Archive for the ‘NOAA’ Tag

NOAA Scientist Helps Make Mapping Vital Seagrass Habitat Easier and More Accurate 

Shoal grass seagrass on a sandy ocean floor.

Seagrass beds serve as important habitat for a variety of marine life, and understanding their growth patterns better can help fisheries management and restoration efforts. (NOAA)

MARCH 3, 2016 — Amy Uhrin was sensing a challenge ahead of her.

As a NOAA scientist working on her PhD, she was studying the way seagrasses grow in different patterns along the coast, and she knew that these underwater plants don’t always create lush, unbroken lawns beneath the water’s surface.

Where she was working, off the North Carolina coast near the Outer Banks, things like the churning motion of waves and the speed of tides can cause seagrass beds to grow in patchy formations.

Clusters of bigger patches of seagrass here, some clusters of smaller patches over there. Round patches here, elongated patches over there.

Uhrin wanted to be able to look at aerial images showing large swaths of seagrass habitat and measure how much was actually seagrass, rather than bare sand on the bottom of the estuary. Unfortunately, traditional methods for doing this were tedious and tended to produce rather rough estimates. These involved viewing high-resolution aerial photographs, taken from fixed-wing planes, on a computer monitor and having a person digitally draw lines around the approximate edges of seagrass beds.

While that can be fairly accurate for continuous seagrass beds, it becomes more problematic for areas with lots of small patches of seagrass included inside a single boundary. For the patchy seagrass beds Uhrin was interested in, these visual methods tended to overestimate the actual area of seagrass by 70% to more than 1,500%. There had to be a better way.

Seeing the Light

Patches of seagrass beds of different sizes visible from the air.

Due to local environmental conditions, some coastal areas are more likely to produce patchy patterns in seagrass, rather than large beds with continuous cover. (NOAA)

At the time, Uhrin was taking a class on remote sensing technology, which uses airborne—or, in the case of satellites, space-borne—sensors to gather information about the Earth’s surface (includinginformation about oil spills). She knew that the imagery gathered from satellites (i.e. Landsat) is usually not at a fine enough resolution to view the details of the seagrass beds she was studying. Each pixel on Landsat images is 30 meters by 30 meters, while the aerial photography gathered from low-flying planes often delivered resolution of less than a meter (a little over three feet).

Uhrin wondered if she could apply to the aerial photographs some of the semi-automated classification tools from imagery visualization and analysis programs which are typically used with satellite imagery. She decided to give it a try.

First, she obtained aerial photographs taken of six sites in the shallow coastal waters of North Carolina’s Albemarle-Pamlico Estuary System. Using a GIS program, she drew boundaries (called “polygons”) around groups of seagrass patches to the best of her ability but in the usual fashion, which includes a lot of unvegetated seabed interspersed among seagrass patches.

Six aerial photographs of seagrass habitat off the North Carolina coast, with yellow boundary lines drawn around general areas of seagrass habitat.

Aerial photographs show varying patterns of seagrass growth at six study sites off the North Carolina coast. The yellow line shows the digitally drawn boundaries around seagrass and how much of that area is unvegetated for patchy seagrass habitat. (North Carolina Department of Transportation)

Next, Uhrin isolated those polygons of seagrass beds and deleted everything else in each image except the polygon. This created a smaller, easier-to-scan area for the imagery visualization program to analyze. Then, she “trained” the program to recognize what was seagrass vs. sand, based on spectral information available in the aerial photographs.

Though limited compared to what is available from satellite sensors, aerial photographs contain red, blue, and green wavelengths of light in the visible spectrum. Because plants absorb red and blue light and reflect green light (giving them their characteristic green appearance), Uhrin could train the computer program to classify as seagrass the patches where green light was reflected.

Classify in the Sky

Amy Uhrin stands in shallow water documenting data about seagrass inside a square frame of PVC pipe.

NOAA scientist Amy Uhrin found a more accurate and efficient approach to measuring how much area was actually seagrass, rather than bare sand, in aerial images of coastal North Carolina. (NOAA)

To Uhrin’s excitement, the technique worked well, allowing her to accurately identify and map smaller patches of seagrass and export those maps to another computer program where she could precisely measure the distance between patches and determine the size, number, and orientation of seagrass patches in a given area.

“This now allows you to calculate how much of the polygon is actually seagrass vegetation,” said Uhrin, “which is good for fisheries management.”

The young of many commercially important species, such as blue crabs, clams, and flounder, live in seagrass beds and actively use the plants. Young scallops, for example, cling to the blades of seagrass before sliding off and burrowing into the sediment as adults.

In addition, being able to better characterize the patterns of seagrass habitat could come in handy during coastal restoration planning and assessment. Due to local environmental conditions, some areas are more likely to produce patchy patterns in seagrass. As a result, efforts to restore seagrass habitat should aim for restoring not just cover but also the original spatial arrangement of the beds.

And, as Uhrin noted, having this information can “help address seagrass resilience in future climate change scenarios and altered hurricane regimes, as patchy seagrass areas are known to be more susceptible to storms than continuous meadows.”

The results of this study, which was done in concert with a colleague at the University of Wisconsin-Madison, have been published in the journal Estuarine, Coastal and Shelf Science.

