User:DachshundLover82/sandbox/Tropical Storm Heidi (1971)

Tropical Storm Heidi

Hurricane (SSHWS/NWS)
Tropical Storm Heidi strengthening off the East Coast of the United States on September 13
Formed	September 11, 1971
Dissipated	September 15, 1971
Highest winds	1-minute sustained: 65 mph (100 km/h)
Lowest pressure	996 mbar (hPa); 29.41 inHg
Fatalities	21 total
Damage	Unknown
Areas affected	Northeastern United States, Eastern Seaboard
Part of the 1971 Atlantic hurricane season

Tropical Storm Heidi was a strong tropical storm that made a rare landfall in Maine. The eighth named storm of the active 1971 Atlantic hurricane season, Heidi originated from a trough of low pressure which had also spawned three other tropical cyclones. The disturbance organized into a tropical depression by September 11 and became Tropical Storm Heidi the next day. Heidi continued intensification until reaching its peak on September 14 with sustained winds of around 65mph (100 km/h) and a minimum pressure of 996 mbar (29.41 inHg). Heidi remained disorganized through its entire lifespan, weakening into a tropical depression just after landfall in Maine by 0:00 UTC on September 15. The cyclone the transitioned into an extratropical-low and drifted into northeastern Canada.

Meteorological history

Map plotting the storm's track and intensity, according to the Saffir–Simpson scale

Map key

Saffir–Simpson scale

  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown

Storm type

Tropical cyclone

Subtropical cyclone

Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

A trough of low pressure which extended across the northern Gulf of Mexico to the southwestern Atlantic Ocean persisted for over a week, the same system responsible for the formation of Hurricane Fern, Hurricane Ginger, and Tropical Depression Eighteen. At times, the trough morphed wind shifts in the low-levels to a sharp shear line. By 0:00 UTC on September 11, the disturbance had developed a warm central core according to Hurricane Hunters Reconnaissance aircraft data, and was designated as a tropical depression. The nascent depression continued to strengthen, growing gale-force winds and being upgraded to a tropical storm about 30 hours later at 6:00 UTC the next day, and was provided the name Heidi from the annual rotating lists for the North Atlantic basin. At this time, Heidi was located roughly 460 miles (740 km) east of Jacksonville, Florida.

Heidi continued to intensify, despite being ill-defined, and reached its peak intensity at 0:00 UTC on September 14 with sustained winds of around 65mph (100 km/h) and a minimum pressure of 996 mbar (29.41 inHg). Satellite imagery depicted that the central dense overcast was covering the western portion of the storm, and a lack of good outflow at the cirrus level. On approach to the Northeastern United States, the circulation of Heidi was almost completely absorbed into an extratropical cyclone over the northern Appalachian Mountains. This also caused moisture from Heidi to be scattered across the Eastern Seaboard, and steered Heidi itself northward. The cyclone began to degrade, weakening to tropical depression status by 0:00 UTC on September 15, shortly after moving onshore in Maine. Heidi degenerated into an extratropical-low later that day as it pulled into northeastern Canada.

Preparations and impact

Mid-Atlantic states

Rainfall totals from Heidi along the East Coast of the United States

Moisture drawn from Heidi into an extratropical cyclone dropped torrential rainfall across the Mid-Atlantic states. In Delaware, this heavy and long-lasting rainfall caused the state's worst flooding in more than a decade. An official peak precipitation accumulation of 10.45 inches (265.43 mm) was recorded at the Porter Reservoir in Wilmington, although, an unofficial peak of 13.46 inches (341.89 mm) was observed close to Talleyville, of such 8.43 inches (214.12 mm) fell on September 13. Streets across the region were left impassible due to flooding. Creeks overtopped their banks, including Naamans Creek, where six families nearby had to be evacuated. Basement flooding was also reported. A funnel cloud was spotted roughly 5 miles (8 km) west of Magnolia.

Destructive flash flooding occurred in Maryland, following severe thunderstorms. In Baltimore, at least 4.36 inches (110.75 mm) of precipitation fell within a 3-hour time period near Herring Run, causing the tributary to overflow. Parked cars were nearly submerged by floodwaters, which also ruined furnishings in 16 garden-level apartments. A total of 32 families were evacuated in the area. A rain gauge reported 6.4 inches (162.56 mm) in Parkville, which had been struck by more severe flooding the month previous, though less significant flooding occurred due to Heidi. Bennett Creek crested at 14 feet (4.27 m) in Frederick County, surpassing the former record of 11 feet (3.35 m) and causing damage to some roads and bridges. Severe road and bridge damage occurred in Harford County after 4.10 inches (104.14 mm) fell at the police barracks in Benson within 3 1/2 hours. The worst hit area in Maryland was considered to be Montgomery County, where 18 vacation or permanent homes in the Seneca Creek area were destroyed while numerous more were damaged. An unofficial rainfall total of 9 inches (229 mm) was recorded at two sites in Germantown. Considerable damage was done to bridges and roads across the county. The highest discharge in the area was recorded in Dawsonville, reaching 30,000 cubic feet (849.5 m3) on September 12, doubling the previous highest from 1930. Worse flooding than the previous month did occur in the Patuxent River basin, the largest discharge in the tributary ever dated back to 1944. A weather station in Prince George's County recorded 4.10 inches (104.14 mm), most of which fell in under 45 minutes. Severe damage was reported in Laurel and surrounding areas. A tornado touched down in Largo on September 12, which crossed the Capital Beltway and destroyed two barns, a shed, and downed trees. Across Largo, a total of 57 homes sustained damage, with four receiving major damage. Debris was littered around some houses, and damage was estimated to total $70,000. Heavy rainfall, peaking at 5 inches (127 mm), caused Mill Run Creek to exceed its banks and damage numerous bridges, even washing out one. Combined losses in Maryland and Delaware from Heidi was estimated at $4 million (1971 USD, $30.1 million 2024 USD).

The same system drawing moisture from Heidi also affected New York and New Jersey. Precipitation amounts ranged from 4.5-7.0 inches (114.3-177.8 mm) across New York City and Nassau County, northward to the counties of Greene and Columbia. Across the New York Metropolitan area, Major traffic disruptions occurred the West Side Highway and FDR Drive was covered in several inches of water, while streets curbs had turned into "rushing rivers". In the Brooklyn neighborhood of Sheepshead Bay, roughly 150 homes reported basement flooding even though a storm sewer had been recently installed in the area. Construction on the Fresh Meadows housing project and Grand Central Parkway was interrupted due to flooding. Power outages were reported in Wantagh and Port Washington according to the Long Island Lighting Company. Flooding shut down a part of the Northern State Parkway for several hours to allow drainage. Flooding also caused the cancellation of five stops on the Staten Island Rapid Transit System. The Penn Central and Long Island railroads were staffers by flooding, prompting detours and schedule changes. Heavy rainfall fell in Central Park, with a weather station recording 2.16 inches (54.86 mm) between September 12-13, nearly breaking the record of 2.35 inches (59.69 mm) set in 1960. Water flowing in from Fifth Avenue caused the closure of 86th Street in Central Park. Some major accidents occurred due to severe weather in the region. One death was reported in the village of Ossining after a person drowned in a swollen river.