Riding on Carousels and Ocean Gyres

I had a little fun Friday with a television expert appearance, helping people understand a little mystery – what might have happened to a real estate sign from New Jersey that was found on a French beach.  The story was mostly already formed, being in the news cycle for nearly a day already, but CBS New York just wanted to hear some expert opinion on the sign’s possible trek and the ocean science to explain it.

Never one to turn down an opportunity to get my little academic institution’s name in the news, I took on the treacherous task!

Image result for carousel asbury park

The sign was lost during Hurricane Sandy, and as it was made of plastic it floated flat just at the surface, making a perfect drifter to follow the ocean currents.  The main question Vanessa Murdoch had was:  Why would the sign take 5.5 years to cross the Atlantic?

The average flow of surface water in the world’s oceans is called the “wind-driven circulation”, and in the North Atlantic this is a clockwise circular pathway called a Gyre. Winds at our latitude tend to travel on average from west to east, whereas in the tropics north of the equator, the trade winds blow from east to west.  Add in Earth’s rotation (via the Coriolis Force) and you get a circulation pattern which is clockwise around the North Atlantic.

Of course, I pointed out that in Jersey Shore terminology, one might think of it as a Carousel or merry-go-round.  A ride around the gyre is known to take about 3.3 years – this stat comes from a fun oceanographer I’ve met before who is famous for tracking and studying floating ocean debris, Curtis Ebbesmeyer.

Nobody can know for certain the exact path followed by the sign, but if it hopped on this carousel and took this typical or average pathway and speed, we can say its likely that it completed one round trip — crossing the Atlantic and back again, and then back across!  In the 5.5 years since Sandy, there would be time for 1.5 trips around the carousel, or three Atlantic crossings.

The Gulf Stream is generally a very reliable current, though the rest of the gyre is less so — mariners discovered these currents centuries ago and often used them successfully for navigation.  That is because these gyre currents don’t rely on local weather and winds, they rely on large scale average weather, or climate, to drive them.

Read the story and see the news clip for yourself – http://newyork.cbslocal.com/2018/06/01/nj-sign-found-in-france-update/

 

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Repetitive Flooding Coming with Winter Storm Riley

Low-lying areas of the NYC Metro area should expect coastal flooding over multiple high tides Friday through Sunday, due to Winter Storm Riley’s winds coinciding with the month’s highest tides.  The forecast for coastal areas is significantly worse than for NY/NJ Harbor areas like Manhattan and Hoboken, so I’ll start with comments on these regions.  Consult the National Weather Service for official consensus guidance, but here I’ll summarize the picture from my perspective interpreting Stevens SFAS forecasts.

gfs_mslp_wind_neus_6

GFS weather model forecast for 7am EST Friday 2 March.  Lines show pressure isobars and wind speeds are colored by knots (scale on right). The storm continues to slowly move eastward from Saturday through Monday.

Areas like Keansburg, Sandy Hook and Jamaica Bay are all looking at moderate flooding and the outside chance of “major” coastal flooding.

sfas_plot-Inwood180301-0737

Stevens Flood Advisory System (SFAS) experimental forecast for water levels at Jamaica Bay’s Inwood, New York City (magenta), relative to NAVD88 (similar to mean sea level). Observed water levels are also shown (red dots), as well as 90% confidence intervals (grey shading).

Thus, there is a good chance of low-lying property flooding, and of water blocking streets and becoming trapped for some parts of the Rockaways and all the ‘usual’ locations (eg Broad Channel, Old Howard Beach), Friday through Sunday, peaking multiple times over several tidal cycles.  In Jamaica Bay, there is potential for a water level as high as 7 feet navd88, though the central estimate is 5.5 feet (moderately high uncertainty – whether the winds are north or northeast, basically).  The highest water level since Sandy was 5.7 feet navd88, and Sandy hit 10.5-11 ft navd88 there, for comparison.

New York /New Jersey Harbor is more likely to see “minor flood” levels, as shown below. The central estimate peak water levels of 5 feet navd88 translate to widespread nuisance flooding of streets and trapped rainfall which won’t drain due to sea levels blocking stormwater drainage.  These lower flood elevations in the harbor areas are expected because the winds will often be out of the north, or north-northeast, which is amenable to offshore surge (blame Earth’s rotation!), but actually blows out of NY/NJ Harbor locally.  However, there is about a 5% chance of seeing 6 ft navd88, which would become problematic at more locations, though still well below levels needed to cause widespread flooding.

sfas_plot-Battery180301-0737

Stevens Flood Advisory System (SFAS) experimental forecast for water levels at Battery Park, New York City (magenta), relative to NAVD88 (similar to mean sea level). Observed water levels are also shown (red dots), as well as 90% confidence intervals (grey shading).