Source: NOAA Scientist Helps Make Mapping Vital Seagrass Habitat Easier and More Accurate | response.restoration.noaa.gov

In the Wake of the Deepwater Horizon Oil Spill, Gulf Dolphins Found Sick and Dying in Larger Numbers Than Ever Before | response.restoration.noaa.gov

Gulf Dolphins Found Sick and Dying in Larger Numbers Than Ever Before

Dolphin with oil on its skin swimming.

A dolphin is observed with oil on its skin on August 5, 2010, in Barataria Bay, Louisiana. (Louisiana Department of Wildlife and Fisheries/Mandy Tumlin)

The Deepwater Horizon Oil Spill: Five Years Later

This is the third in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

APRIL 3, 2015 — Dolphins washing up dead in the northern Gulf of Mexico are not an uncommon phenomenon.

What has been uncommon, however, is how many moredead bottlenose dolphins have been observed in coastal waters affected by the Deepwater Horizon oil spill in the five years since. In addition to these alarmingly high numbers, researchers have found that bottlenose dolphins living in those areas are in poor health, plagued by chronic lung disease and failed pregnancies.

Independent and government scientists have undertaken a number of studies to understand how this oil spill may have affected dolphins, observed swimming through oil and with oil on their skin, living in waters along the Gulf Coast. These ongoing efforts have included examining and analyzing dead dolphins stranded on beaches, using photography to monitor living populations, and performing comprehensive health examinations on live dolphins in areas both affected and unaffected byDeepwater Horizon oil.

The results of these rigorous studies, which recently have been and continue to be published in peer-reviewed scientific journals, show that, in the wake of the 2010 Deepwater Horizon oil spill and in the areas hardest hit, the dolphin populations of the northern Gulf of Mexico have been in crisis.

Troubled Waters

Left, scientists taking a blood sample from one dolphin in the water and right, a team of researchers in the water photographs a dolphin’s dorsal fin against a white square.

Left, in 2011 veterinary scientists took blood samples from bottlenose dolphins in Barataria Bay, Louisiana, as part of an overall health assessment. Right, the same team of researchers photographed dolphins’ dorsal fins as a means of identifying individuals and monitoring populations in the wake of the Deepwater Horizon oil spill. (NOAA)

Due south of New Orleans, Louisiana, and northwest of the Macondo oil well that gushed millions of barrels of oil for 87 days, lies Barataria Bay. Its boundaries are a complex tangle of inlets and islands, part of the marshy delta where the Mississippi River meets the Gulf of Mexico and year-round home to a group of bottlenose dolphins.

During the Deepwater Horizon oil spill, this area was one of the most heavily oiled along the coast. Beginning the summer after the spill, record numbers of dolphins started stranding, or coming ashore, often dead, in Barataria Bay (Venn-Watson et al. 2015). One period of extremely high numbers of dolphin deaths in Barataria Bay, part of the ongoing, largest and longest-lasting dolphin die-off recorded in the Gulf of Mexico, persisted from August 2010 until December 2011.

In the summer of 2011, researchers also measured the health of dolphins living in Barataria Bay, comparing them with dolphins in Sarasota Bay, Florida, an area untouched by the Deepwater Horizonoil spill.

Differences between the two populations were stark.

Many Barataria Bay dolphins were in very poor health, some of them significantly underweight and five times more likely to have moderate-to-severe lung disease. Notably, the dolphins of Barataria Bay also were suffering from disturbingly low levels of key stress hormones which could prevent their bodies from responding appropriately to stressful situations. (Schwacke et al. 2014)

“The magnitude of the health effects that we saw was surprising,” said NOAA scientist Dr. Lori Schwacke, who helped lead this study. “We’ve done these health assessments in a number of locations across the southeast U.S. coast and we’ve never seen animals that were in this poor of condition.”

The types of illnesses observed in live Barataria Bay dolphins, which had sufficient opportunities to inhale or ingest oil following the 2010 spill, match those found in people and other animals also exposed to oil. In addition, the levels of other pollutants, such as DDT and PCBs, which previously have been linked to adverse health effects in marine mammals, were much lower in Barataria Bay dolphins than those from the west coast of Florida.

Dead in the Water

Based on findings from the 2011 study, the outlook for dolphins living in one of the most heavily oiled areas of the Gulf was grim. Nearly 20 percent of the Barataria Bay dolphins examined that year were not expected to live, and in fact, the carcass of one of them was found dead less than six months later (Schwacke et al. 2014). Scientists have continued to monitor the dolphins of Barataria Bay to document their health, survival, and success giving birth.

Left, dolphin Y12 during a health assessment in August 2011 and right, after his carcass was recovered in January 2012.

Left, August 2011: Veterinarians collect a urine sample from Y12, a 16-year-old adult male bottlenose dolphin caught near Grand Isle, LA. Y12’s health evaluation determined that he was significantly underweight, anemic, and had indications of liver and lung disease. (NOAA) Right, January 2012: The carcass of Y12 was recovered on Grand Isle Beach. The visible ribs, prominent vertebral processes and depressions along the back are signs of extreme emaciation. (Louisiana Department of Wildlife and Fisheries)

Considering these health conditions, it should come as little surprise that record high numbers of dolphins have been dying along the coasts of Louisiana (especially Barataria Bay), Alabama, and Mississippi. This ongoing, higher-than-usual marine mammal die-off, known as an unusual mortality event, has lasted over four years and claimed more than a thousand marine mammals, mostly bottlenose dolphins. For comparison, the next longest lasting Gulf die-off (in 2005–2006) ended after roughly a year and a half (Litz et al. 2014 [PDF]).

