Sunday, October 4, 2015

Live Coverage of Storm Surge Flooding in New Jersey

I flew to NJ yesterday evening and I just arrived at the coast. I will document the coastal flooding live today.

I just went on beach at Cape May. Seas were angry and I got sandblasted by sustained winds of at least 35 mph.

Locals told me flooding is worse near Ocean City. Driving coastal road now.

Cannot uploads pics from my phone to blog. Go to my Twiiter for pics, vid and possible Periscope stream!

My Twitter handle is @Hal_Needham.

-Hurricane Hal

Friday, October 2, 2015

Surge Levels Now Exceed 3 ft at Five Locations between Delaware and Chesapeake Bay

Storm surge levels continued to rise this evening as a persistent onshore wind continues to blow from the northeast from North Carolina through New England.

Surge levels are now > 3 ft for at least five locations between Delaware and Chesapeake Bay. The total water level, or storm tide (surge + tide) should continue to rise in most locations as high tide approaches most coastal areas around 1:00AM Eastern Time Saturday. High tide will occur a little later on bays and inlets.

Low tides should be observed around daybreak Saturday, with high tides occurring again around 1:30PM Eastern Time at the coast.

Storm surge observations as of 1000 PM Eastern Time on Fri Oct 2. These data are provided by NOAA Tides and Currents.

A 3-ft storm surge has a greater impact than one might expect because of the following:

1. The tidal range across much of this region is 4-5 feet between low tide and high tide. Adding 3 ft to the high tide level will cause coastal inundation in many low-lying areas.

2. Elevated coastal water levels slow the drainage of heavy rainfall, because most drainage systems are gravity fed. A prolonged storm surge can cause fresh water flooding from 1-2 inches of rain, when typically that much rain runs off quickly.

3. The prolonged nature of this wind/ surge event means storm surge will be added to at least eight high tide cyclones. Such persistent conditions will likely cause much more coastal erosion than usually experienced from a 3-4 ft surge.

Prolonged Surge Event Underway along Eastern Seaboard

A prolonged storm surge event is underway along the Eastern Seaboard. A strong pressure gradient  between a dome of high pressure over Canada and Hurricane Joaquin near the Bahamas is producing a sustained northeast wind from North Carolina to New England.

 Streets flooded in Ocean City, NJ on Fri Oct 2 as high water from both storm surge and steady rain inundated the area.

As of 0800AM EDT today, storm surge levels exceeded 2 ft above predicted tide levels from North Carolina through Southern New Jersey. Several sites near the mouth of the Delaware Bay and Chesapeake Bay reported storm surge levels between 2-3 ft. The highest storm surge level observed by NOAA's National Ocean Service (NOS) tide gauges was 3.05 ft, at Wachapreague, Virginia.

Storm surge levels at 0800AM EDT exceeded 3 ft in Eastern Virginia, with many sites between North Carolina and New Jersey observing surge levels between 2-3 ft. Data: NOAA Tides and Currents; Image: Hal Needham

As this wind and surge event will last for at least four days, storm surges will be added to at least eight high tide cycles. The most noticeable flooding will occur near the time of high tide.

High tide will occur just after noon today for much of the Mid-Atlantic Coast. In most places, high tide occurs approximately every 12.5 hours, so it will occur again Saturday morning after midnight, and again early afternoon on Saturday. High tide in bays and coastal inlets often occurs around an hour after peaking at the coast.

At Wachapreague, Virginia, high tides should occur around 12:30PM Friday, 1:00AM Saturday, and again around 1:30PM Saturday afternoon. The difference between low and high tide at this site exceeds 4 ft.

 Tide gauge graph from Wachapreague, Virginia, depicting observed and predicted water levels. Base Graphic: NOAA Tides and Currents. Edits: Hal Needham

The regional surge map shown at the top of this blog post depicts surge levels at precisely 0800AM EDT. Keep in mind that even if those surge levels do not increase, as high tide approaches, coastal inundation should be more noticeable. Stay tuned to your updates from your local National Weather Service office, and the National Hurricane Center for more updates on this developing event.


