At low latitudes, tropical disturbances usually move with the 

 flow around the large permanent subtropical anticyclones. Existing circu- 

 lation patterns associated with transient mid-latitude weather systems 

 increasingly influence the motion of tropical cyclones when they migrate 

 toward higher latitudes. Here tropical cyclones may be modified by inter- 

 action with nontropical air although winds may remain above hurricane force 

 in some cases. 



During the period 1871-1972 a total of 63 disturbances of tropi- 

 cal origin passed within about 150 miles of the Long Island Sound Region. 

 Sixteen of these storms passed directly over the area and four hit Long Island 

 and Connecticut from the ocean without prior landfall. The endless variety 

 of tracks is a reflection of the continual changes in pattern of the general 

 circulation during the period when tropical cyclones are in existence. Figure 

 5 charts the paths of the four hurricanes which hit the region directly from 

 the sea. 



The time-frequency distribution of tropical storms and hurricanes 

 in the study region is such that no cl imatological summary can be considered 

 a stable assessment of the risk of recurrence of these storms in any locality. 

 Nevertheless, it is important that the best possible information be available 

 for planning purposes. A table, listed in Appendix C and modeled after Crutcher 

 and duinlan ( 15 ) indicates the percent probabilities with which the center of 

 an existing tropical cyclone at a specified latitude and longitude can be 

 expected to be within the Long Island Sound Region after 72, k8 and 2k 

 hours. The greatest probability of occurrence in the region after 2k hours 

 is about 1 in 5 during August for a tropical cyclone located at 35 .5°N and 77 . 5°W. 

 If the current position of the storm were at the same longitude but 5° farther 

 south the probability that the storm center would be within the Long Island 

 Sound Region after 2k hours reduces to 1 in 50 but for occurrence in the 

 region after k8 hours the chances again increase to 1 in 13. 



Although the chance that an individual tropical cyclone will di- 

 rectly hit the region is relatively low, the percentage "strike probability" 

 in any one year is considerably higher — nearly 16 percent for a direct hit 

 and about 60 percent for an occurrence within 150 miles of the area. The 

 region was rarely subject to hurricanes between 1901 and the massive hurri- 

 cane of 1938 but was severely affected several times since, notably in 19^^^ 

 195^, 1955 and i960. The planner should be aware of the effects of intense 

 winds, torrential rainfall and high storm surges produced by these severe 

 hurricanes on a highly developed area not geared to such disasters. 



3 .6 Thunderstorms 



Thunderstorms commonly result in damage to crops and property. 

 In the region the number of days with thunderstorms varies markedly through- 

 out the year from a low of less than one day per month in winter to 5 to 8 

 days per month in summer. The greatest annual total, 20 to 25, occurs in 

 southwest Connecticut, central Long Island and around heavily populated urban 

 areas. The smallest number, approximately 1^, is recorded in eastern Long 

 Island and southeastern Connecticut. The frequency of thunderstorm occurrence 

 is related to distance from water, altitude and perhaps air pollution in 

 industrial areas. 



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