Statistical Prediction of Weekly Tropical Cyclone Activity in the Southern Hemisphere
Anne Leroy and Matthew C. Wheeler
2008: Mon. Wea. Rev., 136, 3637-3654.
Abstract
A statistical prediction scheme, employing logistic regression, is
developed to predict the probability of tropical cyclone (TC) formation
in zones of the
Southern Hemisphere during forthcoming weeks. Through physical
reasoning, examination of previous research, and our own initial
analysis, five predictors were chosen for this purpose: one
representing the climatological seasonal cycle of TC activity in
each zone; two representing the eastward propagation of
the Madden-Julian oscillation (MJO); and a further two representing
the leading patterns of interannual sea-surface temperature (SST)
variability in the Indo-Pacific. Cross-validated hindcasts were
generated being careful to use the predictors at lags that replicate
what can be performed in real time. All predictors contribute
significantly to the skill of the hindcasts for at least some leads in
the majority of zones. In particular, we find that inclusion of indices
of the MJO as predictors leads to increased skill out to about the third
week. Beyond the third week, the skill asymptotes to that which can be
achieved through consideration of the seasonal cycle and interannual
variability alone. Further, we demonstrate the importance of a
simple consideration of the seasonal cycle of TC activity for
intraseasonal TC prediction, for all forecast leads.