Marine

Was 2020 a Record-Breaking Hurricane Season? Yes, But. . .

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Chris Landsea and Eric Blake [1]

An Incredibly Busy Hurricane Season

The 2020 Atlantic hurricane season was extremely active and destructive with 30 named storms.  (The Hurricane Specialists here at the National Hurricane Center use the designation “named storms” to refer to tropical storms, subtropical storms, hurricanes, and major hurricanes.)  We even reached into the Greek alphabet for names for just the second time ever.  The United States was affected by a record 13 named storms (six of them directly impacted Louisiana), and a record yearly total of 7 billion-dollar tropical cyclone damage events was recorded by the National Centers for Environmental Information (https://www.ncdc.noaa.gov/billions/time-series/US).  Nearly every country surrounding the Gulf of Mexico, Caribbean Sea, and tropical/subtropical North Atlantic was threatened or struck in 2020.  Total damage in the United States was around $42 billion with over 240 lives lost in the United States and our neighboring countries in the Caribbean and Central America.

Track map of all 30 named storms during the 2020 Atlantic hurricane season.

The 30 named storms in 2020 sets a record going back to the 1870s when the U.S. Signal Service (a predecessor to the National Weather Service) began tracking tropical storms and hurricanes.  The only year that comes close is 2005 with 28 named storms.  It’s also apparent that a very large increase has occurred in the number of observed named storms from an average of 7 to 10 a year in the late 1800s to an average of 15 to 18 a year in the last decade or so – a doubling in the observed numbers over a century!  (The black curve in the figure below represents a smoothed representation of the data that filters out the year to year variability in order to focus on time scales of a decade or more).

Number of combined tropical storms, subtropical storms, and hurricanes each year from 1878 to 2020.

However, the number of named storms is only one measure of the overall measure of a season’s activity.  And indeed, for the 2020 season, other measures of Atlantic tropical storm and hurricane activity were not record breaking.  For example, the number of hurricanes (14) was well above average, but fell short of the previous record of 15 hurricanes that occurred in 2005. 

For overall monitoring of tropical storm and hurricane activity, tropical meteorologists prefer a metric that combines how strong the peak winds reached in a tropical cyclone, and how long they lasted – called Accumulated Cyclone Energy or ACE[2].   By this measure, 2020 was extremely busy, but not even close to record breaking.  In fact, with a total ACE of 180 units, 2020 was only the 13th busiest season on record since 1878 with seasons like 1893, 1933, 1950, and 2005 substantially more active than 2020.  One can also see that while there is a long-term increase in recorded ACE since the late 1800s, it’s quite a bit less dramatic than the increase seen with named storms.  There also is a pronounced busier/quieter multi-decadal (40- to 60-year) cycle with active conditions in the 1870s to 1890s, late 1920s to 1960s, and again from the mid-1990s onward.  Conversely, quiet conditions occurred in the 1900s to early 1920s and 1970s to early 1990s.

Accumulated Cyclone Energy (ACE), a measure which combines the number, intensity, and duration of tropical storms and hurricanes, each year from 1878 to 2020.

Technology Change and Named Storms

So why would the record for named storms be broken in 2020, while the overall activity as measured by ACE is not even be close to setting a record?                               

The answer is very likely technology change, rather than climate change.  Today we have many advanced tools to help monitor tropical and subtropical cyclones across the entire Atlantic basin such as geostationary and low-earth orbiting satellite imagery, the Hurricane Hunter aircraft of the U.S. Air Force Reserve and National Oceanic and Atmospheric Administration (NOAA), coastal weather radars, and scatterometers (radars in space that provide surface wind measurements).  In addition, the instrumentation and measuring techniques used by the satellites, aircraft and radars are continually improving.  These technological advances allow us at the National Hurricane Center to better identify, track, and forecast tropical and subtropical cyclones with an accuracy and precision never before available.  This is great news for coastal residents and mariners, since these tools help us provide the best possible forecasts and warnings to aid in the best preparedness for these life-threatening systems.

