20th anniversary of the first operational synoptic surveillance mission with the NOAA G-IV



On 14 July, 1997, Tropical Storm Claudette was moving northeastward offshore the east coast of the US.  Eager to test the new Gulfstream-IV (G-IV) jet aircraft and the new Global Positioning System dropwindsonde, the National Hurricane Center tasked the first-ever operational synoptic surveillance mission geared toward improving track forecasts.

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Initial condition differences in the vertically averaged 850 – 200 hPa wind velocity between the Global Spectral Model with no dropwindsonde data assimilated and that with all the data assimilated on 15 July 1997 0000 UTC. The large hurricane symbol is the location of Tropical Storm Claudette at the nominal time. The small hurricane symbols are the locations of Claudette every 12 h previous and after the nominal time. The black dots represent the locations of dropwindsonde observations.

HRD began investigating the possibility of improving hurricane track forecasts by releasing the old Omega dropwindsondes (ODWs) around tropical cyclones in 1982.  By 1996, the results were in:  dropping sondes in the data-void environments of hurricanes led to impressive track forecast improvements.  As a result, NOAA purchased the G-IV, and the GPS sonde was developed to replace the old ODW.  By July, systems were ready, and the first mission was completed.

Claudette didn’t directly impact any land, and, in fact, weakened and dissipated the next day.  However, the first mission proved that the missions could be easily accomplished, and the G-IV and dropwindsondes have gone on to be an important part of NOAA’s efforts to improve hurricane forecasts ever since.

 Some papers that used the data from this first mission:

Aberson, S. D., and J. L. Franklin, 1999:  Impact on hurricane track and intensity forecasts of GPS dropwinsonde observations from the first-season flights of the NOAA Gulfstream-IV jet aircraft.  Bull. Amer. Met. Soc., 80, 421-428.

Aberson, S. D., 2002:  Two years of operational hurricane synoptic surveillance. Wea. Forecast.17, 1101-1110.

 Aberson, S. D., 2003:  Targeted observations to improve operational tropical cyclone track forecast guidance.  Mon. Wea. Rev., 131, 1613-1628.