A global spatiotemporal analysis of inland tropical cyclone maintenance or intensification

Abstract

Forecasting tropical cyclone (TC) intensity changes over land is complicated by interactions of various surface and atmospheric features. Due to generally unfavorable conditions, many TCs weaken and decay soon after landfall. In some cases, TCs may also transition to extratropical cyclones (ETs). Despite the absence of oceanic forcing, a number of TCs have been observed to maintain or increase strength inland, termed "tropical cyclone maintenance or intensification' (TCMIs). This study identifies the environments and characteristic features of TCMIs and explores physical processes that may help to produce an atmosphere conducive for tropical systems. The objectives are to compile an inland TC dataset over a 30-year period, quantify TC traits that may relate to maximum strength over land, and analyse surface and atmospheric conditions leading up to intensification. Of 227 inland TCs globally, 45 maintained or increased strength inland: 17 cold-core (ET), 16 warm-core (TCMI), and 12 hybrid cases. Analysis of synoptic conditions indicates that TCs persist when low-level temperature gradients are weak. Soil moisture gradients were in the vicinity of the cyclones at the time of intensification and may be forcing the TCMIs via increased surface latent heat flux (LHF). The areaaveraged LHF threshold is found to be around 70 W m −2 for TCMI occurrence. In the 2 weeks leading up to each TCMI, the LHF tends to be higher than average over the intensification regions and provides further evidence of land surface forcing.

Spatial characteristics of storm‐total rainfall swaths associated with tropical cyclones over the Eastern United States

“…Thus, we categorized the TCs landfalls into three regions including the Gulf Coast from Texas to Alabama, Florida, and the East Coast from Georgia to Maine (Jagger and Elsner, , ) (Figure ). Tropical cyclones in the Gulf Coast category are expected to move poleward and interact with the relatively dry environment of the mid United States if they do not dissipate shortly after landfall (Kimball, ; Andersen and Shepherd, ), and it should be possible to measure rainfall extent on both sides of the track in most cases. Many TCs making landfall over Florida spend a short amount of time over land and cross back over the ocean without dissipating over land.…”

“…First, TCs were divided into tropical depressions (TD), tropical storms (TS), and hurricanes (HU) according to intensity at the best‐track position immediately prior to landfall, as Konrad and Perry () found a positive correlation between intensity and rainfall pattern over land. As TCs move inland, they might re‐intensify due to the ET process, approaching coastline, or favourable surface conditions (Klein et al ., , Andersen and Shepherd, ). Those TCs which experienced reintensification over land were expected to have increasing left widths due to their structures becoming more symmetrical as moisture is advected to the left side.…”

Seasonal tropical cyclone precipitation in Texas: A statistical modeling approach based on a 60 year climatology

“…This is likely due to uncertainty in the locations of cyclogenesis, and the regional scale employed in this study. There are also many other factors possibly affecting the amount of rainfall in TCs, such as the environmental water vapor [ Jiang et al ., ], topography [ Wu et al ., ], and interactions with other synoptic systems [ Atallah et al ., ; Andersen and Shepherd , ]. Those additional mechanisms warrant further investigation using both observational and modeling approaches.…”

Influence of Land Cover and Soil Moisture based Brown Ocean Effect on an Extreme Rainfall Event from a Louisiana Gulf Coast Tropical System

“…Occasionally, a “Brown Ocean effect” can contribute to the intensification of tropical cyclones over land 5–9 . The Brown Ocean effect refers to saturated soils, swamps, and wetlands in the inland regions providing a source of moist enthalpy for maintaining tropical cyclone warm-core structures and inland intensification 6,8,10 . Thus, realistic representation of surface enthalpy fluxes is important for accurate model predictions of tropical disturbances over land 11 .…”