Joint Poster Session JP3.4 Relating snowfall patterns over the central and eastern US to infrared imagery of extratropical cyclone comma heads

Wednesday, 3 June 2009
Grand Ballroom Center (DoubleTree Hotel & EMC - Downtown, Omaha)
Darren Van Cleave, CIRA/Colorado State Univ., Fort Collins, CO; and J. F. Dostalek and T. H. Vonder Haar

Handout (2.8 MB)

Geostationary satellite imagery is a valuable tool in the analysis and forecasting of a multitude of weather phenomena. In this study, geostationary satellite imagery is applied to wintertime precipitation forecasting. It has been observed that the pattern of cloudiness seen in GOES (Geostationary Operational Environmental Satellite) 10.7 μm imagery may be related to the swath of snowfall deposited by extratropical cyclones affecting the eastern two-thirds of the United States. In an examination of 30 such cases spanning the last 13 years, two broad categories of cloud-top patterns emerged, each representing approximately 10 of the 30 total cases. The first is the classic comma head shape, for which there is a contiguous cloud shield covering both the comma head and the frontal zones. The brightness temperatures within the cloud shield over the comma head are roughly the same as those over the frontal zones. The second category is characterized by a comma head which is distinct (in a brightness temperature sense) from the frontal cloud band. In these cases, the brightness temperatures over the cloud head indicate warmer cloud top temperatures adjacent to the frontal zone, or possibly over the entire cloud head. Composite snowfall maps reveal a difference between the two categories in the snowfall patterns associated with the comma head. The classic cyclones produced a diffuse swath of snow, while the snowfall pattern of the second category tended to be narrower and better defined.

North American Regional Reanalysis (NARR) data were used to determine the different storm structure between the two cases which is responsible for the differing snowfall patterns. In particular, composite maps of various dynamic and thermodynamic fields were created. The maps show that the two cases do have a differing upper-level jet structure. Additionally, differences in the instability pattern and the wind fields may also contribute to the differences in the snowfall patterns.

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