INTERPRETATION
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Regional and Mesoscale Meteorology Team Cooperative Institute for Research in the Atmosphere (CIRA) Colorado State University Fort Collins, Colorado |
May 7, 1999
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April 13, 1999 |
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Click on images to enlarge or to start loops
On April 13, 1999 a dryline formed in eastern New Mexico and propagated eastward during the day acting to trigger severe thunderstorms. The GOES-10 1 km visible imagery (Figure 1) shows the development of thunderstorms along the dryline. The visible imagery shows the line of towering cumulus along the dryline shortly prior to the development of the supercells (click here to see the features of interest pointed out on the image). The supercells developed rapidly, therefore the 30 minute satellite data does not show the key stages in developing storms as well as Rapid Scan Operations (RSO) would show because of the availability of much more frequent imagery (every 7 minutes).
Wind profiler data from Tucumcari, NM (Figure 2) shows the passage of the dryline between 18:00 and 19:00 UTC. Ahead of the dryline, in the unstable air, the shear profile was favorable for the development of supercells as shown in the wind profiler data from Jayton, TX (Figure 3). Note the veering of the winds at low levels as well as strong winds at mid levels (40 knots at 3000 m).
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The radar reflectivity loop from the Lubbock, TXWSR-88D (Figure 4) 19:10 to 23:45 UTC shows the evolution of the storms. There were reports of tornadoes around Midland, Texas as well as near Snyder, Texas around 00:00 UTC. To see where Midland and Snyder are on a map (click here to see the locations of these places on the image.) The GOES precipitable water derived imagery (Figure 5) from 12:00 to 19:00 UTC shows the movement of the dryline during the day. Note, units are in inches and surface observations are overlaid to illustrate the usefulness of integrated data. This product can illustrate dryline position and movement, especially proir to convective initiation and at night. Another interesting feature that shows up in the satellite imagery is the moist soil caused by the rain from the storms as seen in the 3.9 µm imagery (Figure 6). Notice regions of darker gray next to lighter gray behind the thunderstorms.Click here to see the regions of interest The cooler skin temperature shown in the 3.9 µm imagery, are indicitave of the surface moisture gradient between dry and moist soil in the clear air behind the dryline. Surface soil moisture had been quite low across the area before this event due to dry conditions. |
