The Effect of the Ocean Eddy on Tropical Cyclone Intensity

Chun-Chieh Wu; Chia-Ying Lee; I-I. Lin

doi:10.1175/jas4051.1

The Effect of the Ocean Eddy on Tropical Cyclone Intensity

Journal of the Atmospheric Sciences ◽

10.1175/jas4051.1 ◽

2007 ◽

Vol 64 (10) ◽

pp. 3562-3578 ◽

Cited By ~ 105

Author(s):

Chun-Chieh Wu ◽

Chia-Ying Lee ◽

I-I. Lin

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Mixed Layer ◽

Thermal Structure ◽

Critical Role ◽

Strong Mixing ◽

Rapid Intensification ◽

Tropical Cyclone Intensity ◽

Cyclone Intensity ◽

The Impact

Abstract The rapid intensification of Hurricane Katrina followed by the devastation of the U.S. Gulf States highlights the critical role played by an upper-oceanic thermal structure (such as the ocean eddy or Loop Current) in affecting the development of tropical cyclones. In this paper, the impact of the ocean eddy on tropical cyclone intensity is investigated using a simple hurricane–ocean coupled model. Numerical experiments with different oceanic thermal structures are designed to elucidate the responses of tropical cyclones to the ocean eddy and the effects of tropical cyclones on the ocean. This simple model shows that rapid intensification occurs as a storm encounters the ocean eddy because of enhanced heat flux. While strong winds usually cause strong mixing in the mixed layer and thus cool down the sea surface, negative feedback to the storm intensity of this kind is limited by the presence of a warm ocean eddy, which provides an insulating effect against the storm-induced mixing and cooling. Two eddy factors, FEDDY-S and FEDDY-T, are defined to evaluate the effect of the eddy on tropical cyclone intensity. The efficiency of the eddy feedback effect depends on both the oceanic structure and other environmental parameters, including properties of the tropical cyclone. Analysis of the functionality of FEDDY-T shows that the mixed layer depth associated with either the large-scale ocean or the eddy is the most important factor in determining the magnitude of eddy feedback effects. Next to them are the storm’s translation speed and the ambient relative humidity.

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Satellite-based monitoring and prediction of tropical cyclone intensity and movement

MAUSAM ◽

10.54302/mausam.v48i2.3965 ◽

2021 ◽

Vol 48 (2) ◽

pp. 157-168

Author(s):

R. R. KELKAR

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Tropical Cyclone Intensity ◽

Intensity Estimation ◽

Cyclone Intensity ◽

Estimation Scheme ◽

Water Vapour Absorption ◽

Upper Level ◽

Absorption Channel ◽

The Impact

ABSTRACT. Capabilities of meteorological satellites have gone a long way in meeting requirements of synoptic analysis and forecasting of tropical cyclones. This paper shows the impact made by the satellite data in the intensity estimation and track prediction of tropical cyclones in the Indian Seas and also reviews the universally applied Dvorak algorithm for performing tropical cyclone intensity analysis. Extensive use of Dvorak's intensity estimation scheme has revealed many of its limitations and elements of subjectivity in the analysis of tropical cyclones over the Arabian Sea and the Bay of Bengal, which, like cyclones in other ocean basins, also exhibit wide structural variability as seen in the satellite imagery. Satellite-based cyclone tracking techniques include: (i) use of satellite-derived mean wind flow, (ii) animation of sequence of satellite images and extrapolation of the apparent motion of the cloud system and (iii) monitoring changes in the upper level moisture patterns in the water vapour absorption channel imagery. Satellite-based techniques on tropical cyclone intensity estimation and track prediction have led to very significant improvement in disaster warning and consequent saving of life and property.

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Precipitation Properties Observed during Tropical Cyclone Intensity Change

Monthly Weather Review ◽

10.1175/mwr-d-15-0065.1 ◽

2015 ◽

Vol 143 (11) ◽

pp. 4476-4492 ◽

Cited By ~ 45

Author(s):

George R. Alvey III ◽

Jonathan Zawislak ◽

Edward Zipser

Keyword(s):

