North Atlantic Ocean: Hurricane Larry tracking north-northeastward in North Atlantic Ocean early Sept. 10 /update 5

Event

Hurricane Larry is tracking north-northeastward in the North Atlantic Ocean early Sept. 10. As of 05:00 AST, the system's center of circulation was approximately 660 km (410 miles) north-northeast of Bermuda and 1230 km (765 miles) southwest of Cape Race, Newfoundland, Canada.

Forecast models indicate that the system is likely to turn northeastward, weaken slightly, and make landfall as a Category 1 hurricane over southeastern Newfoundland, Canada late Sept. 10. After landfall, the system is forecast to weaken further as it tracks northeastward, transitioning into a post-tropical cyclone with tropical storm strength winds through the afternoon of Sept. 11 and approach southern Greenland early Sept. 12. Some uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days.

Government Advisories
As of 05:00 Sept. 10, the Canadian Hurricane Centre has issued the following watches and warnings:

• Hurricane Warning: Southeastern Newfoundland, Canada from Arnold's Cove to Jones Harbour.

• Tropical Storm Warning: Southeastern Newfoundland from Francois to west of Arnold's Cove as well as from north of Jones Harbor to Fogo Island.

The Meteorological Service of Canada has issued warnings for heavy rainfall over the following areas through at least Sept. 10:

• Anticosti, Bonaventure, Chandler, Gaspe, Grande-Vallee, Minganie, Murdochville, Natashquan, New Carlisle, Percein, Restigouche, Sainte-Anne-des-Monts as well as Forillon and Gaspe national parks in Quebec Province.

• Bathurst, Campbellton, Doaktown, Fredericton, Grand Falls, Mount Carleton, St. Stephen, Stanley, Woodstock, and Blackville Area as well as Chaleur Region and Carleton, Northern Charlotte, Restigouche, Southern York, Victoria counties in New Brunswick Province.

• Eagle River and Upper Lake Melville in Newfoundland and Labrador Province.

Wind warnings are in place for portions of eastern Newfoundland through at least Sept. 11. Storm surge warnings have been issued for the south coast, from McCallum east to Cape Race, including Placentia Bay through Sept. 10. The warnings may be expanded to include the eastern Avalon Peninsula. Coastal flooding is likely within tropical storm warning area in southeastern Newfoundland late Sept. 10 while coastal flooding is possible further north, into Placentia Bay and may cause flooding in Placentia Town. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Hazardous Conditions
Tropical storm conditions are likely to impact southeastern Canada through Sept. 10. Swells generated by Larry are forecast to impact the Greater Antilles and the Bahamas through at least Sept. 10. Significant swells will likely impact Bermuda as well as parts of the US East Coast and Atlantic Canada through Sept. 11.

Sustained heavy rainfall could trigger flooding in low-lying communities in Canda over the coming days. However, significant rainfall totals are unlikely. In addition to the heavy rain, flooding, and storm surge, the storm could produce damaging wind gusts, resulting in power outages due to uprooted trees and toppled utility lines.

Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Forecast models indicate that heavy rainfall is possible over portions of eastern Newfoundland, with 2.5-5 cm (1-2 inches) of rain forecast from late Sept. 10. Flooding could isolate some communities for several days.

Prolonged sea swells and storm surge generated by the system will likely result in coastal flooding as the system approaches land. Persistent onshore flow could make it difficult for surge to recede and for water levels to decrease in coastal river catchments. In addition to the heavy rain, flooding, and storm surge, Larry could produce damaging wind gusts, resulting in power outages due to uprooted trees and toppled utility lines. Swells of up to 2 m (6.5 feet) are possible across the Atlantic coast of Newfoundland through Sept. 10. on the evening of Sept. 10, 7-10 m (23-33 feet) long-period waves are forecasted for the south-facing coastlines of Newfoundland.

Transport
Inclement weather associated with the storm could trigger localized business, transport, and utility disruptions. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles. Heavy rain and low visibility may trigger flight disruptions at regional airports.

Disruptions triggered by inclement weather and resultant hazards, such as flooding could persist well after conditions have improved. If there is severe damage to infrastructure, repair or reconstruction efforts may exacerbate residual disruptions.

Health
Stagnant pools of water during and after flooding increase the incidence of insect- and waterborne diseases, such as dengue fever, cholera, and malaria. The threat of these disease outbreaks is usually elevated in the low-income or underdeveloped areas of major urban centers due to the presence of incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas forecast to be impacted by the storm. Use caution in low-lying areas due to the high potential for flooding. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers.

Resources

US National Hurricane Center
National Weather Service
Meteorological Service of Canada