An east-west oriented trough of low pressure extended from the Gulf of Mexico eastward into the southwest
North Atlantic ocean for a couple weeks during September 1971. Heidi was the fifth tropical cyclone spawned
within this trough, forming east of an upper level low. A large extratropical cyclone formed over the northern
Appalachians, steering Heidi north across the western Atlantic into Maine before moving northeast into Canada
as an extratropical low. Below is the storm total rainfall graphic and track relating to Heidi. Rainfall data was
provided by the National Climatic Data Center in Asheville, North Carolina. Note that most of the rain fell
near the extratropical cyclone (a predecesor rainfall event, or PRE) which used Heidi as a source of moisture.
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