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:

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.

HRD Monthly Science Meeting of June 2015

June’s science meeting consisted of 3 presentations:

  1. Joshua Wadler (Hollings scholar from U. Oklahoma) – Convective Bursts: How their structure and environments vary in shear relative quadrants
  2. Kurt Hansen (Hollings scholar from SUNY Albany) – Downdrafts in Tropical Cyclones
  3. Jun Zhang – Effects of Vertical Diffusion on Forecasts of Rapid Intensifying Storms in HWRF – preliminary results

All the presentations and posters are available on the anonymous ftp site at: ftp://ftp.aoml.noaa.gov/pub/hrd/blog/meetings/2015/science/HRD_SciMeet_20150609.zip

Paper on improvements to hurricane forecasts using data nearest the ocean surface published in Monthly Weather Review

The National Hurricane Center uses the Hurricane Weather Research and Forecasting (HWRF) model to forecast where a hurricane will go, how strong it will be, how large it will be, and where the strongest winds are. This paper looks at changes in what is happening in the atmosphere closest to the ocean surface and how that can change these forecasts. NOAA Hurricane Hunter aircraft observations are compared to the HWRF forecasts. When differences between the model and the observations are found, the model is changed to greatly improve the forecasts. This technique can be used to make future versions of the model even better.

Important conclusions:

1. The differences between HWRF and NOAA Hurricane Hunter aircraft observations have been used to upgrade the model.

2. These upgrades led to large improvements in forecasts of where the hurricane will go and how strong it will be.

3. This technique can be used to make future forecast models even better.

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The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-14-00339.1.

Paper examining the region closest to the ocean surface in hurricanes and typhoons released online in the Journal of Geophysical Research

Global Positioning System dropwindsondes are released by Hurricane Hunter Aircraft to measure temperature, pressure, humidity, and wind speeds. Dropwindsonde data show what the wind, temperature and moisture are like nearest the ocean surface. In this study, hurricanes in the Atlantic Ocean are compared with typhoons in the Pacific Ocean.

Important Conclusions:

1. The atmospheric region nearest the ocean surface is generally similar in typhoons and hurricanes.
2. This region in typhoons tends to be warmer and moister than that in hurricanes.
3. This helps us understand and forecast the way that heat and moisture from the ocean drives tropical cyclones.

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The paper can be accessed at http://onlinelibrary.wiley.com/doi/10.1002/2014JD022640/full.

HRD & AOML researchers at 95th American Meteorological Society Annual Meeting, Phoenix, AZ – 4-8 January 2015

Screen Shot 2015-04-04 at 5.42.29 PMAbstracts and recordings of  the 13 presentations and 4 posters AOML & HRD researchers presented (or were co-authors) at the 95th AMS Annual Meeting are available online from the AMS website:


  1. Improving the Performance of the Basin Scale HWRF SystemJavier Delgado, University of Miami/CIMAS and NOAA/AOML/HRD, Miami, FL; and T. Quirino, X. Zhang, and S. Gopalakrishnan
  2. Targeting on the Research to Operational Transition with the Basin-scale HWRF Modeling SystemXuejin Zhang, NOAA/AOML/HRD, Miami, FL; and T. Quirino, S. Trahan, Q. Liu, Z. Zhang, R. St. Fleur, S. Gopalakrishnan, V. Tallapragada, and F. D. Marks Jr.
  3. A Global to Local-Scale Hurricane Forecasting SystemXuejin Zhang (for Sundararaman Gopalakrishnan), University of Miami/CIMAS and NOAA/AOML/HRD, Miami, FL; and T. Black, T. Quirino, V. Tallapragada, Z. Janjic, and T. L. Schneider
  4. Real-time Airborne Radar Data Quality Control and transmission from NOAA Aircraft for assimilation into HWRFJohn F. Gamache, NOAA/AOML/HRD, Miami, FL; and S. Otero, J. W. Hill, and P. P. Dodge
  5. NOAA’s Hurricane Forecast Improvement Project – HFIPFrank D. Marks Jr., NOAA/AOML/HRD, Miami, FL; and F. Toepfer, R. L. Gall, E. Rappaport, and V. Tallapragada
  6. Tropical Cyclone Research Utilizing the Global Hawk Unmanned AircraftJason Dunion (for Michael Black), University of Miami/CIMAS and NOAA/AOML/HRD, Miami, FL; and R. E. Hood and G. A. Wick
  7. Observing System Simulation Experiments to Assess the Potential Impact of Proposed Observing Systems on Hurricane PredictionRobert Atlas, NOAA/AOML, Miami, FL; and L. Bucci, A. Aksoy, B. Annane, R. N. Hoffman, G. D. Emmitt, Y. Xie, S. J. Majumdar, J. Delgado, and L. Cucurull
  8. Fusion of Hurricane Models and Observations: Developing the Technology to Improve the ForecastsSvetla Hristova-Veleva, JPL, Pasadena, CA; and M. Boothe, S. G. Gopalakrishnan, Z. Haddad, B. Knosp, B. Lambrigtsen, P. P. Li, M. Montgomery, N. Niamsuwan, T. P. Shen, V. Tallapragada, S. Tanelli, and F. J. Turk
  9. North Atlantic OSSEs in support of improved hurricane forecasting: Nature Run evaluationVilly H. Kourafalou, Univ. of Miami/RSMAS, Miami, FL; and G. R. Halliwell Jr., R. Atlas, H. S. Kang, M. F. Mehari, M. Le Henaff, L. K. Shay, R. Lumpkin, and G. Goni

