K.A. Imhoff and G.S. Young, 2014

ENSO influence on tropical cyclone regional landfall counts

Journal of Operational Meteorology. 3, 126-132

Abstract

A simple linear regression analysis investigates the influence of the El Niño/Southern Oscillation (ENSO) on tropical cyclone counts and regional landfall patterns in the North Atlantic basin. Tropical cyclones from the period 1871–2013 are examined using storm locations from the North Atlantic Hurricane Database. The ENSO phase is determined using several well-known indices—the extended Multivariate ENSO Index (MEI), the MEI, the Bivariate ENSO Index, and the Oceanic Niño Index (ONI). Regression statistics are computed over two time periods: a long-term historical period (1871–2005) and the more recent past (since 1950), the latter being necessary because the ONI and MEI data series do not extend prior to the mid-20th century. Landfall counts were computed over three regions of North America: (i) Canada/United States East Coast, (ii) United States Gulf Coast/Florida, and (iii) Central America/Mexico.

Results of this analysis indicate that the phase of ENSO influences interannual variability in tropical cyclone and landfall counts at a statistically significant level, no matter which index is used. However, the relationship between the phase of ENSO and tropical cyclone landfall counts differs markedly between regions. Relationships between ENSO phase and landfall counts for Central America/Mexico and Canada/ United States East Coast predominantly pass the test of statistical significance for all ENSO indices used, whereas United States Gulf Coast/Florida landfall counts fail the test. The regression slope is correspondingly small for the United States Gulf Coast/Florida. Thus, during El Niño events, when tropical cyclones are less likely to form, smaller decreases in landfall probabilities exist for the United States Gulf Coast/Florida than for Canada/United States East Coast and Central America/Mexico. As a result, landfall activity over the United States Gulf Coast/Florida is less influenced by the ENSO phase than in Central America/Mexico or Canada/United States East Coast.

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