scholarly journals Synoptic-Scale Precursors to Tropical Cyclone Rapid Intensification in the Atlantic Basin

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Alexandria Grimes ◽  
Andrew E. Mercer
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Potential Temperature ◽  
Vertical Shear ◽  
Specific Humidity ◽  
Support Vector ◽  
Rapid Intensification ◽  
Synoptic Scale ◽  
Atlantic Basin ◽  
And Cluster Analysis

Forecasting rapid intensification (hereafter referred to as RI) of tropical cyclones in the Atlantic Basin is still a challenge due to a limited understanding of the meteorological processes that are necessary for predicting RI. To address this challenge, this study considered large-scale processes as RI indicators within tropical cyclone environments. The large-scale processes were identified by formulating composite map types of RI and non-RI storms using NASA MERRA data from 1979 to 2009. The composite fields were formulated by a blended RPCA and cluster analysis approach, yielding multiple map types of RI’s and non-RI’s. Additionally, statistical differences in the large-scale processes were identified by formulating permutation tests, based on the composite output, revealing variables that were statistically significantly distinct between RI and non-RI storms. These variables were used as input in two prediction schemes: logistic regression and support vector machine classification. Ultimately, the approach identified midlevel vorticity, pressure vertical velocity, 200–850 hPa vertical shear, low-level potential temperature, and specific humidity as the most significant in diagnosing RI, yielding modest skill in identifying RI storms.

A Revised Tropical Cyclone Rapid Intensification Index for the Atlantic and Eastern North Pacific Basins

2010 ◽  
Vol 25 (1) ◽  
pp. 220-241 ◽  
Author(s):  
John Kaplan ◽  
Mark DeMaria ◽  
John A. Knaff
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Inner Core ◽  
Probability Of Detection ◽  
Vertical Shear ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Atlantic Basin ◽  
Linear Discriminant ◽  
Intensity Index

Abstract A revised rapid intensity index (RII) is developed for the Atlantic and eastern North Pacific basins. The RII uses large-scale predictors from the Statistical Hurricane Intensity Prediction Scheme (SHIPS) to estimate the probability of rapid intensification (RI) over the succeeding 24 h utilizing linear discriminant analysis. Separate versions of the RII are developed for the 25-, 30-, and 35-kt RI thresholds, which represent the 90th (88th), 94th (92nd), and 97th (94th) percentiles of 24-h overwater intensity changes of tropical and subtropical cyclones in the Atlantic (eastern North Pacific) basins from 1989 to 2006, respectively. The revised RII became operational at the NHC prior to the 2008 hurricane season. The relative importance of the individual RI predictors is shown to differ between the two basins. Specifically, the previous 12-h intensity change, upper-level divergence, and vertical shear have the highest weights for the Atlantic basin, while the previous 12-h intensity change, symmetry of inner-core convection, and the difference in a system’s current and maximum potential intensity are weighted highest in the eastern North Pacific basin. A verification of independent forecasts from the 2006 and 2007 hurricane seasons shows that the probabilistic RII forecasts are generally skillful in both basins when compared to climatology. Moreover, when employed in a deterministic manner, the RII forecasts were superior to all other available operational intensity guidance in terms of the probability of detection (POD) and false alarm ratio (FAR). Specifically, the POD for the RII ranged from 15% to 59% (53% to 73%) while the FAR ranged from 71% to 85% (53% to 79%) in the Atlantic (eastern North Pacific) basins, respectively, for the three RI thresholds studied. Nevertheless, the modest POD and relatively high FAR of the RII and other intensity guidance demonstrate the difficulty of predicting RI, particularly in the Atlantic basin.

Response of Tropical Cyclone Potential Intensity to a Global Warming Scenario in the IPCC AR4 CGCMs

2010 ◽  
Vol 23 (6) ◽  
pp. 1354-1373 ◽  
Author(s):  
Jinhua Yu ◽  
Yuqing Wang ◽  
Kevin Hamilton
Keyword(s):  
Global Warming ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Linear Trend ◽  
Relative Effect ◽  
Vertical Shear ◽  
Model Parameters ◽  
Climate Projections ◽  
South Indian ◽  
Projected Changes