Thursday, October 1, 2015

Wind, Rain and Surge Will Not Miss the East Coast, Regardless of Joaquin's Track

The National Hurricane Center's 5PM EDT update forecasts Hurricane Joaquin to track farther east than previous forecasts. These changes reflect eastward shifts in various models, such as HWRF, GFS and UKMET, to reflect solutions closer to the ECMWF (European) model, which all along has been predicting Joaquin to take an eastward turn.

The 5PM EDT update from the NHC shifted Joaquin's track to the east. Source:
While this updated forecast provides a collective relief for many along the Eastern Seaboard, it's not time to celebrate yet. Hurricane Joaquin is just one player in a complex drama that is taking place along the U.S. East Coast, and, in a sense, other characters in this play will not allow Joaquin to "miss" the East Coast.

A large, strong area of high pressure is building over Eastern Canada, and the gradient between Joaquin and this dome of high pressure will generate strong onshore winds for more than four consecutive days from North Carolina through New England. This situation will play out regardless of Joaquin's exact track. Persistent northeast winds will cause prolonged storm surge flooding and coastal erosion, particularly from Virginia through the New York City area.

The maps below show GFS model output. These maps were initialized (run) at 1200UTC (8AM EDT) on Thu Oct 1, and predict conditions for 1200UTC (8AM EDT) on Sat Oct 3 and Sun Oct 4. Note the tightly packed isobars in boxes 1 and 2, which are predicted to occur 24 hours apart.

 The GFS Mean Sea Level Pressure forecast for 1200 UTC (8AM EDT) on Sat Oct 3 depicts Joaquin near the Northern Bahamas and a very tight pressure gradient from North Carolina to New England. Source:, edited by Hal Needham.
  The GFS Mean Sea Level Pressure forecast for 1200 UTC (8AM EDT) on Sun Oct 4 moves Joaquin to the NNE, but keeps the tight pressure gradient along the U.S. East Coast. Source:, edited by Hal Needham.

The two maps below depict ECMWF model forecasts for the same times (1200 UTC/ 0800 EDT on Sat Oct 3 and Sun Oct 4). This model also predicts Joaquin will be centered near the Bahamas on Saturday, but predicts the storm to track NE, away from the U.S. mainland on Sunday.

However, notice how the isobars, or lines of equal pressure, stay packed in the boxes on both of these maps as well. When we step back and look at the scale of this widespread wind event, we begin to understand why Joaquin won't fully "miss" the U.S. East Coast, even if it tracks out to sea.

The ECMWF forecast for 1200UTC (8AM EDT) Oct 3 forecasts Joaquin near the Bahamas and a tight pressure gradient along the U.S. East Coast, from North Carolina to New England. Source:, edited by Hal Needham.

Although the ECMWF model forecast for 1200UTC (8AM EDT) Sun Oct 4 predicts Joaquin to track east of the Bahamas, and away from the U.S. mainland, note the strong pressure gradient that remains in the box. Source:, edited by Hal Needham.

Unfortunately, these strong winds will persist four or five days, which spells trouble because the East Coast will need to endure at least 10 high tide cycles during this surge event. Although surge levels may not reach as high as Hurricane Isabel (2003) or Sandy (2012) in this region, this prolonged surge will generate substantial flooding and excessive coastal erosion.

In addition to prolonged coastal winds and storm surge, a stalled out cold front will produce torrential rains in the Carolinas and Virginia, with portions of South Carolina forecast to receive > 15 inches of rain through late Sunday.

Low pressure tracking along a stationary front off the Southeast Coast will generate torrential rains that may exceed 15 inches in South Carolina through Sunday. Image:

The combination of prolonged onshore winds, storm surge, beach erosion and torrential rains will produce substantial weather impacts along much of the Eastern Seaboard, regardless of Joaquin's exact track.

Extraordinary Onshore Wind and Surge Event to Impact Eastern Seaboard as Hurricane Joaquin Approaches

An extraordinary onshore wind and surge event will develop along the Eastern Seaboard over the next several days. Although Hurricane Joaquin is grabbing the headlines, and may directly produce the greatest wind, rain and surge impacts, Joaquin is just one of three players taking part in a complex drama that will unfold over the next several days.

