SO441
Lab 1 – Understanding tornadoes (100 points)
Background
This semester in Synoptic, we are starting with the R. Tao article and its claims regarding mitigation
of the tornado threat. In order to critically evaluate his claims, however, we must know many details about
severe convective storms, and synoptic meteorology in general. Tao’s major claim regards tornado
prevention. However, he makes many other assertions throughout the article. Some regard geography,
others meteorology. Some of them have good merit, but others are dubious (at best). This lab is designed
to do two things: (1) have you organize the claims and statements in the Tao paper, and (2) have you
begin to unpack the meteorological reasons behind one of nature’s most extreme events, the tornado.
Lab objectives
At the conclusion of this lab, you should be able to:
1. Explain the primary arguments made by R. Tao in “Eliminating the major tornado threat in
Tornado Alley”.
2. Describe a tornado and how it forms.
3. Discuss atmospheric conditions that are favorable (and unfavorable) for tornado formation.
Tasks
1. Read the R. Tao paper. (If you have already read it, read it again).
a. While reading the paper, jot down claims of fact made by Dr. Tao.
b. Also jot down any terms that you do not understand or find confusing.
c. Make note (write them down) of all equations that Dr. Tao uses.
2. Answer the questions on the following pages based on the R. Tao paper and your own research.
Deliverables
1. Answers to questions on the pages to follow using a word processing application. Questions 6
and 9 require you to produce figures and include them with your lab to turn in.
2. Your notes from the Tao paper:
a. Claims of fact made by Dr. Tao.
b. Terms you do not understand or find confusing.
c. All equations used by Dr. Tao.
Questions from R. Tao paper.
Answer all questions individually. You are free to discuss the questions with your classmates, but
splitting up the questions between multiple people is unacceptable.
**Note: the answers to a majority of the questions will most often NOT BE FOUND in the Tao paper! Use
all resources at your disposal: web, each other, your instructors.
1. Action: Read/Re-Read the Tao Paper
a. Deliverables:
i. While reading the paper, jot down claims of fact made by Dr. Tao.
ii. Also jot down any terms that you do not understand or find confusing.
iii. Make note (write them down) of all equations that Dr. Tao uses.
2. Deliverables: (You will need to research this)
a. What is the Enhanced Fujita intensity scale?
b. How does it work?
c. What are its strengths and weaknesses?
3. On page 2, Tao claims that tornadoes in the USA are “much more violent than those in Europe
and China.”
a. Deliverables:
i. What is a “violent” tornado? (You’ll need to research this)
ii. Based on the US data provided by Tao in Table 1, what fraction of the
approximately 811 tornadoes in the US in 2013 were “violent”?
iii. What fraction of the approximately 57 European tornadoes should thus be
“violent” if the US fraction applies to Europe?
1. Now examine the data in Table 2; what fraction of EU Tornadoes were
found to be “violent”?
iv. Closely examine Table 2; how many of the 57 tornadoes were given Fujita
classifications? (Table 2 is poorly formatted, but the Wikipedia entry “Tornadoes
of 2013” contains the same information… unless, of course, one of you [or
anyone, really!] gets a whim to change it…).
1. Now apply the US fraction of “Violent” tornadoes to the number of EU
tornadoes that actually received an EF rating; how many should we
expect? (it is okay to give a decimal answer)
v. Based on your answers to this multi-part question, critically evaluate Tao’s claim
that “Tornadoes in USA are much more violent than those in Europe and China.”
4. Tornado alley. Tao claims certain geographic regions of the U.S. can be classified as “tornado
alley”, and he uses www.tornadochaser.net as his source for these claims.
a. Deliverable:
i. What is classically meant by “tornado alley”? (E.g., when you think of the phrase,
what comes to mind?)
b. Action:
i. Now, use the severe climatology tool of the NOAA Storm Prediction Center,
http://www.spc.noaa.gov/new/SVRclimo/climo.php?parm=anySvr, to examine the
week-by-week evolution of severe weather. Look at “Any Severe”, then loop
through probabilities for just tornadoes, just hail, and just wind.
ii. Look at the geographic distribution of F-5 tornadoes from 1950-present
http://www.spc.noaa.gov/faq/tornado/f5torns.html. Reconcile this map with the
yellow-shaded “tornado alley” areas.
c. Deliverable:
i. Finally, write a few sentences critically evaluating Tao’s choice of “tornado alley.”