Abstract This paper reports on an analysis of the tropical cyclone (TC) potential intensity (PI) and its control parameters in transient global warming simulations. Specifically, the TC PI is calculated for phase 3 of the Coupled Model Intercomparison Project (CMIP3) integrations during the first 70 yr of a transient run forced by a 1% yr−1 CO2 increase. The linear trend over the period is used to project a 70-yr change in relevant model parameters. The results for a 15-model ensemble-mean climate projection show that the thermodynamic potential intensity (THPI) increases on average by 1.0% to ∼3.1% over various TC basins, which is mainly attributed to changes in the disequilibrium in enthalpy between the ocean and atmosphere in the transient response to increasing CO2 concentrations. This modest projected increase in THPI is consistent with that found in other recent studies. In this paper the effects of evolving large-scale dynamical factors on the projected TC PI are also quantified, using an empirical formation that takes into account the effects of vertical shear and translational speed based on a statistical analysis of present-day observations. Including the dynamical efficiency in the formulation of PI leads to larger projected changes in PI relative to that obtained using just THPI in some basins and smaller projected changes in others. The inclusion of the dynamical efficiency has the largest relative effect in the main development region (MDR) of the North Atlantic, where it leads to a 50% reduction in the projected PI change. Results are also presented for the basin-averaged changes in PI for the climate projections from each of the 15 individual models. There is considerable variation among the results for individual model projections, and for some models the projected increase in PI in the eastern Pacific and south Indian Ocean regions exceeds 10%.

scholarly journals Deep Learning for Spatially Explicit Prediction of Synoptic-Scale Fronts

2019 ◽  
Vol 34 (4) ◽  
pp. 1137-1160 ◽  
Author(s):  
Ryan Lagerquist ◽  
Amy McGovern ◽  
David John Gagne II
Keyword(s):  
Deep Learning ◽  
Weather Prediction ◽  
Potential Temperature ◽  
Probability Of Detection ◽  
Neural Nets ◽  
Specific Humidity ◽  
Synoptic Scale ◽  
Cold Fronts ◽  
Critical Success ◽  
The North

AbstractThis paper describes the use of convolutional neural nets (CNN), a type of deep learning, to identify fronts in gridded data, followed by a novel postprocessing method that converts probability grids to objects. Synoptic-scale fronts are often associated with extreme weather in the midlatitudes. Predictors are 1000-mb (1 mb = 1 hPa) grids of wind velocity, temperature, specific humidity, wet-bulb potential temperature, and/or geopotential height from the North American Regional Reanalysis. Labels are human-drawn fronts from Weather Prediction Center bulletins. We present two experiments to optimize parameters of the CNN and object conversion. To evaluate our system, we compare the objects (predicted warm and cold fronts) with human-analyzed warm and cold fronts, matching fronts of the same type within a 100- or 250-km neighborhood distance. At 250 km our system obtains a probability of detection of 0.73, success ratio of 0.65 (or false-alarm rate of 0.35), and critical success index of 0.52. These values drastically outperform the baseline, which is a traditional method from numerical frontal analysis. Our system is not intended to replace human meteorologists, but to provide an objective method that can be applied consistently and easily to a large number of cases. Our system could be used, for example, to create climatologies and quantify the spread in forecast frontal properties across members of a numerical weather prediction ensemble.

scholarly journals Multidecadal Variability of Tropical Cyclone Rapid Intensification in the Western North Pacific

2015 ◽  
Vol 28 (9) ◽  
pp. 3806-3820 ◽  
Author(s):  
Xidong Wang ◽  
Chunzai Wang ◽  
Liping Zhang ◽  
Xin Wang
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Wind Shear ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Trade Wind ◽  
Rapid Intensification ◽  
Multidecadal Variability ◽  
Heat Potential

Abstract This study investigates the variation of tropical cyclone (TC) rapid intensification (RI) in the western North Pacific (WNP) and its relationship with large-scale climate variability. RI events have exhibited strikingly multidecadal variability. During the warm (cold) phase of the Pacific decadal oscillation (PDO), the annual RI number is generally lower (higher) and the average location of RI occurrence tends to shift southeastward (northwestward). The multidecadal variations of RI are associated with the variations of large-scale ocean and atmosphere variables such as sea surface temperature (SST), tropical cyclone heat potential (TCHP), relative humidity (RHUM), and vertical wind shear (VWS). It is shown that their variations on multidecadal time scales depend on the evolution of the PDO phase. The easterly trade wind is strengthened during the cold PDO phase at low levels, which tends to make equatorial warm water spread northward into the main RI region rsulting from meridional ocean advection associated with Ekman transport. Simultaneously, an anticyclonic wind anomaly is formed in the subtropical gyre of the WNP. This therefore may deepen the depth of the 26°C isotherm and directly increase TCHP over the main RI region. These thermodynamic effects associated with the cold PDO phase greatly support RI occurrence. The reverse is true during the warm PDO phase. The results also indicate that the VWS variability in the low wind shear zone along the monsoon trough may not be critical for the multidecadal modulation of RI events.

