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Improvements in Real-Time Tropical Cyclone Products. Mark DeMaria NESDIS/StAR/RAMM Branch. Presented at. Outline. RAMMB Experimental Tropical Cyclone Web Page Experimental Extended/Updated NESDIS Tropical Cyclone Formation Probability Product Annular Hurricane Index

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Improvements in Real-Time Tropical Cyclone Products


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    1. Improvements in Real-Time Tropical Cyclone Products Mark DeMaria NESDIS/StAR/RAMM Branch Presented at

    2. Outline • RAMMB Experimental Tropical Cyclone Web Page • Experimental Extended/Updated NESDIS Tropical Cyclone Formation Probability Product • Annular Hurricane Index • Improvements in the Statistical Hurricane Intensity Prediction Scheme (SHIPS) for the 2007 Hurricane Season

    3. The RAMMB Experimental Tropical Cyclone Web Pagehttp://rammb.cira.colostate.edu/products/tc_realtime/

    4. Purpose To display real-time tropical cyclone products created and/or developed by RAMMB and CIRA scientists and products not available elsewhere. Serve these data to the public via a web integrated database designed to accommodate future product development.

    5. Information Content Globally occurring tropical cyclones • Track history and current forecasts from NOAA (NHC or CPHC) or DOD/JTWC • Earth relative IR loops (4-km Mercator) • Storm relative LEO IR and Vis (1-km Mercator) • AMSU-derived radius vs. height cross sections (T and Vgrad) and intensity estimate time series • Earth relative oceanic heat content + forecast track • Multi-platform satellite only tropical cyclone surface wind analysis • Digital Dvorak intensity estimate time series • Storm relative TPW and water vapor imagery

    6. Experimental Product Examples (TC wind analysis)

    7. Experimental Product Example (oceanic heat content) Data provided by G. Goni at NOAA/AOML http://www.aoml.noaa.gov/phod/cyclone/data/ kJ/cm^2

    8. Operational Product Example (AMSU intensity) Available for all active tropical cyclones at ftp://ftpprd.ncep.noaa.gov/pub/data1/amsu

    9. Example: Subtropical Storm Andrea

    10. Digital Dvorak Intensity Estimates

    11. Example Water Vapor Products Storm Relative Total Precipitable Water Storm Relative Water Vapor Imagery Blending of AMSU and SSM/I TPW is explained in Kidder and Jones (2007, JAOT)

    12. RAMMB Experimental TC Web Page - Future • Add New products • STIPS and SHIPS forecast time series • 1-km forecast track relative visible imagery • Kinetic energy time series derived from the surface wind analyses • Transition (try to) the experimental products • Multi-platform surface wind analysis • Ocean heat content • Use in STIPS based consensus • WMO website (maybe) • Respond to user requests

    13. Extension of the NESDIS Tropical Cyclone Formation Probability Product to the Central and Western Pacific

    14. CURRENT TCFP PRODUCT - OVERVIEW • Determines the 24-hr probability of TC formation within each 5° x 5° lat/lon grid box within the product domain (0° to 45° N, 140° to 350 W°) • Uses the following data sources: • NCEP GFS operational analyses • GOES-East water vapor imagery • NHC Best tracks • Running operationally at SSD since 2004 hurricane season. • Shows plots of domain-wide formation probabilities, predictor values, and sub-basin time series. Updates every 6 hours. • Available at : http://www.ssd.noaa.gov/PS/TROP/genesis.htm

    15. CURRENT TCFP PRODUCT – OVERVIEW (CONT…) CLIMATOLOGICAL FORMATION PROBABILITY (1949 – 2003) PERCENT LAND DISTANCE TO PREXISTING STORM CLIMATOLOGICAL SST VERTICAL SHEAR (800 – 250 hPa) 850 hPa CIRCULATION VERTICAL INSTABILITY GOES COLD PIXEL COUNT CLOUD-CLEARED WATER VAPOR BRIGHTNESS TEMP.

