Hermine a Coastal Flood, Erosion Menace in Delmarva, New Jersey, Long Island, Connecticut, Massachusetts Through Labor Day

Jon Erdman
Published: September 4,2016
Hermine is beginning to stall off the East Coast, and will continue to impact areas from the Delmarva Peninsula to southeast New England with battering waves, coastal flooding and beach erosion through the Labor Day holiday, and beyond.
While this storm will likely not be nearly as large as Superstorm Sandy, you don't need a storm as large as Sandy to be destructive, and moderate coastal flooding is still expected along parts of the East Coast.
(MORE: Latest News | Interactive Hermine Tracker)
Hermine's wind field is anticipated to expand a bit on Monday, which means an uptick in its capability to generate waves and still a chance some of those stronger winds are able to bend back toward the coast.

Hermine's Current Wind Field

Despite being a post-tropical cyclone, tropical storm warnings are in effect from Fenwick Island, Delaware, to Sagamore Beach, Massachusetts, as well as the Delaware Bay south of Slaughter Beach, Block Island (Rhode Island), and the islands of Martha's Vineyard and Nantucket.

Watches and Warnings

National Weather Service (NWS) policy allows the National Hurricane Center (NHC) to issue advisories on and issue tropical storm watches and warnings for post-tropical cyclones when the system continues to pose a significant threat to life and property. This policy change was implemented after Superstorm Sandy.
No matter what meteorologists call this storm off the East Coast in the days ahead, the impacts will be dangerous.
(MORE: Explaining Tropical vs. Non-Tropical Cyclones)
Here are details on the potential impacts and meteorology behind this event.
(MORE: Send Your Hermine Photos)

Impacts

Slow-moving storms inherently have uncertainty. Hermine is no different. Here are the three uncertainties still in play.

• Where exactly the low-pressure center stalls or meanders
• How strong it remains, or how much it may intensify
• How long it lingers

Here are the potential impacts.

Coastal Flooding/Beach Erosion/High Surf

• Probability: Happening now
• Where: From southeast New England to the Delmarva Peninsula, particularly Long Island, the Jersey shore, and Delaware beaches; also, the west end of Long Island Sound, Chesapeake Bay, Delaware Bay, Raritan Bay and other inlets will be susceptible (especially at high tide).
• Threats: Moderate, possibly damaging surf with battering waves, potentially moderate coastal flooding, significant beach/dune erosion, rip currents over multiple high tide cycles. Flooding of back bays and sounds are also a threat, given the long-lived nature of this event.
• Timing: Seas continue to build from south to north into Monday, peaking with Monday's midday high tide, before slowly winding down Tuesday into Wednesday.
• Forecast water levels above ground at high tide, according to the latest NHC forecast:
  • Rehoboth Beach, Delaware, to Montauk Point, New York (incliding the North Shore of Long Island east of Flushing) : 1 to 3 feet
• Maps: NHC Potential Storm Surge Inundation | NHC Prototype Storm Surge Alert Map

(FORECAST: Montauk, New York | Atlantic City, New Jersey | Nantucket Island)

Waves will only continue to grow larger on Monday, and those waves will top the following tidal levels.
Below is a table of the next three high tides for various points along the East Coast.
For now, the majority of forecast guidance is pointing toward the highest tide levels with the Monday late morning/midday high tide, though coastal flooding will continue through several high tide cycles. Flooding of back bays may become worse with each high tide, as water cannot drain to the ocean.

Hampton Roads, Virginia (Sewells Point)	12:25 pm Monday	12:39 am Tuesday	1:05 pm Tuesday
Ocean City, Maryland	11:11 am Monday	11:24 pm Monday	11:52 am Tuesday
Atlantic City, New Jersey	10:45 am Monday	10:55 pm Monday	11:25 am Tuesday
Sandy Hook, New Jersey	11:15 am Monday	11:27 pm Monday	11:58 am Tuesday

Model Forecast Wave Heights 24 Hours From Now

High Winds

• Probability:
  • Slight (Delaware beaches to Long Island, Connecticut shore)
  • Slight (Rhode Island coast, bays, Nantucket, Martha's Vineyard, Cape Cod)
• Threats: Wind gusts over 40 mph may lead to sporadic power outages and downed tree limbs near the coast.
• Timing: Best chance appears to be now into Monday, though this all depends on the exact path of Hermine.

Current Winds, Gusts

Heavy Rain

• Probability: Low (Delmarva Peninsula to Long Island), Moderate (southeast New England): 1 to 2 inches possible
• Threats: The heaviest rain should remain offshore, but far southeastern Massachusetts, including Cape Cod and its offshore islands, run the greatest risk for heavy rain.
• Timing: Mainly Monday and Tuesday for southeast New England.
• Uncertainty: The exact path of this storm will dictate if any rain can back in from the Atlantic.