Developing versus Nondeveloping Disturbances for Tropical Cyclone Formation. Part I: North Atlantic

2012 ◽  
Vol 140 (4) ◽  
pp. 1047-1066 ◽  
Author(s):  
Melinda S. Peng ◽  
Bing Fu ◽  
Tim Li ◽  
Duane E. Stevens
Keyword(s):  
Water Vapor ◽  
North Atlantic ◽  
Large Scale ◽  
Relative Vorticity ◽  
Water Vapor Content ◽  
Vertical Shear ◽  
Horizontal Shear ◽  
Synoptic Scale ◽  
The North ◽  
The North Atlantic

This study investigates the characteristic differences of tropical disturbances that eventually develop into tropical cyclones (TCs) versus those that did not, using global daily analysis fields of the Navy Operational Global Atmospheric Prediction System (NOGAPS) from the years 2003 to 2008. Time filtering is applied to the data to extract tropical waves with different frequencies. Waves with a 3–8-day period represent the synoptic-scale disturbances that are representatives as precursors of TCs, and waves with periods greater than 20 days represent the large-scale background environmental flow. Composites are made for the developing and nondeveloping synoptic-scale disturbances in a Lagrangian frame following the disturbances. Similarities and differences between them are analyzed to understand the dynamics and thermodynamics of TC genesis. Part I of this study focuses on events in the North Atlantic, while Part II focuses on the western North Pacific. A box difference index (BDI), accounting for both the mean and variability of the individual sample, is introduced to subjectively and quantitatively identify controlling parameters measuring the differences between developing and nondeveloping disturbances. Larger amplitude of the BDI implies a greater possibility to differentiate the difference between two groups. Based on their BDI values, the following parameters are identified as the best predictors for cyclogenesis in the North Atlantic, in the order of importance: 1) water vapor content within 925 and 400 hPa, 2) rain rate, 3) sea surface temperature (SST), 4) 700-hPa maximum relative vorticity, 5) 1000–600-hPa vertical shear, 6) translational speed, and 7) vertically averaged horizontal shear. This list identifies thermodynamic variables as more important controlling parameters than dynamic variables for TC genesis in the North Atlantic. When the east and west (separated by 40°W) Atlantic are examined separately, the 925–400-hPa water vapor content remains as the most important parameter for both regions. The SST and maximum vorticity at 700 hPa have higher importance in the east Atlantic, while SST becomes less important and the vertically averaged horizontal shear and horizontal divergence become more important in the west Atlantic.

scholarly journals Reassessing the Use of Inner-Core Hot Towers to Predict Tropical Cyclone Rapid Intensification*

2015 ◽  
Vol 30 (5) ◽  
pp. 1265-1279 ◽  
Author(s):  
Xiao-Yong Zhuge ◽  
Jie Ming ◽  
Yuan Wang
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Prediction Method ◽  
Vertical Shear ◽  
Intensity Change ◽  
False Alarms ◽  
Rapid Intensification ◽  
Central Pacific ◽  
Prediction Scheme ◽  
Skill Scores

Abstract The hot tower (HT) in the inner core plays an important role in tropical cyclone (TC) rapid intensification (RI). With the help of Tropical Rainfall Measurement Mission (TRMM) data and the Statistical Hurricane Intensity Prediction Scheme dataset, the potential of HTs in operational RI prediction is reassessed in this study. The stand-alone HT-based RI prediction scheme showed little skill in the northern Atlantic (NA) and eastern and central Pacific (ECP), but yielded skill scores of >0.3 in the southern Indian Ocean (SI) and western North Pacific (WNP) basins. The inaccurate predictions are due to four scenarios: 1) RI events may have already begun prior to the TRMM overpass. 2) RI events are driven by non-HT factors. 3) The HT has already dissipated or has not occurred at the TRMM overpass time. 4) Large false alarms result from the unfavorable environment. When the HT was used in conjunction with the TC’s previous 12-h intensity change, the potential intensity, the percentage area from 50 to 200 km of cloud-top brightness temperatures lower than −10°C, and the 850–200-hPa vertical shear magnitude with the vortex removed, the predictive skill score in the SI was 0.56. This score was comparable to that of the RI index scheme, which is considered the most advanced RI prediction method. When the HT information was combined with the aforementioned four environmental factors in the NA, ECP, South Pacific, and WNP, the skill scores were 0.23, 0.32, 0.42, and 0.42, respectively.