Such technology, though, was not available back at the advent of the U.S. Signal Service’s tropical monitoring in the 1870s.  Without these sophisticated tools, meteorologists in earlier times not only had difficulty in forecasting tropical cyclones, but they also struggled in even knowing if a system existed over the open ocean.  In the late 19th and early 20th Centuries, the only resource hurricane forecasters could use to monitor tropical cyclones were weather station observations provided via telegraph.  Such an approach is problematic for observing – much less forecasting – tropical cyclones that develop and spend most of their lifecycle over the open ocean.  Here’s a timeline of critical technologies that have dramatically improved tropical meteorologists’ ability to “see” and monitor tropical cyclones:

Technological improvements for monitoring tropical storm and hurricanes between 1878 and 2018.

The upshot of all of these advances in the last century is much better identification of the existence of tropical cyclones and their strongest winds (or what meteorologists call “Intensity”).  So, the further one goes back in time, the more tropical cyclones (and portions of their life cycle) were missed, even for systems that may have been a major hurricane. This holds for both counting named storms back in time as well as integrated measures like ACE.  Our database is incomplete and has – as statisticians would say – a severe undersampling bias that is much more prominent earlier in the record.  HURDAT2 – our Atlantic hurricane database – is an extremely helpful record which is a “by-product” of NHC’s forecasting operations, but it is very deficient for determining real long-term trends.  (It’s important to point out that many data entries in HURDAT2 for intensity and even the position of the named storms are educated guesses as opposed to being based on observations before the 1970s advent of regular satellite imagery). To be able to examine questions about any impact from man-made global warming (aka climate change) on long-term changes in the number of named storms, for example, one must first account for the massive technology change over the last century.

Fortunately, to help address this issue, researchers at NOAA’s Geophysical Fluid Dynamics Laboratory (GFDL) – (Gabe Vecchi and Tom Knutson in 2008’s Journal of Climate) have invented a way to estimate how many named storms were missed in the pre-geostationary satellite era (before the 1970s).  This was done by comparing the population of tracks and sizes of named storms that have occurred versus the density of observations from ships that were traversing the ocean.  If there were ships everywhere all of the time back to the 1870s (and these ships didn’t try to avoid running into tropical cyclones, which they certainly did), there would be very few named storms unaccounted for.  But the reality is that much of the Atlantic Ocean, Gulf of Mexico, and Caribbean Sea was sparsely traversed by ships from the late 19th Century until the middle of the 20th Century.  (The plots below indicate the amount of shipping traffic and weather observations from those ships – Orange/Red are numerous, Green/Yellow are moderate, Gray are few, and White are no measurements).

Plots showing the density of shipping traffic across the northern Atlantic Ocean between 1878-1914, 1915-1945, and 1946-1965. White and blue areas indicate little to no ship traffic, while oranges and red indicate a high level of ship traffic.

In addition to the issue of named storms that were previously missed, due to the lack of ability to observe them, technological improvements also have effectively allowed the standards for naming a storm to be refined resulting in better identification of weak (near the 39-mph/63-kph threshold) systems.   Tropical warnings for many of the weak, short-lived named storms in past eras were not issued, and thus these systems were not automatically included into the HURDAT2 database.  In the cases when forecasters in earlier years were either 1) not sure that the system possessed the required 39-mph/63-kph winds, 2) assumed that it would be too short in duration, or 3) thought that the system was non-tropical (i.e., with a warm to cold gradient of temperature across the system’s center), they usually did not issue named storm advisories, and therefore these systems did not get added into the historical database[3].

In research that the lead author had investigated (Chris Landsea and company in 2010’s Journal of Climate), we discovered that weak, short-lived (lasting less than or equal to two days) named storms – aka “Shorties” – had shown a dramatic increase in occurrence over time.  There were only about one a year in HURDAT2 up until the 1920s, about 3 per year from the 1930s to the 1990s, and jumping up to around 5 per year since 2000.

Number of tropical storms and subtropical storm “Shorties,” those which had a duration of 2 days or less, each year from 1878 to 2020.

