An Examination of Wind Decay, Sustained Wind Speed Forecasts, and Gust Factors for Recent Tropical Cyclones in the Mid-Atlantic Region of the United States

Bryce Tyner North Carolina State University, Raleigh, North Carolina

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Anantha Aiyyer North Carolina State University, Raleigh, North Carolina

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Jonathan Blaes NOAA/NWS, Raleigh, North Carolina

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Donald Reid Hawkins NOAA/NWS, Wilmington, North Carolina

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Abstract

In this study, several analyses were conducted that were aimed at improving sustained wind speed and gust forecasts for tropical cyclones (TCs) affecting coastal regions. An objective wind speed forecast analysis of recent TCs affecting the mid-Atlantic region was first conducted to set a benchmark for improvement. Forecasts from the National Digital Forecast Database were compared to observations and surface wind analyses in the region. The analysis suggests a general overprediction of sustained wind speeds, especially for areas affected by the strongest winds. Currently, National Weather Service Weather Forecast Offices use a software tool known as the Tropical Cyclone Forecast/Advisory (TCM) wind tool (TCMWindTool) to develop their wind forecast grids. The tool assumes linear decay in the sustained wind speeds when interpolating the National Hurricane Center 12–24-hourly TCM product to hourly grids. An analysis of postlandfall wind decay for recent TCs was conducted to evaluate this assumption. Results indicate that large errors in the forecasted wind speeds can emerge, especially for stronger storms. Finally, an analysis of gust factors for recent TCs affecting the region was conducted. Gust factors associated with weak sustained wind speeds are shown to be highly variable but average around 1.5. The gust factors decrease to values around 1.2 for wind speeds above 40 knots (kt; 1 kt = 0.51 m s−1) and are in general insensitive to the wind direction, suggesting local rather than upstream surface roughness largely dictates the gust factor at a given location. Forecasters are encouraged to increase land reduction factors used in the TCMWindTool and to modify gust factors to account for factors including the sustained wind speed and local surface roughness.

Corresponding author address: Bryce Tyner, Dept. of Marine, Earth, and Atmospheric Sciences, 2800 Faucette Drive, Rm. 1125 Jordan Hall, North Carolina State University, Raleigh, NC 27695-8208. E-mail: bptyner@ncsu.edu

Abstract

In this study, several analyses were conducted that were aimed at improving sustained wind speed and gust forecasts for tropical cyclones (TCs) affecting coastal regions. An objective wind speed forecast analysis of recent TCs affecting the mid-Atlantic region was first conducted to set a benchmark for improvement. Forecasts from the National Digital Forecast Database were compared to observations and surface wind analyses in the region. The analysis suggests a general overprediction of sustained wind speeds, especially for areas affected by the strongest winds. Currently, National Weather Service Weather Forecast Offices use a software tool known as the Tropical Cyclone Forecast/Advisory (TCM) wind tool (TCMWindTool) to develop their wind forecast grids. The tool assumes linear decay in the sustained wind speeds when interpolating the National Hurricane Center 12–24-hourly TCM product to hourly grids. An analysis of postlandfall wind decay for recent TCs was conducted to evaluate this assumption. Results indicate that large errors in the forecasted wind speeds can emerge, especially for stronger storms. Finally, an analysis of gust factors for recent TCs affecting the region was conducted. Gust factors associated with weak sustained wind speeds are shown to be highly variable but average around 1.5. The gust factors decrease to values around 1.2 for wind speeds above 40 knots (kt; 1 kt = 0.51 m s−1) and are in general insensitive to the wind direction, suggesting local rather than upstream surface roughness largely dictates the gust factor at a given location. Forecasters are encouraged to increase land reduction factors used in the TCMWindTool and to modify gust factors to account for factors including the sustained wind speed and local surface roughness.

Corresponding author address: Bryce Tyner, Dept. of Marine, Earth, and Atmospheric Sciences, 2800 Faucette Drive, Rm. 1125 Jordan Hall, North Carolina State University, Raleigh, NC 27695-8208. E-mail: bptyner@ncsu.edu
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  • Avila, L. A., 2009: Tropical cyclone report: Hurricane Cristobal. NOAA/National Hurricane Center Tech. Rep. AL032008, 8 pp. [Available online at http://www.nhc.noaa.gov/data/tcr/AL032008_Cristobal.pdf.]

