How Joaquin is Different From Superstorm Sandy

Jon Erdman
Published: September 29,2015

With Joaquin festering east of the Bahamas and a clogged atmospheric pattern developing, you may wonder whether this is another Sandy in the making.
(SANDY RECAPS: Daily Diary | Forecast Triumph | One of Most Destructive in U.S. History)
Fortunately, for now, there are many more differences than similarities between Joaquin and Sandy.
However, significant, dangerous impacts are still on the table for parts of the East even if Joaquin itself never directly affects the East Coast.
(In the sections below, click on each map to enlarge.)

Sandy Was Much Stronger, Earlier

Sandy formed in the central Caribbean Sea, strengthened to a Category 3 hurricane as it made landfall in eastern Cuba, then briefly stepped down to tropical storm strength near the northwest Bahamas.
With the Caribbean Sea hostile for tropical formation much of the 2015 season, Joaquin instead formed northeast of the Bahamas. Its intensity was being held in check initially by wind shear. It's not out of the question that once shear weakens Joaquin could become a hurricane not too far east of the Bahamas, where Sandy passed overhead as a hurricane.

Sandy	Joaquin

A Huge Superstorm vs. One Part of a Gyre

Sandy grew to mammoth size after it crossed the Bahamas, with tropical storm-force winds (at least 39 mph sustained winds) estimated over a diameter of roughly 1,000 miles before landfall in New Jersey. This huge wind field is indicated by the orange shading in the map below at left.
Instead of dominating the wind flow over much of the eastern U.S. and western Atlantic, Joaquin's wind field remains comparatively miniscule and may be just one piece of a broad area of low pressure near the Eastern Seaboard ahead.
(Image credit below at left: National Hurricane Center)

Sandy	Joaquin

Sandy Slammed Into the East Coast; Joaquin May Not

Sandy's massive circulation took a bizarre, hard left turn into New Jersey and the interior Northeast.
(INTERACTIVE: Evolution of Sandy's Projected Path)
Joaquin may never make it ashore, and wind shear may rip it apart. Instead, another non-tropical low pressure center may form near the Northeast seaboard, certainly much weaker than Superstorm Sandy.
(Image credit below at left: NOAA)

Sandy	Joaquin

Rainfall Flood Threat Much Higher Ahead

Rainfall wasn't the big impact with Sandy.
Sandy wrung out over six inches of rain in a swath of the Mid-Atlantic states, not to mention, yes, snow. There won't be any snow this time.
However, the combination of a stalling frontal boundary with a deep layer of tropically moist air flowing into and over it, either from Joaquin itself or another non-tropical low, appears poised to dump more widespread, torrential rainfall over a much larger area and population than Sandy did.
Areas from the Carolinas to Maine could be dealing with serious flooding from this complicated setup, which is likely to occur even if Joaquin never makes landfall. Some of these areas are already dealing with flooding from a slug of moist air originating from the Gulf of Mexico.
Research presented by Steven Decker of Rutgers University at the American Meteorological Society's annual meeting in 2014 used computer modeling to show that if Hurricane Sandy hadn't formed, a nor'easter would have formed anyway – but with far weaker impacts both inland and at the coast.
(Image credit below at left: David Roth/NOAA/WPC; Red shading corresponds to 5 inches or more, brown to 7 inches or more, purple to 10 inches or more. The image at right is The Weather Channel rainfall forecast for the next seven days.)

Sandy	Joaquin

No "Sandy Surge," But Coastal Flooding, Beach Erosion, High Surf Impacts Expected

Sandy's large, intense circulation crashing ashore along the Eastern Seaboard sent a destructive storm surge up and down the Eastern Seaboard, from the Carolinas to New England.
As we mentioned earlier, Joaquin itself may get pushed well out to sea, which would take off the table any kind of a storm surge, per se.
However, the surface pressure difference between high pressure in eastern Canada and whatever form low pressure takes near the Eastern Seaboard is likely to lead to a period of coastal flooding, beach erosion and dangerous surf.
The precise details of who sees the worst coastal flooding and when that occurs remain uncertain at this early stage, depending on where onshore flow can persist the longest, through multiple high-tide cycles.
This is the last thing those along the storm-weary stretch of the Outer Banks of North Carolina, Virginia Tidewater, Delmarva Peninsula and Jersey shore want to see following the past weekend's high surf, coastal flooding and beach erosion event.
And this event could yield much more rain.
(Photo at left: The Seaside Heights, New Jersey, roller coaster washed out to sea by Superstorm Sandy; Credit: AP/Mike Groll)

Sandy	Joaquin

The bottom line, here, is this is very unlikely to turn out the way Superstorm Sandy did.
However, there are potentially dangerous impacts from this setup, regardless of what happens with Joaquin.
(MORE: The Flood Danger of Your Vehicle)
Check back with us at weather.com and The Weather Channel for the latest on Joaquin and the East Coast flood threat.

MORE: Superstorm Sandy (PHOTOS)