SO441
Lab 2 – Tornado Forecast Parameter Manipulation
Background
You learned in Lab 1 and Homework 1 that two of the most important parameters in forecasting environments where tornadoes are possible are CAPE and Storm Relative Helicity (SRH). In addition, you were introduced to the shear necessary to separate the updraft and downdraft within the storm in lecture lessons 1 and 2. As you know, the one thing that all of the parameters have in common is that they are dependent on observed state of the atmosphere in time and space, and even if all of the parameters line up in time and space,there is no guarantee that it will produce a tornado. This lab is designed to explore an actual sounding in an environment that produced a tornado, then use MATLAB to calculate the CAPE, SRH0-1, SRH0-3, and 0-6km AGL Shear, and then manipulate the sounding information to observe and document the effect each change has on tornado forecast parameters
Objective
At the conclusion of this lab, you should be able to:
1. Describe the sensitivity of CAPE values to varying temperature and moisture profiles
2. Describe the sensitivity of helicity and shear to varying combinations of storm motion and vertical wind profile.
Tasks:
1. Answer the questions on the pages to follow based on parameter response to changes in the observed atmosphere on 11 May 2014 in Omaha, NE.
Deliverables:
1. Answers to questions on the pages to follow using a word processing application. Many questions will also require you to produce a figure and include them in your write up so pay close attention to the direction in each question.
1. Action: Create a working folder on your computer and download all of the files located here: ???. Now open MATLAB and navigate to your working folder.
2. We will now grab the raw data from a sounding near a tornado that the 2014 SWIFT team chased Southeast of York, NE on 11 May 2014.
Action: Retrieve sounding data for 0000Z 051214, copy to text file, ingest into an Excel file, ingest the Excel file into MATLAB, and then plot the sounding / calculate CAPE and CIN usingprovided MATLAB scripts.
a. For reference, go to the SPC website and download the already processed sounding with all of the parameters already calculated.
1) Go to this link and click on the star representing Omaha, NE
2) Verify that you are looking at OAX 140512/0000 (Observed) then right click on the sounding and “Save image as” a gif file in your working folder.
3) Include this graphic as the last page of your lab
b. Now navigate to the UofW page here: to download the text data from the sounding above.
1) Make the search criteria look like this: (Enter station number then press enter)
2) Scroll down to the sounding labeled “72558 OAX Omaha Observations at 00Z 12 May 2014”
3) Ignore the headers and the 1000.0mb row and select all other rows trough the row with 10.5mb (10.1mb is missing data). Right click on the selection and copy
4) Go to your desktop and right click in open space and select new -> text document
5) Open the new text document and paste your data
6) Immediately go to file, save as, and place the file in your working folder.
7) Now align the first row with the rest of the rows by clicking to the left of 960.0 and hitting the space bar enough to align the zero in the 10ths position with the rest of the pressure values. If it is already there….just leave it
8) Save your file.
9) You may have noted that you are missing some data from 200mb up. This will not affect any of the calculations you will be using in this lab.
c. Now open Microsoft Excel and ingest the text data into Excel and save the resulting spreadsheet in your working folder with the name provided below
1) Open a new Microsoft Excel workbook and select the data tab then the “from text” icon on the left
2) Navigate to your text file from the previous section and select “Open”
3) A dialog box will pop up that should already have “fixed width” selected…leave it where it is and select “next” then select “finish” on the next page.
4) Now ensure that the first cell is selected when it asks you where to put the data and press “OK”
5) You should now have columns A-K filled with data through the top of the sounding
6) Select all of the data, right click on the selection, format cells, number, then select 1 decimal place.
7) Save your file to your working folder with the name “KOAX_0000_051214”, and make sure you select Excel 97-2003 Workbook (*.xls) under “Save as type:”
d. Now plot the sounding in MATLAB and compare your sounding to the SPC sounding that you downloaded earlier
1) In your MATLAB “Current Folder (normally on the left)”(this should be the working folder that contains all of the .m files you downloaded in step 1), right click on “SO441_plot_sounding_v_2_0.m” and select Run……..after 10-15 seconds a plot will pop up.
2) Compare your plot with the SPC plot to verify that you have successfully imported the correct data.
3) Note that your workspace is now populated with many variables and you willcalculate CAPE in the following section using this data.
4) Save your plot figure as a .jpg file in your working folder.
e. Now calculate CAPE and CIN using “getcape_v_2_1.m”. Note that you are determining CAPE based on a surface parcel.
1) Open “getcape_v_2_1.m” and “SO441_plot_sounding_v_2_0.m” in your editor
2) First look at “getcape_v_2_1.m” to determine the required inputs to the function
3) Now look at “SO441_plot_sounding_v_2_0.m” to determine what variablesmeet the input requirements of getcape_v_2_1.m so you know that the command line call below is correct.
4) Type “format shortg” in your command window (switches from scientific notation to standard notation).
