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Rapid Intensity Changes of Tropical Cyclones

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A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Meteorology".

Deadline for manuscript submissions: closed (25 January 2021) | Viewed by 34374

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Dr. Sundararaman Gopalakrishnan

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Guest Editor

NOAA/Atlantic Oceanographic and Meteorological Laboratory/Hurricane Research Division, Miami, FL 33149, USA
Interests: hurricanes; next-generation numerical model developments; numerical weather predictions; boundary layer meteorology; LES and dispersion modeling

Dr. Ghassan Alaka

E-Mail Website
Guest Editor

NOAA/Atlantic Oceanographic and Meteorological Laboratory/Hurricane Research Division, Miami, FL 33149, USA
Interests: numerical weather prediction; hurricane genesis; hurricane-hurricane interactions; large-scale dynamics

Special Issue Information

Dear Colleagues,

Timely warning of tropical cyclone (TC) location and strength has the potential to save lives and reduce property damages. TC forecast models have been constantly improving in track predictions since the 1970s. In the North Atlantic Basin, while track errors by 48 hours were on the order of 250 nautical miles in the 1970s and 1980s, and about 150 nautical miles in the 1990s, further reduction of track errors to less than 100 nautical miles during the last decade has been possible due to improved numerical weather prediction models, observations to improve initialization of those models, and above all, advancements in our understanding of the environment in which the TC forms and evolves. The forecast improvement trend has been noticed in 5-day track predictions over the Atlantic and also over other global basins. For instance, the very severe cyclonic storm (VSCS) Phailin (2013) was the strongest cyclone to have hit the eastern coast of the India Odisha state since the super cyclone of 1999. However, there has never been a number of casualties as large as that of 1999, when approximately 10,000 fatalities were reported. Studies have correlated the reduction of loss of lives to improved warnings and better track predictions from numerical models.

Forecasting intensity changes in tropical cyclones is also an important forecast problem and becomes increasingly so especially in the case of storms that rapidly intensify or weaken just prior to landfall (e.g., TCs; Charley, 2004; Katrina and Wilma, 2005; Humberto, 2007; Karl, 2010, Phailin and Lehar, 2013; Michael, 2018; and Dorain, 2019). Evacuation becomes a challenge both when a tropical cyclone rapidly intensifies or if there is a false alarm of a rapidly weakening event. However, forecasting intensity changes in TCs is a complex and challenging multiscale problem. While cloud-resolving numerical models using a horizontal grid resolution of 1–3 km are starting to show results in predicting intensity changes in individual cases, improvements in predicting TC intensity changes have not kept pace with track predictions. Nevertheless, in order to address the intensity forecast problem, the National Oceanic and Atmospheric Administration (NOAA) created the Hurricane Forecast Improvement Program (HFIP) in 2009. The high-resolution Hurricane Weather Research and Forecasting (HWRF) system was created under this program. The HWRF system is showing some promise in removing the initial roadblocks associated with predicting intensity changes, dynamical prediction of which was nearly non-existent until 2009. Over the Atlantic basin, the model has shown about 20% improvements in intensity guidance. Similarly, the National Center for Atmospheric Research’s (NCAR’s) Weather Research and Forecasting (WRF) model has been used by the university community to gain some basic understanding on the TC intensification problem. Nevertheless, rapid intensification (RI), as measured by growth of the storm strength by 30 knots in 24 hours, as well as rapid dissipation of TCs, continues to be a great challenge to the forecasting community. For the most part, the lack of improvement in RI forecast ability is rooted in our lack of understanding of when and how RI occurs in different environmental conditions and the historic inability of dynamical models to accurately predict not only convection in the hurricane core, but also large-scale environmental factors such as shear and moisture that produce an RI event. We will dedicate this Special Volume of the journal Atmosphere to provide state-of-the-art and next generation efforts to advance our understanding of the TC rapid intensification and weakening problem.

