Department of Earth & Climate Sciences                                            Spring 2018

Meteorology 260                                                         Name _____________________

 

Laboratory #11:  Joplin Tornado Day

Subsynoptic, Thermodynamic, and Wind Shear Setting

Due Date:  Friday 4 May

 

Part A:  2200 UTC Midafternoon Surface Chart Subsynoptic Analyses (100 pts)

Part B:  1200 UTC Sounding Analyses (100 pts)

Part C:  1200 UTC  CAPE Analyses (100 pts)

Part D:  1200 UTC Hodograph Analyses (100 pts)

 

Purpose of this Assignment:

Š       Operational and Practical Purposes: 

o   To study the subsynoptic, thermodynamic, and wind shear environments in which the Joplin tornadic thunderstorm developed;

Š       Skills and Techniques Learned or Applied

o   To have the students apply the techniques they have learned in the Skew-T/log P Sounding and hodograph analyses part of the class;

o   To give students an opportunity to visualize how instability manifests itself in the morning environment in severe weather settings;

o   To show students how severe weather meteorologists estimate afternoon instability by transforming the morning sounding;

o   To show students how to evaluate the instability graphically, and computationally;

o   To introduce students to the finite difference approximation of summation;(integration) graphically and computationally;




Part A:  2200 UTC Surface Chart Subsynoptic Analyses

 

Fig. 1:  Surface plot with isobars, 2200 UTC 22 May 2011

 

Figure 1 is the 2200 UTC surface chart on 22 May 2011.  Isobars are drawn at two millibar intervals, with two labeled.  You are also provided a separate clean copy of this chart for your final analyses.  You have the 1200 and 1600 UTC analyzed surface charts from Lab 9 (100 pts)

 

1.     On the copy above, draw blue, brown, green, and red streamlines, as we have have done in class many times to help find important boundaries (10 pts);

2.     On the copy ablove, label lows and highs (if present) using the correct color convention,  shade in the area in which dew points are 60F or greater in light green (10 pts);

3.     On the copy above, note that the isobars are strongly kinked away from low pressure in certain locations.  It turns out that isobars are strongly kinked usually in areas in which they cross boundaries.  Using this knowledge, and your results in (1) above, now draw in all the boundaries, using correct symbols and color conventions.  (40 pts)

4.     Transfer all that you’ve done above to the final clean copy.  This is what you will turn in and what will be graded.  Neatness counts here. (10 pts for Neat Analysis)

5.     How does your analysis conform to the pre-thunderstorm environment generally considered to be associated with severe weather in the Great Plains (30 pts)

 

 

Part B:  1200 UTC Sounding Analyses (100 pts)

 

You are provided with two color copies of Fig. 1 below,  the Springfield MO sounding and hodograph for 12 UTC 22 May 2011

 

 

Fig. 1:  KSGF Sounding and Hodograph, 12 UTC 5/22/11

 

1.     Determine the morning stability at KSGF (Springfield, MO) by analysis of one of the copies of the morning sounding for 1200 UTC 22 May 2011 by completing the following tasks:

a.     Estimate the height (in millibars) of the Lifting Condensation Level, Level of Free Convection, 500 mb Lifted Index, Equilibrium Level.  Be sure to indicate the parcel ascent curve, LCL, LFC and EL right on the diagram. And shade in the areas of CAPE and CIN with proper colors; (30 pts)

b.     Is the sounding absolutely unstable, absolutely stable or conditionally unstable for a surface lifted parcel.  Explain your answer in several sentences. (20 pts)

 

2.     On the second copy of the sounding for for 1200 UTC 22 May 2011 (second copy), estimate the afternoon stability at KSGF (Springfield, MO by completing the following tasks:

a.     Estimate the Convective Temperature, Convective Condensation Level and determine if the sounding is potentially unstable.  Indicate the Convective Temperature (CT), Convective Condensation Level (CCL),  and “afternoon” parcel ascent curve, positive area on sounding (CAPE) (shaded red), and negative area on sounding (CIN) (shaded blue); (30 pts)

b.     Is the sounding you modified for afternoon surface heating potentially stable or unstable for a surface lifted parcel.  Explain your answer in several sentences. (20 pts)

 

Part C:  Calculation of CAPE

 

