WELCOME BACK: Procedure continued from STUDY GUIDE.
According to statistics from the Storm Prediction Center in Norman, Oklahoma, this year so far, has been below average in the total number of tornadoes. While March and July were about average, most months were below average in tornado occurrence. February was the exception. The number of deaths this year is also below average, although February was again the exception. Those February numbers included a deadly outbreak on 13-14 February in southwest Georgia. From Sunday evening, 13 February, into the morning hours of Monday, the 14th, the Tallahassee, Florida NWS office issued 26 tornado, 21 severe thunderstorm, and 3 special marine warnings. Three tornadoes occurred which caused the loss of 18 lives in 3 Georgia counties, an event unequaled in south Georgia in nearly 50 years.
One supercell thunderstorm developed in the panhandle of Florida at 8:45 PM EST on 13 February and caused wind damage in Florida before temporarily weakening as it moved northeastward into Georgia. It then rapidly regained strength and became tornadic around 11:42 and passed just south of Camilla as an F3 tornado before dissipating around midnight. This tornado was responsible for 11 deaths in the Camilla vicinity. Another cell developed about the same time as the one near Camilla dissipated and followed nearly the same track, but fortunately its circulation did not reach the ground! (The information and images used in this activity were provided by the National Weather Service Office in Tallahassee.)
Image 1 is a portion of a NWS map (north is toward the top) showing the tracks of three deadly tornadoes in southwest Georgia during the episode. Camilla is located just above the middle of the track labelled "Camilla F3 Tornado". The heavy line represents the approximately 9 mile path of damage produced by the tornado. Draw a bold arrowhead on the upper right end of the Camilla track to show its direction of motion. The Camilla tornado and its parent thunderstorm, like the others, traveled from [(southwest to northeast) (northwest to southeast)].
An F3 tornado, according to the Fujita Tornado Intensity Scale, Table 11.3, p. 216 of the Study Guide Part A, Narrative, is estimated to have wind speeds of _________ to _________ km/hr (_________ to _________ mi/hr).
Image 2 is a combination display of radar reflectivity (on left) and of radial velocity (on right) from the thunderstorms in the area north of the Tallahassee radar site at 0529Z. Precipitation particles inside the thunderstorm cells returned radar signals which can be interpreted to show both the intensity of the precipitation and the motions toward or away from the radar site. In the displays, north is toward the top of each view. The radar site is located to the south beyond each view, as may be inferred by the curvature of the picture elements (pixels) in the displays.
Each display square is about 40 miles on a side. On the left, reflectivity display, the dark and medium grays (best seen as the reds in screen view) within the shaded area of the center represent the strongest radar returns from the heaviest precipitation (largest particles) and possibly from hail. These shadings correspond to the radar depictions seen in Activity 7A.
On the right, radial velocity display, the darker shadings from lower center to upper right (reds in screen view) depict motion away from the radar site (bottom) and are denoted as "positive" velocities. Medium gray shadings (greens in screen view) to the left center depict motion toward the radar site ("negative" velocities). Computer analysis of the motion patterns allows identification of "mesocyclone" signatures or strong wind shear where motion away and motion toward the radar are side-by-side. These mesocyclones are shown as circles (yellow on screen). The large circle labelled "3" about 9 miles southwest of Camilla is located near the beginning of the damage path of the tornado shown in Image 1. A stronger wind shear is identified as a "tornadic vortex signature" and is represented by the small triangle "a" (red on screen) within the circle. (The mesocyclone and tornadic vortex signature symbols are determined by computer analysis of the changes in radial wind speeds.)
Draw short, bold arrows on circle #3 to depict the orientations of the radial velocities to the right and left of the circle. The arrow to the right is in the area of red and so would be directed [(toward) (away from)] the radar site (at bottom). The arrow to the left is in the area of green and so would be directed [(toward) (away from)] the radar site. Draw arrows to the north and south of the circle to complete the probable rotational motion. [This mesocyclone appearance is often a predictor of tornado formation at the ground. The tornadic vortex signature is even stronger evidence.]
The mesocyclone circulation you have outlined with the arrows is [(clockwise) (counterclockwise)] as seen from above. This rotation is in the [(same) (opposite)] direction as that of winds around a low-pressure center. (Other mesocyclones are indicated by circles 1 and 2. And a second tornadic vortex signature is shown in circle 1.)
A line from the radar's position through the center of the circle you drew would be [(parallel) (perpendicular)] to the arrows you drew on the top and bottom parts of the circle. The shading change of the pixels (red/green on screen) along this line within the circle indicate essentially no radial velocity relative to the radar. While this "Doppler wind" is small or zero along this line, there [(was) (was not)] an actual wind motion (as depicted by your arrows). [The color scheme indicates that speeds at the locations of the right and left arrows were approximately 50 knots.]
For a complete description of this Camilla tornado and a picture of the damage, go to http://www.srh.noaa.gov/tlh/feb14event/text.htm. For other reports of severe weather, including tornadoes, in your area, you can go to the National Climatic Data Center page at: http://www.ncdc.noaa.gov/ol/climate/severeweather/extremes.html and choose "US Local Storm Reports", or "US Tornadoes".
NOAA Weather radio and television often provide local radar information. When storm systems threaten, compare DataStreme radar products and maps with local media reports to monitor how large scale weather systems affect your local area.
After completing this week's applications, fax the following pages to your LIT mentor by Monday, 30 October 2000:
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