105th Anniversary of the SS Koombana disaster

On 20 March, 1912, the passenger, cargo, and mail-carrying ship SS Koombana encountered a tropical cyclone off Western Australia, killing 74 passengers and 76 crew members.

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Most of the tale is known from the captain of the SS Bullarra that survived the disaster.  Despite a falling barometer and a strong northeasterly wind, the Koombana departed Port Hedland for Broome that morning, with the Bullarra following shortly afterward.  A few hours after departure, the ships encountered a heavy gale, and the ships were separated.  The Bullarra reported that the cyclone’s eye had gone directly overhead, ripping the smokestack from the ship.  It made it back to the port at Cossack, but the Koombana was never seen again.  Only a few small parts of the Koombara were recovered from subsequent searches.

The cyclone made landfall two days later just west of Balla Balla, with damage reported along at least 200 km of the sparsely populated coastline.  As a result of the loss, the Adelaide Steamship Company pulled out of the region, and the state-run State Shipping Service took over ship transport in the region, a franchise it still runs.

The search for the remains of the Koombana continue, including a 1987 investigation by the NOAA Hurricane Hunter Aircraft as part of Project Magnet.

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New and Improved SFMR data set

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The technique to process data from the Stepped Frequency Microwave Radiometer (SFMR), which observes surface wind speeds and rain rates within tropical cyclones, was upgraded prior to the 2015 hurricane season on all NOAA and Air Force Reserve Command hurricane reconnaissance aircraft. The processing method improves the observations across all wind speeds and rain rates. Brad Klotz and Eric Uhlhorn published a peer-reviewed article describing the updated method in the Journal of Atmospheric and Oceanic Technology in November 2014. Due to this change, two versions of the SFMR data were present on the HRD data web page. In an effort to provide a consistent dataset and remove confusion among users, Brad Klotz and a student intern, Ailen Garcia of Florida International University, reprocessed all data prior to 2015 using the updated method described in Brad’s paper. These data have been validated and are now available for use. Neal Dorst was instrumental in making these data publicly available. A few key improvements to the dataset include:

 

  • All data are now in the same NetCDF file format and processing version
  • An overestimation of wind speeds in all rain conditions was reduced significantly
  • More accurate and realistic rain rates based on instrument limitations are provided

Reference

Klotz, B. W. and E. W. Uhlhorn, 2014: “Improved Stepped Frequency Microwave Radiometer Tropical Cyclone Surface Winds in Heavy Precipitation.” J. Atmos. Oceanic Technol., 31, 2392-2408.

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HRD Monthly Science Meeting of March 2017

March’s science meeting consisted of 2 presentations:

  1. Lisa Bucci: P3DWL Observation Verification
  2. Jonathan Poterjoy: Getting the Most Out of Your Models and Observations: A Short Introduction to My Work

All the presentations are available on the anonymous ftp site at: ftp://ftp.aoml.noaa.gov/hrd/pub/blog/meetings/2017/Science/HRD_SciMeet_20170309.zip

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HRD Seminar – Prof. John Molinari, University of Albany/SUNY – 7 March 2017

Prof. Molinari presented a seminar on “Outflow Layer Influences on Tropical Cyclones”.

A recording of the presentation (audio begins 1 min into recording) is available on the anonymous ftp site: ftp://ftp.aoml.noaa.gov/hrd/pub/blog/seminars/2017/Molinari_HRD_Seminar_20170307.mp4

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Paper on observations of hurricanes from satellite-based Synthetic Aperture Radar published in IEEE Transactions on Geosciences and Remote Sensing

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Paper on forecast improvements due to dropsonde data from the Global Hawk aircraft released online in Weather Review

Starting in 2010, the National Aeronautic and Space Administration and the National Oceanic and Atmospheric Administration have used the Global Hawk, an unmanned aircraft that can fly at 65,000 feet for 24 hours at a time, to make observations in tropical cyclones. The Global Hawk can release dropsondes that measure temperature, humidity, pressure, and wind velocity 4 times every second as it falls to the earth. These data are put into a forecast model using the most up-to-date methods. This study looks at whether Global Hawk dropsonde data can improve forecasts of where the tropical cyclone will go and how strong it will be when it gets there.

 Important Conclusions:

  1. Global Hawk dropsonde data can be combined with data from regular Hurricane Hunter aircraft and from satellites to improve tropical cyclone forecasts.
  2. Global Hawk dropsonde data close to the center improves forecasts of how strong the tropical cyclone will be. This is due to the large amount of accurate data obtained in that region that cannot be gathered in any other way.
  3. Global Hawk dropsonde data further away from the center may improve forecasts of where the tropical cyclone will go.
  4. This study can help to design Global Hawk flights to get the largest forecast improvement possible.

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You can read the paper at http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-16-0332.1.

