DataStreme Activity 11B:

TORNADOES

Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1, Image 2, and Image 3 Files.
  3. Print (when available) the Thursday, 30 November 2000, Daily Summary File.

Notice: Please download and print the Fall 2000 DataStreme Participant Evaluation form in the "Image 3" position with today's Activity. Complete the questionnaire and give it to your LIT leader at the final course meeting.

To Do Activity:

  1. Read Chapter 11 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 11B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 11B Now


Note: Your Study Guide, Part B: Applications binder may be missing page 11B-4 containing questions 4 and 5. They are included below.



centers (usually counterclockwise when viewed from above) and translational motion across the Earth's surface. Where the tornado's movement across the Earth's surface adds to its rotational motion, winds relative to the Earth's surface are strongest. On the other side where the tornado's motion across the Earth's surface subtracts from the tornado's spinning motion, winds are not quite as strong. In the Oklahoma City tornado, the strongest winds were likely on the [(southeast) (northwest)] side of the tornado.

  1. Thunderstorm cells that spawn intense tornadoes such as the Oklahoma City tornado, typically are associated with the warm sector of a mature midlatitude cyclone. Considering the circulation surrounding a low-pressure system and the path of the Oklahoma City tornado, it is likely that its parent thunderstorm formed generally to the [(northwest) (southeast)] of the center of a midlatitude cyclone.

For further reports of this tornado outbreak and images of the destruction, see:

http://www.srh.noaa.gov/oun/storms/19990503/

GO TO: The electronic portion of the DataStreme Activity File.



WELCOME BACK: Procedure continued from STUDY GUIDE.

History repeats! (Well, almost.) In an otherwise unremarkable year for tornadoes (see details in the Wednesday, 29 November Supplemental Information file), Xenia, Ohio experienced dèjá vu this past September. On April 3-4, 1974, the US was hammered by the greatest outbreak of tornadoes in recorded history, termed the "Super-Outbreak" when 148 occurred. Of the dozens of tornadoes in the Ohio area, an F-5 tornado struck Xenia, Ohio, killing 34 people, injuring 1100, and destroying more than 1000 homes. On September 20, 2000, a killer tornado struck Xenia once again. Fortunately because of prior watches and warnings, only one man was killed when a tree fell on his car. The F-4 tornado swept through Xenia on a track almost duplicating that of twenty-six years earlier.

  1. Image 1 is the map of the destruction paths of the Xenia tornadoes. (The map and storm information were provided by the Wilmington, Ohio NWS office. A link to the complete report is given below.) The September 2000 tornado touched down to the southwest of the town about 7:35 PM EDT. The tornado's destruction path across the city was approximately 8 miles long as shown by the darker shaded line (green on-screen) on the map.

    In Image 1, North is to the top of the page. The "F" designations with events along the track refer to levels of destruction based on the Fujita Tornado Intensity Scale, (see Table 11.3 on page 216 of the DataStreme Study Guide, Part A: Narrative). The highest category listed for this tornado was [(F0) (F2) (F4)] which is denoted by the large box indicating damage to one of the houses. Table 11.3 indicates this was due to damage produced by wind speeds estimated to be in the range of _________ - _________ kilometers per hour or _________ - _________ miles per hour.

  2. The tornado path was from [(northwest to southeast) (southwest to northeast)]. This path direction is typical of the majority of tornadoes.

    Conditions at the 700-mb pressure level are representative of the lower to mid-troposphere. Winds at the 700-mb level are frequently associated with the direction of movement of thunderstorms. Upper-air soundings at 00Z 21 SEP 2000 (8 PM EDT on the 20th) over Wilmington indicated that the wind at the 700-mb pressure level was from the west-southwest at 70 knots. This southwesterly wind direction [(was) (was not)] broadly consistent with the northeastward movement of the tornado and, hence, its parent thunderstorm cell.

    The lighter shaded path (dark yellow on-screen) was the damage track of the Xenia tornado of April 3, 1974. The 1974 tornado followed a similar direction roughly parallel to the September 2000 tornado path, but about one mile to the southeast.

Image 2 is a Wilmington NWS Doppler radar display of storm precipitation intensity near the time of tornado touchdown. The radar site is located at the bottom center of the image (circle). The location of Xenia is in the center of the image (name partially visible). Xenia is located just to the north of the medium gray shaded area of most intense echoes (red on-screen). The radar shows the typical view of a supercell thunderstorm. The frequent position for tornado formation in supercell thunderstorms is the southwest edge of the storm. This location is the light shaded wedge (yellow on-screen) about 7 pixel blocks southwest of Xenia. With the supercell thunderstorm radar structure, aforementioned lower tropospheric wind direction, typical direction of tornado travel, and other meteorological indicators, an NWS meteorologist would seriously consider issuing a tornado warning for the Xenia area.


The Wilmington, OH, National Weather Service page that contains the maps, radar images, and pictures of the tornado destruction is at: http://www.nws.noaa.gov/er/iln/past.htm. The most recent listing of deadly tornado occurrences compiled by the NWS Storm Prediction Center can be found at: http://www.spc.noaa.gov/climo/torn/2000deadlytorn.html.

Additional reports of other tornado episodes containing NWS radar imagery can be found at the following links:

Your local NWS office homepages may have links to notable severe weather episodes in your area. Finally, for an account of the historic Super Tornado Outbreak of 1974, see: http://www.publicaffairs.noaa.gov/storms/.


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday, 4 December 2000:


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