Researchers studying this exceptionally long unusual mortality event, which began in February 2010, identified within it multiple distinct groupings of dolphin deaths. All but one of them occurred after the Deepwater Horizon oil spill, which released oil from April to July 2010, and corresponded with areas exposed heavily to the oil, particularly Barataria Bay (Venn-Watson et al. 2015).

In early 2011, the spring following the oil spill, Mississippi and Alabama saw a marked increase in dead dolphin calves, which either died late in pregnancy or soon after birth, and which would have been exposed to oil as they were developing.

The Gulf coasts of Florida and Texas, which received comparatively little oiling from the Deepwater Horizon spill, did not see the same significant annual increases in dead dolphins as the other Gulf states (Venn-Watson et al. 2015). For example, Louisiana sees an average of 20 dead whales and dolphins wash up each year, but in 2011 alone, this state recorded 163 (Litz et al. 2014 [PDF]).

The one grouping of dolphin deaths starting before the spill, from March to May 2010, took place in Louisiana’s Lake Pontchartrain (a brackish lagoon) and western Mississippi. Researchers observed both low salinity levels in this lake and tell-tale skin lesions thought to be associated with low salinity levels on this group of dolphins. This combined evidence supports that short-term, freshwater exposure in addition to cold weather early in 2010 may have been key contributors to those dolphin deaths prior to the Deepwater Horizon spill.

Legacy of a Spill?

A bottlenose dolphin swims in the shallow waters along a sandy beach with orange oil boom.

A bottlenose dolphin swims in the shallow waters along the beach in Grand Isle, Louisiana, near oil containment boom that was deployed on May 28, 2010. Oil from the Deepwater Horizon oil spill began washing up on beaches here one month after the drilling unit exploded. (U.S. Coast Guard)

In the past, large dolphin die-offs in the Gulf of Mexico could usually be tied to short-lived, discrete events, such as morbillivirus and marine biotoxins (resulting from harmful algal blooms). While studies are ongoing, the current evidence does not support that these past causes are responsible for the current increases in dolphin deaths in the northern Gulf since 2010 (Litz et al. 2014).

However, the Deepwater Horizon oil spill—its timing, location, and nature—offers the strongest evidence for explaining why so many dolphins have been sick and dying in the Gulf since 2010. Ongoing studies are assessing disease among dolphins that have died and potential changes in dolphin health over the years since the spill.

As is the case for deep-sea corals, the full effects of this oil spill on the long-lived and slow-to-mature bottlenose dolphins and other dolphins and whales in the Gulf may not appear for years. Find more information related to dolphin health in the Gulf of Mexico on NOAA’s Unusual Mortality Event andGulf Spill Restoration websites.

By Ashley Braun, NOAA’s Office of Response and Restoration Web Editor.

Source: In the Wake of the Deepwater Horizon Oil Spill, Gulf Dolphins Found Sick and Dying in Larger Numbers Than Ever Before | response.restoration.noaa.gov

Attempting to Answer One Question Over and Over Again: Where Will the Oil Go?

 Where Will the Oil Go?

A heavy band of oil is visible on the surface of the Gulf of Mexico.

A heavy band of oil is visible on the surface of the Gulf of Mexico during an overflight of the Deepwater Horizon oil spill on May 12, 2010. Predicting where oil like this will travel depends on variable factors including wind and currents. (NOAA)

 

Overflight surveys from airplanes or helicopters help responders find oil slicks as they move and break up across a potentially wide expanse of water. They give snapshots of where the oil is located and how it is behaving at a specific date and time, which NOAA uses to compare to our oceanographic models. (U.S. Coast Guard)

 

Two people in a helicopter over water.

The Deepwater Horizon Oil Spill: Five Years Later

This is the first in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

MARCH 30, 2015 — Oil spills raise all sorts of scientific questions, andNOAA’s job is to help answer them.

We have a saying that each oil spill is unique, but there is one question we get after almost every spill: Where will the oil go? One of our primary scientific products during a spill is a trajectory forecast, which often takes the form of a map showing where the oil is likely to travel and which shorelines and other environmentally or culturally sensitive areas might be at risk.

Oil spill responders need to know this information to know which shorelines to protect with containment boom, or where to stage cleanup equipment, or which areas should be closed to fishing or boating during a spill.

To help predict the movement of oil, wedeveloped the computer model GNOME to forecast the complex interactions among currents, winds, and other physical processes affecting oil’s movement in the ocean. We update this model daily with information gathered from field observations, such as those from trained observers tasked with flying over a spill to verify its often-changing location, and new forecasts for ocean currents and winds.