The first player is a cold front and associated low-pressure system that dumped 2-4 inches of rain across a wide area from Virginia through Maine from Tuesday through Wednesday. This heavy rainfall saturated soils and elevated rivers, which will compound impacts from approaching Joaquin. Saturated soils will cause more of Joaquin's rainfall to runoff and cause flooding, while increasing the risk of downed trees, as wet soil provides less support than dry soil.

During the 24 hours preceding 1200GMT (8:00AM EDT) on Wed Sep 30, between 2 and 4 inches of rain fell across a widespread area from Virginia through Maine. Image:

Player #2 is a large area of high pressure building over eastern Canada behind this cold front. The strong pressure gradient between this massive area of high pressure and Hurricane Joaquin, Player #3, will generate prolonged onshore winds from North Carolina through New York. These winds will begin to blow hard long before Joaquin's arrival.
 GOES Floater RBTOP-IR Satellite Image of Hurricane Joaquin accessed 4:46AM EDT on Thu Oct 1. The pressure gradient between Joaquin and strong high pressure over Canada will enhance wind and surge impacts. Image:

The duration of this wind event is absolutely mind-boggling. Data from the National Weather Service point forecast for Atlantic City International Airport (ACY), New Jersey, suggest a strong onshore wind event will occur over coastal New Jersey for more than 100 consecutive hours (Yes, four days and then some)! Let me explain in more detail.

I've defined a "prolonged onshore coastal wind event" as a scenario in which winds along the Mid-Atlantic (New Jersey in this case) coast blow from between the N and E (compass bearings 0 to 90 degrees), with maximum sustained winds 20 mph for at least 75% of the observed hours. I chose these compass directions because Ekman Transport tends to deflect water to the right of the wind direction in the northern hemisphere, making a NE wind very efficient at piling up water along the East Coast.

 A strong onshore wind event is forecast to impact the Mid-Atlantic Coast along the Jersey Shore for more than four consecutive days (112 hours), generating a prolonged storm surge. Image of Atlantic City:

Using this metric, coastal New Jersey will observe a strong onshore wind event lasting 112 hours, based on point forecast data for ACY. This forecast predicts that winds will exceed 20 mph by 12PM EDT on Thu Oct 1 and remain above this threshold for 88 out of 90 hours, until 5AM EDT on Mon Oct 5. Mind you that this extraordinary wind event occurs before Joaquin even makes its closest approach!

 The National Weather Service Point Forecast for Atlantic City International Airport, New Jersey, predicts northeast winds will reach 25 mph, with gusts to 40 mph during the day on Friday. An extended view of this graph reveals a strong onshore wind event will last ~ 90 hours before Joaquin even arrives. Image:; edited by Hal Needham.

Winds are then forecast to drop slightly below the 20 mph threshold, before quickly increasing with the closest approach of Joaquin. Adding the winds from Joaquin's closest approach increases our coastal wind event to 112 hours, with onshore winds 20 mph forecast at 102 of those 112 hours (91.1% of observations).

Of course, much uncertainty remains regarding Joaquin's track, timing and intensity.  But the big picture here is that a prolonged coastal wind event will occur even before Joaquin arrives, making coastal flooding and erosion impacts more likely.

  The strongest winds along the Mid-Atlantic coast should arrive late Mon into early Tue, according to this National Weather Service point wind forecast for Atlantic City. Note that Joaquin is forecast to impact this area AFTER a 90-hour strong onshore wind event.  Image:; edited by Hal Needham.

This developing situation is truly historic and has not been observed in the modern history of the Mid-Atlantic Coast. I worked with Josh Gilliland, a PHD student at Louisiana State University, and the only Cleveland Brown's fan I know, to analyze the wind history for ACY. We were interested to find previous events that may have resembled the current forecast. Hourly wind data were from 1950-2015 were provided by the National Climate Data Center's Integrated Surface Database (NCDC-ISD), available at Gilliland adjusted these obs to 10 m height, in accordance with wind data standards.

