Irene Alarm: Mass evacuations? Worst in 70 years? NYC Flood?

The hurricane models have shifted west today, and that's sounding alarm bells from North Carolina through New Jersey, New York City, all the way to New England.

Hurricane Irene is ready to move out of the Bahamas and head for North Carolina.

The new track and intensity forecasts are raising the alarm level of several hurricane experts (and this forecaster) about the growing threat of major storm surge flooding and damage to highly populated coastal areas; including New York City.

(Click to enlarge images)

First, the latest on Irene late Thursday.

BULLETIN

HURRICANE IRENE ADVISORY NUMBER 22

NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011

500 PM EDT THU AUG 25 2011

...IRENE STILL BATTERING ABACO ISLAND...NEW WATCHES AND WARNINGS

ISSUED FOR THE EAST COAST OF THE UNITED STATES...

SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION

----------------------------------------------

LOCATION...27.0N 77.3W

ABOUT 575 MI...930 KM S OF CAPE HATTERAS NORTH CAROLINA

MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H

PRESENT MOVEMENT...NNW OR 335 DEGREES AT 14 MPH...22 KM/H

MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

Irene is already showing the expected intensification as it moves out of the northern Bahamas.

The storm is so large that squalls in spiral rain bands are spinning though Florida.

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Track forecasts shift west:

The major development today is that the forecast tracks for Irene have shifted slightly west. This is a big deal, and a major hurricane landfall in North Carolina is now almost certain Saturday.

What's worse, the later tracks bring a Category 2 Irene near or along the Jersey Shore, and perilously close to a rare direct hit on New York City late Sunday.

If that timing works out, the storm could hit at high tide, which could add 5 feet of water to a potential 10-5 foot storm surge.

Below, some eye openeing (and rather alarming) discussion form hurricane expert Jeff Masters and other sources.

Irene an extremely dangerous storm surge threat to the mid-Atlantic and New England

"Back in 1938, long before satellites, radar, the hurricane hunters, and the modern weather forecasting system, the great New England hurricane of 1938 roared northwards into Long Island, New York at 60 mph, pushing a storm surge more than 15 feet high to the coast. Hundreds of Americans died in this greatest Northeast U.S. hurricane on record, the only Category 3 storm to hit the Northeast since the 1800s. Since 1938, there have been a number of significant hurricanes in the Northeast--the Great Atlantic hurricane of 1944, Hazel of 1954, Diane of 1955, Donna of 1960, Gloria of 1985, Bob of 1991, and Floyd of 1999--but none of these were as formidable as the great 1938 storm. Today, we have a hurricane over the Bahamas--Hurricane Irene--that threatens to be the Northeast's most dangerous storm since the 1938 hurricane."

"Irene will likely hit Eastern North Carolina, but the storm is going northwards after that, and may deliver an extremely destructive blow to the mid-Atlantic and New England states. I am most concerned about the storm surge danger to North Carolina, Virginia, Maryland, Delaware, New Jersey, New York, and the rest of the New England coast. Irene is capable of inundating portions of the coast under 10 - 15 feet of water, to the highest storm surge depths ever recorded. I strongly recommend that all residents of the mid-Atlantic and New England coast familiarize themselves with their storm surge risk."

"Mass evacuations of low-lying areas along the entire coast of New Jersey, Delaware, Maryland, and Virginia are at least 50% likely to be ordered by Saturday. The threat to the coasts of New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, and Maine is less certain, but evacuations may be ordered in those states, as well. Irene is an extremely dangerous storm for an area that has no experience with hurricanes, and I strongly urge you to evacuate from the coast if an evacuation is ordered by local officials. My area of greatest concern is the coast from Ocean City, Maryland, to Atlantic City, New Jersey. It is possible that this stretch of coast will receive a direct hit from a slow-moving Category 2 hurricane hitting during the highest tide of the month, bringing a 10 - 15 foot storm surge."

Track forecast for Irene

"The models have edged their tracks westwards in the last cycle of runs, and there are no longer any models suggesting that Irene will miss hitting the U.S. The threat to eastern North Carolina has increased, with several of our top models now suggesting a landfall slightly west of the Outer Banks is likely, near Morehead City. After making landfall on the North Carolina coast Saturday afternoon or evening, Irene is likely to continue almost due north, bringing hurricane conditions to the entire mid-Atlantic coast, from North Carolina to Long Island, New York. This makes for a difficult forecast, since a slight change in Irene's track will make a huge difference in where hurricane conditions will be felt. If Irene stays inland over eastern North Carolina, like the ECMWF and GFDL models are predicting, this will knock down the storm's strength enough so that it may no longer be a hurricane once it reaches New Jersey. On the other hand, if Irene grazes the Outer Banks and continues northwards into New Jersey, like the GFS model is predicting, this could easily be a Category 2 hurricane for New Jersey and Category 1 hurricane for New York City. A more easterly track into Long Island would likely mean a Category 2 landfall there.