Dr. Sundararaman Gopalakrishnan
Dr. Ghassan Alaka
Guest Editors

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Keywords

tropical cyclone (TC)
tropical cyclone intensification
rapid intensification (RI)
rapid weakening in TC
numerical weather prediction (NWP)
tropical cyclone forecasting
hurricane weather research and forecasting (HWRF)
multiscale interactions in TCs
cumulus convection
vortical hot towers
rain band
inner-core TC structure
shear

Published Papers (9 papers)

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Research

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28 pages, 10311 KiB

Open AccessEditor’s ChoiceArticle

Relationship between Early-Stage Features and Lifetime Maximum Intensity of Tropical Cyclones over the Western North Pacific

by Ren Lu and Xiaodong Tang

Atmosphere 2021, 12(7), 815; https://doi.org/10.3390/atmos12070815 - 24 Jun 2021

Cited by 2 | Viewed by 2839

Abstract

The relationship between early-stage features and lifetime maximum intensity (LMI) of tropical cyclones (TCs) over the Western North Pacific (WNP) was investigated by ensemble machine learning methods and composite analysis in this study. By selecting key features of TCs’ vortex attributes and environmental conditions, a two-step AdaBoost model demonstrated accuracy of about 75% in distinguishing weak and strong TCs at genesis and a coefficient of determination (

R^{2}

) of 0.30 for LMI estimation from the early stage of strong TCs, suggesting an underlying relationship between LMI and early-stage features. The composite analysis reveals that TCs with higher LMI are characterized by lower latitude embedded in a continuous band of high low-troposphere vorticity, more compact circulation at both the upper and lower levels of the troposphere, stronger circulation at the mid-troposphere, a higher outflow layer with stronger convection, a more symmetrical structure of high-level moisture distribution, a slower translation speed, and a greater intensification rate around genesis. Specifically, TCs with greater “tightness” at genesis may have a better chance of strengthening to major TCs (LMI ≥ 96 kt), since it represents a combination of the inner and outer-core wind structure related to TCs’ rapid intensification and eyewall replacement cycle. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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20 pages, 3714 KiB

Open AccessArticle

Can a Warm Ocean Feature Cause a Typhoon to Intensify Rapidly?

by Leo Oey and Shimin Huang

Atmosphere 2021, 12(6), 797; https://doi.org/10.3390/atmos12060797 - 21 Jun 2021

Cited by 3 | Viewed by 4317

Abstract

The hypothesis that a warm ocean feature (WOF) such as a warm eddy may cause a passing typhoon to undergo rapid intensification (RI), that is, the storm’s maximum 1-min wind speed at 10-m height increases by more than 15.4 m/s in 1 day, is of interest to forecasters. Testing the hypothesis is a challenge, however. Besides the storm’s internal dynamics, typhoon intensity depends on other environmental factors such as vertical wind shear and storm translation. Here we designed numerical experiments that exclude these other factors, retaining only the WOF’s influence on the storm’s intensity change. We use a storm’s translation speed U_h = 5 m/s when surface cooling is predominantly due to 1D vertical mixing. Observations have shown that the vast majority (70%) of RI events occur in storms that translate between 3 to 7 m/s. We conducted a large ensemble of twin experiments with and without ocean feedback and with and without the WOF to estimate model uncertainty due to internal variability. The results show that the WOF increases surface enthalpy flux and moisture convergence in the storm’s core, resulting in stronger updrafts and intensity. However, the intensification rate is, in general, insufficiently rapid. Consequently, the number of RIs is not statistically significantly different between simulations with and without the WOF. An analytical coupled model supports the numerical findings. Furthermore, it shows that WOF-induced RI can develop only over eddies and ambient waters that are a few °C warmer than presently observed in the ocean. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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27 pages, 6836 KiB

Open AccessArticle

Operational Forecasting of Tropical Cyclone Rapid Intensification at the National Hurricane Center

by Mark DeMaria, James L. Franklin, Matthew J. Onderlinde and John Kaplan

Atmosphere 2021, 12(6), 683; https://doi.org/10.3390/atmos12060683 - 26 May 2021

Cited by 47 | Viewed by 6600

Abstract

Although some recent progress has been made in operational tropical cyclone (TC) intensity forecasting, the prediction of rapid intensification (RI) remains a challenging problem. To document RI forecast progress, deterministic and probabilistic operational intensity models used by the National Hurricane Center (NHC) are briefly reviewed. Results show that none of the deterministic models had RI utility from 1991 to about 2015 due to very low probability of detection, very high false alarm ratio, or both. Some ability to forecast RI has emerged since 2015, with dynamical models being the best guidance for the Atlantic and statistical models the best RI guidance for the eastern North Pacific. The first probabilistic RI guidance became available in 2001, with several upgrades since then leading to modest skill in recent years. A tool introduced in 2018 (DTOPS) is currently the most skillful among NHC’s probabilistic RI guidance. To measure programmatic progress in forecasting RI, the Hurricane Forecast Improvement Program has introduced a new RI metric that uses the traditional mean absolute error but restricts the sample to only those cases where RI occurred in the verifying best track or was forecast. By this metric, RI forecasts have improved by ~20–25% since the 2015–2017 baseline period. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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22 pages, 20329 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Role of Mean and Eddy Momentum Transport in the Rapid Intensification of Hurricane Irma (2017) and Hurricane Michael (2018)

by Alrick Green, Sundararaman G. Gopalakrishnan, Ghassan J. Alaka, Jr. and Sen Chiao

