Leslie (2012)

A tropical depression formed from a strong tropical wave about 1,300 nautical miles east‑southeast of the northern Leeward Islands around 0000 UTC on 30 August 2012. The system strengthened to Tropical Storm Leslie later that day and tracked generally west‑northwest and then northward, moving slowly for several days south of Bermuda while its circulation expanded. Leslie briefly became a Category 1 hurricane on 5 September, weakened, then regained hurricane strength on 10 September as it accelerated northeastward toward Newfoundland. The cyclone became post‑tropical about 0900 UTC 11 September and merged with a larger extratropical low by 12 September.

Leslie did not make a tropical hurricane landfall on any U.S. or island mainlands, but it passed about 115 nautical miles east of Bermuda on 9 September, producing tropical‑storm‑force winds and rain there. The system made landfall as a powerful post‑tropical (extratropical) cyclone with hurricane‑force winds on the Burin Peninsula of southeastern Newfoundland near St. Lawrence and Lawn around 1045 UTC on 11 September.

The peak intensity while tropical was estimated at 70 knots (80 mph) with a minimum central pressure near 982 mb on 5 September, making Leslie briefly a Category 1 hurricane at that time. At landfall in Newfoundland as a post‑tropical cyclone the best estimate of minimum pressure was about 968–969 mb and the estimated maximum sustained winds were about 65 knots (75 mph).

Storm surge observations in Newfoundland reached as high as 3.61 ft (1.10 m) at Argentia and St. Lawrence, although those surges occurred near low tide so there was no significant coastal inundation reported. Rainfall totals included 5.17 inches (131 mm) at Commissioner’s Point / Dockyard area on Bermuda (total during 8–10 September), up to 6.50 inches (165 mm) at Shubenacadie, Nova Scotia, and maxima across Newfoundland of about 4.25 inches (108 mm) at Cow Head and as little as 0.28 inch (7 mm) at St. John’s Airport. Many locations in Nova Scotia and Newfoundland saw 2–4 inches (50–100 mm).

There were no reported deaths attributable to Leslie. Impacts included scattered power outages and broken tree limbs across Bermuda, and more significant damage on Newfoundland’s Avalon Peninsula where Leslie’s rapid passage ripped off roofs, caused widespread tree damage, destroyed a partially built house in Pouch Cove, and left about 45,000 homes without power for roughly six hours. Localized flooding made some roads and bridges impassable and temporarily isolated the Port au Port Peninsula.

Noteworthy aspects include Leslie’s unusually long life and very large wind field (tropical‑storm‑force winds extended about 150 nautical miles on average, over 1,000 n mi in diameter at times), production of cold upwelling that weakened the cyclone in early September, and its transition to a strong extratropical cyclone with a rapid pressure fall just before Newfoundland landfall. NHC track forecasts for Leslie were generally better than recent averages, but intensity forecasts struggled to anticipate the amount of self‑induced ocean cooling that caused Leslie’s mid‑life weakening.