A Global Statistical–Dynamical Tropical Cyclone Wind Radii Forecast Scheme

2017 ◽  
Vol 32 (2) ◽  
pp. 629-644 ◽  
Author(s):  
John A. Knaff ◽  
Charles R. Sampson ◽  
Galina Chirokova
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Global Model ◽  
Wind Pressure ◽  
Forecast Method ◽  
Wind Model ◽  
Global Models ◽  
Forecast Performance ◽  
Wind Structure ◽  
Dynamical Method

Abstract Forecasts of tropical cyclone (TC) surface wind structure have recently begun to show some skill, but the number of reliable forecast tools, mostly regional hurricane and select global models, remains limited. To provide additional wind structure guidance, this work presents the development of a statistical–dynamical method to predict tropical cyclone wind structure in terms of wind radii, which are defined as the maximum extent of the 34-, 50-, and 64-kt (1 kt = 0.514 m s−1) winds in geographical quadrants about the center of the storm. The basis for TC size variations is developed from an infrared satellite-based record of TC size, which is homogenously calculated from a global sample. The change in TC size is predicted using a statistical–dynamical approach where predictors are based on environmental diagnostics derived from global model forecasts and observed storm conditions. Once the TC size has been predicted, the forecast intensity and track are used along with a parametric wind model to estimate the resulting wind radii. To provide additional guidance for applications and users that require forecasts of central pressure, a wind–pressure relationship that is a function of TC motion, intensity, wind radii (i.e., size), and latitude is then applied to these forecasts. This forecast method compares well with similar wind structure forecasts made by global forecast and regional hurricane models and when these forecasts are used as a member of a simple consensus; its inclusion improves the forecast performance of the consensus.

Statistical Tropical Cyclone Wind Radii Prediction Using Climatology and Persistence

2007 ◽  
Vol 22 (4) ◽  
pp. 781-791 ◽  
Author(s):  
John A. Knaff ◽  
Charles R. Sampson ◽  
Mark DeMaria ◽  
Timothy P. Marchok ◽  
James M. Gross ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Department Of Defense ◽  
Parametric Model ◽  
Forecast Method ◽  
Operational Model ◽  
Wind Structure ◽  
East Pacific ◽  
Operational Forecasts ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center

Abstract An operational model used to predict tropical cyclone wind structure in terms of significant wind radii (i.e., 34-, 50-, and 64-kt wind radii, where 1 kt = 0.52 m s−1) at the National Oceanic and Atmospheric Administration/National Hurricane Center (NHC) and the Department of Defense/Joint Typhoon Warning Center (JTWC) is described. The statistical-parametric model employs aspects of climatology and persistence to forecast tropical cyclone wind radii through 5 days. Separate versions of the model are created for the Atlantic, east Pacific, and western North Pacific by statistically fitting a modified Rankine vortex, which is generalized to allow wavenumber-1 asymmetries, to observed values of tropical cyclone wind radii as reported by NHC and JTWC. Descriptions of the developmental data and methods used to formulate the model are given. A 2-yr verification and comparison with operational forecasts and an independently developed wind radii forecast method that also employs climatology and persistence suggests that the statistical-parametric model does a good job of forecasting wind radii. The statistical-parametric model also provides reliable operational forecasts that serve as a baseline for evaluating the skill of operational forecasts and other wind radii forecast methods in these tropical cyclone basins.

scholarly journals The Development and Evaluation of a Statistical–Dynamical Tropical Cyclone Genesis Guidance Tool

2016 ◽  
Vol 32 (1) ◽  
pp. 27-46 ◽  
Author(s):  
Daniel J. Halperin ◽  
Robert E. Hart ◽  
Henry E. Fuelberg ◽  
Joshua H. Cossuth
Keyword(s):  
Tropical Cyclone ◽  
Prediction Models ◽  
Weather Prediction ◽  
Multiscale Model ◽  
Global Model ◽  
Tropical Cyclone Genesis ◽  
Regression Equations ◽  
Global Models ◽  
Tropical Weather ◽  
Cyclone Genesis