Of the 30 named storms in 2020, seven were Shorties and a few more were just longer than two days in duration.  Of these seven Shorties, four are very unlikely to have been “named” before around 2000:  Dolly, Edouard, Omar, and Alpha.  (Of the remaining Shorties, Bertha and Kyle may have been named, while Fay likely would have been named).  These and other weak, short-lived systems since 2000 have been observed and recognized as tropical storms due to new tools available to forecasters including scatterometers, Advanced Microwave Sounding Units, the Advanced Dvorak Technique, and the Cyclone Phase Space diagrams.   The Hurricane Specialists here at the National Hurricane Center then are able to issue advisories on these named storms in real-time and then include them into the HURDAT2 database at the end of the season.

Examples of four “Shorties” in 2020 that were very unlikely to have been designated as named storms in the past.

From a warning perspective for mariners and coastal residents, it is very beneficial that the National Hurricane Center is now naming (and recording) these Shorties.  But without accounting for how technology affects our records, one can come to some unfounded conclusions about true long-term changes in named storm activity.  In addition, it is worth pointing out, but perhaps not too surprising, that it has been shown by the researchers at Princeton University and at GFDL (Villarini et al. 2011, Journal of Geophysical Research) that the observed increase in Shorties has no association with any environmental factor known to influence named storms including man-made global warming.  It is therefore reasonable to conclude that the dramatic increase in the number of these Shorties is simply due to better observational technology.

An “Apples-to-Apples” Comparison of the 2020 Long-Lived Named Storms with the Past

So how can we come up then with a more apples-to-apples comparison of how the number of named storms has actually changed over the last 100 years plus?  Here are the steps that were performed in the 2010 Journal of Climate paper, about Shorties, updated for data through the 2020 hurricane season:

(1) Start with the original HURDAT2 database of named storms from 1878 onward:

Number of combined tropical storms, subtropical storms, and hurricanes each year from 1878 to 2020.

(2) Remove all of the Shorties from the original database, leaving just the long-lived named storms:

Number of combined long-lived (more than 2 days) tropical storms, subtropical storms, and hurricanes each year from 1878 to 2020.

(3) Add in the best estimate of the number of missed long-lived named storms before geostationary satellite imagery and the Dvorak technique became available:

Number of combined long-lived (more than 2 days) tropical storms, subtropical storms, and hurricanes each year from 1878 to 2020, adjusted by adding “missed” systems.

The resulting final time series shows tremendous variability, with highest values of 23 in 2020 and 20 in 1887 and 2005, and lowest values of 2 in 1914, and 3 in 1925, 1982, and 1994.  Overall, there remains a modest upward trend in the database over the entire time series superimposed with quasi-cyclic variations seen in the ACE data as was discussed earlier: higher activity in the late 1800s, mid-1900s, and from the mid-1990s onward, but lower activity in the early 1900s, and in the 1970s to early 1990s. These cycles of higher and lower activity have been linked to a natural phenomenon called the Atlantic Multidecadal Oscillation (AMO) (see paper by Stan Goldenberg, Chris Landsea, and colleagues in 2001’s Science).  Recent controversial research, however, is calling into question whether the AMO actually exists (see paper by Michael Mann and company in 2021’s Science).  Regardless of the validity of the AMO, the bottom line is that the doubling in the number of named storms over a century is very likely due to technology change, not natural or man-made climate change.

(4) And finally, add in the uncertainty to these estimates with the reasonable largest number of missed long-lived named storms. This represents the 95% method uncertainty value, or in layman’s terms, the largest reasonable number of missed systems.

Highest reasonable number of combined long-lived (more than 2 days) tropical storms, subtropical storms, and hurricane each year from 1878 to 2020, adjusted by adding a high estimate of “missed” systems.

Note that after adding on the uncertainty to the missed number of long-lived named storms (blue coloring), we can conclude that 1887 and 2020 may be just as busy for the number of long-lived named storms. 

