Mention a hurricane in Maryland and the first thing that comes to mind for many people is Hurricane Isabel in 2003. Others might think of Agnes in 1972. Both storms were responsible for flooding, but for different reasons. The main elements in a land falling tropical system besides the wind is the water. Whether it is a surge pushed up against the land or rain falling down and flowing through the tributaries, water will likely rise. Which one is worse than the other?
What is Storm Surge?
The track of a tropical system will determine the surge at landfall. With the winds circulating counter-clockwise, the right side of the storm will get the winds moving with the forward speed and both forces push onshore. That is where the worst conditions will be location. Just to the left side of the center, the winds move in the opposite direction. So while the storm is moving forward, the winds are pushing the reverse directions. On the east coast, a storm moving to the west will have those winds moving from the west, limiting the impact of the water pushed onshore.
Storm Surge on the Chesapeake Bay
For water to push up the Chesapeake Bay, the storm track has to be up the Bay to the north, or to the west side of the Bay. A storm moving up the east coast will produce a wind from the north, flowing down the Bay. The surge of water would stay out in the ocean.
In 2003 the worst flooding ever experienced in Annapolis, Baltimore, and Havre de Grace. That storm actually moved inland well south into North Carolina, but made its way into western Pennsylvania. It is important to note that Isabel was once a Category 5 storm in the Atlantic, so there was wave memory and momentum that carried on shore with and behind it. The arrival of that wall of water along with high tide, brought water levels 8-10 feet above normal. That was too much for other communities like Bowley’s Quarters, and a 1 million dollar promenade in Havre de Grace was destroyed. The wind helped to carry the water on up north to the western side of the Bay. The Chesapeake was on the right side of that storm track.
In 1972, another monster storm hit the Gulf Coast and snaked its way through the southeast until moving off of the North Carolina coast. It then turned north past Maryland and into New York and the Poconos. This storm produced record flooding but it was mostly from the rainfall, and especially the flow of water down the Susquehanna into the Conowingo Dam. But at the same time, the water levels in the Chesapeake Bay dropped below normal, but a few feet. This was due to the strong winds from the north, pushing the water south and draining it into the Atlantic. The Chesapeake was on the left side of the track.
What will Sandy do?
The present storm tracks for Sandy show a sharp turn to the west hitting the Mid Atlantic Coast. Throw in the added high tide from a full moon on Monday, and we will see devastation somewhere. But where will it be the worst? There are two general scenarios or tracks based on all of the models right now most protect Maryland from the brunt, but it will still be bad. For now we are just focusing on the surge.
Track 1 is from the National Hurricane Center. It takes Sandy onshore by the Delaware Beaches. It then crosses the Delmarva and passes over the northern Chesapeake Bay through Harford or Cecil County and on to York, PA. This would produce a storm surge on the right side of the track for Delaware and perhaps up into Philadelphia similar to our Isabel up to 10 feet high. But that keeps the winds form the north and west, which pull the water down the Chesapeake. A landfall would have to drop farther south by Virginia Beach to push the water up the Bay. There will be some sloshing, and the high water with that wind would end up on the Eastern shore, not the western side of the Bay. Rainfall may add to the flooding, but in terms of surge, this is the best expectation.
Track 2 is form the European, GFS, and other global models. It focuses north into New Jersey for the landfall. That would funnel the water along the coastline from Long Island and New Jersey into New York City. This is farther away from Maryland, and it would result in more of a westerly wind. However this track drops the Sandy into southern PA and stalls if for a day. That would shift and increase the winds form the northwest, also out, not into the Bay. Both essentially keep the Chesapeake on the left side of the track.
Which track for Sandy?
At the point of writing this article on Saturday evening, October 27, 2012- there is no sure answer. For three days I have been confident saying Ocean City to New York City. The National Hurricane Center will often post a Hurricane Warning for 300 miles of coastline, but only 100 miles has the biggest impact from the surge and strength on the right front side. This window is growing smaller, between Delaware and central New Jersey now. However pin pointing the landfall all hinges on when Sandy makes ‘the turn’. That is when the storm actually strengthens even more and pulls back to the west. That turning point will help plot the trajectory to the coast. So until then, this wide window appears to be the best bet. That turn will take place on Sunday afternoon or evening at the latest.
The rainfall outlook for Sandy puts 6-12 inches of rain in much of the general path of the storm. Throw in the seasonal aspect of the foliage, and what leaves have not fallen yet, will be stripped from the trees. Those have and tendency to stick together and pack into storm drains, making potential flooding even worse.
Sunday: Showers, becoming breezier in the afternoon and evening.
Monday: Developing rain, which may become very heavy as the outer bands of Sandy approach in the afternoon.
Monday Night: Landfall will be within a few hours before or after midnight.
Tuesday Morning: The path crosses inland. If the southern track holds, winds in northern Maryland will reach over 65 mph. If it tracks through New Jersey most of Maryland will be in the wind field for 50 mph winds.
Tuesday Afternoon and Wednesday: Sandy may reach and stall in southern Pennsylvania. Strong winds of 40-50 mph will continue with higher gusts. There is a small chance colder air feeds into the core of the storm and snow gets a little closer, but doubtful in metro areas.
More on the set up for ‘The Perfect Storm’
Sandy back to hurricane strength and will grow for US landfall on Monday
Hurricane Sandy 3-day satellite loop and landfall forecast for the US
Hurricane Sandy weaker but staging a massive US hit
I will monitor that part of the storm on my Hurricane Examiner Page. Also follow along for updates through:
Facebook: Justin Berk, Meteorologist
Tropical storm and hurricane history of naming. 2012 Atlantic list
Tropical Storm formation history: Storm origin maps every 10 days of season
Hurricane Preparedness Week: Storm Surge is the most deadly and destructive
Hurricane Destruction Animation based on Saffir Simpson Scale
NASA Global Hawk: Hurricane drone planes run by locals at Goddard