5. Tao makes a claim about “tornado outbreaks,” but never defines what an outbreak is. The
meteorology community has taken great pains to define a tornado outbreak (and disagreement
still exists).
a. Action:
i. Quickly read
https://www.sercc.com/Fuhrmann_etal_Outbreak_Climatology_WAF.pdf, and
pay special attention to the methods section (2b, page 4).
b. Deliverable:
i. Write some definitions of a “tornado outbreak”, as given in the literature. (Don’t
forget to include the citations.. e.g., “Galway (1977) requires an outbreak to be
one with 10 or more tornadoes.”)
6. Tao makes some very interesting claims regarding seasonal variability of general circulation (the
bit about the Ferrel Cell and “zone of mixing”). Here, it is interesting that the approximately 46degree variability in the latitude of maximum solar radiation (23N on June 21, and 23S on Dec
21), however, Tao’s claim about upper-level wind speeds is incomplete. In winter, most U.S.
tornadoes occur in the Deep South, and in summer, most occur near the Canadian border (you
saw that in your climatological analysis back in question 3).
a. Action: Use the online plotting tool of the NCEP/NCAR Reanalysis,
http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.derived.pressure.html, to
make two figures:
i. Monthly mean zonal (east-west, so that’s the u component) 500 mb wind, for the
months of December and June.
1. To create these two images, click on the little picture to the right of the
row with the first column “u-wind” and second column “Monthly Long
Term Means” in the “Download/Plot Data” table in the link provided,
then…
2. Click the picture to the left of the Monthly Long Term Mean from 19812010 (it’s the 5th picture in the table from the bottom of the page).
3. Choose
a. 500 mb
b. Begin Dec and End Dec
c. Plot on a white background
d. Contour Fill
e. scale plot at 175%
f. Contour interval 2.5
g. Contour range -5 to 25
ii. Monthly mean zonal 500mb wind for June
1. Repeat for June
b. Deliverable: Include the figures you produced then Write a few sentences about the
differences in zonal (east-west) wind speed over the US in December vs June. Based on
these two plots alone, where might you expect U.S. tornadoes in December? What
about June? (i.e. Where is the jet stream?)
7. Tao says “At a certain season, the warm air flow front clashes with the cold air flow front at some
place in Tornado Alley. Major tornadoes in Tornado Alley all start with such clashes.” This is a
very bold claim that requires much more in-depth analysis. Here, let’s tackle one part of this
claim. On Pg. 5, Tao claims that “vortex turbulence” (a term he may have invented, as it’s not
commonly used in meteorology) is created from “northbound winds near the ground and strong
cold southbound winds aloft”. Fortunately, decades of careful and time-consuming field work and
analysis has provided us with much more detail than the simple process described by Tao. To
specifically examine his claim of the south winds at the surface and north winds aloft we will look
at the following
a. Action: Visit http://www.srh.noaa.gov/oun/?n=events-19990503-maps. Here the NWS
has compiled a wealth of information about the most studied tornado outbreak, the one in
central Oklahoma in May 1999. There’s lots of information here (feel free to while away
your free time reading and looking), but we’re specifically interested in the Norman
sounding (KOUN) at 00UTC. It’s hyperlinked near the bottom. Pay special attention to
the winds along the right-hand side (yellow barbs are 00UTC, while purple barbs are the
12UTC morning sounding before the tornado event).
b. Deliverable: What is the wind direction at the surface? What is the wind direction at 850
mb? At 700 mb? At 500 mb? At 250 mb? Based on this sounding, which very nicely
captured the tornadic environment that produced the violent F-5 tornado that afternoon,
critically examine Tao’s claim of “vortex turbulence” being created by south winds at the
surface and north winds aloft.
8. Let’s leave behind the claim of vortex stretching and reduction in the diameter of the vortex tube
(pages 6 and 7, and Table 3). The final major claim of Tao is the role of topography in reducing
tornado threats.
a. Deliverable: Summarize his argument, including the anecdotal evidence from China.
9. One of the other anecdotal evidences Tao gives in support of his wall hypothesis is the case of
the Ozark Mountains (AR and MO) and the Shawnee Hills (IL).
a. Action: Use the SPC Severe Plot 3.0 tool to play around with tornado occurrences in the
US over this period. http://www.spc.noaa.gov/climo/online/sp3/plot.php
i. (Trick: there is sometimes a bug in the plotter, with the date defaulting back to
one day after the start. To get around this, change the other parameters (suggest
you isolate tornadoes), then click submit, then in the URL, change the start
and/or end dates to suit you similar to below in the address bar).
ii. Plot all tornado occurrences (F0-F5) for 2000-2013. Try to identify either the
Ozarks or the Shawnee Hills.
b. Write Up: Include that figure you generated above in your write up. Then, critically
analyze Tao’s evidence for his wall theory, based on the case of the Ozarks and
Shawnee Hills.