scholarly journals The imprint of surface fluxes and transport on variations in total column carbon dioxide

2011 ◽  
Vol 8 (4) ◽  
pp. 7475-7524 ◽  
Author(s):  
G. Keppel-Aleks ◽  
P. O. Wennberg ◽  
R. A. Washenfelder ◽  
D. Wunch ◽  
T. Schneider ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Carbon Sink ◽  
Potential Temperature ◽  
Surface Flux ◽  
Growing Season ◽  
Temporal Variations ◽  
Surface Fluxes ◽  
Synoptic Scale ◽  
Meridional Gradient

Abstract. New observations of the vertically integrated CO2 mixing ratio, ⟨CO2⟩, from ground-based remote sensing show that variations in ⟨CO2⟩ are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large scale and local fluxes. Observations of both ⟨CO2⟩ and CO2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in ⟨CO2⟩ in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO2, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in ⟨CO2⟩ from covariations in ⟨CO2⟩ and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the ⟨CO2⟩ seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes as well as the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better reflect the observations. Our simulations suggest that boreal growing season NEE (between 45–65° N) is underestimated by ~40 % in CASA. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

scholarly journals The Development and Assessment of a Model-, Grid-, and Basin-Independent Tropical Cyclone Detection Scheme

2013 ◽  
Vol 26 (15) ◽  
pp. 5493-5507 ◽  
Author(s):  
K. J. Tory ◽  
S. S. Chand ◽  
R. A. Dare ◽  
J. L. McBride
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
Model Data ◽  
Detector Performance ◽  
Detection Scheme

Abstract A novel approach to tropical cyclone (TC) detection in coarse-resolution numerical model data is introduced and assessed. This approach differs from traditional detectors in two main ways. First, it was developed and tuned using 20 yr of ECMWF Interim Re-Analysis (ERA-Interim) data, rather than using climate model data. This ensures that the detector is independent of any climate models to which it will later be applied. Second, only relatively large-scale parameters resolvable in climate models are included, in order to minimize any grid-resolution dependence on parameter thresholds. This approach is taken in an attempt to construct a unified TC detection procedure applicable to all climate models without the need for any further tuning or adjustment. Unlike traditional detectors that seek to identify TCs directly, the authors' method seeks to identify conditions favorable for TC formation. Favorable TC formation regions at the center of closed circulations in the lower troposphere to the midtroposphere are identified using a low-deformation vorticity parameter. Additional relative and specific humidity thresholds are applied to ensure the thermodynamic environment is favorable, and a vertical wind shear threshold is applied to eliminate storms in a destructive shear environment. A further requirement is that thresholds for all parameters must be satisfied for at least 48 h before a TC is deemed to have developed. A thorough assessment of the detector performance is provided. It is demonstrated that the method reproduces realistic TC genesis frequency and spatial distributions in the ERA-Interim data. Application of the detector to four climate models is presented in a companion paper.

scholarly journals Multiscale Interactions in the Life Cycle of a Tropical Cyclone Simulated in a Global Cloud-System-Resolving Model. Part I: Large-Scale and Storm-Scale Evolutions*

2010 ◽  
Vol 138 (12) ◽  
pp. 4285-4304 ◽  
Author(s):  
Hironori Fudeyasu ◽  
Yuqing Wang ◽  
Masaki Satoh ◽  
Tomoe Nasuno ◽  
Hiroaki Miura ◽  
...  
Keyword(s):  
Life Cycle ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Convective Available Potential Energy ◽  
Vertical Shear ◽  
Cloud System ◽  
Small Scale ◽  
Low Level ◽  
Multiscale Interactions ◽  
Java Sea