Student presentations (HRD Hollings Scholars):

  1. An Extreme Event in the Eyewall of Hurricane FelixKelly Marie Nunez Ocasio, University of Puerto Rico, Mayagüez,, PR; and S. D. Aberson and J. Zhang
  2. A Statistical Take on the Hurricane’s Structure and Its Spatial ExtentRobert G. Nystrom, University of Illinois at Urbana-Champaign, Urbana, IL; and A. Askoy


  1. Impact of CYGNSS Data on Hurricane Analyses and Forecasts in a Regional OSSE FrameworkBachir Annane, Univ. of Miami/CIMAS and NOAA/AOML/HRD, Miami, FL; and B. McNoldy, J. Delgado, L. Bucci, R. Atlas, and S. Majumdar
  2. OSSE Evaluation of a Hyperspectral Sounder and its Potential Impact on Hurricane PredictionLisa Bucci, Univ. of Miami/RSMAS and NOAA/AOML/HRD, Miami, FL; and B. Annane, J. Delgado, and R. Atlas
  3. Wave and Wind Direction Effects on SFMR Brightness Temperatures – Heather M. Holbach, Florida State University, Tallahassee, FL; and E. W. Uhlhorn and M. A. Bourassa
  4. Improving Physical Parameterizations of the Operational Hurricane Model Using Aircraft ObservationsJun Zhang, NOAA/AOML/HRD and Univ. of Miami/CIMAS, Miami, FL; and F. D. Marks Jr., S. Gopalakrishnan, R. Rogers, and V. Tallapragada

HRD/NHC CHART Seminar – Dr. Jun Zhang, CIMAS and AOML/HRD – 13 February 2015

Dr. Zhang presented a seminar on “Improving Hurricane Model Physics using Aircraft Observations ” which is available on the NHC science presentation web site or at:



This talk addresses the important role of aircraft observations in hurricane model physics validation and improvement. As part of NOAA’s Hurricane Forecast Improvement Project (HFIP), a model  framework for improving the physical parameterizations using quality-controlled and post-processed aircraft observations is developed, with steps that include model diagnostics, physics development, physics implementation and further evaluation. Model deficiencies are first identified through model diagnostics by comparing the simulated axisymmetric multi-scale structures to observational composites. New physical parameterizations are developed in parallel based on in-situ observational data from specially designed hurricane field programs. The new physics package is then implemented in the model, which is followed by further evaluation. The developmental framework presented here is found to be successful in improving the surface layer and boundary layer parameterization schemes in the operational Hurricane Weather Research and Forecast (HWRF) model that leads to improved hurricane track and intensity forecasts.

J. Zhang presentation

J. Zhang presentation

Paper on the rapid intensification of Hurricane Earl in 2010 published in Monthly Weather Review

The paper discusses changes to the structure of Hurricane Earl (2010) as it rapidly intensified.   It found

  • Earl tilted with height before it intensified, but was upright during the intensification.
  • Strong thunderstorms played a significant role in the rapid intensification of Hurricane Earl.
  • Thunderstorms located on the inside of the eyewall are a condition favorable for intensification.
  • It is important to learn why thunderstorms form where they do to improve forecasts.
  • It is also important to observe the structure of the hurricane to better represent where these thunderstorms may occur in forecast models and improve hurricane forecasts.

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The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-14-00175.1.