Rainfall Outlook Through Wednesday

(VIDEO: Where More Than a Foot of Rain Fell)

Forecast Track: Stuck

Hermine is located about 325 miles southeast of the eastern tip of Long Island, as of Sunday evening.

Current Storm Status

As the NHC forecast path shows, Hermine's center is not forecast to move much over the next few days.

Projected Path

Hermine was steered northeast around the west side of the Bermuda-Azores high-pressure system. It was also pulled somewhat by a southward dip in the jet stream, or trough, moving through the Great Lakes and Northeast.
But changes are about to occur.
That Great Lakes/Northeast upper trough will bypass Hermine into the North Atlantic without grabbing hold of the storm and taking it along, as more frequently happens in the western Atlantic.

Potential Labor Day weekend atmospheric setup.

Upper-level high pressure building to the north and east of Hermine will trap the system for several days, including the Labor Day holiday, and several days after.

Not in Sandy's League

Hermine's post-tropical remnant will be an impactful coastal storm, but its size will pale in comparison to Sandy.
Sandy's destruction was due to its giant wind field, churning up the ocean ahead of it, then piling it into the East Coast. Hermine's wind field will be impressive, but Sandy was in another class.

Wind field size of Superstorm Sandy versus forecast wind field for post-tropical Hermine.

Sandy had a previous pedigree of a Category 3 hurricane coming north from the Caribbean Sea, spending days churning the western Atlantic Ocean water up.
(MORE: Sandy Track History from Weather Underground)
Hermine spent some time over land Friday and early Saturday before re-emerging over the ocean.
Occurring just before Halloween, Sandy also had a sharper air mass contrast to feed its intensification near landfall, with temperatures in the 30s and 40s over the Ohio Valley, Appalachians, and eastern Great Lakes. You may recall it even snowed heavily in the Appalachians during Superstorm Sandy.
(MORE: The 35 Strangest Weather Events I've Seen)

Daily surface weather map on October 29, 2012 prior to the landfall of Superstorm Sandy.
(NOAA/WPC)

Post-tropical Hermine won't have nearly that sharp a temperature contrast in early September.
The upper-level pattern was also more extreme for Sandy, featuring a bizarre blocking upper high from the north Atlantic Ocean to the Canadian Maritimes, helping to shove Sandy westward into New Jersey, and a rather pronounced southward jet-stream dip from the Ohio Valley helping to provide atmospheric lift for its final explosive development moving ashore.

Jet stream pattern in place during Superstorm Sandy, featuring strong blocking high pressure aloft over the north Atlantic Ocean, and a pronounced southward jet stream nosedive from the Ohio Valley. This graphic was originally prepared in the days before Sandy's landfall.

Post-tropical Hermine is being trapped by high pressure aloft, and a bit of a blocking high to its east, but that won't likely steer it abruptly ashore. It should just linger and loiter.
Also, the upper-level low poised to meet up with Hermine is much weaker than the bullish Sandy upper trough.
However, one thing "Hermine" may have that Sandy didn't is longevity, one important factor in wave generation by any storm.
(MORE: Why Hermine Caused Extreme Forecast Headaches)
With the potential to hover offshore for 4 days over multiple high tide cycles in some areas, this storm may be able to inflict more beach erosion and coastal flooding than a faster-moving storm of similar intensity.
That longevity may also produce peak inundation levels but nearly the level of Sandy
However, that is not to say Hermine will produce the catastrophic inundations to the magnitude  (~9 feet, etc.) witnessed along the north Jersey shore, New York City, etc., where the worst inundation of Sandy occurred.
"The extreme (peak inundation levels expected for Hermine) isn't even in the same ballpark (as the highest totals from Sandy)," said The Weather Channel hurricane and storm surge expert, Michael Lowry. "Neither is the scale of the surge threat."
"No two storms are exactly alike, so of course some spots could see worse flooding than during Sandy but the overall scope of flooding will be far less extensive."

Peak estimated inundation values (feet above ground) from Superstorm Sandy in late October 2012. Values rounded to the nearest half foot.

The legendary March 1962 "Ash Wednesday" storm hammered the coast from Long Island to North Carolina, damaging or destroying 45,000 homes, destroying the boardwalk in Ocean City, Maryland and cutting a new inlet through Hatteras Island.
While a storm of this magnitude is far from a certainty in this case, we're pointing out the potential of Hermine.
Check back with us at weather.com for the latest on this situation.

MORE: Hermine Impacts (PHOTOS)