Hurricane Sandy is still expected by the National Hurricane Center (NHC) to interact with a cold frontal system from the mainland to produce a historic post-tropical cyclone that will impact the Mid-Atlantic and Northeast United States early next week. Given the expansive nature of the storm, tropical storm force winds are anticipated at least 200 miles away from the track. It is possible that an area 50-100 miles on either side of the track could experience sustained hurricane force winds.
Light to moderate wind damage can be expected across a vast area. For coastal areas, significant storm surge north of the future track can be expected from high tides (under a full moon), and strong winds over a large area of the Atlantic. Heavy rains may also produce inland flooding, and even impressive snowfall could occur at higher elevations.
Hazard data illustrated in the CAT-i map was taken from i-aXs®, Guy Carpenter’s web-based risk management platform. i-aXs users can view impacted areas on any map as well as see how their portfolios were affected. Please contact your broker or GC Analytics® representative for assistance or go to www.i-axs.info for further information.
For the immediate term, Hurricane Sandy is now a category-1 hurricane on the Saffir-Simpson Scale, with winds of 75 mph. Sandy has slowed down considerably overnight and is moving north at 7 mph away from the northwestern Bahamas. Rain bands will continue to bring tropical storm conditions to the central and northern Florida Coast for the remainder of Friday. Sandy is forecast to weaken slightly over the next 12-24 hours before re-intensifying later in the forecast period.
Sandy is currently pulling north away from Great Abaco in the Bahamas with 75 mph winds, as a category-1 hurricane on the Saffir-Simpson Scale. Sandy has been interacting with an upper level low over the southeast Gulf of Mexico, and associated wind shear has caused some weakening since yesterday. As the storm pulls away from this low over the next 12-24 hours it should accelerate into a northeasterly turn while roughly maintaining its current intensity.
As the strong frontal system leaves the mainland and approaches Sandy on Sunday, the storm should start to curve back to the northwest, approaching the U.S. coastline. The exact timing and placement of this interaction is very complex and leads to uncertainty in the future landfall track.
The large tropical air mass drawn north with Hurricane Sandy will interact with a potent arctic air mass spilling down from northern Canada causing aggressive development of a powerful post-tropical cyclone, very similar to a “nor-easter.” Much of the model guidance suggests a historic storm that would set a record for the lowest pressure in the Northeast U.S., deeper in central pressure then the great Long Island Express hurricane of 1938. Given the difference in structure and size of this storm, peak winds speeds are anticipated to be significantly less than the 1938 hurricane. However, if Sandy maintains a warm core during landfall, hurricane force winds could be found 50-100 miles on either side of the storm track.
A landfall is still possible anywhere from northern North Carolina to Maine, though the majority of model guidance scenarios suggest landfall between Delaware and eastern Long Island, New York. Given the large wind field associated with this storm, effects will be felt several hundred miles away from the center of the storm, on either side of the track.
Potential Hazards and Impacts
Impacts should include storm surge with large and destructive waves, affecting coastal regions over a large area. Tropical storm or hurricane force winds are also possible along large swaths of the mid and north Atlantic coast. Excessive rainfall could also trigger inland flooding, particularly if waterways are inundated by storm surge, or if stormwater systems become overwhelmed.
Severe coastal flooding, coastal damage, wind damage, inland flooding, downed trees, downed power lines and power outages are all possible over a very large area.
Such a combination of meteorological factors is very rare, but it appears that this scenario will actually unfold. The most recent historical event remotely comparable to this potential scenario is the “perfect storm” of October 1991, which made landfall in Nova Scotia as the equivalent of a weak tropical storm.
Interests along the U.S. east coast should closely monitor the progress of this feature in the coming days, and have response plans ready for implementation should it become necessary. Interests between Delaware and Massachusetts may especially want to prepare for the possible hazards under this event.
Interests in Florida and the Bahamas are of course facing a far more imminent threat.
Watches and Warnings
- Tropical Storm Warnings
Florida Coast from Ocean Reef to Flagler Beach
Northwest Bahamas except Grand Bahama & Great Abaco
Grand Bahama and Great Abaco Islands in the Bahamas
- Tropical Storm Watch
Florida Coast from Flagler Beach to Fernandina Beach
Savannah River, South Carolina to Oregon Inlet, North Carolina
Hurricane and tropical storm force winds extend outward from the center to 35 and 275 miles (55 and 445 km), respectively.
Hurricane conditions for Grand Bahama and Great Abaco Islands with tropical storm conditions in northwestern Bahamas today
3-6 inches of rain, with isolated amounts to 12 inches
Storm surge 5-8 feet
Florida Coast & Lake Okeechobee
Tropical storm conditions through Friday evening
1-3 inches of rain
Storm surge 1-2 feet
Hurricane Sandy battered the Bahamas early Friday, leaving power outages, flooded roads and inaccessibility to islands in its wake. One fatality has been blamed on the storm.
The human toll was more heavily felt in Cuba, where there were reports of 11 fatalities in eastern Santiago and Guantanamo provinces. Authorities claim Sandy is the deadliest storm to impact Cuba since Hurricane Dennis came ashore in 2005 killing 16 people.
While Haiti did not suffer a direct hit, the storm claimed 16 lives according to a spokesman for the civil protection office in Haiti. Many of the 370,000 people still displaced from the devastating 2010 earthquake scrambled for shelter as Sandy brought flooding to the region.
- United States
With a current death toll of 31 across the Caribbean, Sandy is expected to move past the Bahamas on Friday and head towards the northeastern U.S. by late Monday or early Tuesday. High seas and wave action are already causing some beach erosion.
Sources: National Hurricane Center (NOAA), Storm Prediction Center (NOAA), National Weather Service (NOAA), Hydrometeorological Prediction Center (HPC/NCEP/NOAA), Associated Press, Reuters, Agence France Presse.
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