The New “Normal” for Named Storm Numbers

With the completion of the 2011 to 2020 decade, climatologists are updating records to provide a new “normal” (or average) to compare against new weather.  The previous 30-year based climate period to decide if a weather event or season was unusual or expected was 1981-2010.  For weather phenomena around the world, we’re now changing the years to compute normal conditions to 1991-2020.  (The 30-year normal concept is designed to provide a long enough time period to obtain relatively stable statistics, and to also have the time period reflect the most recent weather experienced over a human generation.  Thirty years is a good compromise between these two aspects.) It might seem odd to non-meteorologists to change the definition of “average” every ten years, but meteorologists/climatologists do so because climate is never stationary, i.e., the climate is always changing.  The climate has both natural variations (like El Niño/La Niña, effects from volcanic eruptions, and the Atlantic Multidecadal Oscillation) and man-made changes (like urban heat island, land use changes, and greenhouse gas emissions) that affect what’s been observed around the last three decades.  These revisions of new averages are done around the world in conjunction with the World Meteorological Organization.  Thus NOAA is updating the average of temperature, precipitation, and other meteorological parameters to reflect what has been observed.

This shift in the period used for the 30-year climate standard changes the definitions of average (or “normal”) levels of tropical cyclone activity to the following for the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico (see this report by NOAA for more details):

System TypeOld 1981-2010 AverageNew 1991-2020 Average
Named Storms1214
Hurricanes67
Major Hurricanes33
Comparison of the number of named storms, hurricanes, and major hurricanes in the Atlantic basin using the old 30-year (1981-2020) averaging period with the new 30-year (1991-2020) averaging period.

              

These changes, therefore, reflect that most of the new 1991-2020 climatology period is within an active period that began in 1995 and includes the impact of the technology changes discussed above that have led to the National Hurricane Center more accurately diagnosing and naming more systems in the last couple of decades.    

Take Aways

The answers and conclusions to “Was 2020 a Record-Breaking Hurricane Season? Yes, but…”:

  • Doubling in the number of named storms over a century is very likely due to technology change, not natural or man-made climate change;
  • 2020 set a record for number of named storms, but given the limitations in our records it is possible that other years (such as 1887) were just as active for long-lived named storms; and
  • The boost in average or “normal” conditions from 12 to 14 named storms is due to a combination of a busy era that began in 1995 as well as the ability of the National Hurricane Center to observe and accurately diagnose more weak, short-lived named storms than had been done previously, mostly due to technology advancements.

A follow-on blog post, putting these observed changes of the number of named storms into context of what may be expected to occur in the future, is expected to be published in the near future.


[1] Christopher W. Landsea is the Chief of the Tropical Analysis and Forecast Branch at the National Weather Service’s National Hurricane Center in Miami, Florida. Eric Blake is a Senior Hurricane Specialist at the National Hurricane Center.  It should be noted that the following discussion is Chris’ and Eric’s opinions only and does not represent any official position of NHC, NWS or NOAA in general. Various scientists within NOAA have differing opinions about global warming’s impact on hurricanes and there is no official NOAA policy on the topic. Varying ideas on an issue often mean that it is a science in progress with no definitive answers. That is certainly the case with regards to global warming and hurricanes. Helpful comments on an earlier version of this writeup were provided by Neal Dorst, Stan Goldenberg, Robbie Berg, and Mike Brennan.

[2] Accumulated Cyclone Energy is calculated by squaring the named storm’s intensity – maximum sustained surface winds (expressed in knots)  – for every six hours that the system had at least a 39-mph (63-kph) intensity. 

[3] There is on-going research into updating and revising the HURDAT2 database for the seasons of 1851 to 1999 in order to improve and make more complete the records that currently exist.  This is done by obtaining the original named storm observations from ships, weather stations, Hurricane Hunter aircraft, radars, and satellites and using today’s best meteorological analyses to revise the positions, intensities, and statuses in the database.  This work also adds in newly discovered named storms that were not identified as such at the time. Currently, the reanalysis project has added 35 years (1851 to 1885) to our official records and has revised the 1886 through 1965 hurricane seasons. 

Lifesaving NOAA Support Following the Sinking of the Bourbon Rhode

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Visible satellite imagery of Hurricane Lorenzo over the eastern North Atlantic Ocean on September 26, 2019, from the MODIS instrument aboard NASA’s Terra satellite.  Credit: NASA Worldview, Earth Observing System Data and Information System.