Tropical Cyclone ◽

Passive Microwave ◽

Intensity Change ◽

Rapid Intensification ◽

Relative Importance ◽

Tropical Cyclone Intensity ◽

Cyclone Intensity ◽

East Pacific ◽

Intensity Changes ◽

Strong Convection

Abstract Using a 15-yr (1998–2012) multiplatform dataset of passive microwave satellite data [tropical cyclone–passive microwave (TC-PMW)] for Atlantic and east Pacific storms, this study examines the relative importance of various precipitation properties, specifically convective intensity, symmetry, and area, to the spectrum of intensity changes observed in tropical cyclones. Analyses are presented not only spatially in shear-relative quadrants around the center, but also every 6 h during a 42-h period encompassing 18 h prior to onset of intensification to 24 h after. Compared to those with slower intensification rates, storms with higher intensification rates (including rapid intensification) have more symmetric distributions of precipitation prior to onset of intensification, as well as a greater overall areal coverage of precipitation. The rate of symmetrization prior to, and during, intensification increases with increasing intensity change as rapidly intensifying storms are more symmetric than slowly intensifying storms. While results also clearly show important contributions from strong convection, it is concluded that intensification is more closely related to the evolution of the areal, radial, and symmetric distribution of precipitation that is not necessarily intense.

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The Advanced Dvorak Technique (ADT) for Estimating Tropical Cyclone Intensity: Update and New Capabilities

Weather and Forecasting ◽

10.1175/waf-d-19-0007.1 ◽

2019 ◽

Vol 34 (4) ◽

pp. 905-922 ◽

Cited By ~ 14

Author(s):

Timothy L. Olander ◽

Christopher S. Velden

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Surface Wind ◽

Performance Characteristics ◽

Tropical Cyclone Intensity ◽

Algorithm Development ◽

Intensity Estimation ◽

Development Team ◽

Cyclone Intensity ◽

Estimation Scheme

Abstract The advanced Dvorak technique (ADT) is used operationally by tropical cyclone forecast centers worldwide to help estimate the intensity of tropical cyclones (TCs) from operational geostationary meteorological satellites. New enhancements to the objective ADT have been implemented by the algorithm development team to further expand its capabilities and precision. The advancements include the following: 1) finer tuning to aircraft-based TC intensity estimates in an expanded development sample, 2) the incorporation of satellite-based microwave information into the intensity estimation scheme, 3) more sophisticated automated TC center-fixing routines, 4) adjustments to the intensity estimates for subtropical systems and TCs undergoing extratropical transition, and 5) addition of a surface wind radii estimation routine. The goals of these upgrades and others are to provide TC analysts/forecasters with an expanded objective guidance tool to more accurately estimate the intensity of TCs and those storms forming from, or converting into, hybrid/nontropical systems. The 2018 TC season is used to illustrate the performance characteristics of the upgraded ADT.

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The Impact of Targeted Dropwindsonde Observations on Tropical Cyclone Intensity Forecasts of Four Weak Systems during PREDICT

Monthly Weather Review ◽

10.1175/mwr-d-13-00284.1 ◽

2014 ◽

Vol 142 (8) ◽

pp. 2860-2878 ◽

Cited By ~ 14

Author(s):

Ryan D. Torn

Keyword(s):

Tropical Cyclone ◽

Meridional Wind ◽

Horizontal Wind ◽

Small Subset ◽

Tropical Cyclone Intensity ◽

Ensemble Forecasts ◽

Cyclone Intensity ◽

Intensity Forecast ◽

Tropical Cyclone Intensity Forecasts ◽

The Impact

Abstract The value of assimilating targeted dropwindsonde observations meant to improve tropical cyclone intensity forecasts is evaluated using data collected during the Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) field project and a cycling ensemble Kalman filter. For each of the four initialization times studied, four different sets of Weather Research and Forecasting Model (WRF) ensemble forecasts are produced: one without any dropwindsonde data, one with all dropwindsonde data assimilated, one where a small subset of “targeted” dropwindsondes are identified using the ensemble-based sensitivity method, and a set of randomly selected dropwindsondes. For all four cases, the assimilation of dropwindsondes leads to an improved intensity forecast, with the targeted dropwindsonde experiment recovering at least 80% of the difference between the experiment where all dropwindsondes and no dropwindsondes are assimilated. By contrast, assimilating randomly selected dropwindsondes leads to a smaller impact in three of the four cases. In general, zonal and meridional wind observations at or below 700 hPa have the largest impact on the forecast due to the large sensitivity of the intensity forecast to the horizontal wind components at these levels and relatively large ensemble standard deviation relative to the assumed observation errors.

