what is the seasonal variation seen in this last mentioned hurricane?
Approximately 97 percent of tropical cyclones that form in the North Atlantic develop between the dates of June 1 and November 30 and the official end has shifted from its initial date of October 31.
Atlantic hurricane
approximately 97 percent of tropical cyclones that form in the North Atlantic develop between the dates of June 1 and November 30 – dates which delimit the modern-day Atlantic hurricane season. 
what is tropical storm arlene (1981)? It was a rare off-season tropical cyclone. what is the physical structure of this above type of cyclone just mentioned? Its formation was unusual, originating from a tropical disturbance that crossed from the eastern Pacific Ocean into the Caribbean Sea; few Atlantic hurricanes develop in this manner.
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Atlantic hurricane [SEP] Seasonal variation
Hurricane Hattie (October 27 – November 1, 1961) was initially thought to have been the latest forming Category 5 hurricane ever documented, though reanalysis indicated that a devastating hurricane in 1932 reached such an intensity at a later date. Consequently, this made the hurricane the latest developing tropical cyclone to reach all four Saffir–Simpson hurricane wind scale classifications past Category 1 intensity.