15th anniversary of publication of seminal work on wind profiles in the tropical cyclone eyewall from dropwindsondes

GPS dropwindsonde descends via parachute

Starting in 1996, NOAA phased out use of the obsolete Omega DropWindsondes (ODW) in favor of the Global Positioning Satellite (GPS) Dropwindsondes.  In addition to being more accurate due to the superior navigation system, this next-generation sonde was also more moisture tolerant.  ODWs would fail in they were launched in areas of heavy rain, but the GPS probes survived.  This meant they could be deployed in heavy rain areas of tropical cyclones that had never been sampled before by sonde.  In 1997, the GPS sondes were first deployed into a hurricane eyewall during missions into East Pacific Hurricane Guillermo.

Mike Black, Krystal Valde, James Franklin

Over the next few years, several more hurricane eyewalls were similarly measured by these new sondes.  By 2003, there were enough cases that HRD scientists could publish some astounding findings“GPS Dropwindsonde Wind Profiles in Hurricanes and Their Operational Implications” by James Franklin, Michael Black and Krystal Valde was published in the February 2003 issue of Weather and Forecasting.  They documented that the actual measured wind-speed maxima were much closer to the surface than had been assumed. Also they found the maximum wind speed at the surface is generally about 90% of that measured by reconnaissance aircraft flying at about 700 hPa.  This was higher than previous estimates that had been used by NHC to reduce flight-level observations to surface estimates.

The results led to changes in building codes and evacuation guidelines, as emergency managers had previously recommended vertical evacuations in tall buildings to avoid storm surge. The study showed that the upper floors of high rises could experience one or two category higher winds than at the surface.  The paper also led to changes in operational procedures and to re-evaluations of intensities of historic hurricanes such as Hurricane Andrew.

The paper subsequently won the prestigious American Meteorological Society Banner I. Miller Award, presented for an outstanding contribution to the science of hurricane and tropical weather forecasting published in a journal with international circulation.  And it earned the authors the Department of Commerce Gold Medal.

References

Franklin, J. L., M. L. Black, and K. Valde, 2003: GPS dropwindsonde wind profiles in hurricanes and their operational implications. Wea. Forecasting, 18, 3244

 

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