Vorticity-Based Detection of Tropical Cyclogenesis (original) (raw)
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Geophysical Research Letters, 2001
Far from land and surface ship observations, most tropical depressions are identified by examining images from geostationary satellites for the presence of rotation of the convective cloud masses. During the 1999 hurricane season, surface wind vectors obtained by the SeaWinds scatterometer on the QuikSCAT satellite for the tropical Atlantic and Caribbean Sea were examined to test the hypothesis that developing tropical depressions (TDs) could be observed with this satellite sensor, before identification by the traditional means. QuikSCAT was able to detect the presence of closed circulation in the surface winds before the systems were designated as depressions. The satellite's unprecedented large swath width of 1800 km allows twice a day observation of most of the tropical oceans. SeaWinds data can, therefore, provide valuable guidance that are an important addition to the tools available to the tropical cyclone forecasting community.
Journal of the Atmospheric Sciences, 2007
This is the first 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. The primary TC-LAPS vortex enhancement mechanism is presented in Part I, the entire genesis process is illustrated in Part II using a single TC-LAPS simulation, and in Part III a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in TC-LAPS.
Observational analysis of tropical cyclone formation
1979
This study investigates the genesis of tropical cyclones through a combination of the compositing approach and the case study approach. Twelve composite data sets are analyzed from the tropical Northwest Pacific and tropical Northwest Atlantic Oceans. Each data set is a composite average of approximately 80 individual disturbances. Four different types of non-developing oceanic tropical disturbances are composited. They are compared with pre-hurricane and pre-typhoon disturbances in each ocean composited at four different stages of intensification. In total 912 different tropical weather systems go into the composites and approximately 40,000 rawinsonde observations are used. The main findings from the analysis of the composite fields are: (i) pre-typhoon and pre-hurricane systems are located in large areas of high values of low level relative vorticity. The low level vorticity in the vicinity of a developing cloud cluster is approximately twice as large as that observed with non-de...
Birth of a hurricane: early detection of large-scale vortex instability
Journal of Physics: Conference Series, 2020
A way is substantiated for detecting new large-scale vortex instability in the tropical atmosphere. The instability may occur several hours or even several dozens of hours before the formation of a tropical depression or tropical storm. The diagnosis of instability was developed on the basis of data from idealized cloud-resolving atmospheric simulation for tropical cyclogenesis. It is suggested how the evolving instability may be traced by combining highresolution numerical modeling and GOES Imagery. As an illustration, it is speculated and discussed that the instability may have emerged in future Hurricane Isaias (2020) when it had a status of Potential Tropical Cyclone for 36 hours before it was diagnosed as Tropical Storm.
The AMS 34th Conference on Hurricanes and Tropical Meteorology, Virtual Meeting. 10–14 May 2021.
Helical tropical cyclogenesis: detection of pre-depression large-scale vortex instability, 2021
Results are presented on detection of a large-scale vortex instability emerging on the background of seemingly disorganized convection and pronouncedly preceding, from a few hours up to several dozens of hours, the formation of tropical depression (TD). The approach is advanced for identifying and tracking the discovered instability by means of operational analysis based on GOES Imagery and supported by the cloud-resolving numerical modeling. We propose the fundamental ground and based on it, diagnostic patterns in satellite data supported by cloud-resolving numerical analysis to give visual and quantitative criteria for the option “Potential Tropical Cyclone” introduced by the National Hurricane Center since 2017.
Weather and Forecasting, 2011
An automated technique has been developed for the detection and tracking of tropical cyclone–like vortices (TCLVs) in numerical weather prediction models, and especially for ensemble-based models. A TCLV is detected in the model grid when selected dynamic and thermodynamic fields meet specified criteria. A backward-and-forward extension from the mature stage of the track is utilized to complete the track. In addition, a fuzzy logic approach is utilized to calculate the TCLV fuzzy combined-likelihood value (TFCV) for representing the TCLV characteristics in the ensemble forecast outputs. The primary objective of the TCLV tracking and TFCV maps is for use as an evaluation tool for the operational forecasters. It is demonstrated that this algorithm efficiently extracts western North Pacific TCLV information from the vast amount of ensemble data from the NCEP Global Ensemble Forecast System (GEFS). The predictability of typhoon formation and activity during June–December 2008 is also ev...
Фундаментальная и прикладная гидрофизика, 2022
The climate change is becoming more and more obvious, which leads to an increase in the number of intense atmospheric vortices (tropical and quasi-tropical cyclones, polar hurricanes, tornadoes) and an expansion of the geographical and seasonal limits of their occurrence. A recent example was the quasi-tropical cyclone in the Black Sea on August 11-16, 2021. Under these conditions, the accurate diagnosis of cyclogenesis is extremely important and, based on it, the forecast of further evolution and the trajectory of the forming vortex. The main source of energy for tropical, quasi-tropical and polar hurricanes is thermal convection caused by significant temperature differences between the atmospheric layer and the underlying water surface. This allows us to propose a unified approach for the diagnosis of cyclogenesis in all three cases. For the first time, an original approach is proposed for determining the exact time of the onset of tropical cyclogenesis. This approach includes a combined analysis of satellite images of cloudiness and the corresponding data of cloud-resolving numerical modeling for the region of developing vortex disturbance. The theoretical basis is the fundamental hypothesis of a turbulent vortex dynamo. The theory provides quantitative criteria that determine the excitation of large-scale vortex instability in the atmosphere. Atmospheric numerical modeling makes it possible to accurately determine the moment of time at which the necessary conditions for the onset of instability are realized. This moment is interpreted as the beginning of cyclogenesis. The specific configurations of vortical cloud convection found in the work, which correspond to the initial stage of cyclogenesis, can be used in operational meteorological diagnostics when analyzing satellite images of cloudiness. The approach is illustrated by the example of diagnostics of tropical cyclogenesis.
Development of Tropical Cyclones in Relation to Circulation Patterns at the 200-MILLIBAR Level*
Monthly Weather Review, 1963
The 200-mb. flow existing abovc low-lcvel perturbations at the time of development into tropical storm or hurricane intensity was studied. On the basis of observations in a sample of 40 cases, i t is concludcd that poleward flow aloft, such as is found in the eastern side of troughs in the westerlies and tropical upper-level cold Lows or in the western side of anticyclones, is more favorable for development of low-level perturbations underncath than equatorward flow. It is also shown that flow aloft with antie3c:lonic vorticity is more favorable than flow with cyclonic \ orticitg.