The National Oceanic and Atmospheric Administration (NOAA) provided critical assistance during the international search and rescue (SAR) and recovery efforts that followed the sinking of the M/V Bourbon Rhode in Hurricane Lorenzo last fall.  This intra-agency NOAA effort (see figure below) included Hurricane Hunters from the Aircraft Operations Center (AOC), scientists from the National Environmental Satellite, Data, and Information Service (NESDIS) and the Hurricane Research Division (HRD), and marine forecasters from the Tropical Analysis and Forecast Branch (TAFB) of the National Hurricane Center (NHC)

An organizational chart of NOAA offices that provided assistance during SAR and recovery efforts following the sinking of the M/V Bourbon Rhode in Hurricane Lorenzo.

 

On the morning of Thursday, September 26, 2019, French authorities received a distress signal from the M/V Bourbon Rhode, an offshore tugboat that was en route from Las Palmas, Canary Islands, to Georgetown, Guyana, with 14 crew members on board.  The Bourbon Rhode had made a dangerously close approach to the eye of rapidly intensifying Hurricane Lorenzo in the central Atlantic Ocean, and water was entering through the rear of the vessel.  At 0600 UTC (2 AM Atlantic Standard Time [AST]) September 26, Lorenzo was a Category 2 hurricane with 95-kt (110-mph) winds and seas 12 feet or greater that extended 240 to 330 nautical miles (275 to 380 statute miles) outward from its center. A 1200 UTC (8 AM AST) TAFB sea state analysis, issued around the same time as the last automatic identification system (AIS) signal from the Bourbon Rhode, showed peak significant wave heights in Lorenzo up to 41 feet.  By 1800 UTC (2 PM AST), Lorenzo had strengthened to a Category 4 hurricane with maximum sustained winds of 115 kt (130 mph).  The Bourbon Rhode ultimately sank on September 26 in the central Atlantic Ocean.  

File photo of M/V Bourbon Rhode.  Credit: Bourbon Offshore

 

Since Hurricane Lorenzo was a major hurricane that posed no imminent threat to land, both of NOAA’s P-3 aircraft were preparing to fly dedicated research missions into the storm. As NOAA43 (nicknamed Miss Piggy) transited from Lakeland, Florida, to Barbados on September 26, the French Government and the United States Coast Guard (USCG) reached out and requested SAR assistance.  Meanwhile, the nearest marine vessel to the incident site — a bulk carrier named SSI EXCELLENT – was redirected toward the last-known position of the Bourbon Rhode.  Later on September 26, NHC/TAFB was contacted by the USCG Rescue Coordination Center (RCC) Miami to begin providing spot forecasts for surface wind and wave conditions that would impact vessels aiding in the SAR efforts.  The first TAFB point forecast for the rescue detailed the dangerous marine conditions that were still ongoing in the wake of Lorenzo, with gusty tropical-storm-force winds and combined seas of 20 feet near the incident site.

NOAA aircraft fleet in Barbados for Hurricane Lorenzo research missions. The NOAA P-3 aircraft provided critical SAR support for the Bourbon Rhode incident.  Credit: LCDR Sam Urato, NOAA Corps

 

Flight track from NOAA43 during the Bourbon Rhode SAR mission over the central Atlantic Ocean on Sept. 27. Credit: Jon Zawislak, NOAA/AOML/HRD

NOAA43 departed Barbados on September 27 with a crew (see list at the end of the post) of AOC personnel as well as HRD and NESDIS researchers.  As requested, they planned to fly over the locations of the last Bourbon Rhode distress signals and report any findings.  If nothing was sighted, the crew would continue on with the planned research mission into Lorenzo.  NOAA43 was the first SAR-capable asset to reach the incident site, but the crew did not find anything upon arrival.  With growing concern about the fate of Bourbon Rhode crew members, the NOAA43 crew quickly decided to abandon the Lorenzo research mission and continue SAR support.  With little information besides the last-known location of the Bourbon Rhode, they quickly adapted to the situation and developed a SAR flight plan.  Crew members rearranged themselves by any available window and called out locations of suspected targets or debris while surveying in the vicinity of the last known Bourbon Rhode position.  Poor visibility, extremely large waves, and turbulence from strong rainbands posed difficult challenges as NOAA43 received sporadic emergency beacon signals.  With only minutes left before the plane needed to head back to Barbados due to fuel limitations, crew members spotted debris and what appeared to be a life raft.  This information was relayed to SSI EXCELLENT, which was en route to the SAR area.