Abstract The National Hurricane Center (NHC) has stated that guidance on tropical cyclone (TC) genesis is an operational forecast improvement need, particularly since numerical weather prediction models produce TC-like features and operationally required forecast lead times recently have increased. Using previously defined criteria for TC genesis in global models, this study bias corrects TC genesis forecasts from global models using multiple logistic regression. The derived regression equations provide 48- and 120-h probabilistic genesis forecasts for each TC genesis event that occurs in the Environment Canada Global Environmental Multiscale Model (CMC), the NCEP Global Forecast System (GFS), and the Met Office's global model (UKMET). Results show select global model output variables are good discriminators between successful and unsuccessful TC genesis forecasts. Independent verification of the regression-based probabilistic genesis forecasts during 2014 and 2015 are presented. Brier scores and reliability diagrams indicate that the forecasts generally are well calibrated and can be used as guidance for NHC’s Tropical Weather Outlook product. The regression-based TC genesis forecasts are available in real time online.

Tropical Cyclone Inner-Core Kinetic Energy Evolution

2008 ◽  
Vol 136 (12) ◽  
pp. 4882-4898 ◽  
Author(s):  
Katherine S. Maclay ◽  
Mark DeMaria ◽  
Thomas H. Vonder Haar
Keyword(s):  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Inner Core ◽  
Surface Wind ◽  
Statistical Testing ◽  
Vertical Shear ◽  
Structure Evolution ◽  
Wind Fields ◽  
Secondary Eyewall Formation ◽  
Wind Structure

Abstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind field. To gain a better understanding of wind structure evolution, TC 0–200-km wind fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change and, for convenience, are referred to as measurements of storm size [storms with greater (less) KE for their given intensity are considered large (small)]. It is established that TCs generally either intensify and do not grow or they weaken/maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus nongrowing storms in each intensification regime. Results suggest two primary types of growth processes: (i) secondary eyewall formation and eyewall replacement cycles, an internally dominated process, and (ii) external forcing from the synoptic environment. One of the most significant environmental forcings is the vertical shear. Under light shear, TCs intensify but do not grow; under moderate shear, they intensify less but grow more; under very high shear, they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir–Simpson hurricane scale.

Wind Structure Discrepancies between Two Best Track Datasets for Western North Pacific Tropical Cyclones

2016 ◽  
Vol 144 (12) ◽  
pp. 4533-4551 ◽  
Author(s):  
Jinjie Song ◽  
Philip J. Klotzbach
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Shape Parameter ◽  
Surface Wind ◽  
Japan Meteorological Agency ◽  
Wind Structure ◽  
Linear Relationships ◽  
Wind Analysis ◽  
Joint Typhoon Warning Center

Abstract Symmetric and wavenumber-1 asymmetric characteristics of western North Pacific tropical cyclone (TC) outer wind structures are compared between best tracks from the Joint Typhoon Warning Center (JTWC) and the Japan Meteorological Agency (JMA) from 2004 to 2014 as well as the Multiplatform Tropical Cyclone Surface Wind Analysis (MTCSWA) product from 2007 to 2014. Significant linear relationships of averaged wind radii are obtained among datasets, in which both gale-force and storm-force wind radii are generally estimated slightly smaller (much larger) by JTWC (JMA) than by MTCSWA. These correlations are strongly related to TC intensity relationships discussed in earlier work. Moreover, JTWC (JMA) on average represents a smaller (greater) derived shape parameter than MTCSWA does, implying that JTWC (JMA) typically assesses a more compact (less compact) storm than MTCSWA. For the wavenumber-1 asymmetry, large differences among datasets are found regardless of the magnitude or the direction of the longest radius. JTWC estimates more asymmetric storms than JMA, and it provides greater wavenumber-1 asymmetry magnitudes on average. Asymmetric storms are most frequently oriented toward the east, northeast, and north in JTWC and MTCSWA, whereas they are most frequently oriented toward the southeast, east, and northeast in JMA. The direction of the longest gale-force (storm force) wind radius in JTWC is statistically rotated 18° (32°) clockwise to that in JMA. Although the wind radii in JTWC are of higher quality than those in JMA when using MTCSWA as a baseline, there remains a need to provide a consistent and reliable wind radii estimating process among operational centers.

