The NOAA Aircraft Operations Center (AOC) has operated the Gulfstream IV-SP (known as the G-IV) since 1996. Its primary role has been to fly high altitude long range tracks (more than 3500 miles) releasing up to 35 dropwindsondes in a single mission into the tropical cyclone (TC) environment as well as its synoptic surroundings. The G-IV WMO TEMPDROP messages, which are ingested into the global models, have made an important contribution to the significant improvement in the skill of NHC TC track forecasts noted during the past 15 years. Soundings from the G-IV have also become a vital component to the improvement of forecasting baroclinic storms each winter over the data-sparse North Pacific Ocean.

Addition of a Tail Doppler Radar (TDR), functionally similar to those introduced in 1989 onboard the two WP-3D aircraft, but taking advantage of advances in signal processing made over the past two decades, offers the possibility of furthering what is already a vital component to the Hurricane Forecast Improvement Project (HFIP). The introduction of “Superobs” (reflectivity and velocity products generated by the WP-3D TDR) of the TC core region into fine resolution mesoscale models such as the HRD's HWRFx or EMC's Advanced Research WRF has shown to be the most promising lead yet in solving the mystery of TC intensification. After completion of G-IV TDR operational testing during the summer of 2011, much more will be known as to how much this new tool may compliment the WP-3D TDR Superobs by observing convection within the Central Dense Overcast (CDO) above the melting layer of the TC.

In addition to the TDR, adaptation and testing is underway to employ the Stepped Frequency Microwave Radiometer (SFMR) on the G-IV. The SFMR is currently used on low altitude reconnaissance platforms (both the WP-3D and the USAF Reserve WC-130J). The much higher operational altitude of the G-IV (between 41,000 and 45,000 feet) presents a challenge in calibrating the instrument to the very cold ambient air temperatures in which it will be collecting microwave emissivity data from the surface below. Successful calibration is the key to the G-IV SFMR becoming a useful tool for mapping the spatial distribution of both tropical cyclone surface winds as well as those of winter storms.

Efforts are also underway to improve the accuracy and fidelity of the G-IV flight level data, especially wind direction, wind speed and ambient temperature. Should the efforts to improve these data sets along with calibration of the SFMR prove to be successful, transmission of High Density Observations (HDOBs) from the near 150 millibar level will be added to the G-IV operational capability. This will provide a unique opportunity for contiguous sampling of the outflow regime surrounding a TC, thus providing yet another piece of the intensity puzzle.