Category 2 landfalls may not sound that significant, since Hurricane Bob of 1991 made landfall over Rhode Island as a Category 2, and did only $1.5 billion in damage (1991 dollars), killing 17. But Irene is a far larger and more dangerous storm than Bob. The latest wind analysis from NOAA/HRD puts Irene's storm surge danger at 4.8 on a scale of 0 to 6, equivalent to a borderline Category 3 or 4 hurricane's storm surge. Bob had a much lower surge potential, due to its smaller size, and the fact it was moving at 32 mph when it hit land. Irene will be moving much slower, near 18 mph, which will give it more time to pile up a big storm surge. The slower motion also means Irene's surge will last longer, and be more likely to be around during high tide. Sunday is a new moon, and tides will be at their highest levels of the month during Sunday night's high tide cycle. Tides at The Battery in New York City (Figure 3) will be a full foot higher than they were during the middle of August. Irene will expand in size as it heads north, and we should expect its storm surge to be one full Saffir-Simpson Category higher than the winds would suggest."

Irene's storm surge potentially extremely dangerous for the mid-Atlantic coast

"Irene's large size, slow motion, arrival at high tide, and Category 3 strength at landfall in North Carolina will likely drive a storm surge of 8 - 10 feet into the heads of bays in Pamlico Sound, and 3 - 6 feet in Albemarle Sound. As the storm progresses northwards, potential storm surge heights grow due to the shape of the coast and depth of the ocean, though the storm will be weakening. If Irene is a Category 1 storm as it crosses into Virginia, it can send a storm surge of 4 - 8 feet into Chesapeake Bay and Norfolk. I give a 50% chance that the surge from Irene in those locations will exceed the record surges observed in 2003 during Hurricane Isabel. The region I am most concerned about, though, is the stretch of coast running from southern Maryland to Central New Jersey, including Delaware and the cities of Ocean City and Atlantic City. A Category 1 hurricane can bring a storm surge of 5 - 9 feet here. Irene's large size, slow movement, and arrival at the highest tide of the month could easily bring a surge one Category higher than the storm's winds might suggest, resulting in a Category 2 type inundation along the coast, near 10 - 15 feet. This portion of the coast has no hurricane experience, and loss of life could be heavy if evacuation orders are not heeded. I give a 30% chance that the storm surge from Irene will bring water depths in excess of 10 feet to the coasts of Maryland, Delaware, and New Jersey."

Irene's storm surge may flood New York City's subway system

"The floodwalls protecting Manhattan are only five feet above mean sea level. During the December 12, 1992 Nor'easter, powerful winds from the 990 mb storm drove an 8-foot storm surge into the Battery Park on the south end of Manhattan. The ocean poured over the city's seawall for several hours, flooding the NYC subway and the Port Authority Trans-Hudson Corporation (PATH) train systems in Hoboken New Jersey. FDR Drive in lower Manhattan was flooded with 4 feet of water, which stranded more than 50 cars and required scuba divers to rescue some of the drivers. Mass transit between New Jersey and New York was down for ten days, and the storm did hundreds of millions in damage to the city. Tropical Storm Floyd of 1999 generated a storm surge just over 3 feet at the Battery, but the surge came at low tide, and did not flood Manhattan. The highest water level recorded at the Battery in the past century came in September 1960 during Hurricane Donna, which brought a storm surge of 8.36 feet to the Battery and flooded lower Manhattan to West and Cortland Streets. However, the highest storm surge on record in New York City occurred during the September 3, 1821 hurricane, the only hurricane ever to make a direct hit on the city. The water rose 13 feet in just one hour at the Battery, and flooded lower Manhattan as far north as Canal Street, an area that now has the nation's financial center. The total surge is unknown from this greatest New York City hurricane, which was probably a Category 2 storm with 110 mph winds. NOAA's SLOSH model predicts that a mid-strength Category 2 hurricane with 100-mph winds could drive a 15 - 20 foot storm surge to Manhattan, Queens, Kings, and up the Hudson River. JFK airport could be swamped, southern Manhattan would flood north to Canal Street, and a surge traveling westwards down Long Island Sound might breach the sea walls that protect La Guardia Airport. Many of the power plants that supply the city with electricity might be knocked out, or their docks to supply them with fuel destroyed. The more likely case of a Category 1 hurricane hitting at high tide would still be plenty dangerous, with waters reaching 8 - 12 feet above ground level in Lower Manhattan. Given the spread in the models, I predict a 20% chance that New York City will experience a storm surge in excess of 8 feet that will over-top the flood walls in Manhattan and flood the subway system. This would most likely occur near 8 pm Sunday night, when high tide will occur and Irene should be near its point of closest approach. Such a storm surge could occur even if Irene weakens to a tropical storm on its closest approach to New York City."

Stay tuned as Irene continues to develop and move toward the eastern USA.

I want to emphasize that it's still too early to make the call on a direct hit for New York City, but the threat is growing with each passing model run. This could very well develop into a major weather disaster.

PH