Modeling a Moving Target

One of the biggest challenges we’ve faced in trying to answer this question was, not surprisingly, the 2010 Deepwater Horizon oil spill. Because of the continual release of oil—tens of thousands of barrels of oil each day—over nearly three months, we had to prepare hundreds of forecasts as more oil entered the Gulf of Mexico each day, was moved by ocean currents and winds, and was weathered, or physically, biologically, or chemically changed, by the environment and response efforts.

A typical forecast includes modeling the outlook of the oil’s spread over the next 24, 48, and 72 hours. This task began with the first trajectory our oceanographers issued early in the morning April 21, 2010 after being notified of the accident, and continued for the next 107 days in a row. (You canaccess all of the forecasts from this spill online.)

Once spilled into the marine environment, oil begins to move and spread surprisingly quickly but not necessarily in a straight line. In the open ocean, winds and currents can easily move oil 20 miles or more per day, and in the presence of strong ocean currents such as the Gulf Stream, oil and other drifting materials can travel more than 100 miles per day. Closer to the coast, tidal currents also can move and spread oil across coastal waters.

While the Deepwater Horizon drilling rig and wellhead were located only 50 miles offshore of Louisiana, it took several weeks for the slick to reach shore as shifting winds and meandering currents slowly moved the oil.

A Spill Playing on Loop

Over the duration of a typical spill, we’ll revise and reissue our forecast maps on a daily basis. These maps include our best prediction of where the oil might go and the regions of highest oil coverage, as well as what is known as a “confidence boundary.” This is a line encircling not just our best predictions for oil coverage but also a broader area on the map reflecting the full possible range in our forecasts [PDF].

Our oceanographers include this confidence boundary on the forecast maps to indicate that there is a chance that oil could be located anywhere inside its borders, depending on actual conditions for wind, weather, and currents.

Why is there a range of possible locations in the oil forecasts? Well, the movement of oil is very sensitive to ocean currents and wind, and predictions of oil movement rely on accurate predictions of the currents and wind at the spill site. In addition, sometimes the information we put into the model is based on an incomplete picture of a spill. Much of the time, the immense size of the Deepwater Horizon spill on the ocean surface meant that observations from specialists flying over the spill and even satellites couldn’t capture the full picture of where all the oil was each day.

Left, woman pointing and explaining maps on desk to man. Right, dark brown and red oil on ocean surface with two response ships.

Forecasters attempt to assess all the possible outcomes for a given scenario, estimate the likelihood of the different possibilities, and ultimately communicate risks to the decision makers. Left, NOAA oceanographer Amy MacFadyen explains how NOAA creates oil trajectory maps to then-Department of Commerce Secretary Gary Locke. Photo at right taken on May 27, 2010 near an ocean convergence zone shows dark brown and red emulsified oil from the Deepwater Horizon oil spill. The movement of oil is very sensitive to ocean currents and wind, and the size of this spill further complicated our attempts to model where the oil would go. (NOAA)

Our inevitably inexact knowledge of the many factors informing the trajectory model introduces a certain level of expected variation in its predictions, which is the situation with many models. Forecasters attempt to assess all the possible outcomes for a given scenario, estimate the likelihood of the different possibilities, and ultimately communicate risks to the decision makers.

In the case of the Deepwater Horizon oil spill, we had the added complexity of a spill that spanned many different regions—from the deep Gulf of Mexico, where ocean circulation is dominated by the swift Loop Current, to the continental shelf and nearshore area where ocean circulation is influenced by freshwater flowing from the Mississippi River.  And let’s not forget that several tropical storms andhurricanes crossed the Gulf that summer [PDF].

A big concern was that if oil got into the main loop current, it could be transported to the Florida Keys, Cuba, the Bahamas, or up the eastern coast of the United States. Fortunately (for the Florida Keys) a giant eddy formed in the Gulf of Mexico in June 2010 (nicknamed Eddy Franklin after Benjamin Franklin, who did some of the early research on the Gulf Stream). This “Eddy Franklin” created a giant circular water current that kept the oil largely contained in the Gulf of Mexico.

Some of the NOAA forecast team likened our efforts that spring and summer to the movie Groundhog Day, in which the main character is forced to relive the same day over and over again. For our team, every day involved modeling the same oil spill again and again, but with constantly changing results.

Thinking back on that intense forecasting effort brings back memories packed with emotion—and exhaustion. But mostly, we recall with pride the important role our forecast team in Seattle played in answering the question “where will the oil go?”

By Doug Helton, NOAA’s Office of Response and Restoration Incident Operations Coordinator.

Source: Attempting to Answer One Question Over and Over Again: Where Will the Oil Go? | response.restoration.noaa.gov

What Happens When Oil Spills Meet Massive Islands of Seaweed?

Floating rafts of sargassum, a large brown seaweed, can stretch for miles across the ocean.

Floating bits of brown seaweed at ocean surface
                                                            (Credit: Sean Nash/Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

The young loggerhead sea turtle, its ridged shell only a few inches across, is perched calmly among the floating islands of large brown seaweed, known as sargassum. Casually, it nibbles on the leaf-like blades of the seaweed, startling a nearby crab. Open ocean stretches for miles around these large free-floating seaweed mats where myriad creatures make their home.

Suddenly, a shadow passes overhead. A hungry seabird?

