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of the North Atlantic waveguide, NAWDEX also offered a unique opportunity to explore HIW predictability. To the best of our knowledge, the NAWDEX period provides the most complete set of combined wind, humidity, temperature, and cloud profile observations of the North Atlantic jet stream yet assembled. This dataset will form the basis of detailed case studies and evaluations of weather and climate prediction models for many years. The widespread coverage of high-resolution multivariate cross
of the North Atlantic waveguide, NAWDEX also offered a unique opportunity to explore HIW predictability. To the best of our knowledge, the NAWDEX period provides the most complete set of combined wind, humidity, temperature, and cloud profile observations of the North Atlantic jet stream yet assembled. This dataset will form the basis of detailed case studies and evaluations of weather and climate prediction models for many years. The widespread coverage of high-resolution multivariate cross
nondivergent wind field by inverting the vorticity enclosed in a circle of radius R = 600 km, centered at TC location in IBTrACS. Second, the algorithm does not consider the axis of the troughs but evaluates so-called “trough objects,” contiguous regions of cyclonic vorticity advection (CVA) larger than , where and is the component of vorticity due to the curvature of the flow only. Finally, unlike African easterly waves, midlatitude troughs propagate along the westerly jet stream, and therefore
nondivergent wind field by inverting the vorticity enclosed in a circle of radius R = 600 km, centered at TC location in IBTrACS. Second, the algorithm does not consider the axis of the troughs but evaluates so-called “trough objects,” contiguous regions of cyclonic vorticity advection (CVA) larger than , where and is the component of vorticity due to the curvature of the flow only. Finally, unlike African easterly waves, midlatitude troughs propagate along the westerly jet stream, and therefore
data assimilation based on a study of equatorial waves in ECMWF short-range forecast errors . Quart. J. Roy. Meteor. Soc. , 131 , 987 – 1011 , https://doi.org/10.1256/qj.04.54 . 10.1256/qj.04.54 Žagar , N. , M. Blaauw , B. Jesenko , and L. Magnusson , 2016 : Diagnosing model performance in the tropics. ECMWF Newsletter , No. 147, ECMWF, Reading, United Kingdom, 26–33. Zaitchik , B. F. , 2017 : Madden–Julian oscillation impacts on tropical African precipitation . Atmos. Res
data assimilation based on a study of equatorial waves in ECMWF short-range forecast errors . Quart. J. Roy. Meteor. Soc. , 131 , 987 – 1011 , https://doi.org/10.1256/qj.04.54 . 10.1256/qj.04.54 Žagar , N. , M. Blaauw , B. Jesenko , and L. Magnusson , 2016 : Diagnosing model performance in the tropics. ECMWF Newsletter , No. 147, ECMWF, Reading, United Kingdom, 26–33. Zaitchik , B. F. , 2017 : Madden–Julian oscillation impacts on tropical African precipitation . Atmos. Res
; moreover, the forecast became rather poor after a lead time of as little as 5 days. The latter result seems to be at odds with the commonly held view that large-scale phenomena such as RWPs should be predictable on a rather long time scale. However, this evaluation was for a single case only involving a single forecast model; further systematic studies are required to possibly generalize these results. Regarding the waveguide, several operational forecast models are fraught with a spurious decrease of
; moreover, the forecast became rather poor after a lead time of as little as 5 days. The latter result seems to be at odds with the commonly held view that large-scale phenomena such as RWPs should be predictable on a rather long time scale. However, this evaluation was for a single case only involving a single forecast model; further systematic studies are required to possibly generalize these results. Regarding the waveguide, several operational forecast models are fraught with a spurious decrease of
pre-Chris cyclone. An ensemble member thus belongs to the cyclone (no-cyclone) group when it predicts (lacks) such a “similar track.” Group names are italicized hereafter to better distinguish them from text. c. Cyclone tracking and evaluation of forecast tracks The simple cyclone tracking algorithm described by Hart (2003) is employed here because its performance compared to manual tracking was found to be acceptable. Based on mean sea level pressure data, this approach successively evaluates 5
pre-Chris cyclone. An ensemble member thus belongs to the cyclone (no-cyclone) group when it predicts (lacks) such a “similar track.” Group names are italicized hereafter to better distinguish them from text. c. Cyclone tracking and evaluation of forecast tracks The simple cyclone tracking algorithm described by Hart (2003) is employed here because its performance compared to manual tracking was found to be acceptable. Based on mean sea level pressure data, this approach successively evaluates 5
circumglobal waves (e.g., Lee and Held 1993 ; Chang 1993 ). Although theoretical arguments for the evolution of Rossby waves in idealized setups had already been put forward in the middle of the twentieth century ( Dickinson 1978 , and references therein), their actual behavior and role in the atmosphere started being investigated in recent decades, facilitated by the increasing data availability and advances in computer performance [see Wirth et al. (2018) for a review of recent developments]. In this
circumglobal waves (e.g., Lee and Held 1993 ; Chang 1993 ). Although theoretical arguments for the evolution of Rossby waves in idealized setups had already been put forward in the middle of the twentieth century ( Dickinson 1978 , and references therein), their actual behavior and role in the atmosphere started being investigated in recent decades, facilitated by the increasing data availability and advances in computer performance [see Wirth et al. (2018) for a review of recent developments]. In this
appropriate in the current context is the wave activity flux of Takaya and Nakamura (2001) . One particular feature of this formulation is its phase independence; this means that it discounts individual troughs and ridges and focuses on the dynamics of the entire wave packet instead ( Danielson et al. 2006 ). Focus on the entire wave packet is desirable, for instance, when studying model errors as opposed to initial condition errors ( Gray et al. 2014 ), and it would be interesting to find out whether
appropriate in the current context is the wave activity flux of Takaya and Nakamura (2001) . One particular feature of this formulation is its phase independence; this means that it discounts individual troughs and ridges and focuses on the dynamics of the entire wave packet instead ( Danielson et al. 2006 ). Focus on the entire wave packet is desirable, for instance, when studying model errors as opposed to initial condition errors ( Gray et al. 2014 ), and it would be interesting to find out whether
