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Ocean Initialization System for Coupled Hurricane-Ocean Models and its Transition to HWRF

Isaac Ginis and Richard M. Yablonsky Graduate School of Oceanography University of Rhode Island Narragansett, RI 02882 E-mail: iginis@gso.uri.edu

Our experience with the GFDL coupled model indicates the importance of proper initialization of the coupled modeling system. It is well known that successful forecasts of the structure and movement of tropical cyclones using an atmospheric model are strongly dependent on good initialization. In the coupled model, the ocean initialization is equally important because the SST response is very sensitive to the upper ocean structure. One major challenge for proper ocean initialization in a coupled hurricane- ocean model is accurate representation of mesoscale oceanic features that do not follow an annual (or even a regular) cycle, such as the penetration of the Loop Current (LC) into the Gulf of Mexico (GoM) and the shedding (and perhaps reattachment) of Loop Current

eddies (LCEs). We will implemented operationally 2006 hurricane season. The

discuss the ocean initialization procedure developed and to the GFDL coupled hurricane prediction system for the new procedure accounts for spatial and temporal variability

of mesoscale oceanic and cold core rings.

features Using

in the GoM, including the LC, LCEs (i.e. warm core rings), near real-time satellite altimetry and in situ temperature

profiles produce

(when available), a more realistic

these features are assimilated into an three-dimensional temperature field

ocean valid

climatology to at the model

initialization time. Relative accuracy by comparing the model temperature

of the initialization procedure will be profiles to temperature profiles in the

demonstrated pre-hurricane

environment (AXBT), the

obtained by HRD ocean climatology,

scientists via airborne and an alternative data

expendable assimilation

bathythermograph technique. During

the 2006 hurricane season, Michelle parameters for initialization of the

Mainelli, a forecaster at GFDL coupled model

NHC, provided LC and LCE operational forecasts using

maps of the depth ocean component

of

the

of

the

26°C isotherm derived from GFDL coupled model, the

satellite altimetry. At present, the Princeton Ocean Model, is being

transitioned to NCEP’s Hurricane WRF model. recently to the initialization system, including more realistic structure of the LC.

Further improvements have been made the initialization of cold core rings and

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