The storm surge continues to roam around the 1-3 foot level all weekend due to the storm tracking offshore and then “bombing out” and sticking around.  Winds will continue from the north and northeast all weekend, pumping water into New York Bight and sending large waves toward the New Jersey and Mid-Atlantic coastlines.

gfs_mslp_wind_neus_11

GFS weather model forecast for 1pm EST Saturday 3 March.  Lines show pressure isobars and wind speeds are colored by knots (scale on right). The storm continues to slowly move eastward from Saturday through Monday.  The storm central pressure is forecast to be 972 mbar at this time, the forecast minimum (by GFS).

Tip of the hat to Nickitas Georgas and Alan Blumberg, now based at Jupiter Intel, who lead creation and development of the Stevens Flood Advisory System.  If you value the SFAS flood forecasts, as we all should (they define the state-of-the-art), you might contact them to inquire about the future of the system and its possible funding.

 

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Investing in NOAA Ocean and Atmospheric Research

The Washington Post reported Friday that the Trump Administration is seeking huge cuts from the National Oceanic and Atmospheric Administration (NOAA) 2018 budget, including eliminating the Sea Grant Program and shaving 26% from the Office of Oceanic and Atmospheric Research (OAR).

My background is in studying the physics of the ocean, and my main area of research is coastal flood risk and mitigation.  Coming from a region that is still recovering from Hurricane Sandy, NYC’s largest flood in at least 300-years, I have some expertise on the return on investment of government funding under NOAA-OAR.  This funding enables research that has directly helped guide societal decisions that save money and make communities safer from extreme weather.

Among other things, OAR funds to the Climate Program Office have supported my research for the Consortium for Climate Risk in the Urban Northeast (CCRUN), under the Regional Integrated Sciences and Assessments program.  This funding enables our consortium of about ten lead scientists at six research institutions to study present and future risk from flooding, hurricanes, heat waves, drought, and other natural hazards.

This funding, typically below a hundred thousand dollars per year at each institution, can have huge economic benefits.  What people probably won’t realize from the headlines is that NOAA’s “climate” research, under the department of Commerce, is about both weather and climate risk, conducted arm-in-arm with governments and other stakeholders, and has a main goal of providing economic benefits.

For example, I just published a paper that quantified present-day coastal flood risk for the New York City region, a region with an annual economic output of about 1.5 trillion dollars in commerce.  Hurricane Sandy disabled this commercial capital for days and changed some people’s lives for years, with total damages at New York City alone of about $20 billion.  Nobody was adequately prepared for Sandy’s record-setting flood, which was far higher than anything in the prior century.

In the years before Sandy, CCRUN scientists were warning what could occur and how preparations and protections should be made.  During Sandy, CCRUN scientists were on blogs, television, making forecasts, helping explain what could occur, and demonstrably saving lives.

After Sandy, decisions had to be made quickly on what to do to prevent such devastation from occurring again.  But while FEMA’s work suggested a flood like Sandy’s could happen again soon, with a 10% chance of occurring within a decade, other studies suggested it was a much less likely event, with less than a 1% chance or less.  My recent published research has shown that the reality is likely in between the two results, has helped to reduce the uncertainty, and is now improving the basis on which multi-billion-dollar flood protection decisions are being made – I have met with or discussed these results many times with city planners and the director of New York City’s $20 billion flood mitigation plan.

Looking beyond present-day risks from extreme weather, climate change causing the planet and ocean to warm, and sea level is rising and accelerating.  NOAA funding sensibly enables scientists to evaluate how flood risks are growing and evaluate potential adaptation options that will save money, such as wetlands, levees or storm surge barriers.

Risk assessment builds the understanding of probabilities of damaging hazards, which enables successful decision-making.  On the heels of three straight temperature record-breaking years (2014, 2015, 2016) and three straight record-breaking decades (1980s, 1990s, 2000s), many in the Trump Administration are conceding that the planet is warming.  A sensible risk management approach will avoid severe cuts to NOAA-OAR, and enable scientists to seek to better understand the problem and help stakeholders prepare for its potential impacts.

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A “new normal” or drowning by a million drops?

I was interviewed the other day on WNYC regarding flood events of the past few months — there is a concern that the three events that flooded some low-lying neighborhoods with roughly a foot of water signify a “new normal”, but what I’m seeing from the science and data is that we just had an unlucky few months where wind events coincided with the largest tides (spring tides).

