Irene hits North Carolina

Hurricane Irene roared ashore over Cape Lookout, North Carolina at 7:30 am this morning. The Cedar Island Ferry Terminal measured sustained winds of 90 mph, gusting to 110 mph at 7:19am, and a trained spotter on Atlantic Beach measured sustained winds of 85 mph, gusting to 101 mph at 10:35 am. The Hurricane Hunters measured 80 mph winds over water at the time of landfall. Winds at the Cape Lookout, North Carolina buoy, which the eye passed directly over, peaked at 67 mph as Irene made landfall. At 10am EDT, top winds observed at Cape Hatteras on the Outer Banks of North Carolina were 53 mph, gusting to 73 mph. Winds are rising now along the coast of Virginia, with sustained winds of 56 mph, gusting to 62 mph observed at 10 am EDT at Chesapeake Bay Light. Satellite loops show a large but deteriorating storm with dry air intruding to the southwest. The radar presentation of Irene visible on the Norfolk, VA radar is very impressive--Irene is dropping torrential rains over a huge area.


Figure 1. Radar-estimated precipitation from Irene as of 12:18 pm EDT August 27, 2011. An expanding region of rains in excess of ten inches (pick colors) was observed north of where the center made landfall.

Storm surge damage from Irene
The storm surge and wave action from Irene is likely to cause the greatest damage, and this will be a historic coastal flooding event for many regions of the mid-Atlantic and Northeast. A storm surge of 8.5 feet was reported this morning in North Harlow, NC, and three feet in New Bern, NC. Significant wave heights (the average height of the largest 1/3 of the waves) reached 27 feet at Onslow Bay, NC this morning, and wave heights along the New Jersey shore Sunday morning during the time of high tide are expected to be 15 - 20 feet, according to the NOAA Wavewatch III model (Figure 2.) A storm surge of 3 - 6 feet is expected near Atlantic City, NJ Sunday morning, during the time of high tide. With 15 - 20 foot waves expected on top of this storm surge, there will be tremendous damage to the coast and low-lying structures. Storm surge is also a major concern for New York City. The latest NWS forecast is calling for a 5 - 8 foot storm surge in New York Harbor, which would easily top the flood walls protecting the south end of Manhattan if the storm surge occurs at high tide. High tide is near 8 am Sunday morning. A research storm surge model run by SUNY Stonybrook predicts that water levels at The Battery at the south end of Manhattan will peak at 2.2 meters above Mean Lower Low Water (MLLW) at high tide Sunday morning, which would be about six inches below the top of the flood wall (which is 5 feet above mean sea level.) Waves on top of the surge would likely spill over the top of the floodwall in this scenario, and cause some flooding in southern Manhattan. Andy Revkin's Dot Earth blog has links to a storm surge animation for New York City done by the SUNY Stonybrook group. Climate Central has a nice satellite image showing which parts of New York Harbor are below five feet in elevation. Storm surge heights of up to eight feet are predicted in Western Long Island Sound, and 3 - 6 feet along much of the New England coast from New York to Massachusetts. This is going to be a damaging coastal flooding event for this stretch of coast, though perhaps not as damaging as the one New Jersey will experience.


Figure 2. Predicted wave heights along the U.S. coast from NOAA's Wavewatch III model for 8am EDT Sunday, August 28, 2011. This is the time of high tide, and this model is suggesting that the coast of New Jersey will be subject to battering waves 15 - 20 feet high at the time of high tide.

Inland flooding damage from Irene
Inland flash flooding and river flooding from torrential rains are a major concern. Latest radar-estimated rainfall amounts in North Carolina already exceed ten inches in some locations. Cedar Island, NC has reported 7.21" as of 11am EDT, and a 100 mile-wide swath of 8+ inches of rain will likely fall from Eastern North Carolina northwards along the coast, through New York City, and into Vermont and New Hampshire during the next two days. Destructive river flooding will be a significant danger from New Jersey northwards to Southeast New York, where soils are saturated and run-off will be the greatest.


Figure 3. Distribution of Irene's wind field at 9:30 am EDT Saturday August 27, 2011, as observed by the Hurricane Hunters, land stations, and buoys. The right front quadrant of the hurricane had all of the storm's hurricane-force winds (yellow and warmer colors, bounded by the heavy black line between the "50" and "60" knot thin black lines.) Tropical storm-force winds (heavy black like bounding the light blue area) extended out 260 miles from the center of Irene. Irene's storm surge damage potential has dropped to 4.3 on a scale of 0 to 6, down from a high of 5.1 yesterday. Image credit: NOAA/AOML/HRD.

Wind damage
Irene is slowly deteriorating, but the storm is too large to weaken quickly. The latest wind distribution map from NOAA's Hurricane Research Division (Figure 3) shows that all of Irene's hurricane-force winds are on the storm's east side, so only North Carolina's Outer Banks will get winds of 75 - 80 mph. The coast from Virginia northwards through New Jersey will see tropical storm-force winds of 50 - 70 mph from Irene. These strong winds, when combined with the torrential rains that are falling, will cause widespread tree damage and power failures that will affect millions of people. When Irene makes its 2nd landfall on Long Island, NY on Sunday, coastal locations to the right of the eye will likely experience top sustained winds of 60 -70 mph.

Lady Liberty not in danger from Irene
The Statue of Liberty is not vulnerable to a storm surge, since the good lady stands atop a 65-foot high foundation and 89-foot high granite pedestal. However, the 305' height of the lady's torch above the foundation means the statue will experience winds a full Saffir-Simpson category higher than winds at the surface. The statue is rated to survive a wind load of 58 psf, which is roughly equivalent to 120 mph winds (Category 3 hurricane). However, a mid-strength Category 2 hurricane with 105 mph winds will be able to generate 120 mph winds at a height of 300 feet, and would theoretically be capable of toppling the Statue of Liberty. Winds from Irene should stay below 80 mph at 300 feet, and not pose a threat to the Statue of Liberty.

Tornadoes
Two tornadoes were reported in coastal North Carolina last night. One tornado destroyed 2 homes and damaged 6 others in Columbia, with several minor injuries, and the other hit Belhaven, damaging multiple trailers. NOAA's Storm Prediction Center is calling for a slight risk of severe weather along coast Virginia, Maryland, and Delaware today. We might see five or ten tornadoes from Irene over the next two days, but the atmosphere is not unstable enough for Irene to generate as many tornadoes as we're used to seeing from a landfalling hurricane. A tornado watch is posted for coastal areas from Eastern North Carolina northwards to Southern New Jersey.

Insurance company AIR-Worldwide is estimating that insured damages from Irene in the U.S. will be $1.5 - $6 billion. They estimate losses in the Caribbean at $0.5 - $1.1 billion from Irene, 60% in the Bahamas.

Typhoon Nanmadol
Over in the Western Pacific, Typhoon Nanmadol has weakened to a Category 3 storm after battering the Philippines as a Category 4 super typhoon with 155 mph winds. At least two people have been killed in the heavy flooding there. Nanmadol is a threat to Taiwan, and Wunderground meteorologist Elaine Yang (who hails from Taiwan), has the details in her blog.

Links
Our Weather Historian, Christopher C. Burt, has an excellent post on Historic Hurricanes from New Jersey to New England.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Jeff Masters