10th Anniversary of Hurricane Katrina

Hurricane Katrina near its peak intensity as seen on NOAA P3's radar

Hurricane Katrina near its peak intensity as seen on NOAA P3’s radar

Early on the morning of August 29th, 2005, Hurricane Katrina made landfall on the Louisiana delta region and the Mississippi coast.  The storm surge brought enormous damage to the Gulf Coast and, when the levees around New Orleans failed, a great number of fatalities.  Coming amidst the very busy 2005 hurricane season, Katrina brought death and destruction not seen in a U.S. land-falling hurricane in decades.

Katrina formed out of a complex interaction of a tropical wave, the mid-level remnants of Tropical Depression 10, and an upper-tropospheric trough.  The disturbed weather consolidated into a circulation on Aug. 24th over the Bahama Islands.  As it moved northward through the archipelago, it strengthened into a Tropical Storm then turned westward toward Florida.  As NOAA 43 flew a reconnaissance mission into Katrina, it reached hurricane strength, then swerved to a southwesterly course as it came ashore in south Florida.  The hurricane brought drenching rains up to 14 inches (35.5 cm) to the peninsula.

Katrina diminished only slightly during its trek across Florida.  Once it reached the warm Gulf of Mexico, it quickly regained hurricane status and began to rapidly intensify.  While NOAA 49 flew a series of Synoptic Surveillance missions, dropping sondes in an effort to improve the track-forecast models, NOAA 43 flew two missions into the hurricane during its intensification stage, once on the 27th and another on the 28th when Katrina reached Category 5 status with its winds reaching a peak sustained wind speed of 170 mph (275 km/hr).

NOAA 43 landfall mission

NOAA 43 landfall mission

Thankfully, the hurricane began a rapid weakening as it approached the Gulf Coast.  A landfall flight by NOAA 43 documented this decline and tracked the center as it passed over the Mississippi delta and made final landfall near the Louisiana/Mississippi border.  The highest sustained wind speeds at landfall were estimated by NHC at 120 mph (193 km/hr).  Even though the top winds were much less than before, the water pushed inland by the storm was great. Pass Christian, MS observed nearly 28 feet of surge, and the Gulf waters intruded six miles inland.  Ninety percent of buildings within a half mile of the coast suffered substantial damage, and thousands of structures were completely destroyed.

Animated radar of Katrina's landfall (NOAA/NCDC)

Animated radar of Katrina’s landfall (NOAA/NCDC)

However, it wasn’t until the hurricane eye had passed well inland that the levees that protected New Orleans began to fail.  Over 50 breeches in the defense opened up, flooding large portions of the city that lay below sea level.  Homes and businesses were inundated and would remain so for weeks after the storm, and over a thousand people who had not evacuated either drowned in this flood or in the days afterward from exposure or lack of water and food.  Katrina caused over US$100 billion in damage and an estimated 1800 people’s deaths.

The data collected from the NOAA research flights proved extremely important to researchers.  It helped them better understand how storms form, evolve, and change in intensity. This understanding  has led to improvements  in NOAA’s hurricane models and our ability to better prepare communities.  Some papers written by Hurricane Research Division scientists using Hurricane Katrina data:

HRD-ESRL/PSD seminar – Dr. Evan Kalina – 13 August 2015

Dr. Kalina presented a seminar “Plowable hailstorms and hurricanes: Using novel observing platforms to improve forecasts of extreme weather events”


New observing technologies, including dual-polarization radars, total lightning networks, and unmanned aircraft systems, are greatly enhancing our ability to monitor and predict severe and hazardous weather events.