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Rapid Weakening of Tropical Cyclones in Monsoon Gyres over the Tropical Western North Pacific

Journal of Climate ◽

10.1175/jcli-d-16-0784.1 ◽

2018 ◽

Vol 31 (3) ◽

pp. 1015-1028 ◽

Cited By ~ 9

Author(s):

Jia Liang ◽

Liguang Wu ◽

Guojun Gu

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

North Pacific ◽

Western North Pacific ◽

Large Scale ◽

Vertical Wind Shear ◽

Tropical Cyclone Intensity ◽

Cyclone Intensity ◽

Operational Forecasts ◽

Tropical Western North Pacific

Abstract As one major source of forecasting errors in tropical cyclone intensity, rapid weakening of tropical cyclones [an intensity reduction of 20 kt (1 kt = 0.51 m s−1) or more over a 24-h period] over the tropical open ocean can result from the interaction between tropical cyclones and monsoon gyres. This study aims to examine rapid weakening events occurring in monsoon gyres in the tropical western North Pacific (WNP) basin during May–October 2000–14. Although less than one-third of rapid weakening events happened in the tropical WNP basin south of 25°N, more than 40% of them were associated with monsoon gyres. About 85% of rapid weakening events in monsoon gyres occurred in September and October. The rapid weakening events associated with monsoon gyres are usually observed near the center of monsoon gyres when tropical cyclone tracks make a sudden northward turn. The gyres can enlarge the outer size of tropical cyclones and tend to induce prolonged rapid weakening events with an average duration of 33.2 h. Large-scale environmental factors, including sea surface temperature changes, vertical wind shear, and midlevel environmental humidity, are not primary contributors to them, suggesting the possible effect of monsoon gyres on these rapid weakening events by modulating the tropical cyclone structure. This conclusion is conducive to improving operational forecasts of tropical cyclone intensity.

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Using Mesoscale Simulations to Train Statistical Models of Tropical Cyclone Intensity over Land

Monthly Weather Review ◽

10.1175/2010mwr3079.1 ◽

2010 ◽

Vol 138 (6) ◽

pp. 2058-2073 ◽

Cited By ~ 10

Author(s):

Augustin Colette ◽

Nadja Leith ◽

Vincent Daniel ◽

Enrica Bellone ◽

David S. Nolan

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Statistical Models ◽

Mesoscale Model ◽

Low Frequency ◽

Historical Record ◽

Tropical Cyclone Intensity ◽

Cyclone Intensity ◽

Key Factor ◽

Mesoscale Simulations

Abstract The decay of tropical cyclones after landfall is a key factor in estimating the extent of the hazard overland. Yet our current understanding of this decay is challenged by the low frequency of past events. Consequently, one cannot rely solely upon the historical record when attempting to quantify robustly the inland penetration of tropical cyclones. Thus, a framework designed to complement the historical record of landfalling storms by means of numerical modeling is introduced. Historical meteorological situations that could potentially have led to a landfall on the coast of the Gulf of Mexico are targeted and, using a bogus vortex technique in conjunction with a mesoscale model, a large number of landfalling hurricanes are simulated. The numerical ensemble constitutes a more comprehensive sample of possible landfalling hurricanes: it encompasses the range of events observed in the past but is not constrained to it. This allows us to revisit existing statistical models of the decay of tropical cyclones after landfall. A range of statistical models trained on the numerical ensemble of storms are evaluated on their ability to reproduce the inland decay of historical storms. These models have more skill at predicting tropical cyclone intensity over land than similar models trained exclusively on historical data.

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Observational Evidence for Oceanic Controls on Hurricane Intensity

Journal of Climate ◽

10.1175/2010jcli3763.1 ◽

2011 ◽

Vol 24 (4) ◽

pp. 1138-1153 ◽

Cited By ~ 95

Author(s):

