The 2009 Hurricane Season in the Eastern North Pacific Basin: An Analysis of Environmental Conditions

Jennifer M. Collins Department of Geography, University of South Florida, Tampa, Florida

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David R. Roache Department of Geography, University of South Florida, Tampa, Florida

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Abstract

Despite the presence of an intensifying El Niño event, the 2009 eastern North Pacific hurricane season was near normal when considering overall hurricane activity. This is in contrast to the relative lull in activity observed between 1998 and 2008. Previous research has noted that the eastern North Pacific should be subdivided into two development regions, the western development region (WDR; 10°–20°N, 116°W–180°) and the eastern development region (EDR; 10°–20°N, North American coastline to 115.9°W), when examining interannual hurricane variability. In 2009, the EDR saw below average numbers of tropical cyclones of all intensities, while the WDR saw near-normal activity. However, activity in both regions varied sharply from month to month with periods of high activity in August and October and lower activity in July and September. This monthly variability was also observed in primary environmental forcing factors such as total precipitable water, tropospheric vertical wind shear, and low-level relative vorticity, particularly for the WDR. This variability was obscured by simply examining seasonal means. It is shown that for the 2009 season, large-scale environmental factors forced by the El Niño event and two cycles of the Madden–Julian oscillation contributed strongly to the observed patterns of cyclone activity across the basin.

Corresponding author address: Jennifer M. Collins, Department of Geography, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620. E-mail: collinsjm@usf.edu

Abstract

Despite the presence of an intensifying El Niño event, the 2009 eastern North Pacific hurricane season was near normal when considering overall hurricane activity. This is in contrast to the relative lull in activity observed between 1998 and 2008. Previous research has noted that the eastern North Pacific should be subdivided into two development regions, the western development region (WDR; 10°–20°N, 116°W–180°) and the eastern development region (EDR; 10°–20°N, North American coastline to 115.9°W), when examining interannual hurricane variability. In 2009, the EDR saw below average numbers of tropical cyclones of all intensities, while the WDR saw near-normal activity. However, activity in both regions varied sharply from month to month with periods of high activity in August and October and lower activity in July and September. This monthly variability was also observed in primary environmental forcing factors such as total precipitable water, tropospheric vertical wind shear, and low-level relative vorticity, particularly for the WDR. This variability was obscured by simply examining seasonal means. It is shown that for the 2009 season, large-scale environmental factors forced by the El Niño event and two cycles of the Madden–Julian oscillation contributed strongly to the observed patterns of cyclone activity across the basin.

Corresponding author address: Jennifer M. Collins, Department of Geography, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620. E-mail: collinsjm@usf.edu
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  • Allan, R. J., N. Nicholls, P. D. Jones, and I. J. Butterworth, 1991: A further extension of the Tahiti–Darwin SOI, early ENSO events and Darwin pressure. J. Climate, 4, 743749.

    • Search Google Scholar
    • Export Citation
  • Bell, G. D., and Coauthors, 2000: Climate assessment for 1999. Bull. Amer. Meteor. Soc., 81, S1S50.

  • Brown, G. M., and P. W. Leftwich, 1982: A compilation of eastern and central North Pacific tropical cyclone data. NOAA Tech. Memo. NWS NHC 16, 13 pp.

    • Search Google Scholar
    • Export Citation
  • Camargo, S., A. W. Robertson, A. G. Barnston, and M. Ghil, 2008: Clustering of eastern North Pacific tropical cyclone tracks: ENSO and MJO effects. Geochem. Geophys. Geosyst., 9, Q06V05, doi:10.1029/2007GC001861.

    • Search Google Scholar
    • Export Citation
  • Collins, J. M., 2007: The relationship of ENSO and relative humidity to interannual variations of hurricane frequency in the north-east Pacific Ocean. Pap. Appl. Geogr. Conf., 30, 324333.

    • Search Google Scholar
    • Export Citation
  • Collins, J. M., and I. M. Mason, 2000: Local environmental conditions related to seasonal tropical cyclone activity in the northeast Pacific basin. Geophys. Res. Lett., 27, 38813884.

    • Search Google Scholar
    • Export Citation
  • CPC, cited 2009: ENSO impacts on the U.S.: Cold and warm episodes by season. Climate Prediction Center. [Available online at www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml.]