Convective cell in an outer rainband of Hurricane Lorenzo, taken during a NOAA43 SAR mission on September 27, 2019.  The bulk carrier SSI EXCELLENT is also pictured. Credit: Kelly Ryan, NOAA/AOML/HRD

 

Flight track from NOAA42 during the Bourbon Rhode SAR mission over the central Atlantic Ocean on Sept. 28. Credit: Jon Zawislak, NOAA/AOML/HRD

On September 28, NOAA42 (nicknamed Kermit) flew a SAR mission in coordination with SSI EXCELLENT and other supporting marine vessels across the search area.  As Hurricane Lorenzo moved farther away, improving weather and marine conditions allowed the plane to fly as low as 200 feet above the ocean surface.  The NOAA42 crew (see list at the end of the post) conducted visual searches while listening for emergency beacon signals, guided by previous reports from NOAA43 as well as new information from supporting ships.  Crew members located a large debris field and the remains of several sailors, and they directed ships to these locations so the victims could be recovered.  The dedicated efforts of NOAA personnel significantly narrowed the search region and guided ships toward the area where a life raft was discovered later that day.  Three Bourbon Rhode survivors were rescued from that life raft in the Atlantic Ocean.

 

Aerial photo of the life raft carrying three surviving Bourbon Rhode crew members on September 28, 2019.  Credit: Marine Nationale (French Navy) via Facebook

 

NOAA assets played a pivotal role in early SAR efforts, which were led by the Maritime RCC Fort-de-France on the island of Martinique.  As the international search efforts continued, TAFB provided six-hourly forecast updates on wind, wave, and weather conditions.  From September 26 to October 5, 2019, TAFB produced 35 spot forecasts (see example below) that were shared with RCC Miami and MRCC Fort-de-France in support of this unprecedented SAR operation.  Over two weeks, 21 ships and four aircraft searched over 110,000 km2 (about 42,500 mi2) of the central Atlantic Ocean for survivors.  Four bodies were recovered, and seven others were declared lost at sea after SAR efforts were officially called off on October 5, 2019.

The first of 35 spot forecasts that NHC/TAFB marine forecasters sent to USCG and international partners in support of Bourbon Rhode SAR efforts.

 

The Bourbon Rhode incident is just one example of how TAFB has evolved to provide impact-based decision support services (IDSS) to the USCG, its primary core governmental partner.  Last year, TAFB forecasters produced 56 spot forecasts for 13 marine incidents including SAR missions, distressed vessels, and even a medical rescue. In July 2019, the USCG and U.S. Air Force coordinated a rescue operation of two critically injured people off a disabled fishing vessel in the eastern North Pacific Ocean.  TAFB provided spot forecast support for the rescue operation and subsequent transport of the injured people to a Mexican naval medical clinic on Socorro Island.  “This information is truly impacting operations,” said Douglas Samp, Search Mission Coordinator for RCC Alameda (USCG District 11).

Additionally, TAFB forecasters prepare and deliver live briefings to USCG District leadership when tropical cyclones threaten USCG SAR regions and U.S. ports.  In 2019, TAFB delivered 42 tropical briefings combined to USCG District 7 and District 8, including 25 briefings for Hurricane Dorian.  “I cannot overstate how much your [NHC/TAFB] insight into the storm’s effects is vital to our planning and response efforts,” commented Captain Eric Smith, Chief of the Incident Management Branch for USCG District 7.

Tragedies like the Bourbon Rhode highlight the importance of TAFB standing ready to provide year-round IDSS support to core partners.  In this case, the dedicated IDSS provided by TAFB forecasters, combined with the valiant efforts of NOAA AOC crew members and HRD and NESDIS researchers, played a critical role in the international rescue efforts that ultimately saved three lives.

