Sunday, October 28, 2012

Massive and dangerous Hurricane Sandy has grown to record size as it barrels northeastwards along the North Carolina coast at 10 mph. At 8 am EDT, Sandy's tropical storm-force winds extended northeastwards 520 miles from the center, and twelve-foot high seas covered a diameter of ocean 1,030 miles across. Since records of storm size began in 1988, only one tropical storm or hurricane has been larger--Tropical Storm Olga of 2001, which had a 690 mile radius of tropical storm-force winds when it was near Bermuda (note: I earlier reported this was a subtropical storm, as per the original NHC advisory, but it was later re-analyzed as a tropical storm.) Sandy has put an colossal volume of ocean water in motion with its widespread and powerful winds, and the hurricane's massive storm surge is already impacting the coast. A 2' storm surge has been recorded at numerous locations this morning from Virginia to Connecticut, including a 3' surge at Virginia's Chesapeake Bay Bridge Tunnel and Sewells Point at 9 am EDT. Huge, 10 - 15 foot-high battering waves on top of the storm surge have washed over Highway 12 connecting North Carolina's Outer Banks to the mainland at South Nags Head this morning. The highway is now impassable, and has been closed. The coast guard station on Cape Hatteras, NC, recorded sustained winds of 50 mph, gusting to 61 mph, at 5:53 am EDT this morning. In Delaware, the coastal highway Route 1 between Dewey Beach and Bethany Beach has been closed due to high water. Even though Sandy is a minimal Category 1 hurricane, its storm surge is extremely dangerous, and if you are in a low-lying area that is asked to evacuate, I strongly recommend that you leave.Sandy was a brutal storm for the Caribbean, the storm's death toll now stands at 65. The death toll is highest in Haiti, with 51 deaths. Prime Minister Laurent Lamothe told the Associated Press that "This is a disaster of major proportions. The whole south is under water." Approximately 8 - 10" of rain (200 - 250 mm) fell in the capital of Port-au-Prince. Eleven people were killed in Cuba, where 35,000 homes were damaged or destroyed. Sandy is also being blamed for 1 death in Jamaica, 1 in Puerto Rico, and 1 in the Bahamas. Sandy has a rather unusual structure, with the strongest winds on the southwest side of the center, but a larger area of tropical storm-force winds to the northeast of the center. Most of the storm's heavy thunderstorm activity is on the storm's west side, in a thick band several hundred miles removed from the center, giving Sandy more the appearance of a subtropical storm rather than a hurricane. Satellite loops show that the low-level center of Sandy is no longer exposed to view, and heavy thunderstorms are increasing in areal extent near the center, due to a reduction in wind shear from 35 - 40 knots last night to 25 - 30 knots this morning. Wind shear is expected to drop another 5 knots today, which may allow the storm to build an increased amount of heavy thunderstorms near its center and intensify by 5 - 10 mph over the next 24 hours. The NOAA Hurricane Hunters noted this morning that Sandy had a partial eyewall on the west through SE sides of the center, and the storm may be able to build a nearly complete eyewall by Monday morning. By Monday afternoon, though, Sandy will be moving over cool 25°C waters, which should slow down this intensification process. However, the trough of low pressure that will be pulling Sandy to the northwest towards landfall on Monday will strengthen the storm by injecting "baroclinic" energy--the energy one can derive from the atmosphere when warm and cold air masses lie in close proximity to each other. Sandy should have sustained winds at hurricane force, 75 - 80 mph, at landfall. Sandy's central pressure is expected to drop from its current 951 mb to 945 - 950 mb at landfall Monday night. A pressure this low is extremely rare; according to wunderground weather historian Christopher C. Burt, the lowest pressure ever measured anywhere in the U.S. north of Cape Hatteras, NC, is 946 mb (27.94") measured at the Bellport Coast Guard Station on Long Island, NY on September 21, 1938 during the great "Long Island Express" hurricane. The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) computer model runs are in agreement that Sandy will make landfall between 10 pm Monday night and 4 am Tuesday morning in New Jersey.

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