In part 1 of this talk, I will discuss how the recently upgraded Denver, CO Weather Service Radar-1988 Doppler (WSR-88D) can be used in conjunction with the Colorado Lightning Mapping Array (COLMA) to detect and forecast accumulating hailstorms in northeast Colorado. Previous such hailstorms have triggered motor vehicle accidents, road closures, airport delays, urban flooding, and water rescues in the Denver metropolitan area. Radar data from these events demonstrate that accumulating hailstorms result from slow storm motions (< 10 m s-1) that cause exceptionally long hailfall durations (9-28 min versus 1-7 min for more typical hailstorms) at the location(s) that experience accumulating hail. A new algorithm will be presented that uses the radar-estimated hailfall duration and the hail mass concentration to estimate the hail depth on the ground. I will also show that the radar data provide evidence of distinct peaks in storm intensity that occur shortly prior to accumulating hail. These markers of storm intensity include the presence of reflectivities greater than 70 dBZ, descending columns of differential reflectivity (ZDR) and correlation coefficient (ρHV) as small as -4 dB and 0.4, respectively, maxima in 50 dBZ echo top height of 11-15 km MSL, the development of bounded weak echo regions (BWERs), and enhanced graupel production. The increase in graupel particles results in a large supply of hailstone embryos and also enhances cloud electrification through the non-inductive charging mechanism. Therefore, lightning data from COLMA depict peaks in lightning flash rate that coincide with hail accumulation.

In part 2, I will show how the Coyote Unmanned Aircraft System (UAS) is being used to collect crucial meteorological data within the tropical cyclone boundary layer, a traditionally undersampled region of the hurricane. Two Coyote UAS flights in Major Hurricane Edouard (2014) collected pressure, temperature, moisture, and wind measurements in the eye, eyewall, and inflow layer, all within the lowest 1 km of the hurricane. Comparisons with dropsonde and airborne radar data demonstrate that the time-averaged Coyote data agree to within 1.4 m s-1 for winds, 0.4 °C for temperature, and 1.3 °C for dew point temperature. I will also present a preliminary comparison between the Coyote measurements and the boundary layer temperature and moisture fields used to initialize the Hurricane Weather Research and Forecasting (HWRF) Model for two of its Hurricane Edouard simulations.

The presentation is available on the anonymous ftp site:


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Joe Cione earns Department of Commerce Silver Medal

josephjcioneCongratulations to Joe Cione, part of the team to earn a Department of Commerce Silver Medal “for successfully executing the first-ever launch of an Unmanned Aircraft System from a manned aircraft into a major hurricane, Hurricane Edouard.”  The entire team includes AOML’s Erica Rule, as well as crew members from NOAA’s Office of Marine and Aviation Operations CDR Nancy Hann, CDR Kristie Twining, LCDR Justin Kibbey, James Roles, Jeff Smith, Steven Paul, Andrew Hornbeck, Joseph Bosko.  Congratulations to everyone!

HRD Monthly Science Meeting of July 2015

July’s science meeting consisted of 7 presentations:

  1. Hugh Willoughby (FIU) – Synthesis of Vortex Rossby Waves
  2. Lisa Bucci – Aircraft Simulation Study
  3. Jon Zawislak (FIU) – Evolution of the Thermodynamic Structure During Intensification of Hurricane Edouard (2014)
  4. Evan Kalina – Sensitivity of dropsonde temperature and moisture analyses to the averaging time scale
  5. Joshua Wadler (Hollings scholar from U. Oklahoma) – Radial Variations in Convective Burst Structure in Tropical Cyclones from Airborne Doppler Observations
  6. John D’Alessandro (summer intern) – Simulating SFMR flight data from an HWRF model simulation of Hurricane Earl
  7. Kurt Hansen (Hollings scholar from SUNY Albany) – Downdrafts in Tropical Cyclones

All the presentations are available on the anonymous ftp site at:


Paper on the statistical prediction of hurricane rapid intensification released online in Weather and Forecasting

Summary: The paper describes new models to forecast the probability of when tropical cyclones may strengthen rapidly during the next 48 h when the National Hurricane Center issues watches and warnings to the public. The models are expected to be run during the latter portion of the 2015 Hurricane season.

Important Conclusions:

  • The new models are more skillful in predicting when a tropical cyclone may intensify rapidly than existing models.
  • The new models are far more accurate for systems located in the Eastern North Pacific region than those in the Atlantic.
  • Conditions in the Atlantic overall appear to be less favorable for rapid strengthening than in the East Pacific, and are therefore less predictable.
  • The new models show the potential to provide more accurate forecasts than provided by existing models.

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The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/WAF-D-15-0032.1.

