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Tropical Cyclone Research and Review  
  Tropical Cyclone Research and Review--2012, 1 (4)   Published: 2012-12-15
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A Developmental Framework for Improving Hurricane Model Physical Parameterizations Using Aircraft Observations

Jun A. Zhang, Sundararaman Gopalakrishnan, Frank D. Marks, Robert F. Rogers
Tropical Cyclone Research and Review. 2012, 1 (4): 419;  doi: 10.6057/2012TCRR04.01
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As part of NOAA’s Hurricane Forecast Improvement Program (HFIP), this paper addresses the important role of aircraft observations in hurricane model physics validation and improvement. A model developmental framework for improving the physical parameterizations using quality-controlled and post-processed aircraft observations is presented, with steps that include model diagnostics, physics development, physics implementation and further evaluation. Model deficiencies are first identified through model diagnostics by comparing the simulated axisymmetric multi-scale structures to observational composites. New physical parameterizations are developed in parallel based on in-situ observational data from specially designed hurricane field programs. The new physics package is then implemented in the model, which is followed by further evaluation. The developmental framework presented here is found to be successful in improving the surface layer and boundary layer parameterization schemes in the operational Hurricane Weather Research and Forecast (HWRF) model. Observations for improving physics packages other than boundary layer scheme are also discussed.

Downstream Development During the Extratropical Transition of Tropical Cyclones: Observational Evidence and Influence on Storm Structure

Lili Liu, Noel E. Davidson, Hongyan Zhu, Charlie C. F. Lok
Tropical Cyclone Research and Review. 2012, 1 (4): 430;  doi: 10.6057/2012TCR04.02
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Observational evidence is presented that during Extratropical Transition (ET) of Tropical Cyclones (TCs), Downstream Development (DD) is frequently underway. We show that DD results in rapid changes to the environment. A critical flow change is the development of a low-level trough, sandwiched between two developing anticyclones. The trough appears to merge with the storm, seemingly holding it upright and allowing it to withstand the damaging effects of wind shear. In this way the storm can eventually reach the favourable equatorward entrance region of the upper jet. To evaluate the mechanism, two sets of simulations have been run: one using high-resolution, full physics integrations and another using coarse-resolution with dry physics and the TC removed from the initial condition. We show that the dry dynamics can establish the large scale environment to enable the transition to proceed. The process can produce: (a) the deep, vertically-aligned, low-level pressure trough that merges with the storm, and (b) a partial inhibition through subsidence to embedded convection, allowing the boundary layer to moisten via (i) sustained surface fluxes, and (ii) enhanced horizontal moisture flux convergence from the environmental flow changes. This produces potential for more intense convective activity and vortex resiliency even in relatively strong, deep vertical wind shear.

Vertical Wind Shear and Ocean Heat Content as Environmental Modulators of Western North Pacific Tropical Cyclone Intensification and Decay

Myung-Sook Park, Russell L. Elsberry, Patrick A. Harr
Tropical Cyclone Research and Review. 2012, 1 (4): 448;  doi: 10.6057/2012TCRR04.03
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A general framework in which Ocean Heat Content (OHC) may modulate tropical cyclone intensification and decay in conjunction with Vertical Wind Shear (VWS) as the primary environmental control is formulated in terms of a two-dimensional phase diagram. Case studies of the life cycles of three tropical cyclones during the Impact of Typhoons on the Ocean in the Pacific (ITOP) field experiment during August-October 2010 are selected as examples owing to numerous Air-deployed eXpendable BathyThermographs (AXBTs) and special atmospheric observations. Vertical wind shears calculated from European Center for Medium-range Weather Forecasting analyses within a 3°-5° lat. annulus around the center may not properly represent the VWS in nonuniform,
asymmetric, and time-varying conditions in the western North Pacific. As expected, VWS is the primary environmental control during the formation and early intensification stage over regions of large OHC, and during the decay phase over regions of small OHC. The challenging intensity forecasting problems are in the intermediate conditions of an intense tropical cyclone moving slowly over a region of low to moderate OHC when the negative feedback from the ocean may or may not lead to a decrease in intensity.