— Brad Reinhart

 

Crew of NOAA43 September 27th Flight

All female science crew aboard NOAA43, pictured before the research flight was diverted to provide Bourbon Rhode SAR support. L-R: Kelly Ryan, Jezabel Viraldell, Ashley Lundry, Zorana Jelenak, and Heather Holbach. Credit: Paul Flaherty, NOAA

Cmdr. Pat Didier – Aircraft Commander
Lt. Cmdr John Rossi – Co-pilot
Lt. Cmdr Dean Legidakes – Co-pilot
Lt. Cmdr Peter Freeman – Navigator
Mr. Joshua Sanchez – Flight Engineer
Mr. Chris Lalonde – Flight Engineer
Mr. Paul Flaherty – Flight Director
Mrs. Ashley Lundry – Flight Director
Mr. Dana Naeher – Data Technician
Mr. Joe Greene – AVAPS Technician
Mr. Todd Richards – System Engineer
Mr. Damon San Souci – Avionics Technician
Dr. Zorana Jelenak – Principle Investigator (Scientist)
Jezabel Viraldell Sanchez – NESDIS Scientist
Heather Holback – Lead Project Scientist / Radar Scientist
Kelly Ryan – Dropsonde / Radar Scientist

Crew of NOAA42 September 28th Flight

Cmdr. Nathan Kahn – Aircraft Commander
Lt. Cmdr Adam Abitbol – Co-pilot
Lt. Cmdr Robert Mitchell – Co-pilot
Lt. Cmdr Brian Richards – Navigator
Mr. Paul Darby – Flight Engineer
Mr. Ken Heystek- Flight Engineer
Mr. Mike Holmes – Flight Director
Mr. Mike Mascaro – Data Technician
Mr. Joe Greene – System Engineer
Mr. Nick Underwood – AVAPS Technician
Dr. Jon Zawislak – Lead Project Scientist
Trey Alvey – Radar Scientist
Kathryn Sellwood – Dropsonde Scientist
Joe Sapp – NESDIS scientist

Acknowledgments: Special thanks to Zorana Jelenak, Kelly Ryan, and Joe Sapp for sharing their personal accounts of this experience with the author. Additional thanks to Jonathan Shannon, Shirley Murillo, Jon Zawislak, Nathan Kahn, Patrick Didier, and Erica Rule for their helpful input and feedback.

Additional References:
https://gcaptain.com/bourbon-offshore-tug-in-distress-after-getting-caught-in-hurricane-lorenzo/
https://www.maritime-executive.com/article/bourbon-rhode-confirmed-sunk
https://gcaptain.com/bourbon-rhode-sinks-in-the-atlantic-ocean-three-rescued/

National Hurricane Center Decision Support Services for the United States Coast Guard

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United States Coast Guard Cutter (image courtesy of uscg.mil)

Semper Paratus (Always Ready): A Shared Mission of Watching Over a Vast Blue Ocean

The National Hurricane Center (NHC) has the responsibility for issuing weather forecasts and warnings for a wide expanse of the Atlantic and eastern North Pacific Oceans.  Within NHC, the Hurricane Specialist Unit (HSU) issues forecasts for tropical storms and hurricanes in these regions, issues associated U. S. watches and warnings, and provides guidance for the issuance of watches and warnings for international land areas.  NHC’s Tropical Analysis and Forecast Branch (TAFB) makes forecasts of wind speeds and wave heights and issues wind warnings year-round for the eastern North Pacific Ocean north of the equator to 30°N, and for the Atlantic Ocean north of the equator to 31°N and west of 35°W (including the Gulf of Mexico and Caribbean Sea).  These wind warnings include tropical storms and hurricanes as well as winter storms, tradewind gales, and severe gap-wind events (for example, the “Tehuantepecers” south of Mexico).

The United States Coast Guard (USCG) has areas of responsibility (AORs) that extend well beyond those of NHC, with potential weather hazards affecting the fleet and their missions over the ocean, inland U.S. waterways, and flood-prone U.S. land areas. Although the USCG is responsible for search and rescue missions that may occur due to weather hazards, they are also vulnerable to severe weather and must also protect their own fleet and crews from these hazards.