10th Anniversary of Hurricane Dennis

Hurricane Dennis on July 7th (NASA)

Hurricane Dennis on July 7th (NASA)

On July 8, 2005, Hurricane Dennis became one of the strongest Atlantic hurricanes ever recorded in July.  It formed into a tropical depression on July 4th and struck the island of Grenada in the eastern Caribbean Sea.  It moved quickly northwestward while it strengthened.  It became a hurricane on July 6th while south of the island of Hispañola, then underwent rapid intensification.  By the 7th it was a Category Four hurricane, the earliest in the hurricane season that a tropical cyclone has been recorded at that strength.  Later that day, Dennis made landfall at Punta del Inglés, Cuba with sustained winds of 140 mph (220 km/hr).  While its strength dipped as it was briefly over land, its wind grew to 150 mph (240 km/hr) once it moved back over the Sea.  It then made a second landfall at Punta Mangles Altos, Cuba with as much force as it had struck Punta del Inglés.  Crossing Cuba reduced Dennis to Category One status, but in again rebounded once over the warm Gulf Loop Current north of the island.  As it tracked north-northwest toward the Florida/Alabama coast, its winds peaked at 145 mph (234 km/hr), but luckily diminished to 120 mph (195 km/hr) just prior to landfall.  The remnants of Dennis persisted for another three days as it meandered over the Midwest and Canada, dumping heavy tropical rains along the way.

Dennis 2005 track (Unisys)

Dennis 2005 track (Unisys)

38 people lost their lives when Dennis had its impact on Cuba and Haiti, and another 15 in the United States.  The storm caused an estimated US $4 billion in damages along its path.  The name Dennis was retired from the Atlantic lists.  Dennis was also a harbinger of the very busy 2005 hurricane season that would witness many new record-breaking storms.  Indeed, Hurricane Emily would surpass Dennis’ early-season record only six days later.

HRD flew many missions into Hurricane Dennis, and six manuscripts on the data have been published:

Kaplan, J., C. M. Rozoff, M. DeMaria, C. R. Sampson, J. P. Kossin, C. S. Velden, J. J. Cione, J. P. Dunion, J. A. Knaff, J. A. Zhang, J. F. Dostalek, J. D. Hawkins, T. F. Lee, and J. E. Solbrig, 2015:  Evaluating environmental impacts on tropical cyclone rapid intensification predictability utilizing statistical models.  Wea. and Forecast., in press.

Rozoff, C. M., C. S. Velden, J. Kaplan, J. P. Kossin, and A. J. Wimmers, 2015:  Improvements in the probabilistic prediction of tropical cyclone rapid intensification with passive microwave observations. Wea. and Forecast., in press.

Rogers, R., 2010:  Convective-Scale Structure and Evolution during a High-Resolution Simulation of Tropical Cyclone Rapid Intensification.  J. Atmos. Sci., 67, 44-70.

Halverson, J., M. Black, R. Rogers, S. Braun, G. Heymsfield, D. Cecil, M. Goodman, R. Hood, A. Heymsfield, T. Krishnamurti, G. McFarquhar, M. J. Mahoney, J. Molinari, J. Turk, C. Velden, D-L. Zhang, E. Zipser, R. Kakar, 2007:  Nasa’s Tropical Cloud Systems and Processes Experiment.  Bull. Amer. Met. Soc., 88, 867-882.

Rogers, R., S. Aberson, M. Black, P. Black, J. Cione, P. Dodge, J. Gamache, J. Kaplan, M. Powell, J. Dunion, E. Uhlhorn, N. Shay, N. Surgi, 2006:  The Intensity Forecasting Experiment: A NOAA Multiyear Field Program for Improving Tropical Cyclone Intensity Forecasts.  Bull. Amer. Met. Soc., 87, 1523-1537.

DeMaria, M., J. A. Knaff, J. Kaplan, 2006:  On the Decay of Tropical Cyclone Winds Crossing Narrow Landmasses.  J. Appl. Met. Clim., 45, 491-499.

Frank Marks and Jason Dunion discuss how good hurricane forecasts are and plans for the upcoming hurricane season with the New Orleans Times-Picayune

Joe Cione and Paul Reasor also appear in this article, which can be found at http://www.nola.com/hurricane/index.ssf/2015/05/major_improvements_in_hurrican.html. Screen Shot 2015-06-02 at 12.39.04 PMScreen Shot 2015-06-02 at 12.39.47 PMScreen Shot 2015-06-02 at 12.39.10 PMScreen Shot 2015-06-02 at 12.39.24 PM Screen Shot 2015-06-02 at 12.40.25 PM