Taking no chances, the small sea turtle dips beneath the ocean surface. It dives through the yellow-brown sargassum with its tangle of branches and bladders filled with air, keeping everything afloat.

Home Sweet Sargassum

This little turtle isn’t alone in seeking safety and food in these buoyant mazes of seaweed. Perhaps nowhere is this more obvious than a dynamic stretch of the Atlantic Ocean off the East Coast of North America named for this seaweed: the Sargasso Sea. Sargassum is also an important part of the Gulf of Mexico, which contains the second most productive sargassum ecosystem in the world.

Some shrimp, crabs, and fish are specially suited to life in sargassum. Certain species of eel, fish, and shark spawn there. Each year, humpback whales, tuna, and seabirds migrate across these fruitful waters, taking advantage of the gathering of life that occurs where ocean currents converge.

Cutaway graphic of ocean with healthy sargassum seaweed habitat supporting marine life.

The Wide and Oily Sargasso Sea

However, an abundance of marine life isn’t the only other thing that can accumulate with these large patches of sargassum. Spilled oil, carried by currents, can also end up swirling among the seaweed.

If an oil spill made its way somewhere like the Sargasso Sea, a young sea turtle would encounter a much different scene. As the ocean currents brought the spill into contact with sargassum, oil would coat those same snarled branches and bladders of the seaweed. The turtles and other marine life living within and near the oiled sargassum would come into contact with the oil too, as they dove, swam, and rested among the floating mats.

That oil can be inhaled as vapors, be swallowed or consumed with food, and foul feathers, skin, scales, shell, and fur, which in turn smothers, suffocates, or strips the animal of its ability to stay insulated. The effects can be toxic and deadly.

Cutaway graphic of ocean with potential impacts of oil on sargassum seaweed habitat and marine life.

While sea turtles, for example, as cold-blooded reptiles, may enjoy the relatively warmer waters of sargassum islands, a hot sun beating down on an oiled ocean surface can raise water temperatures to extreme levels. What starts as soothing can soon become stressful.

Depending on how much oil arrived, the sargassum would grow less, or not at all, or even die. These floating seaweed oases begin shrinking. Where will young sea turtles take cover as they cross the unforgiving open ocean?

As life in the sargassum starts to perish, it may drop to the ocean bottom, potentially bringing oil and the toxic effects with it. Microbes in the water may munch on the oil and decompose the dead marine life, but this can lead to ocean oxygen dropping to critical levels and causing further harm in the area.

From Pollution to Protection

Young sea turtles swims through floating seaweed mats.

NOAA and the U.S. Fish and Wildlife Service havedesignated sargassum as a critical habitat for threatened loggerhead sea turtles.

Sargassum has also been designated as Essential Fish Habitat by Gulf of Mexico Fishery Management Council and National Marine Fisheries Service since it also provides nursery habitat for many important fishery species (e.g., dolphinfish, triggerfishes, tripletail, billfishes, tunas, and amberjacks) and for ecologically important forage fish species (e.g., butterfishes and flyingfishes).

Sargassum and its inhabitants are particularly vulnerable to threats such as oil spills and marine debris due to the fact that ocean currents naturally tend to concentrate all of these things together in the same places. In turn, this concentrating effect can lead to marine life being exposed to oil and other pollutants for more extended periods of time and perhaps greater impacts.

However, protecting sargassum habitat isn’t impossible and it isn’t out of reach for most people. Some of the same things you might do to lower your impact on the planet—using less plastic, reducing your demand for oil, properly disposing of trash, discussing these issues with elected officials—can lead to fewer oil spills and less trash turning these magnificent islands of sargassum into floating islands of pollution.

And maybe protect a baby sea turtle or two along the way.

Source: What Happens When Oil Spills Meet Massive Islands of Seaweed?

NOAA 2014 Atlantic Hurricane Season Outlook

NOAA PRESS RELEASE
NOAA 2014 Atlantic Hurricane Season Outlook

Issued: 22 May 2014

Realtime monitoring of tropical Atlantic conditions
Realtime monitoring of tropical East Pacific conditions

The 2014 Atlantic hurricane season outlook is an official product of the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC). The outlook is produced in collaboration with hurricane experts from the National Hurricane Center (NHC) and the Hurricane Research Division (HRD). The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.

Interpretation of NOAA’s Atlantic hurricane season outlook
This outlook is a general guide to the expected overall activity during the upcoming hurricane season. It is not a seasonal hurricane landfall forecast, and it does not predict levels of activity for any particular region.

Preparedness
Hurricane disasters can occur whether the season is active or relatively quiet. It only takes one hurricane (or tropical storm) to cause a disaster. Residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare for every hurricane season regardless of this, or any other, seasonal outlook. NOAA, the Federal Emergency Management Agency (FEMA), the National Hurricane Center (NHC), the Small Business Administration, and the American Red Cross all provide important hurricane preparedness information on their web sites.

NOAA does not make seasonal hurricane landfall predictions
NOAA does not make seasonal hurricane landfall predictions. Hurricane landfalls are largely determined by the weather patterns in place as the hurricane approaches, which are only predictable when the storm is within several days of making landfall.

