A PV-streamer is an elongated band of potential vorticity located at the top of the troposphere. It is mesoscale in width and synoptic scale in length. See Fig. 1 for an example. PV-streamers are being investigated as contributing causes to severe local storms and flash floods through organized convection such as in mesoscale convective systems. A PV-streamer occurring the week following 27 June 1999 brought a succession of mesoscale convective systems to the southern Midwest. 
Severe weather and flash flooding did millions of dollars in damage. One of the mesoscale convective system that has been studied is the one depicted in Fig. 2.

 PV1_strmr.gif (39615 bytes)Fig. 1.  A 250 hPa analysis of potential vorticity (shaded, K kg-1 s-1 10-6 ) and height field based on the 1200 UTC 28 June 1999, 32 km Eta initial analysis in terpolated to an 80 km horizontal grid.

 

PV2cld_wv.gif (253732 bytes)Fig. 2.  A GOES 8 water vapor image for 1215 UTC 28 June 1999 on which is superposed contours of the cloud top temperature computed from the corresponding 11 micron IR satellite image. Note that the PV-streamer is visualized as a dark band in the water vapor image.