# Presentation: 672683

## Impact of Satellite Observations

** ****and Forecast Model Improvements**
** ****on Tropical Cyclone Track Forecasts**
**James S. Goerss and Timothy F. Hogan**
**NRL  Monterey **
**March 21, 2006**

## Observation and Forecast System Experiments

**The purpose of this study was to determine the impact that the assimilation of satellite observations and forecast model improvements have had upon the tropical cyclone track forecasting performance of global numerical weather prediction systems. **
**The current operational NOGAPS/NAVDAS data assimilation system was run with different combinations of observational data and with different configurations of the NOGAPS global spectral model over the period from August 14-September 30, 2004.  This was a particularly active period with 12 hurricanes (including**
**Charley, Frances, Ivan, and Jeanne), 5 typhoons, and 7 tropical**
**storms.**
**Tropical cyclone track forecast error was evaluated.**

## Observation and Forecast System Experiments

_**Summary of Experiments**_
**NCNV – Conventional observations only**
**NATV – NCNV plus AMSU-A radiances**
**NRPW – NATV plus SSM/I precipitable water**
**NSPW – NRPW plus satellite feature-track winds**
**NCTL**** – NSPW plus scatterometer winds (control system)**
**NRTR – NCNV plus NESDIS retrievals**
**NOBG – ****NCTL**** minus Synthetic TC observations**
**T79L18 and T159L24 – Relaxed Arakawa Schubert**
**T159L24E and ****T239L30E (NCTL) ****- Emanuel**

## Observation System

**Experiments**

## Observation System Experiments

**TC Forecast Error (nm)**

## Observation System Experiments

**TC Forecast Error (nm)**

## Observation System Experiments

**Percent Improvement**

## Impact of Synthetic

**Tropical Cyclone**
** ****Observations**

## Observation System Experiments

**TC Forecast Error (nm)**

## Forecast System

**Experiments**

## Forecast System Experiments

**TC Forecast Error (nm)**

## Forecast System Experiments

**Percent Improvement**

## Forecast System Experiments

**TC Forecast Error (nm)**

## Summary and Conclusions

**The feature-track winds proved to be the most important set of satellite **
**observations.  With respect to the other types of satellite observations, **
**the assimilation of feature-track winds had the largest impact at 24 h to **
**96 h.  The assimilation of AMSU-A radiances had the largest impact at **
**120 h.  At all forecast lengths, the assimilation of AMSU-A radiances **
**(NESDIS retrievals) had a positive (negative) impact on TC track forecast **
**skill. **
**The impact of the assimilation of all satellite observations was comparable **
**to the impact of all forecast model improvements at 24 h to 72 h.  At 96 h **
**and 120 h, the impact of the assimilation of all satellite observations was **
**roughly comparable to the impact of replacing the relaxed Arakawa-**
**Schubert convective parameterization with the Emanuel convective **
**parameterization.**

**Summary and Conclusions**

## Summary and Conclusions

**The impact obtained when the forecast model resolution improved from **
**T79L18 to T159L24 increased with increasing forecast length.  As a result, **
**the impact of all model improvements was two to three times greater than **
**the impact of the assimilation of all satellite observations at 96 h and 120 h.**
**The impact of the assimilation of synthetic TC observations was found to be **
**greater than the impact of the assimilation of all satellite observations at 24 h **
**and 48 h and comparable at 72 h and 96 h.**

## Questions?