Atmosphere 2021, 12(4), 492; https://doi.org/10.3390/atmos12040492 - 14 Apr 2021

Cited by 4 | Viewed by 2848

Abstract

The prediction of rapid intensification (RI) in tropical cyclones (TCs) is a challenging problem. In this study, the RI process and factors contributing to it are compared for two TCs: an axis-symmetric case (Hurricane Irma, 2017) and an asymmetric case (Hurricane Michael, 2018). Both Irma and Michael became major hurricanes that made significant impacts in the United States. The Hurricane Weather Research and Forecasting (HWRF) Model was used to examine the connection between RI with forcing from the large-scale environment and the subsequent evolution of TC structure and convection. The observed large-scale environment was reasonably reproduced by HWRF forecasts. Hurricane Irma rapidly intensified in an environment with weak-to-moderate vertical wind shear (VWS), typically favorable for RI, leading to the symmetric development of vortical convective clouds in the cyclonic, vorticity-rich environment. Conversely, Hurricane Michael rapidly intensified in an environment of strong VWS, typically unfavorable for RI, leading to major asymmetries in the development of vortical convective clouds. The tangential wind momentum budget was analyzed for these two hurricanes to identify similarities and differences in the pathways to RI. Results suggest that eddy transport terms associated with convective processes positively contributed to vortex spin up in the early stages of RI and inhibited spin up in the later stages of RI in both TCs. In the early stages of RI, the mean transport terms exhibited notable differences in these TCs; they dominated the spin-up process in Irma and were of secondary importance to the spin-up process in Michael. Favorable aspects of the environment surrounding Michael appeared to aid in the RI process despite hostile VWS. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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19 pages, 1387 KiB

Open AccessEditor’s ChoiceArticle

Validation of Ensemble-Based Probabilistic Tropical Cyclone Intensity Change

by Ryan D. Torn and Mark DeMaria

Atmosphere 2021, 12(3), 373; https://doi.org/10.3390/atmos12030373 - 12 Mar 2021

Cited by 4 | Viewed by 2137

Abstract

Although there has been substantial improvement to numerical weather prediction models, accurate predictions of tropical cyclone rapid intensification (RI) remain elusive. The processes that govern RI, such as convection, may be inherently less predictable; therefore a probabilistic approach should be adopted. Although there have been numerous studies that have evaluated probabilistic intensity (i.e., maximum wind speed) forecasts from high resolution models, or statistical RI predictions, there has not been a comprehensive analysis of high-resolution ensemble predictions of various intensity change thresholds. Here, ensemble-based probabilities of various intensity changes are computed from experimental Hurricane Weather Research and Forecasting (HWRF) and Hurricanes in a Multi-scale Ocean-coupled Non-hydrostatic (HMON) models that were run for select cases during the 2017–2019 seasons and verified against best track data. Both the HWRF and HMON ensemble systems simulate intensity changes consistent with RI (30 knots 24 h

^{- 1}

; 15.4 m s

^{- 1}

24 h

^{- 1}

) less frequent than observed, do not provide reliable probabilistic predictions, and are less skillful probabilistic forecasts relative to the Statistical Hurricane Intensity Prediction System Rapid Intensification Index (SHIPS-RII) and Deterministic to Probabilistic Statistical (DTOPS) statistical-dynamical systems. This issue is partly alleviated by applying a quantile-based bias correction scheme that preferentially adjusts the model-based intensity change at the upper-end of intensity changes. While such an approach works well for high-resolution models, this bias correction strategy does not substantially improve ECMWF ensemble-based probabilistic predictions. By contrast, both the HWRF and HMON systems provide generally reliable predictions of intensity changes for cases where RI does not take place. Combining the members from the HWRF and HMON ensemble systems into a large multi-model ensemble does not improve upon HMON probablistic forecasts. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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18 pages, 5005 KiB

