Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Monday June 16, 1997
-
Today's discussion concerns a special 1-minute interval super-rapid-scan operation (SRSO)
data set collected last Saturday to study thunderstorms. Routine GOES imagery
is scheduled at 15-minute intervals with the exception of 3-hourly full-disk scans.
Special research requests for rapid scanning can be made from both operational
and research focal points. CIRA/RAMM is such a focal point for requesting
research data sets from NESDIS.
The particular image shown above is a 1km visible image from GOES-8 with cloud-track winds plotted on top. The sequence of imagery used to derive the winds was from 2030z until 2045z. There were 8 1-minute interval images and an additional image on each side of that.
These images had very nice cirrus tracers from which to derive cloud drift winds. Typically, you need to have discrete cloud elements that move and can be identified through the entire sequence. These winds were manually derived in contrast to some of the more automated methods that are also available.
It was quite interesting to find that several of the cloud tracks produced the same or similar velocities. This is a good sign that the flow was in fact similar to the cloud motions. There is a wind at the center-top of the image that was retrieved from the cumulus field at the lower levels. The remaining winds are from tracking cirrus clouds. A few retrievals such as this can be useful in confirming speed maxima and relative motions...especially in the pre-storm and pre-warning time frames.
Some interesting things to note:
1) The max wind retrieved manually is 120 kts and is plotted in the upper-left part of the image.
2) The wind (the cloud!) between the storms is moving considerably slower than those around it.
3) To the south and east of the storms, you can see speed divergence in the cirrus from SW to NE.
Notice the wind speeds decrease from the northeast to the southwest in the region south of the two largest storms.
Notice the difference between the first and second and last and next-to-last frames. The eight frames in the middle are 1-minute interval images. Here's the loop !
Brian Motta