Evaluating the Performance of Western North Pacific Tropical Cyclone Intensity Guidance. Part II: Intensity Forecast Accuracy in Different Life Stages

Qingqing Li, Caizhu Chen, Jinhua Yu, Lin Chen
Tropical Cyclone Research and Review. 2012, 1 (4): 458;  doi: 10.6057/2012TCRR04.04
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The accuracy of eight tropical cyclone (TC) intensity guidance techniques currently used in the East China Regional Meteorological Center during the 2008 and 2009 western North Pacific seasons has been evaluated within two intensity phases: intensification and decay. In the intensification stage, the majority of the techniques indicated > 60% probabilities of the errors of forecast 12-h intensity change within ±5 m s-1 from the 12- to 60-h forecast intervals, while none had capability to predict the rapid intensification and most of them had a bias toward smaller 48-h intensity changes at the beginning of the stage. The majority of the guidance techniques showed > 70% probabilities of the errors of forecast 12-h intensity change within ±5 m s-1 through 60 h during the decay phase, and the techniques had little capability of predicting rapid decay events. It is found that the evaluated statistical models had difficulty in predicting the strongest cases of decay 36 h after peak intensity, whereas the dynamical and official forecasts were seemingly able to produce some large decay rates.

The First International Workshop on Satellite Analysis of Tropical Cyclones: Summary of Current Operational Methods to Estimate Intensity

Christopher Velden, Andrew Burton, Koji Kuroiwa
Tropical Cyclone Research and Review. 2012, 1 (4): 469;  doi: 10.6057/2012TCRR04.05
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This paper summarizes the results and findings from the first International Workshop on Satellite Analyses of Tropical Cyclones (IWSATC). Estimating tropical cyclone intensity in the absence of penetrating reconnaissance aircraft is mainly left to satellite-based remote sensing methods. The primary method used globally since the latter part of the last century is the Dvorak Technique. While this method has withstood the test of time, it is not without limitations, and has been subject to regional modifications by various national tropical cyclone analysis centers. Differences between agencies in both the application of the Dvorak Technique and in general operational procedures to derive final intensity estimates can lead to real-time warning conflicts, as well as issues with final best track values for climatological analyses. As coastal populations increase, the WMO recognizes these issues as potentially serious problems, and organized a workshop in 2011 to bring together tropical cyclone experts to 1) discuss current operational analysis practices, 2) learn about developing satellite techniques, and 3) come up with a set of recommendations to start down a path towards a global congruence on intensity estimation procedures.

Reconstruction of Tropical Cyclone Affecting East China During 1450-1949 From Historical Documents

Ming Xu, Qiuzhen Yang, Ming Ying, Zhiying Deng, Zizhi Yang
Tropical Cyclone Research and Review. 2012, 1 (4): 482;  doi: 10.6057/2012TCR04.06
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The natural disaster information in the historical documents in mainland East China are investigated and collected. A set of criteria is set up to discern the tropical cyclone (hereafter TC) influences from these records. The criteria construction is based on the knowledge of TC and TC disasters in instrumental era. Five TC features are considered in the criteria, they are occurring time, spatial scale, lasting time, disaster characteristics and associated weather phenomena. Altogether 1445 affecting TC events are found from historical documents during 1450-1949 in mainland East China. The contents of the reconstructed data include three parts—the yearly number, the occurring time and influential scope of every event. Some characteristics of the reconstructed data, temporal resolution, seasonal distribution and temporal evolution, are also discussed.

Brief Introduction to Synergized Standard Operating Procedures for Coastal Multi-Hazards Early Warning System

Olavo Rasquinho, Derek Leong, Jinping Liu
Tropical Cyclone Research and Review. 2012, 1 (4): 489;  doi: 10.6057/2012TCRR04.07
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The most countries surrounding the Indian Ocean as well as Southeast Asian countries do not have operational experience in handling a combination of tsunami and other coastal hazard early warning systems. The challenge faced by warning providers, media, disaster managers, and coastal communities is in understanding the similarities and differences among different coastal hazards and the characteristics of the early warnings that are issued. There is a strong need to create synergies among different types of coastal hazard early warnings by reviewing the relevant existing standard operating procedures. These synergies can be achieved through identifying specific gaps and needs for making the existing early warning systems fully operational for the use in multi-hazards context. The project of Synergized Standard Operating Procedures for Coastal Multi-Hazards Early Warning System (SSOP) was proposed by Typhoon Committee Secretariat with the objectives of developing the SSOP Manual/Handbook and establishing the cooperation mechanism on coastal multi-hazard early warning among the target countries. The project will mainly focus on the meteorological and hydrological services for affected areas which become more vulnerable to natural disasters after tsunami and other costal disasters. The synergized standard operating procedure should be easier understandable and interpretable for decision makers, forecasters and dwellers.

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