Abstract The Nonhydrostatic Icosahedral Atmospheric Model (NICAM), a global cloud-system-resolving model, successfully simulated the life cycle of Tropical Storm Isobel that formed over the Timor Sea in the austral summer of 2006. The multiscale interactions in the life cycle of the simulated storm were analyzed in this study. The large-scale aspects that affected Isobel’s life cycle are documented in this paper and the corresponding mesoscale processes are documented in a companion paper. The life cycle of Isobel was largely controlled by a Madden–Julian oscillation (MJO) event and the associated westerly wind burst (WWB). The MJO was found to have both positive and negative effects on the tropical cyclone intensity depending on the location of the storm relative to the WWB center associated with the MJO. The large-scale low-level convergence and high convective available potential energy (CAPE) downwind of the WWB center provided a favorable region to the cyclogenesis and intensification, whereas the strong large-scale stretching deformation field upwind of the WWB center may weaken the storm by exciting wavenumber-2 asymmetries in the eyewall and leading to the eyewall breakdown. Five stages are identified for the life cycle of the simulated Isobel: the initial eddy, intensifying, temporary weakening, reintensifying, and decaying stages. The initial eddy stage was featured by small-scale/mesoscale convective cyclonic vortices developed in the zonally elongated rainband organized in the preconditioned environment characterized by the WWB over the Java Sea associated with the onset of an MJO event over the East Indian Ocean. As the MJO propagated eastward and the cyclonic eddies moved southward into an environment with weak vertical shear and strong low-level cyclonic vorticity, a typical tropical cyclone structure developed over the Java Sea, namely the genesis of Isobel. Isobel experienced an eyewall breakdown and a temporary weakening when it was located upwind of the WWB center as the MJO propagated southeastward and reintensified as its eyewall reformed as a result of the axisymmetrization of an inward spiraling outer rainband that originally formed downwind of the WWB center. Finally Isobel decayed as it approached the northwest coast of Australia.

scholarly journals Prediction and Diagnosis of Tropical Cyclone Formation in an NWP System. Part III: Diagnosis of Developing and Nondeveloping Storms

2007 ◽  
Vol 64 (9) ◽  
pp. 3195-3213 ◽  
Author(s):  
K. J. Tory ◽  
N. E. Davidson ◽  
M. T. Montgomery
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Deep Convection ◽  
Weather Prediction ◽  
Vertical Wind Shear ◽  
Forecast Model ◽  
Vertical Shear ◽  
Limited Area ◽  
Vortex Interactions ◽  
Secondary Mechanism

Abstract This is the third of a three-part investigation into tropical cyclone (TC) genesis in the Australian Bureau of Meteorology’s Tropical Cyclone Limited Area Prediction System (TC-LAPS), an operational numerical weather prediction (NWP) forecast model. In Parts I and II, a primary and two secondary vortex enhancement mechanisms were illustrated, and shown to be responsible for TC genesis in a simulation of TC Chris. In this paper, five more TC-LAPS simulations are investigated: three developing and two nondeveloping. In each developing simulation the pathway to genesis was essentially the same as that reported in Part II. Potential vorticity (PV) cores developed through low- to middle-tropospheric vortex enhancement in model-resolved updraft cores (primary mechanism) and interacted to form larger cores through diabatic upscale vortex cascade (secondary mechanism). On the system scale, vortex intensification resulted from the large-scale mass redistribution forced by the upward mass flux, driven by diabatic heating, in the updraft cores (secondary mechanism). The nondeveloping cases illustrated that genesis can be hampered by (i) vertical wind shear, which may tilt and tear apart the PV cores as they develop, and (ii) an insufficient large-scale cyclonic environment, which may fail to sufficiently confine the warming and enhanced cyclonic winds, associated with the atmospheric adjustment to the convective updrafts. The exact detail of the vortex interactions was found to be unimportant for qualitative genesis forecast success. Instead the critical ingredients were found to be sufficient net deep convection in a sufficiently cyclonic environment in which vertical shear was less than some destructive limit. The often-observed TC genesis pattern of convection convergence, where the active convective regions converge into a 100-km-diameter center, prior to an intense convective burst and development to tropical storm intensity is evident in the developing TC-LAPS simulations. The simulations presented in this study and numerous other simulations not yet reported on have shown good qualitative forecast success. Assuming such success continues in a more rigorous study (currently under way) it could be argued that TC genesis is largely predictable provided the large-scale environment (vorticity, vertical shear, and convective forcing) is sufficiently resolved and initialized.

Sign in / Sign up

Export Citation Format

Share Document