Nature of this Outlook and the “likely” ranges of activity
This outlook is probabilistic, meaning the stated “likely” ranges of activity have a certain likelihood of occurring. The seasonal activity is expected to fall within these ranges in 7 out of 10 seasons with similar climate conditions and uncertainties to those expected this year. They do not represent the total possible ranges of activity seen in past similar years.

This outlook is based on 1) predictions of large-scale climate factors known to influence seasonal hurricane activity, and 2) climate models that directly predict seasonal hurricane activity.

Sources of uncertainty in this seasonal outlook
1. Predicting El Niño and La Niña (also called the El Niño-Southern Oscillation, or ENSO) impacts is an ongoing scientific challenge facing climate scientists today. Such forecasts made during the spring generally have limited skill.

2. Many combinations of named storms and hurricanes can occur for the same general set of climate conditions. For example, one cannot know with certainty whether a given climate signal will be associated with several short-lived storms or fewer longer-lived storms with greater intensity.

3. Model predictions of sea-surface temperatures, vertical wind shear, moisture, and stability have limited skill this far in advance of the peak months (August-October) of the hurricane season.

4. Weather patterns that are unpredictable on seasonal time scales can sometimes develop and last for weeks or months, possibly affecting seasonal hurricane activity.

2014 Atlantic Hurricane Season Outlook: Summary

NOAA’s 2014 Atlantic Hurricane Season Outlook indicates that a near-normal or below-normal hurricane season is likely this year. The outlook calls for a 50% chance of a below-normal season, a 40% chance of a near-normal season, and only a 10% chance of an above-normal season. See NOAA definitions of above-, near-, and below-normal seasons. The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.

The predicted oceanic and atmospheric conditions across the MDR typify a near- or below-normal Atlantic hurricane season, and contrast with those seen throughout the current high activity era for Atlantic hurricanes that began in 1995.

The expected conditions for 2014 reflect the likely development of El Niñoduring the summer or early fall, along with model predictions for near-average or below-average sea-surface temperatures (SSTs) in the Atlantic hurricane Main Development Region (MDR) (which spans the Caribbean Sea and tropical Atlantic Ocean between 9oN-21.5oN). Also, current atmospheric conditions are not showing the typical precursor signals of an above-normal season, further reducing our expectation for an above normal hurricane season.

Based on the current and expected conditions, combined with model forecasts, we estimate a 70% probability for each of the following ranges of activity during 2014:

  • 8-13 Named Storms
  • 3-6 Hurricanes
  • 1-2 Major Hurricanes
  • Accumulated Cyclone Energy (ACE) range of 40%-100% of the median.

 

The seasonal activity is expected to fall within these ranges in 70% of seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years.

These expected ranges are centered below the official NHC 1981-2010 seasonal averages of 12 named storms, 6 hurricanes, and 3 major hurricanes.

Uncertainties
One uncertainty in this 2014 outlook lies in exactly when El Niño will develop and how strong it will become. Another uncertainty lies in how much the oceanic and atmospheric conditions across the MDR will begin to take on characteristics of the current high activity era for Atlantic hurricanes, as they have in most seasons since 1995. Cooler Atlantic SSTs and a stronger El Niño could produce activity levels near the lower end of the predicted ranges, while warmer Atlantic SSTs and a weaker El Niño could result in activity toward the higher end of the predicted ranges.

This Atlantic hurricane season outlook will be updated in early August, which coincides with the onset of the peak months of the hurricane season.

Hurricane Landfalls:
It only takes one storm hitting an area to cause a disaster, regardless of the overall activity predicted in the seasonal outlook. Therefore, residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare every hurricane season regardless of this, or any other, seasonal outlook.

Predicting where and when hurricanes will strike is related to daily weather patterns, which are not reliably predictable weeks or months in advance. Therefore, it is currently not possible to accurately predict the number or intensity of landfalling hurricanes at these extended ranges, or whether a particular locality will be impacted by a hurricane this season.

DISCUSSION

1. Expected 2014 activity

Climate signals and evolving oceanic and atmospheric conditions, combined with model forecasts, indicate that a near-normal or below-normal Atlantic hurricane season is likely in 2014. This outlook calls for a 50% chance of a below-normal season, a 40% chance of a near-normal season, and only a 10% chance of an above-normal season. See NOAA definitions of above-, near-, and below-normal seasons.

An important measure of the total overall seasonal activity is NOAA’sAccumulated Cyclone Energy (ACE) index, which accounts for the combined intensity and duration of named storms and hurricanes during the season. This outlook indicates a 70% chance that the 2014 seasonal ACE range will be 40%-100% of the median. According to NOAA’s hurricane season classifications, an ACE value below 71.4% of the 1981-2010 median reflects a below-normal season, and an ACE value of 71.4%-120% reflects a near-normal season.

The 2014 Atlantic hurricane season is predicted to produce (with 70% probability for each range) 8-13 named storms, of which 3-6 are expected to become hurricanes, and 1-2 are expected to become major hurricanes. These ranges are centered below the 1981-2010 period averages of 12 named storms, 6 hurricanes and 3 major hurricanes.