Some think that the landscape was altered by Sandy and is leading to higher floods — I am skeptical that this has had any measurable effect.  Much like one recent study, we are evaluating whether the tide channels have changed by comparing pre-Sandy sea level data to post-Sandy data, but initial qualitative looks at the data suggest nothing abruptly changed in Jamaica Bay (or places to the east, where people are also concerned that there is “a new normal”).

In the longer-term, of course, Jamaica Bay’s inlet and channels are massively overdredged, and the recent flood was subtly AMPLIFIED (contrasting Sandy Hook and Jamaica Bay Inwood tide gauge peaks) going into the bay, whereas the shallower system of prior decades-to-centuries did not amplify flood levels. One recent research paper of ours addresses this in a very qualitative sense, but we are working on publishing some more detailed analyses comparing the 1880s landscape to the present-day, and how the present-day shipping channel amplifies flooding in the bay.

I also had a recent email exchange with NYC City Planning about whether we can measure compaction of land areas over 5-10 year periods using recent LIDAR data, but this withered and went silent recently.  It is possible that the heavy water from Sandy caused abrupt compaction in some landfilled neighborhoods, perhaps lowering land areas by many inches in one day.  That would lend credence to the claim that things have gotten worse for some locations.

Sea level rise has been about 4 inches in 25 years (10 cm), so is just a gradual change.  Actually the past few years had lower mean sea levels than the few years prior … there is year-to-year variability.  So there isn’t really a “new normal” for sea level rise, just a gradual drowning by a million drops.

Also, tides this year and in recent years and the near future are larger than normal by about an inch … there is a 19-year cycle set by the planes of the earth-moon orbit and earth-sun orbit that is at its peak right now.  So this is a minor factor, but one more …

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Nor’easter Flood Intermission and the Coming Second Act

As things have paused between high tides, we have a sort of intermission in the coastal flood stresses impacting many of us.  Water levels are on their way up again, and here’s an update on what happened and what I expect will happen through the remainder of the storm.  A big concern is obviously that this massive snowstorm could coincide with seawater flooding, and that we’ll have ice floes and water in our neighborhoods.

Major coastal flooding has already severely impacted some southern parts of NJ and states further south. Several neighborhoods there have seen floodwaters, but the worst flooding should be over; flood levels on the coming high tides are forecast to be lower.

All low-lying areas, as well as areas within the New Jersey back bays should remain vigilant over this evening’s high tides, as there is a chance they may experience worse conditions later on in the day.  I can’t make any blanket statements about all sites, as some have complex sea level patterns. However, the Stevens forecasts are available for a great many areas, so check them out.

Around the NY/NJ Metro area, moderate coastal flooding was observed in southern Raritan Bay, Upper East River and near Freeport NY.  Minor flooding was observed in several other places.

The forecasts provided by Stevens Institute, run every 6 hours, are experimental but can compliment NOAA forecasts, and have many additional features such as grey uncertainty errorbars (5th to 95th percentile estimates). This morning’s peak water levels were observed to reach the models’ higher uncertainty limits, but have remained within the range of those predictions.

So here is the good news:  Offshore winds have been dropping for a few hours now, and rotating to come from the north-northeast, and then north this evening or overnight.

As a result, the surge is also dropping.  Also, the evening high tide is a weaker high tide than the morning tide.  As a result, there is only a small likelihood of exceeding the water levels that occurred on the earlier high tide, for the entire region.  For the New York / New Jersey Metro area, at the very most they will only exceed them by roughly a half foot.

You can continue monitoring the observations and forecasts in www.stevens.edu/SFAS.

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Nor’easter Jonas Evening Forecast Addendum

Additional details on the New York / New Jersey Metro Area

Getting it right with “minor” versus “moderate” flooding is particularly important when there is ice and freezing temperatures, as NOAA’s definitions (see below) suggest some evacuation may be needed when they designate flooding as moderate.

As mentioned in the prior post, areas in New York Harbor and up the Hudson like Hoboken, as well as the New Jersey Meadowlands have a good chance of minor flooding, but have a very low chance of moderate flooding.  However, some other parts of the Metro Area have a reasonable chance of “moderate flooding” like the New Jersey coast – sites that are close to the ocean, or in Newark Bay and Arthur Kill.  Examples are Jamaica Bay, Raritan Bay, the south end of Newark Bay, and Arthur Kill.  These areas are likely to have minor flooding and have a good chance (about as likely as not) to see moderate flooding levels (e.g. over 5.4 feet NAVD88 or 8.7 feet MLLW at Inwood, Jamaica Bay).  Detailed forecast plots for these sites are all available on the Stevens Flood Advisory System (http://stevens.edu/SFAS).