5) Call the function “getcape_v_2_1.m” using the following command in your command window
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
b) Note that you will also get CIN, but it will not be used in this lab
c) In approximately 10-20 seconds a value for CAPE will appear
d) Compare your CAPE calculation to the SPC value, and make sure you are in the same ballpark. There will be differences based calculation methodology CAPE
6) Open Excel and start a table of CAPE values with this as your reference sounding CAPE value. In the following section you will add to your table as you manipulate the sounding and recalculate CAPE
Deliverable for this part of Lab 2:
1) SPC Sounding Graphic
2) A jpg of your sounding plotted in MATLAB
3) The first row of CAPE data in an excel file. Your completed table of data will be required in your lab package that you turn in.
3. We will now manipulate certain portions of the sounding to see how sensitive CAPE calculations are to changes in atmospheric parameters. Look at the required deliverables now, as you will repeat the steps 1 through 4 for each change. We recommend that you have your excel file with the original sounding data open so you can double check that your changes and reversals get you back to the original data values. Also note the change in file name for each change.
Action: Adjust the following parameters of the original sounding and recalculate CAPE
a. Adjust surface Temperature higher by 5°C. You can do this directly by assigning an adjusted value to the surface temperature in your original sounding, or you can follow the directions below in the order provided.
1) type the following
a) tz(1,1) %this gives you the current surface value
2) Note the current surface value to make sure your change in the next step takes correctly
3) type the following
a)tz(1,1)=tz(1,1)+5; %provides value 5°C higher than step1
4) now type “tz(1,1)”
5) Note that the value should now be 5 higher than you previously noted
6) Run SO441_plot_sounding_v_2_1.m(note that this is not the same file you ran before).
a) Save this new plot as a jpg for inclusion in your final write up
7) Now answer #1) in your deliverables for this change
8) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
9) Note the change and CAPE value in your table as required in deliverable #2).
10) Now reverse your value change by typing the following, or directly assigning the original value.
a) tz(1,1)=tz(1,1)-5;
b) tz (1,1) %Verify that you are back to original data values
b. Adjust surface Temperature lower by 5°C, or to a value equal to Td at the same level if dew point depression is less than 5°C (Note that the value of T cannot be less than Td at the same level). Either assign the value directly in MATLAB or follow the guidance below in the order provided
1) Recall the original surface value from the previous section
2) To determine if the dew point depression is less than 5 type the following
a) a=tz(1,1)-tdz(1,1) % you are simply subtracting the dew point from the temperature to find the dew point depression “a”
3) After you have determined the dew point depression type the following using the correct value.
a) tz(1,1)=tz(1,1)-(value of “a” from 2)a) or 5 [whichever is least]); %provides T value 5 lower or equal to Td
4) now type “tz(1,1)”
5) Note that the value should now be 5 lower than the original or equal to Tdz(1,1).
6) Right click on SO441_plot_sounding_v_2_2.m and select Run.
a) Save the plot as a jpg for inclusion in your final write up
7) Now answer #1) in your deliverables for this change
8) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
9) Note the change and CAPE value in your table as required in deliverable #2).
10) Now reverse your value change by typing the following
a) tz(1,1)=tz(1,1)+(dew point depression (a) or 5 [whichever is least]);
b) tz (1,1) %Verify that you are back to original data values
c. Adjust surface Dew Point Temperature higher by 5°C, or make it equal to the surface temperature if dew point depression is less than 5°C. Either assign the value directly in MATLAB or follow the guidance below in the order provided
1) Recall the original surface temperature value from the previous section and check the dew point depression by typing the following
a) a=tz(1,1) – tdz(1,1) % You did this before. If you remember the value for dew point depression (a) there is no need for this step
b) If the value of “a” is less than 5 note the value for calculations to follow, and include the value of change in your writeup.
c) type “tdz(1,1)” and note the original surface Td value.
2) type the following
a) tdz(1,1)=tdz(1,1)+(dew point depression (a) or 5 [whichever is least]);
3) now type “tdz(1,1)”
4) Note that the surface dew point temperature should now be either 5°Clarger than the originaldew point temperature, or equal to Tsfc (remember, the dew point temperature can never be larger than the air temperature, hence changing the dew point temperature isn’t as simple as adding 5°C to it.. we have to check it doesn’t exceed air temperature).
5) Right click on SO441_plot_sounding_v_2_3.m and select Run.
a) Save the plot as a jpg for inclusion in your final write up
6) Now answer #1) in your deliverables for this change
7) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
8) Note the change and CAPE value in your table as required in deliverable #2).
9) Now reverse your value change by typing the following
a) tdz(1,1)=tdz(1,1)-(Dew point depression (a) or 5 [whichever is least]);
b) tdz (1,1) %Verify that you are back to original data values
d. Adjust surface Dew Point Temperature lower by 5°C or by the value you used (a) for adjustment in the previous section. You can either assign the values directly in MATLAB or follow the guidance below in the order provided
1) Recall the original surface temperature, surface Td and dew point depression value (a) from the previous section if it was used.
2) type the following
a) tdz(1,1)=tdz(1,1)-(dew point depression (a) or 5 [whichever is least]);
3) now type “tz(1,1)”
4) Note that the value should now be lower than the original Td
5) Right click on SO441_plot_sounding_v_2_4.m and select Run.
a) Save the plot as a jpg for inclusion in your final write up
6) Now answer #1) in your deliverables for this change
7) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
8) Note the change and CAPE value in your table as required in deliverable #2).