For the U.S. and the region around the Caribbean Sea, the historical probability of multiple hurricane strike decreases with decreasing seasonal activity and El Niño. Nonetheless, for each region, there are numerous instances in the historical record of hurricane strikes during below-normal seasons, and even more instances of hurricane strikes during near-normal seasons. Also, the likelihood of at least one U.S. hurricane landfall is the same during El Niño as it is during La Niña and ENSO-Neutral.

Predicting the location, number, timing, and strength of hurricanes landfalls is ultimately related to the daily weather patterns, which are not predictable weeks or months in advance. As a result, it is currently not possible to reliably predict the number or intensity of landfalling hurricanes at these extended ranges, or whether a given locality will be impacted by a hurricane this season. Therefore, NOAA does not make an official seasonal hurricane landfall outlook.

2. Science behind the 2014 Outlook

The 2014 seasonal hurricane outlook reflects the likely development of El Niñoduring the summer or early fall, combined with an expectation of near-average or below-average sea-surface temperatures in the Atlantic hurricane MDR. These non-conducive conditions are expected to be partially offset by the ongoing warm phase of the Atlantic Multi-Decadal Oscillation (AMO) and associated tropical multi-decadal signal, which have contributed strongly to the current high activity era for Atlantic hurricanes that began in 1995. Overall, the predicted oceanic and atmospheric conditions for 2014 across the MDR typify a near- or below-normal Atlantic hurricane season.

The outlook takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), NOAA Geophysical Fluid Dynamics Lab (GFDL) model FLOR-FA, the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble, along with ENSO (El Niño/ Southern Oscillation) forecasts from models contained in the suite of Niño 3.4 SST forecasts compiled by the IRI (International Research Institute for Climate and Society) and the NOAA Climate Prediction Center.

a. El Niño

The main climate factor guiding the 2014 Atlantic hurricane season outlook is the likely development of El Niño during the summer or early fall. El Niño suppresses Atlantic hurricane activity (Gray 1984) by producing a set of non-conducive conditions within the MDR, including 1) enhanced vertical wind shear, 2) stronger easterly trade winds, 3) a configuration of the African easterly jet that is less conducive to hurricane development from easterly waves moving off the African coast, and 4) increased sinking motion.

At present, equatorial Pacific SSTs are above average, with the largest departures (exceeding 1oC) centered on the date line. SST anomalies in all of the Niño regions are also increasing, and anomalies in the Niño 3.4 region, which spans the central and east-central equatorial Pacific between 120oW-170oW, are currently 0.4oC. This value is approaching the CPC’s lower threshold for El Niño (+0.5oC).

Observations show that the atmosphere is also trending to an El Niño state. For example, a time-longitude section of 200-hPa velocity potential anomalies shows anomalous upper-level divergence since January over the central equatorial Pacific. This signal is opposite to that seen during May-September 2013, and is consistent with enhanced convection near the date line, a key feature of El Niño.

Anomalous westerly trade winds across the western equatorial Pacific, along with several westerly wind bursts, have also been present since January. A westerly wind burst triggered a strong downwelling equatorial oceanic Kelvin wave in February, and this wave subsequently reached the west coast of South America in late April. This Kelvin wave acted to shift the oceanic thermocline deeper into the ocean, resulting in above-average temperatures and increased heat content between the thermocline and the ocean surface.

A depth-longitude section of sub-surface temperature anomalies and a time series of the upper-ocean heat content highlight the substantial sub-surface warmth associated with this Kelvin wave. The persistence of the westerly wind anomalies has helped to lock in this anomalous warmth, further setting the stage for El Niño.

The average forecast of the dynamical models (closed markers) contained in the suite of IRI/ CPC Niño 3.4 SST forecasts (yellow line) predicts El Niño to form during the May-July (MJJ) season and to reach moderate strength (SST values of 1oC -1.5,sup>oC) during ASO. The statistical model forecasts (open markers) are generally cooler than the dynamical model predictions, and show a weak El Niño during the ASO season. These differing forecasts produce some uncertainty as to exactly when El Niño will develop and how strong it will become.

b. Sea surface temperatures across the Main Development Region (MDR)

SSTs within the Atlantic hurricane MDR are currently below-average in the central/ eastern tropical Atlantic and slightly above-average in the Caribbean Sea. SST departures averaged across the MDR are near zero, which is comparable to the average departure for the remainder of the global tropics. Neither of these signals is a clear indicator for an above-normal Atlantic hurricane season.

One issue for this outlook is whether or not the SST anomalies in the MDR will warm as the season progresses, as they have during most seasons since 1995 in association with the warm phase of the Atlantic Multi-decadal Oscillation (AMO). The typical warming mechanism is weaker tropical easterly trade winds within the MDR, which reduces the amount of cold water being upwelled in the eastern MDR, the amount of cold water being transported into the MDR, and the amount of evaporative cooling from the ocean surface. El Niño favors stronger easterly trade winds in the MDR, which suggests that additional anomalous warming might be limited or absent.

Consistent with these interpretations, many dynamical models are predicting that SSTs in the MDR will remain near- or below-average throughout the hurricane season. The CFS high-resolution (T-382) and lower resolution (T-126) models are both predicting below-average SSTs across the Caribbean Sea during ASO.

