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Louis W. Uccellini and Paul J. Kocin

Abstract

The interaction of transverse vertical circulations associated with two separate jet steak/trough systems is found to be a common feature of cyclogenetic events which produce heavy snow along the East Coast of the United States. The transverse circulations are identified for eight cases that span the period from 1960 to 1987 utilizing an isentropic analysis of the operational radiosonde data. The analyses depict the interaction of 1) a direct circulation located within the confluent entrance region of an upper-level jet streak over the northeastern United States or southeastern Canada with 2) an indirect circulation in the diffluent exit region of a jet streak associated with a trough nearing the East Coast. This interaction contributes to differential moisture and temperature advections and vertical motions necessary to produce heavy snowfall along the coast. It is suggested that the circulation patterns associated with the jet streak establish an environment within which boundary layer processes (e.g., cold-air damming, coastal frontogenesis, the development of a low-level jet Streak) can further contribute to cyclogenesis and the development of severe winter weather conditions.

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Paul J. Kocin, Alan D. Weiss, and Joseph J. Wagner

Abstract

An unprecedented period of extreme cold accompanied by an intense East Coast blizzard during February 1899 is documented through an examination of detailed surface weather charts constructed from original data. The surface weather analyses depict the passage of several anticyclones of Canadian or polar origin that propagated southward, spreading progressively colder temperatures throughout the central, eastern, and southern United States. This series of cold outbreaks culminated in the southward plunge of one final, massive anticyclone that yielded the coldest temperatures on record for much of the south-central and southeastern United States. The final cold wave was associated with the development of a cyclone that left measurable snow over most of the Gulf Coast and Florida and then produced severe blizzard conditions along much of the East Coast.

To place this period in historical perspective, minimum temperatures recorded during February 1899 are compared with minimum temperatures measured during more recent cold air outbreaks. Snowfall records set during February 1899 that have never been exceeded are also documented. Examples of extreme weather events such as this enable forecasters and students to gain practical experience by visualizing the meteorological patterns these events are associated with, by acquiring a historical perspective when assessing other events, and by gaining an appreciation of the limits of severity that atmospheric phenomena can attain.

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George J. Maglaras, Jeff S. Waldstreicher, Paul J. Kocin, Anthony F. Gigi, and Robert A. Marine

Abstract

The complex combination of synoptic- and mesoscale interactions topographic influences, and large population densities poses a multitude of challenging problems to winter weather forecasters throughout the eastern United States. Over the years, much has been learned about the structure, evolution, and attendant precipitation within winter storms. As a result, numerous operational procedures, forecast applications, and objective techniques have been developed at National Weather Service offices to assess the potential for hazardous winter weather.

An overview of the challenge of forecasting winter weather in the eastern United States is presented, including a historical review of several legendary winter storms, from the Blizzard of 1888 to the Halloween Nor'easter of 1991. The synoptic-scale features associated with East Coast winter storms are described. The mesoscale nature of many eastern winter weather events is illustrated through an examination of the Veterans' Day Snowstorm of 11 November 1987, and the Long Island Snowstorm of 13 December 1988. The development of applied forecast techniques and the potential for new remote sensing technologies (e.g., Doppler weather radar and wind profilers) and mesoscale models to improve operational forecasts of winter weather hazards are also discussed. Companion papers focus on cyclogenesis, terrain-related winter weather forecast considerations in the Southeast, and lake effect snow forecasting.

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Paul J. Kocin, David A. Olson, Arthur C. Wick, and Robert D. Harner

Abstract

The preparation of surface weather analyses at the National Meteorological Center (NMC) is currently under review. The availability of advanced graphics workstations and consideration of revisions to conceptual models of cyclogenesis and frontal analysis present challenges and opportunities for improving surface analysis at NMC. In this paper, current procedures and surface analysis products are reviewed. The adaptation of workstation technology to one surface weather analysis product, the Daily Weather Maps, Weekly Series, is described and presented as a preliminary experiment for assessing the utility of performing surface analyses on interactive workstations. Finally, issues that will impact the future of surface analysis at NMC, such as workstation development, utilization of gridded datasets and their manipulation for improving objective analyses, possible revisions to frontal symbology, incorporation of mesoscale symbology, and changes to sea-level pressure computations, are discussed.

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