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STAFFMEMBERS, UNIVERSITY OF CHICAGO42 1OCTOBER 1956AEXPERIME iT IN FORECASTING THE DISPLACEMENT OF500-MILLIBAR TROUGHS AND RIDGESBy Sta$ Members, Weather Forecasting Research Center, University of Chicago University of Chicago' (Manuscript received 5 December 1955)ABSTRACTA number of simple objective methods of computing the motion of troughs and ridges at the 500-mb levelwere tested for a fifty-day period, with use of data over and near North America. The most
STAFFMEMBERS, UNIVERSITY OF CHICAGO42 1OCTOBER 1956AEXPERIME iT IN FORECASTING THE DISPLACEMENT OF500-MILLIBAR TROUGHS AND RIDGESBy Sta$ Members, Weather Forecasting Research Center, University of Chicago University of Chicago' (Manuscript received 5 December 1955)ABSTRACTA number of simple objective methods of computing the motion of troughs and ridges at the 500-mb levelwere tested for a fifty-day period, with use of data over and near North America. The most
1. Introduction A forecast is an estimate of the future state of the atmosphere or ocean. Forecasts are generally conducted by estimating the current states using observations and then investigating how these states evolve using numerical models. Because of the effect of instability and related nonlinearity, very small errors in initial states can be nonlinearly amplified and lead to large errors in the forecast results ( Lorenz 1963 ). Because we cannot observe every detail of the atmospheric
1. Introduction A forecast is an estimate of the future state of the atmosphere or ocean. Forecasts are generally conducted by estimating the current states using observations and then investigating how these states evolve using numerical models. Because of the effect of instability and related nonlinearity, very small errors in initial states can be nonlinearly amplified and lead to large errors in the forecast results ( Lorenz 1963 ). Because we cannot observe every detail of the atmospheric
1. Introduction Improving prediction of tropical cyclones (TCs) is important because more accurate forecasting of these storms would lead to improved warning and increased potential to reduce their impact on life and property. Based on potential damage concerns, the primary parameters of interest for the TC prediction are track and intensity, where the track is defined in terms of progression of geographical location of a cyclone’s minimum sea level pressure and the intensity is expressed in
1. Introduction Improving prediction of tropical cyclones (TCs) is important because more accurate forecasting of these storms would lead to improved warning and increased potential to reduce their impact on life and property. Based on potential damage concerns, the primary parameters of interest for the TC prediction are track and intensity, where the track is defined in terms of progression of geographical location of a cyclone’s minimum sea level pressure and the intensity is expressed in
coastal regions, and alter the strength of the ENSO cycle, among other effects ( Zhang 2005 ). The BSISO, meanwhile, is closely related to intraseasonal oscillations of the South Asian monsoon ( Goswami 2011 , and references therein) and influences its onset and active and dry spells. More broadly speaking, improved understanding of these two intraseasonal modes would go a long way in filling the gap that is beyond the reach of short-term weather forecasts and below the resolution of long-term climate
coastal regions, and alter the strength of the ENSO cycle, among other effects ( Zhang 2005 ). The BSISO, meanwhile, is closely related to intraseasonal oscillations of the South Asian monsoon ( Goswami 2011 , and references therein) and influences its onset and active and dry spells. More broadly speaking, improved understanding of these two intraseasonal modes would go a long way in filling the gap that is beyond the reach of short-term weather forecasts and below the resolution of long-term climate
with nearby TCs ( Wu et al. 2003 ; Peng and Reynolds 2005 ; Yang et al. 2008 ). In the final stage, they may recurve and transition into an extratropical cyclone or make landfall and dissipate. TC forecast inaccuracy comes both from errors in the numerical weather prediction models and from errors in the analyzed initial conditions. Concerning the latter, the lack of observations over the open-ocean regions where TCs spend most of their lifetime degrades the quality of initial conditions and the
with nearby TCs ( Wu et al. 2003 ; Peng and Reynolds 2005 ; Yang et al. 2008 ). In the final stage, they may recurve and transition into an extratropical cyclone or make landfall and dissipate. TC forecast inaccuracy comes both from errors in the numerical weather prediction models and from errors in the analyzed initial conditions. Concerning the latter, the lack of observations over the open-ocean regions where TCs spend most of their lifetime degrades the quality of initial conditions and the
