In this work we consider a helical flow organization on small and large space scales in a forming tropical cyclone and offer a quantitative analysis for early stages in evolution of large-scale helical vortex based on diagnosis of a set of integral helical and energetic characteristics. Using the data from a near cloud-resolving numerical simulation by Regional Atmospheric Modeling System (RAMS...

The influence of the El Niño–Southern Oscillation (ENSO) on tropical cyclone intensity in the western North Pacific basin is examined. Accumulated cyclone energy (ACE), constructed from the best-track dataset for the region for the period 1950–2002, and other related variables are analyzed. ACE is positively correlated with ENSO indices. This and other statistics of the interannually varying tr...

A physics-based statistical stochastic system is developed for estimating the long-term hazard of rare, high impact landfall events globally from ensembles of synthetic tropical cyclones. There are three components representing the complete storm lifetime: an index-based genesis model, a beta-advection track model and an autoregressive intensity model. All three components depend upon the local...

[1] It is known that in deep and open oceans, the effect of sea surface sensible and evaporative heat fluxes on the tropical cyclone-induced sea surface cooling is small compared to that caused by turbulent mixing and cold water entrainment into the upper ocean mixed-layer. This study shows that tropical cyclone-induced surface heat fluxes dominate the surface cooling in near-coastal shallow oc...

Despite decades of theoretical research and observational studies, a good understanding of Tropical Cyclone Genesis (TCG) remains elusive. One recent theory proposes TCG is contingent upon a necessary condition in the lower tropospheric levels whereby a closed circulation exists in a Lagrangian framework forming a protective region for genesis. This thesis work contends that while lower-troposp...

Atlantic basin increased markedly in the years 1995– 2000, compared with levels in the 1970s and 1980s. For example, the accumulated cyclone energy (ACE) index in the At lantic has been above the 1951–2000 median for all years from 1995 to 2005 except for the El Niño years of 1997 and 2002 (e.g., Bell et al. 2006). The increase in activity since the early 1980s has been confirmed using homogeni...

[1] Both El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO) have previously been documented to impact Atlantic basin tropical cyclone (TC) activity through alterations in large-scale fields such as vertical wind shear, mid-level moisture, sea level pressure and sea surface temperature. Atlantic TC activity has been shown to be enhanced when La Niña conditions are presen...

Tropical cyclogenesis is attributed to an equatorial wave when the filtered rainfall anomaly exceeds a threshold value at the genesis location. It is argued that 0 mm day (simply requiring a positive anomaly) is too small a threshold because unrelated noise can produce a positive anomaly. A threshold of 6 mm day is too large because two-thirds of storms would have no precursor disturbance. Betw...

Tropical cyclone (TC) tornadoes represent a relatively small subset of total tornado reports, but garner specialized attention in applied research and operational forecasting because of their distinctive origin within the envelope of either a landfalling or remnant TC. As with midlatitude weather systems, the predominant vehicle for tornadogenesis in TCs appears to be the supercell, particularl...

The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but th...