# Presentation: 200365

## SUMMARY OF 2003 GFDL HURRICANE PREDICTION SYSTEM AND PLANS FOR 2004

**Morris Bender, Timothy Marchok (GFDL) **
**Robert Tuleya, Hua-Lu Pan, Naomi Surgi (NCEP)**
**Isaac Ginis, Biju Thomas (URI) **

## CHANGES IMPLEMENTED IN 2003

- Ocean Coupling over entire Ocean Domain, Gulf Stream Assimilation.
- Increase of Vertical Levels from 18 to 42.
- Simplified Arakawa-Schubert Cumulus Parameterization (SAS).
- GFS Boundary Layer Scheme (Replaced M&Y).
- Virtual Temperature used in Pressure Gradient Computation instead of dry temperature.

## CHANGES IMPLEMENTED IN 2003 (cont’d)

- Improved Mass Initialization for computation of  Sea-level Pressure & Temperature.
-     (Greatly Reduced Noise over Mountains )
- Computed Virtual Temperature directly in the Mass initialization.
- Improved Interpolation of Winds over mountains.
- Improved Vortex removal algorithm in Initialization (enabled all of the vortex to be removed for weak or asymmetric storms).
- More consistent target wind in initialization.

## Track Verifications for 2003 Season

## Track Verifications for 2003 Season

## Track Verifications for 2003 Season

## Intensity Verifications for 2003 Season

##  TREND IN TRACK ERROR

- GFS

- TPC

- GFDL

## TREND IN INTENSITY  ERROR

## SUMMARY of 2003 SEASON

- Overall the GFDL was the best performing dynamical model  in both basins for track, particularly in the 12 to 72h range.
- The GFDL Model had its lowest track errors ever in both the Atlantic and Eastern Pacific.
- The average GFDL track error in the Atlantic Basin was about 15% less than 2002 and 30% less than the 2001 seasons.
- The GFDL model still exhibited little or no skill for intensity although the severe positive bias was removed in the Atlantic Basin.
- The 2003 GFDL model exhibited a severe negative intensity bias for weak storms as these storms often did not develop or incorrectly dissipated. Addressing this problem is a primary focus in the system upgrades for 2004.

## PROPOSED CHANGES FOR 2004

- Evaporation of Rain in Large-Scale Condensation
-       (** Implemented July 28th, 2003 **)
- Modify Downdraft Formulation in SAS Scheme in Boundary Layer.
- Reduction of Momentum Mixing in Storm Region.
- Reduction of Threshold for Large-Scale Condensation from 100% to 98%.
- Implementation of new axi-symmetric bogus in Vortex Initialization   ????

## SUMMARY OF CASES RUN

- Hurricane Isidore	(2002) 	18 Cases
- Hurricane Lili 		(2002) 	20 Cases
- Hurricane Fabian	(2003)	20 Cases
- Hurricane Isabel	(2003)	23 Cases
- Hurricane Kate		(2003) 	16 Cases
- T. S. Nicholas	        (2003) 	10 Cases
- Hurricane Claudette	(2003)	7 Cases
**TOTAL CASES****	****	****	****114 Cases**

## Intensity Forecast of Fabian with Current 2003 and New GFDL Model(Initial Time: 0000 UTC 28 August)

## Intensity Forecast of Lili with Current 2003 and New GFDL Model

## Intensity Forecasts of Isidore with 2002, 2003 and 2004 and GFDL Models

## Comparison of 2003 and 2004 GFDL Track Error

## Comparison of Operational GFDL, GFDL Upgraded in July and 2004 GFDLHurricane Claudette (0000 UTC, 13 July)

## SUMMARY OF NEW 2004 GFDL MODEL

- New System Resulted in a Dramatic Reduction in the Severe Negative Intensity Bias for Weak Systems.
- The Number of Systems That Incorrectly Dissipated Was Greatly Reduced.
- The Overall Skill in the Intensity Prediction Was only Marginally Improved.
- The Average Track Error Was Not Significantly Impacted.

## Future GFDL Model Development

- Continue development of high-resolution GFDL model with Bulk microphysics.
- Testing of new momentum mixing scheme in operational hurricane model.
- Parallel testing of high resolution GFDL model with Bulk microphysics in summer of 2004 on limited basis.
- Possible operational implementation in 2005.