However, these two models differ in their predicted intensity of El Niño, with the lower-resolution model predicting a strong El Niño. Cooler Atlantic SSTs and a stronger El Niño could produce activity levels near the lower end of the predicted ranges, while warmer Atlantic SSTs and a weaker El Niño could result in activity toward the higher end of the predicted ranges.

c. Atmospheric conditions across the Main Development Region (MDR)

The AMO is coupled with the atmospheric tropical multi-decadal signal(Goldenberg et al. 2001, Bell and Chelliah 2006). Within the MDR, key atmospheric features of these climate signals have contributed to the current high-activity era in the Atlantic basin that began in 1995 (Bell et al. 2014). These features include: 1) reduced vertical wind shear, 2) weaker easterly trade winds, 3) a configuration of the African easterly jet (i.e. increased cyclonic shear) that is much more conducive to hurricane development from tropical cloud systems (aka easterly waves) moving off the African coast, 4) warm, moist, and unstable air, and 5) reduced sinking motion.

As has been seen since 1995, reduced vertical wind shear within the MDR is typically present prior to the start of an above-normal season. However, thevertical wind shear is currently stronger than average across much of the MDR. The mid-and upper-atmospheric sinking motion is also currently stronger than average. The development of El Niño would mean a likely continuation of these non-conducive conditions, and both versions of the CFS model are predicting enhanced vertical wind shear across the western MDR during ASO 2014. Strong vertical wind shear and sinking motion, linked to a rare jet stream pattern of record strength, were key suppressing factors during the 2013 Atlantic hurricane season (Bell et al. 2014).

3. Multi-decadal fluctuations in Atlantic hurricane activity

Atlantic hurricane seasons exhibit extended periods lasting decades (25-40 years) of generally above-normal or below-normal activity. These multi-decadal fluctuations in hurricane activity result almost entirely from differences in the number of hurricanes and major hurricanes forming from tropical storms that first develop in the MDR.

The current high-activity era began in 1995 (Goldenberg et al. 2001). Hurricane seasons during 1995-2013 have averaged about 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index of 151% of the median. NOAA classifies 12 of the 20 seasons since 1995 as above normal, with eight being very active (i.e., hyperactive defined by ACE > 165% of median). Only three seasons since 1995 were below normal (1997, 2009, and 2013).

This high level of activity contrasts sharply to the low-activity era of 1971-1994 (Goldenberg et al. 2001), which averaged 8.5 named storms, 5 hurricanes, and 1.5 major hurricanes, with an ACE index of only 74% of the median. One-half of the seasons during this period were below normal, only two were above normal (1980, 1989), and none were hyperactive.

Within the MDR, the atmospheric circulation anomalies that contribute to these long-period fluctuations in hurricane activity are strongly linked to the Tropics-wide multi-decadal signal (Bell and Chelliah 2006), which incorporates the warm phase of the AMO and an enhanced west African monsoon system. A change in the phase of the tropical multi-decadal signal coincides with the transition in 1995 from a low-activity era to the current high-activity era.

4. Uncertainties in the Outlook

The 2014 Atlantic hurricane season will likely be near- or below- normal. Key indications for this outlook are 1) the expected development of El Niño, 2) expected near- or below-average SSTs in the MDR during ASO, and 3) no strong indication from current atmospheric conditions within the MDR (i.e. vertical wind shear, vertical motion) that the season will be above normal.

Uncertainties in the outlook are related to the timing and strength of El Niño, and to a limited confidence in model forecasts for Atlantic SST anomalies. Therefore, there is uncertainty in the extent to which these factors will suppress the warm phase of the AMO and tropical multi-decadal signal.

NOAA FORECASTERS

Climate Prediction Center
Dr. Gerry Bell, Lead Forecaster, Meteorologist; Gerry.Bell@noaa.gov
Dr. Jae Schemm, Meteorologist; Jae.Schemm@noaa.gov

National Hurricane Center
Eric Blake, Hurricane Specialist; Eric.S.Blake@noaa.gov
Todd Kimberlain, Hurricane Specialist; Todd Kimberlain@noaa.gov
Dr. Chris Landsea, Meteorologist; Chris.Landsea@noaa.gov
Dr. Richard Pasch, Hurricane Specialist; Richard.J.Pasch@noaa.gov

Hurricane Research Division
Stanley Goldenberg, Meteorologist; Stanley.Goldenberg@noaa.gov

REFERENCES

Bell, G. D., and co-authors, 2014: [The Tropics] The 2013 North Atlantic Hurricane Season: A Climate Perspective [in “State of the Climate in 2013”].Bull. Amer. Meteor. Soc.95 (8), In press.

Bell, G. D., and M. Chelliah, 2006: Leading tropical modes associated with interannual and multi-decadal fluctuations in North Atlantic hurricane activity.J. of Climate19, 590-612.

Goldenberg, S. B., C. W. Landsea, A. M. Mestas-Nuñez, and W. M. Gray, 2001: The recent increase in Atlantic hurricane activity: Causes and implications.Science, 293, 474-479.

Gray, W. M., 1984: Atlantic seasonal hurricane frequency: Part I: El Niño and 30-mb quasi-bienniel oscillation influences. Mon. Wea. Rev., 112, 1649-1668.

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