 10% of the winter winds in Maine, and these are dominated by the lowest three 

 wind speed classes. High wind speeds come from every sector, however, and 

 these are associated with storm activity. High seas during wind-driven 

 winter storms occasionally cause serious damage to the coast. 



In spring, regional variations are more pronounced. Winds at Portland come 

 from the west (including the northwest and southwest) but the south winds 

 increase in frequency due to the onset of sea-breeze conditions. Channeling 

 effects at the other locations are more pronounced, again a result of the 

 increased frequency of south winds. Throughout the coastal region, the south 

 winds and north winds are equally prevalent. By summer, south winds clearly 

 dominate, especially at the stations closest to the shore. These winds, 



2-22 