  • Avila, L. A., and Cangialosi J. , 2012: Tropical cyclone report: Hurricane Irene. NOAA/National Hurricane Center Tech. Rep. AL092011, 45 pp. [Available online at http://www.nhc.noaa.gov/data/tcr/AL092011_Irene.pdf.]

  • Bailey, C. M., Hartfield G. , Lackmann G. M. , Keeter K. , and Sharp S. , 2003: An objective climatology, classification scheme, and assessment of sensible weather impacts for Appalachian cold-air damming. Wea. Forecasting, 18, 641661, doi:10.1175/1520-0434(2003)018<0641:AOCCSA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Benjamin, S. G., and Coauthors, 2004: An hourly assimilation forecast cycle: The RUC. Mon. Wea. Rev., 132, 495, doi:10.1175/1520-0493(2004)132<0495:AHACTR>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Brown, D., 2008: Tropical cyclone report: Hurricane Gabrielle. NOAA/National Hurricane Center Tech. Rep. AL072007, 13 pp. [Available online at http://www.nhc.noaa.gov/data/tcr/AL072007_Gabrielle.pdf.]

  • Childs, B., and Lewis R. , 2001: Investigating the impact of changing the ASOS wind gust averaging period from five to three seconds. Preprints, 11th Symp. on Meteorological Observations and Instrumentation, Albuquerque, NM, Amer. Meteor. Soc., 2.5.[Available online at https://ams.confex.com/ams/annual2001/techprogram/paper_18249.htm.]

  • Davies, J., 2006: Hurricane and tropical cyclone tornado environments from RUC proximity soundings. Preprints, 23rd Conf. Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc., 12.6A. [Available online at https://ams.confex.com/ams/pdfpapers/115483.pdf.]

  • Durst, C. S., 1960: Wind speeds over short periods of time. Meteor. Mag., 89, 181187.

  • Eastin, M. D., Gardner T. L. , Link M. C. , and Smith K. C. , 2012: Surface cold pools in the outer rainbands of Tropical Storm Hanna (2008) near landfall. Mon. Wea. Rev., 140, 471491, doi:10.1175/MWR-D-11-00099.1.

    • Search Google Scholar
    • Export Citation
  • Glahn, B., 2005: Comments on implementation and refinement of digital forecasting databases. Bull. Amer. Meteor. Soc., 86, 13151318, doi:10.1175/BAMS-86-9-1315.

    • Search Google Scholar
    • Export Citation
  • Glahn, H. R., and Ruth D. P. , 2003: The New Digital Forecast Database of the National Weather Service. Bull. Amer. Meteor. Soc., 84, 195201, doi:10.1175/BAMS-84-2-195.

    • Search Google Scholar
    • Export Citation
  • Hanson, T., Matthewson M. , and Romberg M. , 2001: Forecast methodology using the GFE Suite. Preprints, 17th Int. Conf. on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Albuquerque, NM, Amer. Meteor. Soc., 1.13. [Available online at https://ams.confex.com/ams/annual2001/techprogram/paper_18722.htm.]

  • Harper, B. A., Kepert J. D. , and Ginger J. D. , 2010: Guidelines for converting between various wind averaging periods in tropical cyclone conditions. World Meteorological Organization Tech. Rep. WMO/TD-1555, 54 pp.

  • Hsu, S. A., 2001: Spatial variations in gust factor across the coastal zone during Hurricane Opal in 1995. Natl. Wea. Dig., 25, 2123. [Available online at http://www.nwas.org/digest/papers/2001/Vol25No12/Pg21-Hsu.pdf.]

    • Search Google Scholar
    • Export Citation
  • Hsu, S. A., 2003: Nowcasting the variation of wind speed with height using gust factor measurement. Natl. Wea. Dig., 27, 6769. [Available online at http://www.nwas.org/digest/papers/2003/Vol27No1/Pg67-Hsu.pdf.]

