Reference no: EM131856867

Image 1 is the surface weather map for 12Z 24 MAR 2016. This map was also examined inCurrent Weather Studies 9A, 10A, and 10B. The storm system was centered within the closed1000-mb isobar at the intersection of the Iowa-Missouri-Illinois borders. A stationary frontextended eastward while a cold front stretched southward to southern Texas.

1. Note the temperature and dewpoint in the station model at Jackson, in central MS. Jackson'stemperature at map time was 67 °F and the dewpoint was [(72)(61)(57)] °F. Jackson wasahead of the approaching cold front.

2. The temperature at Dallas, in northeastern Texas, was 47 °F with a dewpoint of[(29)(31)(38)] °F. Dallas was behind the cold front and was representative of the cold airmass advancing across the center of the country.

3. Dewpoints as shown by station models across the Southeastern states indicated air withrelatively [(high)(low)] concentrations of water vapor compared to stations behind the coldfront. (A guide is that an increase of 18 F° in dewpoint indicates about a doubling of watervapor concentration.)

4. Winds from Lake Charles, in southwestern Louisiana, to Indianapolis, in central Indiana,displayed a generally [(northward)(southward)] flow of humid air ahead of the cold front.

5. A line of red dashes and double dots was plotted from eastern Arkansas to eastern Texas.This indicated the location of a squall line, as noted in the Extras section of the RealTimeWeather Portal, Fronts Symbols. The accompanying text for the squall line symbol on thePortal states that this identifies a line of [(snow squalls)(high winds)(thunderstorms)].CWS 11A - 2

6. Radar reflectivity shadings of red and orange splotches extended from the Gulf Coast tosouthern Wisconsin. These shadings showed that precipitation intensities associated withboth the precipitation associated with the squall line and thunderstorms further north wererelatively [(weak)(strong)].NOAA's Storm Prediction Center compiles storm reports for daily periods over the contiguousU.S. The Storm Prediction Center received reports for the twenty-four hour period ending at12Z on 25 March 2016 of incidents of 5 tornadoes, 72 incidents of damaging winds, and 7 casesof hail exceeding 1 inch diameter.

7. These weather conditions [(are)(are not)] generally associated with thunderstorm activity.

8. One of the tornadoes and the vast majority of the winds were located along the Gulf Coastfrom east Texas to northern Florida. The location of the reports [(were)(were not)] likelyrelated to the passing cold front and squall line of the storm system.

9. Image 2 is an animation of radar imagery across the southern Mississippi River Valley from1618Z to 1728Z on 24 MAR 2016. This would have been the passing of the squall line alongthe coastal area. The curvature of the most intense radar echoes in southern Mississippi andAlabama and over southeastern Louisiana are termed "bow echoes". These curves areindicative of possible severe weather, particularly strong thunderstorm wind outflows. Suchradar information [(would)(would not)] be valuable to forecasters in alerting the public topotential damage.

Image 3 is the 300-mb constant pressure map for 12Z 24 MAR 2016 from NOAA's StormPrediction Center. This was the same time as the Image 1 surface map. Mark the location of thesurface Low at the IA-IL-MO border intersection and the cold front on the 300-mb map. Also,shade the approximate location of the heavy precipitation associated with the squall line on theupper air map.

10. The surface Low center was positioned slightly [(west of)(along)(east of)] the trough axis ofthe upper air wind pattern in the central U.S. Such positioning often occurs with strong,rapidly moving cyclonic systems.

11. The light blue shading in central Missouri indicates wind speeds greater than 125 knots. Thisrelatively high wind speed region is evidence that a [(jet streak)(calm area)] existed aloftwithin jet stream winds.

12. Furthermore, Image 3 contains tightly enclosed yellow contours centered over southeasternMissouri. These lines identify areas of strong divergence at this level in the uppertroposphere, a lifting mechanism for surface and lower tropospheric air. These upper levelwind features suggest that support in the upper troposphere needed for thunderstormformation and spread [(did)(did not)] exist across this region.CWS 11A - 3In summary, to form, thunderstorm cells require sufficient moisture at low levels, a liftingmechanism (an advancing front, convergence or orographic lifting) to "trigger" their formation,and supportive upper atmospheric conditions to develop.

13. The Image 1 surface map [(does)(does not)] show favorable low-level moisture and a triggermechanism while Image 3 shows evidence of supportive upper atmospheric conditions, all ofwhich contributed to thunderstorm development.

