Strong nor’easter will provide myriad of threats midweek

GFS Model showing a strong nor’easter off the coast on Wednesday evening/early Thursday morning, with a surface pressure down to 978mb. Contours are winds at 900mb (max 72-74kts over NJ).

No rest for the weary. Just a week after Hurricane Sandy slammed into the New Jersey shore with widespread damaging impacts, another strong nor’easter is forecast to strengthen off the Mid Atlantic coast on Wednesday bringing more unsettled weather to the area — with the potential for heavy rain, high winds and even snow inland. The storm system is expected to provide a myriad of threats, but the exact details remain uncertain with the storm still 60 hours away and forecast models still struggling with the details.  We detail the threats below, and try to answer as many as your questions as we can.

How is this storm system developing? A piece of energy over the Southeast United States will swing eastward towards the coast, while another disturbance drops south out of Canada into the Tennessee Valley and phases with it. Yes, we’ve heard these terms before. The phase will allow the storm to strengthen off the coast once again. This time, the blocking to the north won’t be strong enough to force the storm well inland (it’s also not a tropical system hybrid) but the storm system is still forecast to be plenty strong as it develops off the coast and then gets tugged near the shore.

What are the main threats with the system? There are plenty. The system will be entering a very cool airmass which is in place across the region (check out how chilly it is today and tonight), and the high pressure will shift to the north and do its best to keep the cold air in place. This, with the storm system strengthening offshore, creates a threat for wind and rain along the coast, some storm surge, and the possibility of frozen precipitation for a period of time especially inland.

  • Rain: The system looks to  provide moderate amounts of rainfall throughout the entire area, with the potential for some heavier rain along the coasts and on Long Island. The one caveat to this is that the storm’s best period for strengthening and heavy precipitation will be south of the area — so the rain may be lighter by the time it gets here. We’ll have to watch this carefully.
  • Wind: This is not something you want to hear, we know. But the storm system looks to have a significant amount of wind with it, especially aloft. The difference between this storm and Hurricane Sandy other than the size and intensity is that the atmosphere will be less favorably set up for mixing these winds down to the surface. However, there may still be gusts over 60 miles per hour especially near the coasts. These type of wind gusts are still dangerous and could cause some downed trees and power lines, especially ones weakened by Sandy. The wind should be less of a threat over inland areas due to the stable northerly wind component, but still capable of gusts near 40-50mph.
  • Storm Surge/Flooding: This storm will occur, luckily, at a period between full moons and astro-low tides, whereas  Sandy occurred during a full moon at high tide. However, such a strong storm system as this one can still often produce a storm surge…yet it should be at least somewhat mitigated by the fact that the system is expected to remain offshore. That being said, prepare for the possibility of some coastal flooding once again — to repeat…we are not expecting widespread storm surge/coastal flooding..but it remains a distinct possibility that it will occur, to a lesser extent than it did during  Sandy.
  • Snow: Yes, snow is actually a threat with this system. The main area for potential snow and ice will be over interior New Jersey (Sussex, Warren counties) and New York (Orange County), but the threat for a period of snow or sleet could exist as far south as the immediate suburbs of New York City as the storm begins. Accumulations should be limited to the aforementioned inland counties and higher elevations, where if enough cold air works in, 2 to 4 inches of snow and ice aren’t out of the question.

What’s the timing for this storm system and how can I prepare for it? Clouds look to increase during the day on Wednesday with showers becoming likely by Wednesday afternoon. Steady rain will approach the area from the south and east on Wednesday afternoon and evening, beginning at the shores and moving inland. The precipitation (some of it frozen over the interior) will continue through Thursday morning throughout much of the area. The strongest winds look to occur Wednesday Night as the system makes its closest approach to the area.

What can change with this system and the forecast? A whole lot, actually, as forecast models are still fairly inconsistent with the track of the storm system. There has been some convergence on a track closer to the coast over the past 12 hours, but in general the forecast confidence remains low to moderate at best. This could change a whole lot in terms of sensible weather impacts, so stay tuned over the next day or so and we should be able to get a much higher confidence forecast.