USCG Search and Rescue Regions (SRRs) cover vast ocean areas affected by tropical cyclones. Superimposed on the Pacific SRRs is the NHC tropical cyclone area of responsibility, which overlaps with two eastern Pacific USCG SRRs as well as all Atlantic SRRs. The number of briefings provided by NHC to each USCG district in 2018 are shown. (Map images courtesy of uscg.mil)

One of the USCG’s oldest missions and highest priorities is to render aid to save lives and property in the maritime environment.  To meet these goals, the United States’ area of search-and-rescue responsibility is divided into internationally recognized inland and maritime regions.  There are five Atlantic USCG Search and Rescue Regions (SRRs) (Boston, Norfolk, Miami, New Orleans, and San Juan) and two Pacific USCG SRRs (Alameda and Honolulu) that overlap with NHC’s hurricane and marine areas of responsibility. The other eastern Pacific regions north of the Alameda SRR do not typically, if ever, experience hurricane activity. The multi-million square mile area of the agencies’ overlap allows NHC to provide weather hazard Decision Support Services (DSS) for the USCG.

Building Partnerships with the Districts

The National Weather Service (NWS) signed a Memorandum of Agreement (MOA) with the USCG to provide them with weather support. Over the past couple of years, staff at NHC have had numerous discussions with several of the USCG districts in order to build stronger partnerships. These discussions, primarily involving how NHC can better serve the USCG, established criteria for requiring TAFB to provide weather briefings to key decision makers within the USCG. When criteria are met, TAFB provides the relevant USCG District with once- or twice-a-day briefing packages detailing the weather impacts on their area of responsibility. This information provides the USCG districts with the details necessary to make efficient and effective decisions about potential mobilization of their fleet.

Example of a briefing slide of NHC’s earliest reasonable arrival time of tropical-storm-force winds graphic, which is one of the USCG’s most-desired decision support tools provided by NHC.  This example, from Hurricane Michael, illustrates the timing of the earliest reasonable onset of tropical-storm-force winds at a given location. This information is critical for fleet mobilization, as once these winds arrive preparations become difficult, if not impossible, to complete.

2018 Hurricane Season Briefing Support

During the 2018 hurricane season, TAFB provided 30 briefings to USCG Districts 5 (Norfolk), 7 (Miami), 8 (New Orleans), and 11 (Alameda) for the several tropical storms and hurricanes that affected them. These interactions helped to build the relationships between NHC and the USCG districts and aided the districts in making decisions regarding fleet mobilization, conducting search and rescue missions, and preparation for USCG’s land-based assets and personnel. Some of these briefings occurred during rapidly evolving high impact scenarios, including Hurricane Michael. Michael was forecast to become a hurricane within 72 hours of developing into a tropical depression and was forecast to make landfall within 96 hours of its formation. Ultimately, Michael rapidly intensified into a category 5 hurricane only 3½ days after formation, before making landfall on the Florida Panhandle. Hurricane Michael’s track across the east-central Gulf of Mexico straddled the border of USCG Districts 7 (Miami) and 8 (New Orleans), leading to both Districts taking action in advance of the hurricane.

Support for District 5 (Norfolk)

The NWS’s Ocean Prediction Center, the NHC (through TAFB), and the NWS National Operations Center have worked together to provide weekly high-level coordination briefings to USCG District 5 on upcoming hazards focused on the Atlantic Ocean north of 31°N over the following seven days.  Each Monday (except Tuesday if Monday is a holiday) by noon Eastern Time, the NWS provides a briefing that covers the mid-Atlantic region from New Jersey through North Carolina.  Typically, the briefing covers the area to roughly 65°W, though the exact area covered can vary based on the week’s expected weather hazards.  The USCG, in turn, has been sharing the information with mariners, port partners, and industry groups for situational awareness and critical decision-making.

Future Support

NHC’s TAFB is ready to provide decision support services to the USCG Districts for the 2019 hurricane season. Plans are being developed to continue this type of support for many years to come.

— Andy Latto