    • Search Google Scholar
    • Export Citation
  • Dvorak, V. F., 1975: Tropical cyclone intensity analysis and forecasting from satellite imagery. Mon. Wea. Rev., 103, 420430.

  • Gray, W. M., 1979: Hurricanes: Their formation, structure and likely role in the tropical circulation. Supplement to Meteorology over the Tropical Oceans, D. B. Shaw, Ed., Royal Meteorological Society, 155–218.

    • Search Google Scholar
    • Export Citation
  • Gray, W. M., C. W. Landsea, P. W. Mielke Jr., and K. J. Berry, 1994: Predicting Atlantic basin seasonal tropical cyclone activity by 1 June. Wea. Forecasting, 9, 103115.

    • Search Google Scholar
    • Export Citation
  • Hendon, H. H., and M. L. Salby, 1994: The life cycle of the Madden–Julian oscillation. J. Atmos. Sci., 51, 22252237.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437471.

  • Kessler, W. S., 2001: EOF representations of the Madden–Julian oscillation and its connection with ENSO. J. Climate, 14, 30553061.

  • Madden, R. A., and P. R. Julian, 1971: Detection of a 40–50 day oscillation in the zonal wind in the tropical Pacific. J. Atmos. Sci., 28, 702708.

    • Search Google Scholar
    • Export Citation
  • Madden, R. A., and P. R. Julian, 1994: Observations of the 40–50-day tropical oscillation—A review. Mon. Wea. Rev., 122, 814837.

  • Maloney, E. D., and D. L. Hartmann, 2000: Modulation of eastern North Pacific hurricanes by the Madden–Julian oscillation. J. Climate, 13, 14511460.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., and D. Vollaro, 2000: Planetary- and synoptic-scale influences on eastern Pacific tropical cyclogenesis. Mon. Wea. Rev., 128, 32963307.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., D. Knight, M. Dickinson, D. Vollaro, and S. Skubis, 1997: Potential vorticity, easterly waves, and eastern Pacific tropical cyclogenesis. Mon. Wea. Rev., 125, 26992708.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., D. Vollaro, S. Skubis, and M. Dickinson, 2000: Origins and mechanisms of eastern Pacific tropical cyclogenesis: A case study. Mon. Wea. Rev., 128, 125139.

    • Search Google Scholar
    • Export Citation
  • Namias, J., 1954: Long range factors affecting the genesis and paths of tropical cyclones. Proc. UNESCO Symp. on Typhoons, Tokyo, Japan, UNESCO, 213–219.

    • Search Google Scholar
    • Export Citation
  • Palmén, E., 1948: On the formation and structure of tropical hurricanes. Geophysica, 3, 2638.

  • Rasmusson, E. G., and T. H. Carpenter, 1982: Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño. Mon. Wea. Rev., 110, 354384.

    • Search Google Scholar
    • Export Citation
  • Riehl, H., 1954: Tropical Meteorology. McGraw-Hill, 392 pp.

  • TPC, cited 2010: Northeast Pacific tropical cyclone best-track file. NOAA/NWS/Tropical Prediction Center. [Available online at ftp://ftp.nhc.noaa.gov.pub/tracks/tracks.epa.]

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1997: The definition of El Niño. Bull. Amer. Meteor. Soc., 78, 27712777.

  • Trenberth, K. E., and D. P. Stepaniak, 2001: Indices of El Niño evolution. J. Climate, 14, 16971701.

  • Wang, C., 2002: Atmospheric circulation cells associated with the El Niño–Southern Oscillation. J. Climate, 15, 399419.

  • Whitney, L. D., and J. S. Hobgood, 1997: The relationship between sea surface temperatures and maximum intensities of tropical cyclones in the eastern North Pacific Ocean. J. Climate, 10, 29212930.

    • Search Google Scholar
    • Export Citation
  • Wolter, K., and M. S. Timlin, 1993: Monitoring ENSO in COADS with a seasonally adjusted principal component index. Proc. 17th Climate Diagnostics Workshop, Norman, OK, NOAA, 52–57.

    • Search Google Scholar
    • Export Citation
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