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Developing an Inner-Core SST Cooling Parameter for use in SHIPS

Developing an Inner-Core SST Cooling Parameter for use in SHIPS. Principal Investigator : Joseph J. Cione NOAA’s Hurricane Research Division Co-Investigators: John Kaplan (HRD) ; Chelle Gentemann (Remote Sensing Systems) ; Mark Demaria (NESDIS) IHC 2004 Joint Hurricane Testbed

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Developing an Inner-Core SST Cooling Parameter for use in SHIPS

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  1. Developing an Inner-Core SST Cooling Parameter for use in SHIPS Principal Investigator: Joseph J. Cione NOAA’s Hurricane Research Division Co-Investigators:John Kaplan (HRD); Chelle Gentemann (Remote Sensing Systems); Mark Demaria (NESDIS) IHC 2004 Joint Hurricane Testbed March 3, 2004

  2. Project Motivation…..On average do post storm ‘cold wake’ SST reductions on the order of 4-6oC adequately approximate SST cooling patterns typically found within the high wind TC inner core ? + What is the magnitude of inner core SST cooling typically observed ? + What about storm to storm variability ?

  3. A focused effort to answer these questions….Cione and Uhlhorn (2003) • Cione and Uhlhorn (2003) documented SST change within the high wind TC inner core environment… • Using existing surface buoy and AXBT observations from 23 hurricanes (33 events) between 1975-2002.

  4. Defining the SST change Parameters used in Cione and Uhlhorn (2003)(inner-core minus ‘ambient’) ‘Ambient’ SST out AHEAD of the storm • (>200km from TC center in RF or LF quadrant) ‘Inner core’ SST/mixed layer temperature • (<60km or <200km from TC center) -SSTIC ; SSTICW Hurricanes only… • Pre-landfall • South of 36N

  5. Key Findings:Cione and Uhlhorn (2003) +Inner core SST change (core - ambient) is MUCH less than 4-6oC ‘cold wake’ SST reductions typically observed • 31/33 horizontal SST transects < 1.5oC (23 Hurricanes) • Mean DSSTIC = 0.7oC • Relatively small changes in inner-core SST(0.5oC) can significantly alter surface energy fluxes (-40% or more) +For the 33 cases analyzed, the magnitude of inner core SST cooling (core - ambient) was highly correlated with subsequent changes storm intensity

  6. Key Findings:Cione and Uhlhorn (2003) Continued… • In addition, TC latitude and initial storm speed were found to be statistically linked to observed changes in inner-core SST for this 33 event sample. • As a direct result of these findings a proposal entitled “Developing an Inner-Core SST Cooling Parameter for use in SHIPS” was submitted to the JHT In the spring of 2003….

  7. Developing an Inner-Core SST Cooling Parameter for use in SHIPS The Overall Goal of this JHT project is… To Investigate how changes in the TC inner-core ocean surface boundary condition potentially impacts changes in storm intensity within the context of SHIPS operation model. Early results….Algorithm Development + Since June 2003, several multiple linear regression relationships designed to predict inner core SST change have been tested and developed… + Continued analysis has yielded a statistically robust baseline TC Inner-Core SST Cooling Algorithm that utilizes three independent predictors: Initial TC latitude, storm speed and ambient SST

  8. Developing an Inner-Core SST Cooling Parameter for use in SHIPS Current JHT Project - Early results….Dependant Testing in SHIPS + Preliminary testing of the TC Inner-Core SST Cooling Algorithm on thousands of TC forecast events found in the 1989-2002 SHIPS storm database have yielded very encouraging results….

  9. SST Cooling Algorithm: Preliminary Findings…. Results using thousands of observations from the 1989-2002 SHIPS data archive show that the inner-core cooling algorithm developed under this JHT project is very stable… Dependant sample testing in SHIPS illustrated significant improvements with respect to observed changes in TC intensity over ALL 12-120h forecast intervals, regardless of sample stratification. Some of the major highlights from this SHIPS analysis include: • For All TC cases (N=12887) an avg 1.0-2.5% improvement in skill was found over the 24-120h fcst pd • For Hurricane cases (N=4528) an avg 1.5-3.5%improvement in skill “ “ • For all Major Hurricanes (N=1011) an avg 2.7-7.0%improvement in skill“ “ • For the Top 10% “Rapid Intensifier” events an avg 4.5-8.0%improvement in skill“ “ • For the Bottom 10% “Rapid Filler” events an avg 2.0-13.5%improvement in skill“ “ NOTE: Regardless of stratification or forecast interval, ZERO degradation in mean SHIPS forecast skill was found when the Inner core SST cooling algorithm was used… Future work, if funded in year two, would include independent testing by running a parallel version of SHIPS during the 2004 Atlantic Hurricane Season. In addition, attempts would be made to identify a reliable subsurface ocean predictor and improve upon existing Reynolds weekly SSTs currently used in SHIPS (Gentemann - high spatial and temporal resolution microwave SSTs). Additionally, focused on potentially incorporating a version of the cooling algorithm into the Atlantic RI index have recently begun (Kaplan). Preliminary findings have been promising.

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