Jeff Masters puts Hurricane Sandy in perspective:
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
Masters notes the biggest threat will be from the storm surge:
[NOAA analysis suggests] the destructive potential of the storm surge [will be] exceptionally high: 5.7 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed between 1969 – 2005, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003. Sandy is now forecast to bring a near-record storm surge of 6 – 11 feet to Northern New Jersey and Long Island Sound, including the New York City Harbor. While Sandy's storm surge will be nowhere near as destructive as Katrina's, the storm surge does have the potential to cause many billions of dollars in damage if it hits near high tide at 9 pm EDT on Monday.
Masters gives "a 50% chance that Sandy's storm surge will end up flooding a portion of the New York City subway system." Stu Ostro emphasizes Sandy's size:
That gigantic size is a crucially important aspect of this storm. The massive breadth of its strong winds will produce a much wider scope of impacts than if it were a tiny system, and some of them will extend very far inland. A cyclone with the same maximum sustained velocities (borderline tropical storm / hurricane) but with a very small diameter of tropical storm / gale force winds would not present nearly the same level of threat or expected effects. Unfortunately, that's not the case. This one's size, threat, and expected impacts are immense.
Mike Smith adds his forecast to the mix:
Landfall in NJ or Delaware. Winds capable of causing power failures extend from around Portland to Richmond and inland to Harrisburg and, perhaps, Buffalo. Wind gusts of 70 mph develop around DC and Baltimore. Wind speeds are increasing throughout the eastern Great Lakes region. The barometric pressure at landfall looks like it will be around 940-942 millibars. The storm from there moves inland and gradually weakens but may still cause gusts above 50 mph over the eastern Great Lakes region.
Mayor Bloomberg has already ordered mandatory evacuations for some 375,000 people living in the low-lying areas of New York City known as Zone A (map here). New Jersey's evacuations are here. NYC's public transit system will also be shut down starting tonight – full list of metro-area transit closures here. The city's emergency updates can be found here. NYT live-blog here. The Guardian's round up of today's storm news is here. Hurricane tips, posted on the Dish during Hurricane Irene, can be read here.
(Photo: NOAA's GOES-13 satellite captured this visible image of the massive Hurricane Sandy on Oct. 28 at 9:02 a.m. EDT. Credit: NASA GOES Project, via NASA Goddard Photo and Video)