Ian D. Lloyd ◽

Gabriel A. Vecchi

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

North Atlantic ◽

Translation Speed ◽

Ocean Stratification ◽

Cyclone Intensity ◽

The North ◽

Sst Cooling ◽

The North Atlantic ◽

The Impact

Abstract The influence of oceanic changes on tropical cyclone activity is investigated using observational estimates of sea surface temperature (SST), air–sea fluxes, and ocean subsurface thermal structure during the period 1998–2007. SST conditions are examined before, during, and after the passage of tropical cyclones, through Lagrangian composites along cyclone tracks across all ocean basins, with particular focus on the North Atlantic. The influence of translation speed is explored by separating tropical cyclones according to the translation speed divided by the Coriolis parameter. On average for tropical cyclones up to category 2, SST cooling becomes larger as cyclone intensity increases, peaking at 1.8 K in the North Atlantic. Beyond category 2 hurricanes, however, the cooling no longer follows an increasing monotonic relationship with intensity. In the North Atlantic, the cooling for stronger hurricanes decreases, while in other ocean basins the cyclone-induced cooling does not significantly differ from category 2 to category 5 tropical cyclones, with the exception of the South Pacific. Since the SST response is nonmonotonic, with stronger cyclones producing more cooling up to category 2, but producing less or approximately equal cooling for categories 3–5, the observations indicate that oceanic feedbacks can inhibit intensification of cyclones. This result implies that large-scale oceanic conditions are a control on tropical cyclone intensity, since they control oceanic sensitivity to atmospheric forcing. Ocean subsurface thermal data provide additional support for this dependence, showing weaker upper-ocean stratification for stronger tropical cyclones. Intensification is suppressed by strong ocean stratification since it favors large SST cooling, but the ability of tropical cyclones to intensify is less inhibited when stratification is weak and cyclone-induced SST cooling is small. Thus, after accounting for tropical cyclone translation speeds and latitudes, it is argued that reduced cooling under extreme tropical cyclones is the manifestation of the impact of oceanic conditions on the ability of tropical cyclones to intensify.

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Estimating Tropical Cyclone Intensity from Infrared Image Data

Weather and Forecasting ◽

10.1175/waf-d-10-05062.1 ◽

2011 ◽

Vol 26 (5) ◽

pp. 690-698 ◽

Cited By ~ 35

Author(s):

Miguel F. Piñeros ◽

Elizabeth A. Ritchie ◽

J. Scott Tyo

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

Tropical Cyclones ◽

North Atlantic Ocean ◽

Infrared Image ◽

Ocean Basin ◽

Maximum Wind Speed ◽

Tropical Cyclone Intensity ◽

Cyclone Intensity ◽

Maximum Wind

Abstract This paper describes results from a near-real-time objective technique for estimating the intensity of tropical cyclones from satellite infrared imagery in the North Atlantic Ocean basin. The technique quantifies the level of organization or axisymmetry of the infrared cloud signature of a tropical cyclone as an indirect measurement of its maximum wind speed. The final maximum wind speed calculated by the technique is an independent estimate of tropical cyclone intensity. Seventy-eight tropical cyclones from the 2004–09 seasons are used both to train and to test independently the intensity estimation technique. Two independent tests are performed to test the ability of the technique to estimate tropical cyclone intensity accurately. The best results from these tests have a root-mean-square intensity error of between 13 and 15 kt (where 1 kt ≈ 0.5 m s−1) for the two test sets.

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The Response of Tropical Cyclone Intensity to Temperature Profile Change

10.5194/wcd-2021-83 ◽

2022 ◽

Author(s):

James M. Done ◽

Gary M. Lackmann ◽

Andreas F. Prein

Keyword(s):

Tropical Cyclone ◽

Temperature Profile ◽

Tropical Cyclones ◽

Intensity Change ◽

Tropical Cyclone Intensity ◽

Vertical Temperature Profile ◽

Cyclone Intensity ◽

Stratospheric Temperature ◽

Stratospheric Cooling ◽

Profile Change

Abstract. Theory indicates that tropical cyclone intensity should respond to changes in the vertical temperature profile. While the sensitivity of tropical cyclone intensity to sea surface temperature is well understood, less is known about sensitivity to the temperature profile. In this paper, we combine historical data analysis and idealised modelling to explore the extent to which historical tropospheric warming and lower stratospheric cooling can explain observed trends in the tropical cyclone intensity distribution. Observations and modelling agree that historical global temperature profile changes coincide with higher lifetime maximum intensities. But observations suggest the response depends on the tropical cyclone intensity itself. Historical lower- and upper-tropospheric temperatures in hurricane environments have warmed significantly faster than the tropical mean. In addition, hurricane-strength storms have intensified at twice the rate of weaker storms per unit warming at the surface and at 300-hPa. Idealized simulations respond in the expected sense to various imposed changes in the temperature profile and agree with tropical cyclones operating as heat engines. Yet lower stratospheric temperature changes have little influence. Idealised modelling further shows an increasing altitude of the TC outflow but little change in outflow temperature. This enables increased efficiency for strong tropical cyclones despite the warming upper troposphere. Observed sensitivities are generally larger than modelled sensitivities, suggesting that observed tropical cyclone intensity change responds to a combination of the temperature profile change and other environmental factors.

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