Image 1 is the surface weather map of the storm system at 00Z 24 FEB 2016 (6 pm local time onthe 23rd in Louisiana). This map showed the weather conditions about two and one-half hoursfollowing the tornado we will be looking at that devastated Louisiana. The low-pressure centerwas located in central Louisiana at this time. New Orleans was located between the warm andcold fronts of the system, a favored location for severe weather formation.

1. The station model for New Orleans showed that skies were overcast with the wind from thesouth-southwest at about [(5)(10)(20)(40)] knots.

2. The present weather symbol showed that [(fog)(haze)(a thunderstorm with rain)(snow)] wasoccurring.

Image 2 is the track map of one of the thirteen tornadoes in the February 23rd outbreak surveyedby the NWS New Orleans/Baton Rouge Office in the southern portion of the state. The mapshows an area of south-central Louisiana between Baton Rouge and New Orleans. The orangeCWS 11B - 2line across the map area shows the path of the tornado that damaged hundreds of homes inAssumption and St. James Counties. There were 75 people injured and 2 killed.North is to the top of the map. The beginning and ending times of the damage evidence havebeen added to the map. The NWS New Orleans Office provided the following statistics:Paincourtville/Convent, LA TornadoDate: Feb. 23, 2016Time (Local): 3:21 pm - 3:42 pmEF Rating: EF - 3Path Length: 21 milesMax. Width: 350 yardsThese values are characteristic of strong to severe tornadoes. The New Orleans NWS report canbe found at: https://www.srh.noaa.gov/lix/?n=02232016severe, then click the Paincourtville, LAand Convent, LA Tornado link.

3. From the elapsed time on the ground and the length of the damage path, the speed of advanceof this tornado was approximately [(15)(25)(40)(60)] mph.

4. According to listing, the most intense tornado damage classification category (rating) wasEF- 3. The EF categories are given in the Weather Studies eInvestigations Manual'sInvestigation 11B. For a description of the EF scale, seehttps://www.spc.ncep.noaa.gov/efscale/. According to the EF scale, maximum wind speeds inthe Paincourtville/Convent tornado were in the range of [(65 - 85)(86 - 109)(110 - 137)(138 - 167)(168 - 199)(greater than 200)] mph.

5. According to the track map, the tornado moved generally toward the [(southwest)(northwest)(northeast)(southeast)]. This direction was generally aligned with the direction of midtroposphericwinds at that time.Image 3 is a composite of views (clockwise from the upper left) of the radar reflectivity, stormrelative velocity, correlation coefficient, and differential phase from the NWS New Orleans/Baton Rouge Doppler radar. The images show views of these quantities at 3:36 pm CST,23 FEB 2016.

6. In the top left view, intense precipitation is shown in reds associated with the supercellthunderstorm. The radar site is off the map area to the upper right of this view. Dark redpixels and a single pink pixel just northeast of the town of Welcome in the view identify themost intense reflectivity, often resulting from large raindrops or hail. A curl area of redpixels around the town of Union denotes a reflectivity structure termed a "hook echo". Ahook echo [(would)(would not)] alert a meteorologist to the likelihood of tornadic activity ator near that location.

7. The view on the top right in Image 3 displays the storm relative radial velocity from theradar. A tornadic vortex signature (TVS) of dark red and adjacent green colors is highlighted CWS 11B - 3in a yellow circle near Union. Recall from Investigation 7B that red denotes Dopplervelocities away from the radar site and green being toward. Draw a short arrow directedaway from the radar site (located off the upper right of the map) across the red patch of thepixels in the circle. Also draw a short arrow directed toward the radar site across the adjacentbright green pixels. Your pair of arrows represents the radial velocities away from andtoward the radar's location of the several mile wide mesocyclone. Recalling Investigation7B, your pattern of arrows suggests a circulation that is [(clockwise)(counterclockwise)] asseen from above.The bottom right panel is the correlation coefficient from the New Orleans radar, a new productfrom the upgrade of the NWS Doppler radars to dual polarization, meaning the radars alternatelytransmit horizontally and vertically polarized pulses. For most precipitation, vertical andhorizontal power returns are nearly equal, e.g. correlation coefficient of about one. For tornadicdebris, the target shapes often vary greatly, i.e. low correlation. Low correlations are shown bydark blue shading inferring the presence of irregular airborne debris.

8. The dark blue shading rectangle within the lighter blue, labelled circle between Union andWelcome in the bottom right view of the correlation coefficient [(does)(does not)] basicallycoincide with the location of the hook echo of the top left reflectivity and the top rightrelative velocity TVS patterns.