    16. CURRENT TCFP PRODUCT EXAMPLE – FLORENCE 2006 - 18 hr - 12 hr - 6 hr - 0 hr = Time of TC Genesis

    17. CURRENT PRODUCT - VERIFICATION Dependent probabilities are skillful by two measures • Brier Skill Score • Relative Operating Characteristic (ROC) score Interannual Variability Expected Yearly # TCs = ∫∫∫ P(x,y,t)dxdydt

    18. NEW TCFP PRODUCT – EXPANDED DOMAIN Expanded domain longitude eastward to 100° E (covers Central & Western N. Pacific Basins) Redefined basins based on satellite coverage Performed separate screening steps and discriminant analysis on each of the 3 basins.

    19. NEW TCFP PRODUCT - MODIFICATIONS • Added 2004 & 2005 to GOES-E sample set • Defined screening values and discriminant weights on each of the 3 basins, separately • Used a Finer Screening Process • Updated screening eliminates 5% of genesis cases and 75% of non-genesis cases (increase in eliminated non-genesis cases of ~5%  improve discriminant analysis) • Added of 850 hPa Horizontal Divergence as a Predictor

    20. NEW TCFP PRODUCT – WEB PAGE Updated/extended TCFP product currently running at CIRA, available at http://rammb.cira.colostate.edu/projects/gparm/ Main Page: points out areas of interest for TC genesis formation, links to web page for each basin Eg. Main Page graphic from 7/8/07 18Z, 18h prior to the formation of WP04 at 11.2N, 140.2 E

    21. UPDATED TCFP PRODUCT – FUTURE The updated NESDIS TCFP product will be run locally at CIRA and compared to the current product (running at SSD) throughout the 2007 hurricane seasons. Extended product will be evaluated/verified at end of 2007 season. After evaluation, the extended product will be transitioned to operations with the help of SSD

    22. SHIPS Annular Hurricane Index

    23. Annular Hurricane Characteristics • ENVIRONMENTAL CONDITIONS: • Weak Easterly/Southeasterly Wind Shear • Weak Relative Eddy Flux Convergence • 200 hPa Easterlies • SSTs in a range 25.4 to 28.6 °C steady or decreasing. OR • Weak Easterly shear, under an upper ridge, over SST <28.6 °C ALSO • Intensity > 85 kt (Knaff et al. 2003) STRUCTURE: • Distinctly axisymmetric • Large circular eyes • Greatly reduced rainband activity • Lasts at least 3 hours • Rare, occur ~4% of the time Isabel (2003)

    24. Annular Hurricane Intensity Characteristics Do not weaken rapidly after max intensity Intensity is very close to 85% MPI wrt SST Have large intensity biases & larger than normal intensity errors

    25. Determining Annular Structure Yellow = Structure Blue = Environment

    26. Annular Hurricane Index (AHI)

    27. AHI Step 1: Screening +/- 3 standard deviations from means of AH’s (1995-2003) 976 (54 AH) cases (6h) > 84 kt intensity  241 cases after screening (53 AH) Hit Rate = 100%, False Alarm Rate = 19%

    28. AHI Step 2: Linear Discriminant Analysis (Overview) DF=0 DF = c0 + c1x + c2y Coordinate transformation that provides maximum separation of groups (From www.doe-mbi.ucla.edu) Graphical Interpretation of LDA for Case With 2 Predictors (x,y) and 2 Groups Refs: Wilks (2006), Hennon & Hobgood (MWR, 2003)

    29. AHI Step 2: Linear Discriminant Analysis (cont…) • Only predictors with significant annular vs. non-annular differences in means were used** • SST • U200 – 200 hPa zonal winds • σc– azimuthal standard deviation of BTs at Rc • VAR –variance of azimuthally-averaged BTs from TC center to 600 km • ΔT eye- max difference between Rc and any azimuthally-averaged BT at smaller radius ** exceeds 95% confidence level using Student’s T test

