HRD marks the end of the 2013 hurricane season

The 2013 Atlantic hurricane season officially ends on Saturday, November 30.  The season was very inactive, having the fewest hurricanes since 1982, and ranks as the sixth-least-active Atlantic hurricane season since 1950.  Despite this, HRD had a very active year in gathering data for research and assimilation into numerical models to improve forecasts.


Tail Doppler Radar and dropwindsonde composite at 3-km altitude from the G-IV flight into the system that eventually became Tropical Storm Gabrielle (left) and from Hurricane Ingrid (right).

Flights during our annual Hurricane Field Program Intensity Forecasting Experiment (IFEx)  were conducted in Tropical Storms Gabrielle and Karen, and Hurricane Ingrid.  A total of 367 dropwindsondes and 136 airborne expendable bathythermographs were released from the aircraft to obtain profiles of important variables in the atmosphere and ocean.  The NOAA G-IV successfully gathered data, especially with its new Tail Doppler Radar, during 9 flights, and the two NOAA P3s flew 17 times during the season, all using a total of 150 flight hours.  Many of the flights were coordinated with the NASA Hurricane Severe Storm Sentinel (HS3) flights conducted during the summer with two Global Hawk aircraft.  You can find more information on the data collected from the debrief presentation for each storm (Gabrielle, Ingrid, and Karen).  One of the highlights of the season is that, for the first time, Tail Doppler Radar data were transmitted from the aircraft to NOAA Central Operations and successfully assimilated into the operational HWRF model.

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Initial total precipitable water (left) and mean sea-level pressure (right) for a basin-scale HWRF run.  Tropical Storm Karen is seen in the central Gulf of Mexico.

On the modeling and data assimilation side, HRD provided near-realtime runs of the Hurricane Weather and Research Forecast (HWRF) model initialized with the Hurricane Ensemble Data Assimilation System (HEDAS), a testbed for improving the assimilation of data into the operational HWRF model.  For the first time, high-resolution cloud-motion vectors as well as some satellite retrievals were ingested into a research version of HWRF.  The model forecasts showed that the assimilation of these data with a sophisticated data assimilation system can provide better forecasts of track and intensity than the current operational system.  A new basin-wide version of HWRF developed at HRD was also run in realtime during the season, allowing for multiple storms to be forecast concurrently for the first time.  And HRD’s HWind group successfully made 33 surface-wind analyses in six storms in the Atlantic basin this year.

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East-west cross section of wind speed and relative humidity through the center of Hurricane Ingrid (left) and average wind speed around the center of Ingrid at the same time (right), from HEDAS analyses.


Left:  Hwind analysis of the surface winds in Tropical Storm Fernand just before landfall on the Gulf coast of Mexico.  Right:  Eric Uhlhorn, Robert Rogers, and Jun Zhang just before a P3 flight into Tropical Storm Gabrielle.


HRD is thankful that we were able to successfully complete the season having achieved some major milestones, all without having a hurricane make landfall in the United States, and with only minimal loss of life and property to the public due to tropical systems.