Impact of Tropical Cyclone Initialization on Its Convection Development and Intensity: A Case Study of Typhoon Megi (2010)

2020 ◽  
Vol 77 (2) ◽  
pp. 443-464 ◽  
Author(s):  
Yi-Pin Chang ◽  
Shu-Chih Yang ◽  
Kuan-Jen Lin ◽  
Guo-Yuan Lien ◽  
Chien-Ming Wu
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Surface Wind ◽  
Synthetic Data ◽  
Asymmetric Structure ◽  
Wind Structure ◽  
Axisymmetric Surface ◽  
Moisture Supply ◽  
High Level ◽  
The Impact

Abstract This study investigates the impact of tropical cyclone (TC) initialization methods on TC intensity prediction under a framework coupling the Weather Research and Forecasting Model with the TC Centered-Local Ensemble Transform Kalman Filter (WRF TCC-LETKF). While the TC environments are constrained by assimilating the same environmental observations, two different initialization strategies, assimilating real dropsonde observations (the DP experiment) and synthetic axisymmetric surface wind structure (the VT experiment), are employed to construct the TC inner-core structure. These two experiments have distinct results on predicting the rapid intensification (RI) of Typhoon Megi (2010), which can be attributed to their different convective burst (CB) development. In DP, the assimilation of the dropsondes helps establish a realistic TC structure with asymmetry information, leading to scattered CB distribution and persistent RI with abundant moisture supply. In VT, assimilating the axisymmetric surface wind structure spins up the TC efficiently. However, the initially excessive CB coverage causes a too-early high-level warm core, and the reduced moisture supply hinders RI. The forecast results imply that if the TC structure is initialized using a scheme considering only the axisymmetric vortex structure, the RI potential can possibly be underestimated due to the inability to represent the realistic asymmetric structure. Finally, assimilation of both the real and synthetic data can be complementary, giving a strong TC initially that undergoes a longer RI period.

scholarly journals Using Routinely Available Information to Estimate Tropical Cyclone Wind Structure

2016 ◽  
Vol 144 (4) ◽  
pp. 1233-1247 ◽  
Author(s):  
John A. Knaff ◽  
Christopher J. Slocum ◽  
Kate D. Musgrave ◽  
Charles R. Sampson ◽  
Brian R. Strahl
Keyword(s):  
Tropical Cyclone ◽  
Satellite Imagery ◽  
Global Model ◽  
Error Statistics ◽  
Simple Method ◽  
Wind Structure ◽  
Practical Research ◽  
Data Location ◽  
Available Information ◽  
Size Estimates

Abstract A relatively simple method to estimate tropical cyclone (TC) wind radii from routinely available information including storm data (location, motion, and intensity) and TC size is introduced. The method is based on a combination of techniques presented in previous works and makes an assumption that TCs are largely symmetric and that asymmetries are based solely on storm motion and location. The method was applied to TC size estimates from two sources: infrared satellite imagery and global model analyses. The validation shows that the methodology is comparable with other objective methods based on the error statistics. The technique has a variety of practical research and operational applications, some of which are also discussed.

