Historic storm system heading for the mid Atlantic and NE US

Historic storm system heading for the mid Atlantic and NE US. 

Potentially life threatening destructive storm surge event for the New Jersey and New York coasts. 

Discussion:

The transition of Sandy from a pure tropical cyclone toward more of mid-latitude cyclone has begun. Sandy is still located near the northern Bahamas this morning, but satellite and radar images along with recon data suggest that the system has made the expected turn toward the NNE and this motion should continue with an increase in forward speed. Aircraft data also shows the wind field is greatly expanding with TS force winds extending outward 435 miles from the center with the highest winds located across the western and northwestern flank of the circulation where sporadic deep convection is found. 

Across the north Atlantic and the US, the upper air pattern continues to “block” with massive high pressure building over eastern Canada and a strong trough (our cold front) pressing into the eastern US. A shortwave over the western states this morning will swing through the base of the main trough and tilt it from SE to NW over the SE and mid Atlantic starting tomorrow. Sandy will become captured by this titling and instead of pushed out to sea, make a hard left turn (NW) back toward the US mid-Atlantic and NE US coast between the trough to her SW and the blocking high to her NE. Global guidance is in very good agreement on this pattern and in fact has very little spread in the track solution given the complex interactions that will be in place. Models show Sandy moving NW to WNW toward the New Jersey coast and making landfall Monday night or Tuesday morning and then slowing down as she moves inland. 

As for intensity, Sandy is gradually taking on more and more mid latitude influences although her center core remains “warm” or tropical. Jet stream phasing with the system is starting to occur with temperature gradient developing on her outer flanks of the large circulation. As Sandy moves northward this process will intensify has the warm Caribbean air mass clashes with a very cold polar air mass resulting in strong baroclinic intensification. Sandy will also be located in the favorable region of the trough and jet stream axis to promote surface deepening of a cyclone. Models continue to advertise “incredibly” low pressures with the ECMWF showing a record 942mb low near landfall on the New Jersey coast which is an astounding 30mb lower than the 1991 Perfect Storm and 6mb lower than anything ever recorded in the NE US. 

Given the continued very good model agreement on both track and the forecasted extreme low pressures, confidence is building that an extremely rare powerful storm system will impact the NE and mid-Atlantic coast from Sunday-Thursday. 

Impacts:

Major travel disruption is likely as numerous major E coast airports will not be able to sustain operations and this will have ripple effects across the nation. Additionally, widespread power outages and down trees will greatly hamper surface and rail travel across the entire region with widespread and potentially prolonged impacts to commerce. 

This will be a long duration multi-day event with prolonged impacts over the entire area from North Carolina to Canada and extending inland into the OH valley affecting some 55-65 million people. 

Coastal flooding or storm surge flooding appears to be significant especially for the New Jersey and New York (NYC and Long Island) coasts. The angle of approach this storm will be taking from (SE to NW) strikes the coast at a right angle instead of the usual grazing by of the coast most storms in this region take (SW to NE or parallel to the coast). This direct hit on the coast will drive onshore winds and massive amounts of Atlantic seawater toward the central and northern New Jersey coast and into the “L” shaped New York Bight area of southern New York City and western Long Island (a worst case track for this area, that has never occurred before with this strong of a storm system). The fetch of wind across the entire north Atlantic will drive large waves and surge to the coast and this will last for several high tide cycles. Tides will be at their maximum due to the full moon on Monday. Massive beach erosion is likely with coastal structures experiences significant damage many to the point of total collapse. Seawater inundation will be extensive and widespread and long lasting and in some places potentially record setting. Due to the rare track of this storm, some locations that have never before experienced coastal flooding, may flood with this event. 

Winds of 50-60mph with gust to 70-80mph will battered a wide area for 24-48 hours. Expect widespread tree damage and power outages which could rival some of the largest power outages ever in the US. The prolonged nature of the event will result in trees giving way over time as the ground saturates from the heavy rainfall. Winds will be higher in an near tall high rise buildings where funneling will take place. Structure damage will be mainly from trees falling into buildings and to roofs from the wind itself. 

Rainfall amounts of 5-8 inches will be common over a very large area with totals of 8-12 inches over New Jersey into southern PA and New York. Isolated amounts of 15 inches are possible as the tropical moisture from Sandy’s air mass crashes into the eastern slopes of the mountains and a stalled frontal boundary. Rainfall of this magnitude over an area of steep terrain will produce life threatening flash flooding and major river flooding.

Ocean seas will be building to staggering heights over the next few days. Already buoys north of the Bahamas have been reporting 30 foot seas, and Wave Watch III guidance is maxed out at 42-48 foot seas over the NW Atlantic Ocean by early next week. The expanding area of strong winds of 50-60mph and the massive fetch of wind all the way from Europe will produce very large swells. Would not be surprised to see reports of wave greater than 50-60 feet over the NW Atlantic. Some of this wave action and energy will be directed toward the US coastline and this will worsen the beach erosion. Large wave setup will also trap water levels near the coast and worsen the coastal flooding threat. 

On the extreme SW flank of the storm heavy wet snow will fall over parts of OH and WV with totals of 1-2 feet possible. 

Power outages will likely last for 1-2 weeks or longer 

Large scale evacuation orders for the New Jersey coast will be underway today with portions of New York also likely requiring evacuation due to the potential for coastal storm surge inundation.