9) Now reverse your value change by typing the following
a) tdz(1,1)=tz(1,1)+(dew point depression (a) or 5 [whichever is least]);
b) tdz (1,1) %Verify that you are back to original data values
e. Now adjust the temperature at 500mb 5°C higher. Follow the guidance below in the order provided
1) Go to your excel file and scroll down the first column until you see 500.0 or the closest number to 500.0 and note the row number (will be used to change the value of tz in the same row)
a) type the following and note the value
i) tz(‘noted number’,1)
2) type the following
a) tz(‘noted number’,1)=tz(‘noted nuber’,1)+ 5;
3) now type “tz(‘noted number’,1)”
4) Note that the value should now be higher
5) Right click on SO441_plot_sounding_v_2_5.m and select Run.
a) Save the plot as a jpg for inclusion in your final write up
6) Now answer #1) in your deliverables for this change
7) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
8) Note the change and CAPE value in your table as required in deliverable #2).
9) Now reverse your value change by typing the following
a) tz(‘noted number’,1)=tz(‘noted nuber’,1)- 5;
b) tz(‘noted number’,1) %Verify that you are back to original data values
f. Now adjust the temperature at 500mb 5°C lower. Follow the guidance below in the order provided
1) Recall the ‘noted number’ from section e. above.
2) type the following
a) tz(‘noted number’,1)=tz(‘noted nuber’,1)- 5;
3) now type “tz(‘noted number’,1)”
4) Note that the value should now be lower
5) Right click on SO441_plot_sounding_v_2_6.m and select Run.
a) Save the plot as a jpg for inclusion in your final write up
6) Now answer #1) in your deliverables for this change
7) Now type the following….it is the same as your original calculation
a) [cape,cin] = getcape_v_2_1(nk,pz,tz,tdz)
8) Note the change and CAPE value in your table as required in deliverable #2).
9) Now reverse your value change by typing the following
a) tz(‘noted number’,1)=tz(‘noted nuber’,1)- 5;
b) tz(‘noted number’,1) %Verify that you are back to original data values
Deliverables:
1) For each change discuss your expectations for calculated CAPE value changes prior to calculating the CAPE, and explain why you think it will have your expected result.
2) Populate the Table you started in Part 2. with each change and the associated CAPE value.
3) For each change discuss whether the new value of CAPE met your going in expectations, and if you were incorrect in your expectation why were you wrong?
4) A copy of the sounding plot generated in each change.
5) After all of the changes are complete and you have a fully populated your table discuss the changes that had the greatest positive and negative effect on CAPE values, and address the reasons why they had the effect that they did.
4. We will now explore the effect of changing wind profiles and storm direction and speed on 0 to 1km helicity and 0 to 3km helicity for the same sounding.
Action:
a. Before you make any changes type “clear all” in your command window, and close all figures (“close all” will do the trick).
b. Your first run will be the based on the actual sounding data.
1) Look at the information from the SPC sounding page and note the storm speed and direction in the left center box at the bottom labeled “bunkers right”. Now verify that rungethelicity_v_2_0.m has the appropriate values on lines 22 and 23 respectively in the script
2) If the values are correct, then run the script.
3) Note the helicity values (0 to 1km and 0 to 3km) in a new excel table
4) Save the figure as a jpg
5) Close the figure
c. Now change the storm speed from your original value to 10 knots higher
1) Go back to the rungethelicity_v_2_0.m file in the editor and make the following change
a) cspd = previous speed + 10 (just change the number in the file)
b) save the file
c) Now answer #1) in your deliverables for this change
c) run the file
2) Populate the table and save the plot as a jpg
3) Return cspd back to its original value
4) Be sure to discuss, in your write up,any interesting features of the 0 to 1km plot
5) close the figure
6) If you wish you can adjust the speed lower to see what happens
d. Now shift the entire wind column counter clockwise by 30 degrees.
1) Go back to the rungethelicity_v_2_0.m file in the editor and make the following change
a) change “wdir=sounding(:,7)” on line 29 to “wdir=sounding(:,7)-30”
b) save the file
c) Now answer #1) in your deliverables for this change
c) run the file
2) Populate the table and save the plot as a jpg
3) Return line 29 back to its original value
d. One last change. What if the storm wasn’t moving?
1) Go straight to a discussion of what you would expect to see in the plot. Recall the equation for helicity, and the reaction of the plots to previous changes.
2) Make the same kind change you did in 4.c., but make cspd 0kt
2) Populate the table and save the plot as jpg
Deliverables:
1) For each change discuss your expectations for changes to calculated 0 to 1km and 0 to 3km SRH prior to calculating the helicity, and explain why you think it will have your expected result.
2) Populate the Table you started for helicity changes with the reference values from the original sounding, and after each change.
3) For each change discuss whether the new values of helicity met your going in expectations, and if you were incorrect in your expectation why were you wrong?
4) A copy of the helicity plot generated in each change.
5) After all of the changes are complete and you have a fully populated table discuss the changes that had the greatest positive and negative effect on SRH values and why they had the effect that they did.