    • Search Google Scholar
    • Export Citation
  • Kaplan, J., and Demaria M. , 1995: A simple empirical model for predicting the decay of tropical cyclone winds after landfall. J. Appl. Meteor., 34, 24992512, doi:10.1175/1520-0450(1995)034<2499:ASEMFP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Knabb, R. D., and Mainelli M. , 2007: Tropical cyclone report: Hurricane Ernesto. NOAA/National Hurricane Center Tech. Rep. AL062006, 36 pp. [Available online at http://www.nhc.noaa.gov/data/tcr/AL062006_Ernesto.pdf.]

  • Krayer, W., and Marshall R. D. , 1992: Gust factors applied to hurricane winds. Bull. Amer. Meteor. Soc., 73, 613618, doi:10.1175/1520-0477(1992)073<0613:GFATHW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Malkin, W., 1959: Filling and intensity changes in hurricanes over land. National Hurricane Research Rep. 34, U.S. Weather Bureau, Washington, DC, 18 pp.

  • Masters, F. J., Vickery P. J. , Bacon P. , and Rappaport E. N. , 2010: Toward objective, standardized intensity estimates from surface wind speed observations. Bull. Amer. Meteor. Soc., 91, 16651681, doi:10.1175/2010BAMS2942.1.

    • Search Google Scholar
    • Export Citation
  • Moore, B. J., Bosart L. F. , Keyser D. , and Jurewicz M. L. , 2013: Synoptic-scale environments of predecessor rain events occurring east of the Rocky Mountains in association with Atlantic basin tropical cyclones. Mon. Wea. Rev., 141, 10221047, doi:10.1175/MWR-D-12-00178.1.

    • Search Google Scholar
    • Export Citation
  • Mueller, K. J., Demaria M. , Knaff J. , Kossin J. P. , and Vonder Haar T. H. , 2006: Objective estimation of tropical cyclone wind structure from infrared satellite data. Wea. Forecasting, 21, 990, doi:10.1175/WAF955.1.

    • Search Google Scholar
    • Export Citation
  • Paulsen, B., and Schroeder J. , 2005: An examination of tropical and extratropical gust factors and the associated wind speed histograms. J. Appl. Meteor., 44, 270280, doi:10.1175/JAM2199.1.

    • Search Google Scholar
    • Export Citation
  • Powell, M. D., and Houston S. H. , 1998: Surface wind fields of 1995 Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Mon. Wea. Rev., 126, 1259, doi:10.1175/1520-0493(1998)126<1259:SWFOHE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Powell, M. D., Houston S. H. , Amat L. R. , and Morisseau-Leroy N. , 1998: The HRD Real-time Hurricane Wind Analysis System. J. Wind Eng. Ind. Aerodyn., 77–78, 5364, doi:10.1016/S0167-6105(98)00131-7.

    • Search Google Scholar
    • Export Citation
  • Schwerdt, R. W., Ho F. P. , and Watkins R. R. , 1979: Meteorological criteria for standard project hurricane and probable maximum hurricane wind fields, Gulf and East Coasts of the United States. NOAA Tech. Rep. NWS 23, 317 pp. [Available online at http://www.nws.noaa.gov/oh/hdsc/Technical_reports/TR23.pdf.]

  • Srock, A. F., and Bosart L. F. , 2009: Heavy precipitation associated with southern Appalachian cold-air damming and Carolina coastal frontogenesis in advance of weak landfalling Tropical Storm Marco (1990). Mon. Wea. Rev., 137, 2448, doi:10.1175/2009MWR2819.1.

    • Search Google Scholar
    • Export Citation
  • Vickery, P., and Skerlj P. , 2005: Hurricane gust factors revisited. J. Struct. Eng., 131, 825832, doi:10.1061/(ASCE)0733-9445(2005)131:5(825).

    • Search Google Scholar
    • Export Citation
  • Walsh, K. J. E., Sandery P. , Brassington G. B. , Entel M. , Siegenthaler-Ledrian C. , Kepert J. D. , and Darbyshire R. , 2010: Constraints on drag and exchange coefficients at extreme wind speeds. J. Geophys. Res., 115, C09007, doi:10.1029/2010JA015748.

    • Search Google Scholar
    • Export Citation
  • Yu, B., and Chowdhury A. G. , 2009: Gust factors and turbulence intensities for the tropical cyclone environment. J. Appl. Meteor. Climatol., 48, 534552, doi:10.1175/2008JAMC1906.1.

    • Search Google Scholar
    • Export Citation
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