# Presentation: 674897

## Impact of Satellite Observations on

**Tropical Cyclone Track Forecasts**
**James S. Goerss **
**NRL  Monterey **
**March 5, 2008**

## NOGAPS Satellite Observation Impact Experiments

**The current operational NOGAPS/NAVDAS data assimilation system was run with different combinations of observational data over two test periods: July-October 2005 and August-September 2006.  The first period was an extremely active one covering most of the record-breaking Atlantic season with 18 hurricanes (including Katrina, Rita, and Wilma), 12 typhoons, and 20 tropical storms.  The second period was not nearly as active with 9 hurricanes, 7 typhoons, and 10 tropical storms.**
**The control run used all available conventional and satellite obser-vations. The satellite observations assimilated in these experiments consisted of feature-track winds from geostationary and polar-orbiting satellites, SSM/I precipitable water and wind speeds, AMSU-A radiances, and QuikSCAT and ERS-2 scatterometer winds.** **A number of exper-iments were run in which one type of satellite data was excluded. A final experiment was run excluding all satellite observations.**

## 2005 Atlantic (July-October)

**Homogeneous TC Forecast Error (nm)**

**Number of Forecasts**

## Atlantic Results

## Atlantic 2005-2006

**TC Forecast Error (nm)**

**Number of Forecasts**

## *

**Percent Improvement**

- * Significant at the 90% level

## Atlantic 2005-2006

**TC Forecast Error (nm)**

## Atlantic 2005-2006

**Percent Improvement**

## Global Results

## Global (2005-2006)

**TC Forecast Error (nm)**

**Number of Forecasts**

## * Significant at the 90% level

**Percent Improvement**

- * Significant at the 90% level

- *

- *

- *

- *

- *

- *

- *

- *

- *

- *

- *

- *

- *

## Global (2005-2006)

**TC Forecast Error (nm)**

**Number of Forecasts**

## Global (2005-2006) 

**Percent Improvement**

## Summary and Conclusions

**Summary and Conclusions**

**For the 2005-2006 test periods the assimilation of the feature-track winds **
**from geostationary satellites had the most impact for both the Atlantic and**
**the combined basins.  For the Atlantic, the impact due to the assimilation of SSM/I precipitable water and the AMSU-A radiances was significant at 24h and 48h and that due to the assimilation of scatterometer winds and SSM/I wind speeds were significant at 24h.  For the combined basins, the impact due to the assimilation of SSM/I precipitable water was significant at all forecast lengths while that due to the assimilation of AMSU-A radiances was significant at 24h, 48h, and 120h.  **
**The impact due to the assimilation of all satellite observations upon the**
**NOGAPS TC track forecasts for the 2005-2006 test periods was similar for**
**both the Atlantic and the combined basins resulting in a gain in skill of **
**roughly 12h for the 48-h and 72-h forecasts and a gain in skill of roughly **
**24h for the 96-h and 120-h forecasts.  Although the assimilation of some **
**satellite observation types did not result in statistically significant improve-**
**ments, their assimilation contributed additively and even multiplicatively **
**at some forecast lengths to reduction in NOGAPS track forecast error.**

## Questions?

## Global (July-September 2005)

**TC Forecast Error (nm)**