1. Introduction Increasing attention has been recently drawn to the possible importance of the stratosphere in seasonal and extended-range forecasts for Northern Hemisphere (NH) winter. A basic idea of the stratospheric importance largely came from the pioneering observational works by Baldwin and Dunkerton (1999 , 2001 ), who showed the downward-propagation tendency of northern annular mode (NAM) anomalies from the stratosphere to the troposphere (see also Kodera et al. 1990 ; Kodera 1995
1. Introduction Increasing attention has been recently drawn to the possible importance of the stratosphere in seasonal and extended-range forecasts for Northern Hemisphere (NH) winter. A basic idea of the stratospheric importance largely came from the pioneering observational works by Baldwin and Dunkerton (1999 , 2001 ), who showed the downward-propagation tendency of northern annular mode (NAM) anomalies from the stratosphere to the troposphere (see also Kodera et al. 1990 ; Kodera 1995
1. Introduction Much attention has been directed in recent years toward improving tropical cyclone intensity forecasts ( Gall et al. 2013 ), especially since there has been comparatively little improvement in measures of intensity skill in the last few decades ( DeMaria et al. 2014 ). Within the community of scientists working on tropical cyclones, efforts have been directed toward improving dedicated tropical cyclone models (e.g., Gopalakrishnan et al. 2011 ), real-time in situ and remote
1. Introduction Much attention has been directed in recent years toward improving tropical cyclone intensity forecasts ( Gall et al. 2013 ), especially since there has been comparatively little improvement in measures of intensity skill in the last few decades ( DeMaria et al. 2014 ). Within the community of scientists working on tropical cyclones, efforts have been directed toward improving dedicated tropical cyclone models (e.g., Gopalakrishnan et al. 2011 ), real-time in situ and remote
given trajectory (and therefore are often referred to as optimal modes). Thus SVs have utility for the study of the growth of initial (small but finite sized) errors in the numerical weather prediction problem. Lorenz (1965) points out that the mean square of the singular values would provide the forecast error variance, given an appropriate initial-time metric. Singular vectors have been applied to fundamental geophysical fluid dynamic studies ( Trefethen et al. 1993 ; Farrell 1982 ; Penland
given trajectory (and therefore are often referred to as optimal modes). Thus SVs have utility for the study of the growth of initial (small but finite sized) errors in the numerical weather prediction problem. Lorenz (1965) points out that the mean square of the singular values would provide the forecast error variance, given an appropriate initial-time metric. Singular vectors have been applied to fundamental geophysical fluid dynamic studies ( Trefethen et al. 1993 ; Farrell 1982 ; Penland
1. Introduction Prediction of tropical cyclone intensity remains a significant challenge, with little improvement in forecast skill over the past few decades ( DeMaria et al. 2014 ). This lack of improvement has been attributed to a variety of factors, from inadequate observations of the atmosphere and upper ocean, to lack of ability to assimilate observations, to model errors, but in recent years there has been a concerted effort to improve intensity forecasts ( Gall et al. 2013 ). In a
1. Introduction Prediction of tropical cyclone intensity remains a significant challenge, with little improvement in forecast skill over the past few decades ( DeMaria et al. 2014 ). This lack of improvement has been attributed to a variety of factors, from inadequate observations of the atmosphere and upper ocean, to lack of ability to assimilate observations, to model errors, but in recent years there has been a concerted effort to improve intensity forecasts ( Gall et al. 2013 ). In a
1. Introduction Improvements have been made over the past three decades in our ability to forecast the track of tropical cyclones (TCs) (see www.nhc.noaa.gov/verification ), which is primarily determined by synoptic-scale environmental flow ( Wu and Emanuel 1993 ; Wu and Kurihara 1996 ; Wang et al. 1998 ). Despite this progress, our ability to accurately predict intensity change remains quite limited ( Elsberry et al. 2007 ; Houze et al. 2007 ). The inner-core region of a TC is governed by
1. Introduction Improvements have been made over the past three decades in our ability to forecast the track of tropical cyclones (TCs) (see www.nhc.noaa.gov/verification ), which is primarily determined by synoptic-scale environmental flow ( Wu and Emanuel 1993 ; Wu and Kurihara 1996 ; Wang et al. 1998 ). Despite this progress, our ability to accurately predict intensity change remains quite limited ( Elsberry et al. 2007 ; Houze et al. 2007 ). The inner-core region of a TC is governed by