    30. Verification STEP 1: Screening Reduced 941 (54) cases to 241 (53) FAR = 19% STEP 2: LDA “N” LDA “Y” Hit Rate ~ 87 % FA Rate ~ 6 % NAH AH STEP 1: Screening Reduced 387 (7) cases to 82 (7) FAR = 19% STEP 2: LDA “N” LDA “Y” Hit Rate ~ 100 % FA Rate ~ 4 % NAH AH Dependent Years (1995-2003) Independent Years (2004-2006)

    31. AHI Output & Interpretation If case doesn’t pass screening, AHI set to 0. If screening is passed, LDA function value is linearly scaled to obtain the Annular Hurricane Index, which ranges between 1 & 100. AHI is displayed at the end of the SHIPS model output file. AHI = 0  No annular structure AHI = 1  Worst match to annular structure AHI = 100  Best match to annular structure

    32. Example: Daniel 2006 7/20/06 0Z, vmax=95 kt AHI = 0 7/22/06 0Z vmax = 130 kt AHI = 100 7/21/06 0Z, vmax=120 kt AHI = 50

    33. Sample Product OutputEP05 (Daniel 2006), 7/22/06 0Z

    34. Annular Hurricane Index - Future For the period 1995-2006, the AHI algorithm had a hit rate of 96% and a false alarm rate of 4% The AHI will be tested in a real-time operational setting, running concurrently with the SHIPS model, at the National Hurricane Center during the 2007 hurricane season. After the 2007 season, if evaluation of the algorithm is favorable the transition to an operational product will be pursued

    35. 2006 Operational SHIPS Intensity Model • Statistical-dynamical TC intensity prediction model • 16 basic predictors • atmospheric from GFS forecast fields • oceanic from Reynold’s weekly SST • climatology and persistence from ATCF input • Satellite input • Ocean heat content from satellite altimetry • Convective parameters from GOES channel 4 • Empirical decay equation over land • Experimental Logistic Growth Equation (LGE) version also run that uses time stepping procedure

    36. Operational SHIPS Includes OHC from Satellite Altimetry Averaged Along the Storm Track as a Predictor OHC SST

    37. OHC Impact on SHIPS Forecasts Atlantic Sample: 3072 SHIPS Model Forecasts 1995-2006

    38. OHC Impact Much Larger for Intense Atlantic Hurricanes Improvements in Operational SHIPS Forecasts from OHC for all 2003-2005 Cat 5 Hurricanes (from Mainelli et al 2007)

    39. SHIPS Improvements for 2007 • Re-tuning of coefficients based on 2006 cases • Refinement of method for calculation of vertical wind shear • Add new vortex predictor from NCEP GFS model • New code installed on the NCEP IBMs (Mist/Dew) on May 9th

    40. Improved Shear Calculation • SHIPS uses NHC official track for center of shear calculation • GFS vortex track can differ from NHC track • Shear calculation uses large annulus to compensate (200-800 km)

    41. Example of NHC and GFS Track Mismatch96 h Forecast for Frances from 27 Aug 2004 12 UTC 850 hPa 200 hPa O O G G G = GFS positionO = NHC Position

    42. New Shear Algorithm • Track location of GFS vortex at 850 hPa • Tracker finds location that maximizes 0 to 600 km symmetric tangential wind • Checks for reasonable translational speeds • Requires minimum cyclonic wind • Symmetric circulation subtracted • Starts from outer radius where symmetric circulation is cyclonic • Subtraction radius decreases with height • Shear calculation at NHC track position after vortex removed • 0-500 km radius rather than 200-800 km annulus

    43. Example of Vortex Removal Total Wind Symmetric Flow Residual 850 hPa 200 hPa

    44. A New Predictor for SHIPS • GFS vortex removal procedure provides 850 tangential wind • 0-600 km average GFS tangential winds found to be significant intensity change predictor • Added to 2007 SHIPS

    45. 2007 Model Compared to Operational SHIPS(Re-runs of 2004-2006 seasons) Atlantic East Pacific