We found only six previous "prolonged wind events" that lasted ≥ 48 hours at ACY. None of these events were produced from onshore wind events, as they all were related to frontal passages, with strong winds blowing from the NW. All of these events occurred during winter or spring. I have listed the six events below:

Duration (hours)
Obs ≥ 20 mph
% Obs 20 mph
Wind Direction
Offshore (NW)
Offshore (NW)
Offshore (NW)
Offshore (NW)
Offshore (NW)
Offshore (NW)
Prolonged wind events (≥ 48 hours) for Atlantic City, New Jersey, from 1950-2014. All of these events occurred in winter or spring and were related with frontal passages (offshore winds).
The longest duration onshore wind event we could find since 1950 was related with a winter storm, from January 9-11, 1956. Within a 42-hour period, onshore winds > 20 mph were observed on 39 hourly observations (92.9%). During a 6-hour period, sustained winds ranged from 28-29.9 mph, but never topped 30 mph.

Duration of prolonged wind events at Atlantic City, NJ, from 1950-2015. Data provided by National Climate Data Center's Integrated Surface Database (NCDC-ISD).

Tide gauges at Sandy Hook, NJ, and The Battery, NY (south end of Manhattan), depict this surge event from 1956 (unfortunately, the ACY tide gauge was not operating from 1951-1959).
Storm surge levels at The Battery reached approximately 2 ft, with a storm tide above MLLW peaking at 6.71 ft. See the graph below.

A storm surge of approximately 2 ft and a storm tide of 6.71 ft above MLLW were recorded at The Battery, NY, during a prolonged onshore wind event in January, 1956. The event this week should last considerably longer
with local onshore winds likely blowing harder than in 1956. Data and Graph: NOAA Tides and Currents.
 The January, 1956, onshore wind event produced even higher storm surges/ storm tides along the New Jersey Coast. The graph below depicts a storm surge of approximately 2.5 ft and a storm tide of 7.09 ft above MLLW at Sandy Hook, New Jersey.

A storm surge of approximately 2.5 ft and a storm tide of 7.09 ft above MLLW were recorded at Sandy Hook, NJ, during a prolonged onshore wind event in January, 1956. The event this week should last considerably longer
with local onshore winds likely blowing harder than in 1956. Data and graph: NOAA Tides and Currents.

Our current forecast predicts onshore winds for a longer time period (nearly 3x as long as 1956), with generally stronger wind speeds and potentially the approach of a hurricane or strong tropical storm. All of these factors would lead us to believe that the upcoming surge will be higher and last longer than the event in 1956.

So what does all this mean?

First of all, we are moving into new territory.

For now, one of the take home points is that this widespread wind event will create a long-duration storm surge even if Hurricane Joaquin does not make a direct landfall on the U.S. Atlantic Coast.

Also, even if Jaoquin's storm surge levels do not come close to those produced by Hurricane Sandy (2012) along the Mid-Atlantic Coast, or Isabel (2003) along the NC/ VA coast and Chesapeake Bay, the combination of long-duration surge and heavy rainfall on previously saturated soils, may flood some areas that were not inundated from Isabel or Sandy.

We should also consider these factors:

1. This surge event will last for many high tide cycles. The impacted region observes two high tides per day, so a 5-day surge event may stick around for 10 high tides. This will increase the risk of flooding in many locations.

 The National Weather Service has already issued coastal flood warnings for New Jersey and Delaware. Water levels may reach between 7.5 and 8.5 ft MLLW between now and 6AM EDT on Fri Oct 2.

2. Joaquin may flood areas not flooded by Sandy or Isabel, even if those storms produced higher surges at the coast. I am particularly concerned about areas "slightly" inland, such as  5-15 miles from the coast. How can rainfall drain into bays and rivers when they are elevated for multiple days from storm surge?

3. Even though our analysis focused on coastal New Jersey, wind, rainfall and surge impacts will likely extend from the Carolinas to New England.