NOAA’s definitions for flooding are:

Minor Flooding – minimal or no property damage, but possibly some public threat (e.g., flooding of roads).

Moderate Flooding – some flooding of structures and roads near stream. Some evacuations of people and/or transfer of property to higher elevations.

Major Flooding – extensive flooding of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.

 

NY/NJ Snow Forecasts

The Global Forecast System (GFS) and ECMWF higher spatial resolution model (HRES) are both showing a range of approximately 4-10 inches of accumulated snow in the Northern parts of New Jersey and the New York City area.

The snow is to begin in the morning of Saturday, January 23 and the end of snow accumulation is expected around early Sunday morning (1:00 am – 5:00 am EST). The highest snow rates are expected on January 23 (between 6 pm and midnight EST) from what the models are showing.

The areas in Southern New Jersey and Trenton are more likely to receive up to 20 inches of snow based on the ECMWF model. However the GFS model is indicating an accumulated snow of 12-16 inches.

 

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Nor’easter “Jonas” Coastal Flood Forecast

A large full-moon tide will coincide with strong winds, snowfall, and a moderate 2-5 foot storm surge this weekend, leading to the possibility of coastal flooding across our region. The areas at most risk for major flooding are Virginia, Maryland, Delaware and southern New Jersey, but minor-to-moderate flooding is likely from Hatteras to Northern New Jersey.  At most, only minor coastal flooding of low-lying areas is expected for the New York / New Jersey metropolitan area with the forecasts seen so far.

Any coastal flooding will likely occur Saturday or the first half of Sunday.

Although there is still moderate uncertainty, forecasted flood levels are roughly similar or slightly worse than those which occurred during the nor’easter that caused flooding in the same areas early last October, at the time that Hurricane Joaquin was threatening to come towards the East Coast.  Winds will be stronger, but the duration of high storm surge will be shorter, lasting through about three high tides.

In terms of waves, NOAA is forecasting maximum 18-foot waves offshore, which are similar to the October storm. However the shorter duration of this storm will likely mean moderate erosion will occur, less than in October.  Beaches that are in good condition should protect the communities behind them; however beaches left vulnerable during the October storm will be weakened even further.

Due to the high tides, any increase in the storm surge or waves could lead to even more flooding or erosion, so we are monitoring our flood forecasts and those of other organizations, which are updated four times per day (www.stevens.edu/SFAS).

 

Detailed Stevens Institute flood forecasts

The above summary interprets all forecasts, including those of NOAA.  Below is a detailed summary of the Stevens forecasts alone, which are experimental and available for hundreds of specific locations.

Focusing on the regions that have a good chance of seeing major flooding:

The southern half of the New Jersey Coast (Atlantic City to Cape May) is likely to have moderate flooding, and while it is unlikely (0-20% chance), it is possible that there will be major flooding. Expected peak flood levels are about 4-6 feet navd88, which would be similar to the 5-foot flood height that occurred early last October (see figure below).

sfas_plot_CapeMay_160121-0944_SNAP-Ex

Figure:  Stevens Flood Advisory System experimental SNAP forecast for water levels at Cape May (blue), relative to NAVD88 (similar to mean sea level). Observed water levels are shown in red, and the forecast uncertainty is shown in grey (90% confidence interval). (www.stevens.edu/SFAS)

Further south, the outer coastline of Delaware, Maryland and southern Chesapeake Bay regions (e.g. the Norfolk area) will likely have moderate flooding, and major flooding is also a reasonable possibility.  Again, expected peak flood levels are about 4-6 feet navd88, which would be similar to the 5-foot flood height that occurred early last October.

Figure: Stevens Flood Advisory System experimental SNAP forecast for water levels at Lewes (blue), relative to NAVD88 (similar to mean sea level). Observed water levels are shown in red, and the forecast uncertainty is shown in grey (90% confidence interval).

Figure: Stevens Flood Advisory System experimental SNAP forecast for water levels at Lewes (blue), relative to NAVD88 (similar to mean sea level). Observed water levels are shown in red, and the forecast uncertainty is shown in grey (90% confidence interval).

 

Below are some forecast comparisons between Stevens and NOAA products, to give a sense of the variation between forecast systems. One of NOAA’s forecasts, ESTOFS, is an outlier on the high side, raising the possibility of an extra 1-2 feet of flooding above what is predicted by the other models.

sfas_plot_CapeMay_160121-1427_ALL

sfas_plot_Lewes_160121-1427_ALL

 

[This is a cross-post from Stevens Institute’s Davidson Laboratory.  It is a multi-contributor post summarizing our flood forecast products and interpretation.]

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