Open AccessArticle

Sensitivity of an Idealized Tropical Cyclone to the Configuration of the Global Forecast System–Eddy Diffusivity Mass Flux Planetary Boundary Layer Scheme

by Evan A. Kalina, Mrinal K. Biswas, Jun A. Zhang and Kathryn M. Newman

Atmosphere 2021, 12(2), 284; https://doi.org/10.3390/atmos12020284 - 23 Feb 2021

Cited by 6 | Viewed by 1996

Abstract

The intensity and structure of simulated tropical cyclones (TCs) are known to be sensitive to the planetary boundary layer (PBL) parameterization in numerical weather prediction models. In this paper, we use an idealized version of the Hurricane Weather Research and Forecast system (HWRF) with constant sea-surface temperature (SST) to examine how the configuration of the PBL scheme used in the operational HWRF affects TC intensity change (including rapid intensification) and structure. The configuration changes explored in this study include disabling non-local vertical mixing, changing the coefficients in the stability functions for momentum and heat, and directly modifying the Prandtl number (Pr), which controls the ratio of momentum to heat and moisture exchange in the PBL. Relative to the control simulation, disabling non-local mixing produced a ~15% larger storm that intensified more gradually, while changing the coefficient values used in the stability functions had little effect. Varying Pr within the PBL had the greatest impact, with the largest Pr (~1.6 versus ~0.8) associated with more rapid intensification (~38 versus 29 m s⁻¹ per day) but a 5–10 m s⁻¹ weaker intensity after the initial period of strengthening. This seemingly paradoxical result is likely due to a decrease in the radius of maximum wind (~15 versus 20 km), but smaller enthalpy fluxes, in simulated storms with larger Pr. These results underscore the importance of measuring the vertical eddy diffusivities of momentum, heat, and moisture under high-wind, open-ocean conditions to reduce uncertainty in Pr in the TC PBL. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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15 pages, 6881 KiB

Open AccessArticle

The Influence of Environments on the Intensity Change of Typhoon Soudelor

by Leo Oey and Yuchen Lin

Atmosphere 2021, 12(2), 162; https://doi.org/10.3390/atmos12020162 - 27 Jan 2021

Cited by 6 | Viewed by 2651

Abstract

Previous studies have shown that background oceanic and atmospheric environments can influence not only the formation but also the intensity of tropical cyclones. Typhoon Soudelor in August 2015 is notable in that it underwent two rapid intensifications as the storm passed over the Philippine Sea where the 26 °C isotherm (Z₂₆) was deeper than 100 m and warm eddies abounded. At the same time, prior to the storm’s arrival, an anomalous upper-level anticyclone developed south of Japan and created a weakened vertical wind shear (V_s) environment that extended into the Philippine Sea. This study examines how the rapid intensification of Typhoon Soudelor may be related to the observed variations of Z₂₆, V_s and other environmental fields as the storm crossed over them. A regression analysis indicates that the contribution to Soudelor’s intensity variation from V_s is the largest (62%), followed by Z₂₆ (27%) and others. Further analyses using composites then indicate that the weak vertical wind shear produced by the aforementioned anomalous anticyclone is a robust feature in the western North Pacific during the developing summer of strong El Ninos with Oceanic Nino Index (ONI) > 1.5. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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26 pages, 12130 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Processes Causing the Early Intensification of Hurricane Dorian through an Ensemble of the Hurricane Analysis and Forecast System (HAFS)

by Andrew Hazelton, Ghassan J. Alaka, Jr., Levi Cowan, Michael Fischer and Sundararaman Gopalakrishnan

Atmosphere 2021, 12(1), 93; https://doi.org/10.3390/atmos12010093 - 10 Jan 2021

Cited by 8 | Viewed by 3968

Abstract

The early stages of a tropical cyclone can be a challenge to forecast, as a storm consolidates and begins to grow based on the local and environmental conditions. A high-resolution ensemble of the Hurricane Analysis and Forecast System (HAFS) is used to study the early intensification of Hurricane Dorian, a catastrophic 2019 storm in which the early period proved challenging for forecasters. There was a clear connection in the ensemble between early storm track and intensity: stronger members moved more northeast initially, although this result did not have much impact on the long-term track. The ensemble results show several key factors determining the early evolution of Dorian. Large-scale divergence northeast of the tropical cyclone (TC) appeared to favor intensification, and this structure was present at model initialization. There was also greater moisture northeast of the TC for stronger members at initialization, favoring more intensification and downshear development of the circulation as these members evolved. This study highlights the complex interplay between synoptic and storm scale processes in the development and intensification of early-stage tropical cyclones. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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Review

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36 pages, 57857 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Our Understanding of Tropical Cyclone Intensity Change Processes from Airborne Observations

by Robert F. Rogers

Atmosphere 2021, 12(5), 650; https://doi.org/10.3390/atmos12050650 - 19 May 2021

Cited by 13 | Viewed by 5044

Abstract

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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