Extended Abstract (304K)P3.4
Water vapor winds in vicinity of convection and winter storms
Robert M. Rabin, NOAA/NSSL, Norman, OK; and J. Brunner, C. Hane, and J. Haynes
Until now, forecast applications of water vapor imagery have included: 1) the assimilation of target-tracked winds into numerical forecast models over ocean areas, and 2) the subjective interpretation of upper-level features from the imagery and comparison with their location and intensity in forecast models. In order to explore the use of target-tracked winds in nowcasting, the CIMSS water vapor wind tracking algorithm has been applied to GOES-8 data on an experimental basis at 30-minute intervals in near real-time over much of the CONUS. This is about 6 times more frequent than the operational water vapor wind products, which are produced at 3-hourly intervals. More importantly, the amount of wind vector editing has been greatly reduced in order to include larger deviations from the model 'guess' fields. This allows the detection of perturbated flow aloft due to convection and other mesoscale features not captured by models.
Analyses from the wind fields include the display of wind vectors and objectively analysed divergence, absolute and relative vorticity, and isotachs at 300 hPa (mb). The objective analysis is based on available wind vectors and a background field from the NOGAPS forecast model. The output of these products is available on the Web and includes interactive displays (http://zonda.ssec.wisc.edu/~rabin/real.html). Comparisons are also available between the analysed fields of divergence, vorticity and isotachs and those from the NOGAPS and RUC-2 models.
The upper air wind fields will be examined for a variety of convective and winter storm events. In the case of convection, the role of inertial instability will be explored by checking for zero or negative absolute vorticity and enhanced upper level divergence during storm growth. The upper air wind properties will also be evaluated for their effect upon storm evolution in comparison with other environmental factors thought to influence lifetime, such as vertical wind shear and thermodynamic stability. Results will be shown for convective events with contrasting evolutionary character, including one system that weakens and one that maintains strength during the early morning hours while crossing the southern Plains.
Supplementary URL: http://zonda.ssec.wisc.edu/~rabin/extendedp.pdf
Poster Session 3, Operational Applications
Tuesday, 16 October 2001, 9:15 AM-11:00 AM
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