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John F. Dostalek
and
Timothy J. Schmit

Abstract

Statistics are compiled comparing calculations of total precipitable water (TPW) as given by GOES sounder derived product imagery (DPI) to that computed from radiosonde data for the 12-month period March 1998–February 1999. In order to investigate the impact of the GOES sounder data, these results are evaluated against statistics generated from the comparison between the first guess fields used by the DPI (essentially Eta Model forecasts) and the radiosonde data. It is found that GOES data produce both positive and negative results. Biases in the first guess are reduced for moist atmospheres, but are increased in dry atmospheres. Time tendencies in TPW as measured by the DPI show a higher correlation to radiosonde data than does the first guess. Two specific examples demonstrating differences between the DPI and Eta Model forecasts are given.

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John F. Dostalek
,
John F. Weaver
, and
G. Loren Phillips

Abstract

A severe left-moving thunderstorm occurred on 25 May 1999 between the cities of Lubbock and Amarillo, Texas. Over its 3.5-h lifetime, the storm was responsible for flash flooding, reports of hail of up to 7 cm in diameter, and two weak tornadoes. Satellite imagery reveals that it was traveling along the northward-moving outflow boundary of the storm from which it formed. The left mover displayed anticyclonic rotation, as was seen in storm-relative radial velocity imagery from the Weather Surveillance Radar-1988 Doppler (WSR-88D) located at Lubbock. The tornadoes developed west of Canyon, Texas, near the intersection of the left mover and a southward-moving boundary. The occurrence of tornadoes with a left mover is a particularly noteworthy event; to the authors' knowledge, only four other tornadic left movers have been reported in the meteorological literature.

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John F. Dostalek
,
John F. Weaver
,
James F. W. Purdom
, and
Karen Y. Winston

Abstract

No abstract available.

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John Kaplan
,
Christopher M. Rozoff
,
Mark DeMaria
,
Charles R. Sampson
,
James P. Kossin
,
Christopher S. Velden
,
Joseph J. Cione
,
Jason P. Dunion
,
John A. Knaff
,
Jun A. Zhang
,
John F. Dostalek
,
Jeffrey D. Hawkins
,
Thomas F. Lee
, and
Jeremy E. Solbrig

Abstract

New multi-lead-time versions of three statistical probabilistic tropical cyclone rapid intensification (RI) prediction models are developed for the Atlantic and eastern North Pacific basins. These are the linear-discriminant analysis–based Statistical Hurricane Intensity Prediction Scheme Rapid Intensification Index (SHIPS-RII), logistic regression, and Bayesian statistical RI models. Consensus RI models derived by averaging the three individual RI model probability forecasts are also generated. A verification of the cross-validated forecasts of the above RI models conducted for the 12-, 24-, 36-, and 48-h lead times indicates that these models generally exhibit skill relative to climatological forecasts, with the eastern Pacific models providing somewhat more skill than the Atlantic ones and the consensus versions providing more skill than the individual models. A verification of the deterministic RI model forecasts indicates that the operational intensity guidance exhibits some limited RI predictive skill, with the National Hurricane Center (NHC) official forecasts possessing the most skill within the first 24 h and the numerical models providing somewhat more skill at longer lead times. The Hurricane Weather Research and Forecasting Model (HWRF) generally provides the most skillful RI forecasts of any of the conventional intensity models while the new consensus RI model shows potential for providing increased skill over the existing operational intensity guidance. Finally, newly developed versions of the deterministic rapid intensification aid guidance that employ the new probabilistic consensus RI model forecasts along with the existing operational intensity model consensus produce lower mean errors and biases than the intensity consensus model alone.

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