Hurricane Wind–Pressure Relationship and Eyewall Replacement Cycles

2015 ◽  
Vol 30 (1) ◽  
pp. 177-181 ◽  
Author(s):  
James P. Kossin
Keyword(s):  
Tropical Cyclone ◽  
Single Point ◽  
Surface Wind ◽  
Wind Pressure ◽  
Minimum Pressure ◽  
Maximum Wind ◽  
Central Surface ◽  
Hurricane Wind ◽  
The Relationship ◽  
Eyewall Replacement Cycles

Abstract The relationship between minimum central surface pressure and the maximum sustained surface wind in tropical cyclones has been studied for many years, motivated by the fact that minimum pressure is generally easier to measure, but maximum wind is a much more relevant metric when considering tropical cyclone risk and potential impacts. It is well understood that tropical cyclone wind is closely related to the radial gradient of pressure through gradient or cyclostrophic balance assumptions, and not to a single point value of the minimum pressure near the storm center. But it is often the case that the maximum wind must be inferred from this single value. To accomplish this, a number of statistical relationships have been documented, such as those used in the Dvorak technique for estimating tropical cyclone intensity from satellite imagery. Here, the relationship between tropical cyclone maximum wind and minimum pressure is explored during eyewall replacement cycles (ERCs) that have been observed in North Atlantic hurricanes. It is shown that the wind–pressure relationship (WPR) can vary substantially during an ERC and generally moves away from the statistically fitted WPR used by the Dvorak technique in that basin. The changes in WPR during an ERC can be quite different depending on the intensity of the hurricane at the start of the ERC.

Objective estimation of tropical cyclone innercore surface wind structure using infrared satellite images

2017 ◽  
Vol 11 (04) ◽  
pp. 1 ◽  
Author(s):  
Changjiang Zhang ◽  
Lijie Dai ◽  
Leiming Ma ◽  
Jinfang Qian ◽  
Bo Yang
Keyword(s):  
Tropical Cyclone ◽  
Satellite Images ◽  
Surface Wind ◽  
Wind Structure

scholarly journals Understanding Hurricane Storm Surge Generation and Propagation Using a Forecasting Model, Forecast Advisories and Best Track in a Wind Model, and Observed Data—Case Study Hurricane Rita

2019 ◽  
Vol 7 (3) ◽  
pp. 77 ◽  
Author(s):  
Abram Musinguzi ◽  
Muhammad K. Akbar ◽  
Jason G. Fleming ◽  
Samuel K. Hargrove
Keyword(s):  
Storm Surge ◽  
Surface Wind ◽  
Storm Surges ◽  
Wind Pressure ◽  
Forecasting Model ◽  
Wind Fields ◽  
Wind Model ◽  
Meteorological Forcing ◽  
Hurricane Rita

Meteorological forcing is the primary driving force and primary source of errors for storm surge forecasting. The objective of this study was to learn how forecasted meteorological forcing influences storm surge generation and propagation during a hurricane so that storm surge models can be reliably used to forecast actual events. Hindcasts and forecasts of Hurricane Rita (2005) storm surge was used as a case study. Meteorological forcing or surface wind/pressure fields for Hurricane Rita were generated using both the Weather Research and Forecasting (WRF) full-scale forecasting model along with archived hurricane advisories ingested into a sophisticated parametric wind model, namely Generalized Asymmetric Holland Model (GAHM). These wind fields were used to forecast Rita storm surges. Observation based wind fields from the OceanWeather Inc. (OWI) Interactive Objective Kinematic Analysis (IOKA) model, and Best track wind data ingested into the GAHM model were used to generate wind fields for comparison purposes. These wind fields were all used to hindcast Rita storm surges with the ADvanced CIRCulation (ADCIRC) model coupled with the Simulating Waves Nearshore (SWAN) model in a tightly coupled storm surge-wave model referred to as ADCIRC+SWAN. The surge results were compared against a quality-controlled database of observed data to assess the performance of these wind fields on storm surge generation and propagation. The surge hindcast produced by the OWI wind field performed the best, although some high water mark (HWM) locations were overpredicted. Although somewhat underpredicted, the WRF wind fields forecasted wider surge extent and wetted most HWM locations. The hindcast using the Best track parameters in the GAHM and the forecast using forecast/advisories from the National Hurricane Center (NHC) in the GAHM produced strong and narrow wind fields causing localized high surges, which resulted in overprediction near landfall while many HWM locations away from wind bands remained dry.

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