Transitioning HWRF upgrades into operations at EMC A

Transitioning HWRF upgrades into operations at EMC A Joint Hurricane Testbed (JHT) Program Robert E. Tuleya*, Yihua Wu, Vijay. Tallapragada, Young Kwon, Hyun-Sook Kim, Zhang, Qingfu Liu, J. O’Connor 65 th Interdepartmental Hurricane Conference *NOAA Visiting Scientist @CCPO/ODU Miami Fl March 2011

JHT project task areas* • Improve HWRF intensity forecasts transition surface flux formulation from V 2 to V 3 • Trouble shoot and diagnose HWRF problems transition surface flux formulation from V 2 to V 3 • Upgrade land model and landfall prediction transition to NOAH LSM *½ time effort

Transition from HWRF 2010 (V 2) Operational Sfc Fluxes to Alternative znot Formulation(V 3) 3

HWRF 2010 V 2 surface fluxes based on observation 2010 Results mixed: ~good track but low intensity bias HEXOS data (1996, Decosmo et al) CBLAST data (2007) HWRF 2010 V 2 used constant CH at high winds

Similarity relationship for surface layer exchange coefficients under neutral condition Stress ~ u*2 ~ Cdumum Enthalpy flux ~ u*. q* ~ Ch um ( qm – qs ) • HWRF 2010 prod sfc flux formulation uses Cd & Ch with low level wind cut-off above which there is no stability dependence • Given Cd & Ch from HWRF 2010 operational code( Kwon ), solve for zo and zot for neutral conditions as function of low level wind • Use function form of zo and zot in MO formulation of GFDL surface flux formulation Assume stability dependence can be important in some cases • Method allows for roughness to be changed later based on more physical basis—e. g. wave coupling, current interaction, etc. 5 • Alternative znot formulation used in V 3 -R 2

Possible differences in results between HWRF prod and znot formulation • Znot formulation does not exactly match CD & CH of Kwon. Algebraic fit of znot for enthalpy and momemtum • Znot formulation has stability dependence of GFDL(HWRF 2009) sfc flux routine 6

HWRF 2010, V 3 -R 2 (neutral) CD, CH CH/CD ratio HWRF V 3 HWRF 2010 CH/CD ratio significantly lower than GFDL & HWRF 2009 7

H 210 test with znot formulation based on H 210 CH~1 x 10 -3 above 10 m/s V 3 znot HWRF 2010 *** Note track nearly identical 8

Red: Oper. HWRF V 2. 0 Cyan: HWRFV 3. 2 w/POM Benchmarking HWRFV 3. 2–POM three season testing, ATLANTIC 2008 -2009 -2010. HWRFV 3. 2 produced nearly identical results compared to operational 2010 HWRFV 3. 2 produced slightly less bias compared to operational 2010 HWRF. Consistent with slightly greater values of CH/CD for HWRFV 3. 2 vs 2010 HWRF

Summary of Znot formulation method • Relatively small difference between operational HWRF V 2 and HWRF V 3 znot formulation method • Some small improvement in reduction of low intensity bias? • Thermal znot can be reformulated to account for low intensity bias? ? (next talk) 10

The NOAH LSM Issues in HWRF ~150 historic 2008 Atlantic cases ~280 2010 Atlantic cases run in parallel

Track NOAH LSM test cases 2010 AL 01 -AL 19 2008 cases Track: Noah LSM ~20 nm worse @96 h Why? ? ? Intensity: Noah LSM slightly better up to 96 h (not shown)

Example of Alex (2010) two problems areas • Hot spots in LST in parent & nest domains • Apparent lateral BC problems

Hot spots (parent grid) in Noah LSM NOAH LSM LST > 330 K GFDL slab 280<LST<310 K

Lateral BC problems (nest): V 3 R 2 makes problems worse HWRFV 2 NOAH LSM Apparent lateral BC problems with NOAH LSM (H 210) V 3 R 2 NOAH LSM LST hot spot >500 K

Apply patch to fix Tsfc values along perimeter after LSM call, hot spots reduced/removed

Hot Spots controlled by • patching LST from one point inside • changing from binary to netcdf!! • turning off gravity wave drag!! Issues and Solutions • Tsfc treated differently than other prognostic variables (e. g. u, v, T, R ? ? ? ) • Apparent lateral BC problems remain for LST and other surface land parameters and variables in nest domain • Fix LSM issues in V 3. 2 and run in parallel for 2011

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