 Tide predictions (blue) and observed water levels (red) at Atlantic City, NJ. The long-duration onshore wind event produce high water through two high tide cycles per day. The National Weather Service predicts water levels could reach 7.5 ft above MLLW at this location by 6AM EDT on Fri Oct 2. Many more days of strong onshore winds will follow.
Image: NOAA Tides and Currents.

We're facing multiple-hazards here and the interactions between rain and surge are complex to say the least.

If you've made it this far I would like to extend a hearty congratulations for making it through one of my longest blog posts ever! Well done, my friend!

Stay tuned to the National Hurricane Center, your local National Weather Service Weather Forecast Office, and your local media for future developments related to this complex forecast. I will continue to update this blog daily through the passage of Hurricane Joaquin.


Wednesday, September 30, 2015

Widespread Storm Surge Event to Impact Eastern Seaboard

A widespread storm surge event will impact the Eastern Seaboard later this week, as the complex interaction between Hurricane Joaquin, a pre-existing cold front, and a building dome of high pressure impact much of the Atlantic Coast with prolonged onshore winds and persistent rain.

The National Hurricane Center upgraded Joaquin to a hurricane as of the 8AM EDT advisory this morning. They forecast Joaquin to slowly drift westward towards the Bahamas through early Friday morning, before picking up forward speed and tracking to the north from Friday through Monday.

The National Hurricane Center upgraded Joaquin to a hurricane on the 8AM EDT advisory this morning. They forecast Joaquin to track up the Eastern Seaboard over the weekend and early next week. Image:

Although many hurricanes that track up the Eastern Seaboard eventually curve towards the northeast and remain offshore, building high pressure over Eastern Canada may block Joaquin from making this turn. This scenario may force Joaquin to either track due north, or even take a turn towards the west, on a path that could potentially resemble that of Hurricane Sandy three years ago.

Strong Pressure Gradient Will Generate Widespread Onshore Winds

Regardless of Joaquin’s exact track, the strong dome of high pressure over Eastern Canada will set up a widespread pressure gradient, which will produce prolonged onshore winds along much of the Eastern Seaboard.  The GFS model output depicted in the image below, initialized at 06Z (2:00AM EDT) this morning, maps this strong gradient for a forecast 48 hours into the future (06Z or 2:00AM EDT on Fri Oct 2). The lines on this map, called isobars, depict lines of equal pressure. Tightly packed isobars indicate large pressure gradients and strong winds.

The GFS model depicts a strong pressure gradient to develop along the Eastern Seaboard, between Hurricane Joaquin to the south and a strong dome of high pressure over Eastern Canada. This model run was initialized at 06Z (2:00AM EDT) and predicts surface pressure for 06Z (2:00AM EDT) on Fri Oct 2. Image:

The National Weather Service (NWS) Hourly Weather Forecast Graphs depict this prolonged wind event visually. The graph for the Atlantic City, NJ, (Point Forecast at Lat: 39.38N, Lon: 74.4W) depicts winds >= 20 mph to begin by 7:00AM EDT on Thu Oct 1 and continue until 12:00AM EDT on Sun Oct 4. The direction of these winds will range from NNE to E. If this forecast holds, it means that an onshore wind, capable of generating substantial storm surge, would exceed 20 mph for 65 consecutive hours. This graph also depicts winds >= 30 mph impacting this area for seven consecutive hours on Sat Oct 3.

This Hourly Forecast Graph for Atlantic City, NJ, depicts sustained winds exceeding 20 mph from Thursday morning through Saturday night. The wind direction is forecast from the NE and E, ideal directions for generating storm surge in this region. Image:

Such forecasts are subject to change, particularly in a complex situation like this one, as Joaquin’s exact track is unknown. Wind speeds should increase dramatically closer to Joaquin’s track. However, such a large pressure gradient between Joaquin and the massive high pressure to the north will mean that a widespread, prolonged onshore wind event is likely, regardless Joaquin’s exact track. This means that hundreds of miles of coastline will likely experience storm surge inundation, even if Joaquin stays offshore or makes landfall somewhere else.

