Nelsie A. Ramos NOAA EPP GradSci /HU PhD Student/NHC NCEP/EMC Research Collaboration Project : NHC: Richard Pasch, Ed

1. Assessment of the impacts of supplemental upper air soundings on tropical cyclone model forecasts Nelsie A. Ramos NOAA EPP GradSci/HU PhD Student/NHC NCEP/EMC Research Collaboration Project: NHC: Richard Pasch, Ed Rappaport, James Franklin NCEP: Kate Howard, Bill Lapenta, Vijay Tallapragada, John Ward Yangrong Ling, Dennis Keyser, Diane Stokes

2. Overview and Background Overview: • A data denial study has been conducted to evaluate the impact of supplemental 0600Z and 1800Z upper air soundings on GFS model forecasts (Preliminary Results) Background: • NHC often requests NWS WFOs in the Southern and/or Eastern Regions to launch soundings at the intermediate synoptic times starting ~ 3 days in advance of a potential TC landfall to assist with forecasts that will be including watches/warnings • It has been hypothesized that inclusion of these additional in situ atmospheric data have a significant positive impact on operational model initialization and TC prediction

3. Motivation and Cases Selection Motivation: • Nonexistent quantitative assessment of the operational benefits from the inclusion of this data • NWS expenses associated with extra sounding supplies and staff time Cases Selection: • Seven TCs from the 2008 Hurricane Season were selected • A large enough sample of 41 cases (initialization times) for which 06Z/18Z upper air soundings were available were identified to assure confidence in results • Partial results (~ 2/3 of the sample) are presented today • 26 experimental cases (total of 53 including 27 cases for the 00Z/12Z times affected by GDAS cycle first guess) • Remaining 12 experimental cases to be completed soon • A complete analysis upon which a decision can be made about future of supplemental soundings will be available before next hurricane season

4. 2008 Tropical Cyclones Cases Available Denial Cases: 26/41 for 6 storms *Note: Number of cases in the following slides will depend on the CNTRL runs cycles data availability (not shown), how far the tracker was able to identify a vortex (=< 126 hr) and Best Track extension. Total preliminary cases 00/12Z Inclusive: 53/58

5. Methodology • Model: • GFS – Version T574 (FY10/Phase II) • Experimental Design: • For each tropical cyclone • CNTRL - operational global model runs, supplemental soundings inclusive • Denial/Experimental - GFS runs with supplemental sounding data • removed • Runs out to 126 hrs (ideally) • Assessment: • For the experimental runs, track forecast errors are calculated at the 12-, 24-, 36-, 48-, 72-, 96-, and 120-h forecast intervals • These errors are compared to those from the CNTRL model runs to verify if there are statistically significant improvements or degradations in the forecasts

6. TS Cristobal: Track and Average Error Control Run Data Denial Run

7. 06Z 20 July 18Z 20 July CNTRL Degrad: 12 -> 48 hr CNTRL Improv: 12 -> 36 hr CNTRL Average FSP: 53% CNTRL Improv: 12 -> 48 hr CNTRL Improv: 36 hr Degrad: 12 & 48 hr 12Z 20 July 00Z 21 July

8. Hurricane Dolly: Track and Average Error Control Run Data Denial Run

9. 06Z 21 July 18Z 21 July 06Z 22 July CNTRL Improv: 12,72,96 hr Degrad: 36, 48 hr CNTRL Improv: 48, 72 hr Degrad: 12, 24 hr CNTRL Improv: 24 -> 72 hr CNTRL Average FSP: 57% 12Z 21 July 00Z 22 July 12Z 22 July CNTRL Improv: 12 -> 48 & 96 hr CNTRL Improv: 24 & 72 hr CNTRL Improv: 24, 72 hr Degrad: 12, 48 hr

10. TS Edouard: Track and Average Error Control Run Data Denial Run

11. 06Z 04 Aug 06Z 05 Aug CNTRL Improv: 12 -> 36 hr CNTRL Improv: 12 hr CNTRL Average FSP: 69% 12Z 04 Aug 12Z 05 Aug CNTRL Improv: 12, 36 hr CNTRL Degrad: 12 hr

12. TS Fay: Track Control Run Data Denial Run

13. TS Fay: Track Average Error • Overall improvement by the extra soundings • Maximum improvement of 18% at 120 hr for 11 cases

14. CNTRL Average FSP: 61%

15. Hurricane Gustav: Track and Average Error CNTRL Average FSP: 43% Control Run Data Denial Run Denial Runs had a 57% of Fcst. Superiority

16. Hurricane Hanna: Track and Average Error Control Run Data Denial Run As the Gustav and Hanna hurricane cases suggest: Occasionally, extra data degrade forecast Denial Runs had a 76% of Fcst. Superiority CNTRL Average FSP: 24%

17. Preliminary Average Results: Track

18. Concluding Remarks • Partial results suggest that on average, there is a positive impact in track by the supplemental 0600Z and 1800Z upper air soundings taken in advance of U.S. TS and hurricane landfall • Composite track skill (overall improvement): 4% • Composite track FSP (forecast superiority): 55% of times • Statistical significance will be determined after remaining cases (Ike) are added • The major impact in the GFS forecast was observed by the runs cycles initialized on 0600Z and 1800Z where the additional data is ingested (includes the 0 h or initialization time) • Composite track skill: 6% • Composite track FSP: 55% • Improvement in track was also observed in the subsequent 0000Z and 1200Z cycles, however in a lesser extent • Composite track skill: 2% • Composite track FSP: 55%

19. Acknowledgements Questions?