NOAA-NESDIS
Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Wednesday May 27, 1998
Today's discussion is a follow-up on the May 21st pic-o-day . On the 21st we showed three views of a severe convective storm in Nebraska. The imagery of that storm showed an enhanced-V signature (V-shaped cold IR cloud top pattern) in the 10.7 micrometer channel. Today's images focus on the warm wake (that region within the V that is warmer than the surrounding cloud tops).
Figure 1 Figure 2
Fig. 1 (NOAA GOES-9 Channel 4, 10.7 micrometers) click to enlarge Fig. 2 (NOAA GOES-9 Visible, .65 micrometers) click to enlarge
These images show that the warm wake (Figure 1, 10.7 micrometer image) is collocated with the cirrus plume (i.e., the latitude and longitude of the warm wake and cirrus plume are the same) as seen in the visible image (Figure 2). The cirrus plume has overshot the main anvil, as shown by the shadow seen on the east side of the plume. Given that the plume is higher than the rest of the anvil in that region, one would expect the IR temperature of the plume to be the coldest point. However, the plume shows up warmer than its surroundings. A possible explanation for this is that the plume has entered the stratosphere. Once within the stratosphere, the plume could mix to become neutrally buoyant and then be carried downstream creating an elongated warm region as seen in this example.

Eric Hilgendorf and Louie Grasso

For those interested in reading more about the warm wake and enhanced-V signatures in satellite imagery and various theories behind their formation, see the following:

Adler, R.F., M.J. Markus, D.D. Fenn, G. Szejwach, and W.E. Shenk, 1983: Thunderstorm top structure observed by aircraft overflights with an infrared radiometer. J. Climate and Appl. Meteor., 22, 579-593.

Heymsfield, G. M., and Blackmer, Jr., 1988: Satellite-observed characteristics of Midwest Severe Thunderstorm Anvils. Mon. Wea. Rev., 116, 2200-2224.

_____, and G. Szejwach, 1983: Upper-level structure of Oklahoma Tornadic Storms on 2 May 1979. II: Proposed explanation of "V" Pattern and Internal Warm Region in Infrared Observations. J. Atmos. Sci., 40, 1756-1767.






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