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Theodore W. Funk

Abstract

Meteorologists within the Forecast Branch (FB) of the National Meteorological Center (NMC) produce operational quantitative precipitation forecasts (QPFs). These manual forecasts are prepared utilizing various forecasting techniques, which are based on the subjective analysis and interpretation of the observed data and numerical model output. The manual QPFs from NMC generally have proven very successful in improving model QPF.

This paper discusses several of the forecasting techniques employed by the FB, emphasizing the importance of subjective interpretation of the model guidance. The use of these methods in preparing a manual QPF for a heavy convective rainfall and flash-flood event that occurred over the southern Plains on 27–28 May 1987 is then examined.

Results indicate that the manual QPF was quite successful in improving the models’ QPF and generally related well to the observed rainfall of up to 8 inches in this case. Thus, the importance of utilizing subjective techniques in preparing precipitation forecasts is illustrated.

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Henry E. Fuelberg
and
Theodore W. Funk

Abstract

Satellite-derived temperature profiles are used to determine if reliable estimates of synoptic-scale vertical motion can be obtained from the adiabatic, vorticity, and omega equation techniques. The period of study contains a short-wave trough over the Midwest and a convective outbreak over the middle Mississippi River Valley. Satellite soundings are available at 1–3 h intervals at five times. The emphasis is on assessing the strengths and weaknesses of the three vertical motion procedures and determining the effects of short-interval observations on the calculations.

Results show that the quasi-geostrophic omega equation provided patterns and magnitudes most consistent with observed weather events and 12 h radiosonde-derived motions. The vorticity method produced less satisfactory results, while adiabatic motions were unacceptable. The time derivative term dominated adiabatic motions and was a major influence in the vorticity method. Unrealistic temperature tendencies resulted from the retrieval algorithm; i.e., a diurnal temperature bias extended upwards to 500 mb, and there was a compensating effect at higher levels.

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Theodore W. Funk
,
Kevin E. Darmofal
,
Joseph D. Kirkpatrick
,
Van L. DeWald
,
Ron W. Przybylinski
,
Gary K. Schmocker
, and
Yeong-Jer Lin

Abstract

A long-lived highly organized squall line moved rapidly across the middle Mississippi and Ohio Valleys on 15 April 1994 within a moderately unstable, strongly sheared environment. Over Kentucky and southern Indiana, the line contained several bowing segments (bow echoes) that resulted in widespread wind damage, numerous shear vortices/rotational circulations, and several tornadoes that produced F0–F2 damage. In this study, the Louisville–Fort Knox WSR-88D is used to present a thorough discussion of a particularly long-tracked bowing line segment over central Kentucky that exhibited a very complex and detailed evolution, more so than any other segment throughout the life span of the squall line. Specifically, this segment produced abundant straight-line wind damage; cyclic, multiple core cyclonic circulations, some of which met mesocyclone criteria; several tornadoes; and embedded high precipitation supercell-like structure that evolved into a rotating comma head–comma tail pattern. The bowing segment also is examined for the presence of bookend vortices aloft and midaltitude radial convergence. In addition, the structure of other bowing segments and their attendant circulations within the squall line are discussed and compared with existing documentation. Radar sampling issues and ramifications of the squall line’s complicated structure on the warning process of future similar severe weather events are touched upon as well.

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