1.     Calculate the CAPE from the morning sounding using the method discussed in class. You'll be approximating the CAPE crudely (explained in class) by summing up the indidividual contributions of layers approximately 1500 m thick. The table below should get you started. (95 points)

 

2.     Using the results from (1) above, calculate the maximum vertical velocity at the EL in the morning.  (Started in class) (5 points)

 

 

Pressure (mb)

Elevation AGL (m)

Temp Env (K)

Temp Parcel (K)

Diff

(LFC) ~700

~3000

 

 

 

600

~4500

 

 

 

500

~6000

 

 

 

400

~7500

 

 

 

300

~9000

 

 

 

(EL) 240

~10500

 

 

 

 

Table 1:  Temperature Information Obtained from Sounding Analyses (completed in Part B) for KSGF 12 UTC 5/22/11

 


 

Part D:  1200 UTC Hodograph Analyses (100 pts)

 

         Table 1 shows the wind directions and speeds observed in the Springfield sounding 12 UTC 22 May 2011.  Figure 2 is a blank diagram called a “hodograph” .  It allows us to visualize the way wind directions and speeds vary with height.

 

Winds_KSGF

Table 1:  Winds and pressures observed in KSGL radiosonde launch, 12 UTC 22 May 2011

 

HodographBlanks

 

Figure 2:  Blank hodograph pape

 

 

 

 

Pressure (mb)

Height (m) AGL

Direction (deg)

Speed (kts)

962

0

 

 

925

340

 

 

850

1071

 

 

700

2709

 

 

500

5361

 

 

479

5704

 

 

 

Table 2:  Wind Directions (deg) and speeds (kts) at selected pressure levels

 

Storm-Relative Helicity (m2/s2)

Midlevel Mesocyclone Strength

Meets Strength Threshold for Categorization as Supercell

100

Weak

No

150

Moderate

Yes

250

Strong

Yes

>350

Violent

Yes

 

Table 3:  Storm Relative Helicity and Mesocyclone Strength

 

1.     Fill in Table 2 with the wind directions and speeds extracted from the radiosonde information in Table 1; (2 pts each for 24 points)

2.     Plot the hodograph as follows:

a.     Plot an arrow (vector) for each level given in Table 2, as shown in class. Label each arrow near its end with the appropriate level (for example, Sfc). (2 pts each for a total of 10 pts)

b.     Put a black dot at the tip of each arrow; (2 pts each for a total of 10 pts)

c.     Draw (neatly) straight line segments connecting each dot. (2 pts each for a total of 10 pts)

3.     In plain english describe how the the wind in the lowest 6 km, as visualized by the hodograph you just constructed, varied with height.  (4 pts)

4.     In plain english describe if this is consistent with your answer in Part A, #5(4 pts)

5.     Storm motions:

a.     Using the method discussed in class, plot a Yellow Circle for the initial storm motion. (4 pts)

b.     Using the method discussed in class, plot Red Circles for the motion of the left and right moving supercells; (4 pts)

6.     The 0-3 km storm relative helicity (SRH) calculated for this hodograph can be found in the box on the upper right of the sounding.  Positive values of this parameter indicate that inflow air entering the updraft of any developing thunderstorm would be rotating.  Answer in complete sentences.

a.     Using the information given in Table 3, categorize the potential strength of the midlevel mesocyclone of any developing thunderstorm;  (10 pts)

b.     How do your values in Table 2 and the plotted hodograph conceptually indicate that the updraft of any developing thunderstorm on this cay would be helical (rotating)? (10 pts)

 

7.     Table 4 contains the values of various parameters for all tornadoes in the Great Plains since 2008 that occurred with the prototype severe weather pattern in the Great Plains AND a loaded gun sounding.  The row highlighted in yellow contains the parameters for the Joplin Tornado.

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Table 4:  Parameters Associated with All Tornado Occurrences in the southern Great Plains since 2008 that occurred with the prototype severe weather pattern discussed in class and a Loaded Gun Sounding.  (from  Davies, J. M., 2017: Meteorological setting for a catastrophic event: The deadly Joplin tornado of 22 May 2011. Electronic J. Severe Storms Meteor., 12 (3), 1–23.)

 

Comment on the relationship between the value of EHI and tornado strength that you can deduce from the information in this table.  (20 points)