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Paper on easterly waves in the Eastern Pacific that can form into tropical cyclones published in The Journal of the Atmospheric Sciences

Easterly waves” are areas of low air pressure in the tropics that move westward and may become tropical cyclones. The most well-known type of easterly wave is the “African easterly wave,” which moves from West Africa north of the equator into the Atlantic Ocean and sometimes into the Pacific. Although almost all Northeast Pacific tropical cyclones develop from easterly waves, it is unclear how important the African waves are to this region. Most previous studies indicate that Northeast Pacific easterly waves are actually African easterly waves that cross Central America. However, it is difficult to observe an African easterly wave moving from the Atlantic to the Northeast Pacific. The authors were curious if easterly waves could develop in the Northeast Pacific. They used the Weather Research and Forecasting (WRF) model to study if strong daily thunderstorms near the Gulf of Panama (i.e., Panama Bight) could produce enough wind to form easterly waves in the Northeast Pacific.Screen Shot 2017-02-24 at 12.47.15 PM.png

Important Conclusions:

  1. Daily thunderstorms near the Gulf of Panama (i.e., Panama Bight) can create easterly waves locally or strengthen African easterly waves that cross over Central America. Either way, these easterly waves may form into tropical cyclones in the Northeast Pacific Ocean.
  2. When Central American mountains were removed in the model, there was less wind produced by thunderstorms near the Gulf of Panama and easterly waves were much weaker in the Northeast Pacific Ocean.
  3. When African easterly waves were blocked from entering the Northeast Pacific Ocean in the model, easterly waves there were weaker than they were if they moved in from the Atlantic.

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http://journals.ametsoc.org/doi/full/10.1175/JAS-D-16-0124.1

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HRD researchers contribute to new textbook on recent advances in tropical cyclone research

The new textbook titled “Advanced Numerical Modeling and Data Assimilation Techniques for Tropical Cyclone Predictions”, was co-edited by HRD scientist Dr. Sundararaman Gopalakrishnan. It is based on a series of lectures by scientists from the US, India and Australia, at a workshop held in Bhubaneswar, India on 9-14 July 2012.  It provides information on recent advances in tropical cyclone observations, data assimilation (the process of getting these observations into forecast models), and these forecast models, and is meant to be used for teaching and reference at universities and research laboratories.  There is specific information about how tropical cyclones move, how their structure and strength changes, and forecasts of impacts like storm surge and rainfall.

The new textbook has 27 chapters, three of them authored by HRD scientists. The first chapter, by HRD Director Frank Marks, provides an overview of NOAA’s Hurricane Field Program, the use of aircraft observations for improving forecasts, and future observing technologies. Drs. Thiago Quirino and Sundararaman Gopalakrishnan discuss how to derive some useful and basic information from forecast models.  And a chapter on the Hurricane Boundary Layer by Dr. Gopalakrishnan and others shows the importance of near-surface processes that control structure and intensity change in tropical cyclones.

The textbook was first released in India during TROPMET 2016 Climate Change and Coastal Vulnerability organized by the Indian Meteorological Society (IMS), and is  available here.

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HRD Seminar – Kelly Ryan, CIMAS and AOML/HRD, NSSL, Norman, OK – 10 February 2017

Kelly Ryan presented a seminar titled  “OSSE Evaluation of the Impact of Aircraft Observations on Hurricane Analyses and Forecasts” at the NOAA National Severe Storms Laboratory NSSL.

ABSTRACT

Each year, NOAA/AOML’s Hurricane Research Division (HRD) conducts its Hurricane Field Program in which observations are collected via NOAA aircraft to improve the understanding and prediction of hurricanes. Mission experiments suggest a variety of flight patterns and sampling strategies aimed towards their respective goals described by the Intensity Forecasting Experiment (IFEX; Rogers et al., BAMS, 2006, 2013), a collaborative effort among HRD, NHC, and EMC. Evaluating the potential impact of various trade-offs in design is valuable for determining the optimal air reconnaissance flight pattern for a given prospective mission. AOML’s HRD has developed a system for performing regional Observing System Simulation Experiments (OSSEs) to assess the potential impact of proposed observing systems on hurricane track and intensity forecasts and analyses. This study focuses on investigating the potential impact of proposed aircraft reconnaissance observing system designs. Aircraft instrument and flight level retrievals were simulated from a regional WRF ARW Nature Run (Nolan et al., 2013) spanning 13 days, covering the life cycle of a rapidly intensifying Atlantic tropical cyclone. The aircraft trajectories are simulated in a variety of ways and are evaluated to investigate the potential impact of aircraft reconnaissance observations on hurricane track and intensity forecasts.

 

A copy of the presentation is available on the anonymous ftp site: ftp://ftp.aoml.noaa.gov/hrd/pub/blog/seminars/2017/Ryan_Seminar_NSSL_20170210.pptx

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HRD observation team monthly meeting – 16 February 2017

The purpose of the observation team meetings is to bring together the people who use observations in their research on a regular basis to discuss issues they’re having, provide updates on observations they’re analyzing or collecting, and any other information that may be of interest to the broader group.  These meetings are also an excellent opportunity to integrate all of the many uses of observations in HRD’s capacity to improve the understanding and prediction of tropical cyclones.

Agenda for February 2017:

  1. Hurricane Field Program (HFP) 2017 plans (Paul Reasor)
    • Updates on planning
    • Online form for submitting experiments/modules for HFP
    • Online form for submitting Lead Project Scientist mission summaries
  2. Potential for web-based aircraft data visualization (Brad Klotz)
  3. HWRF case studies of interest and analysis plans (Gus Alaka)
  4. Initial analysis of Hurricane Hermine and Tropical Storm Karl dropsondes in ashear-relative framework (Zawislak)

The presentation from the meeting is available on the anonymous ftp site: ftp://ftp.aoml.noaa.gov/hrd/pub/blog/meetings/2017/Observations/HRD_ObsMeet_20170216.pptx

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