The National Weather Service point forecast for Atlantic City, New Jersey, forecasts onshore winds > 20 mph could last for more than 60 consecutive hours between Thursday morning and Saturday night. Image:

Heavy Precipitation will Exacerbate both Freshwater and Saltwater Flooding

Heavy precipitation is another factor that should increase Joaquin’s inland and coastal flooding potential. A low-pressure system tracked along a front on Tuesday, producing substantial rains over northern Virginia, the Mid-Atlantic States and New England.  Over the past 24 hours (as of 8:25AM EDT Wed Sep 30), more than 1.5 inches of rain fell across much of this region, with many areas observing more than 3 inches. 

Accumulated rainfall for the 24 hours preceding 8:25AM EDT on Wed Sep 30. 

Unfortunately, the NWS Weather Prediction Center forecasts more than 7 inches of rain to fall during the next five days over a broad area from North Carolina through Southern New Jersey, with amounts exceeding 3 inches across Northern New Jersey, Southern New York and eastern New England.

Such heavy rains increase the risk of multiple hazards. Obviously, more heavy rain from Joaquin falling on soil that is already waterlogged will produce fresh water flooding, as the soil cannot store any more water, increasing runoff into streams and rivers. Waterlogged soil also provides less support for trees, making it more likely that they will fall when struck by strong winds.

The NWS Weather Prediction Center forecasts more than seven inches of rain could fall in the next five days from eastern North Carolina through Southern New Jersey. Image:

From a coastal flooding perspective, waterlogged soil and excessive fresh water runoff exacerbates the impacts of storm surge events for several reasons. It is easier for a storm surge to push inland if the surge finds water levels already elevated in coastal wetlands, estuaries, tidal inlets and rivers. This past Friday evening while I was on a bayou in South Louisiana looking for alligators (it’s quite fun actually), two locals told me that Hurricane Ike’s surge in 2008 was particularly bad because it arrived only 12 days after Hurricane Gustav, and the water levels from Gustav had not yet fallen. New water accumulated on pre-existing water compounds flood potential.

Another complex problem related to heavy rain and storm surge is that rainfall drainage is usually gravity fed, depending on a slope between the land and the nearest water body. When a storm surge pushes inland and elevates the level of a bay, river or tidal inlet, fresh water drainage slows down considerably. In other cases, a storm surge can actually “dam” fresh water discharge near the mouth of a river, causing the river to actually back up and inundate inland communities.

The compound effect of heavy rain and prolonged storm surge from Tropical Storm Debby generated flood waters that surprised many people along Florida's West Coast in 2012. Image:

The compound interaction between heavy rainfall and storm surge exacerbated flooding from two tropical systems in 2012. Tropical Storm Debby produced surprising flooding near Tampa, Florida, in June of that season, followed by substantial flooding from Hurricane Isaac in late August in Louisiana. Isaac's surge elevated the surface of Lake Pontchartrain for more than 60 hours, hindering fresh water drainage from more than 15 inches of rainfall that fell across the region.

Hurricane Isaac's combination of heavy rainfall (exceeding 15 inches in some areas) and prolonged storm surge exacerbated flooding in areas like LaPlace, Louisiana, in 2012. Link:

These interactions are complex and difficult to forecast. However, we do know that storm surge and heavy rainfall work together to compound flooding, and Wahl et al. (2015) recently found that this phenomenon is becoming more frequent, particularly along the U.S. Atlantic and Gulf Coasts.

Long story short, the combination of prolonged onshore winds and heavy rainfall preceding and accompanying the approach of Hurricane Joaquin, should generate substantial coastal flooding impacts along the Eastern Seaboard. Stay tuned to updates from your local National Weather Service and the National Hurricane Center for forecast updates on this developing event. I will attempt to update my blog frequently over the next week, as this complex situation unfolds.


Wahl, T., S. Jain, J. Bender, S.D. Meyers, and M.E. Luther, 2015: Increasing risk of compound flooding from storm surge and rainfall for major US cities. Nature Climate Change, do: 10.1038/nclimate2736. Link: