June 7, 2008 Northeast Illinois Tornado Outbreak: Applying to Fundamentals in Storm Spotting

Transcription

1 June 7, 2008 Northeast Illinois Tornado Outbreak: Applying to Fundamentals in Storm Spotting Near Manhattan, IL Richton Park, IL Ricky Castro National Weather Service Chicago/Romeoville, IL

2 Tornado Crossing I-57 Near Monee, IL Video Courtesy of Adam Lucio

3 Roadmap Overview of Event Meteorological Summary General parameters Expectations for that day Why this event differed from expectations What If You Were Spotting that Day? Safe positioning Cyclic supercell radar analysis and spotter tips Being Prepared for the Next Big Event Conclusion

4 Overview of Event 8 tornadoes (2 EF0, 2 EF1, 4 EF2) Produced by one cyclic supercell that tracked from Livingston County IL to Lake County IN 4:21 PM to 6:49 PM 4 EF2 tornadoes Final EF2 Tornado: Vehicles tossed from I-57 overpass at Steunkel 6 motorists injured Extensive damage in Richton Park, IL

5 Overview of Event: Radar Legend Tornado Watch Tornado Warning Severe Warning Marine Warning

6 Overview of Event Rural northern Kankakee County looking north into Will Co.

7 Overview of Event Green Garden Township, IL Jeremy Hylka

8 Overview of Event Warehouse east of I-57 at Steunkel Road

9 Overview of Event Warehouse east of I-57 at Steunkel Road

10 Overview of Event Richton Park EF2 Damage: Richton Square Apartments

11 Overview of Event Richton Park Damage

12 Overview of Event: Tornado Tracks EF2 Start: 5:51pm End: 5:54pm Path: 1.8 miles Width: 400 yards EF2: Richton Park Start: 6:13pm End: 6:30pm Path: 5.8 miles Width: 150 yards EF0 Start: 6:48pm End: 6:49pm Path: 0.7 mile Width: 50 yards EF2 Start: 5:18pm End: 5:46pm Path: 13.6 miles Width: 200 yards EFO Start: 4:21pm End: 4:23pm Path: 0.8 mile Width: 20 yards EF1 Start: 4:31pm End: 4:45pm Path: 3.6 miles Width: 40 yards EF2 Start: 5:55pm End: 6:08pm Path: 3.7 miles Width: 150 yards EF1 Start: 6:32pm End: 6:37pm Path: 1.8 miles Width: 75 yards Full Review:

13 Meteorological Summary Tornadic Supercell Ingredients Instability (varies, usually CAPE > 1000 J/Kg) CAPE: Convective Available Potential Energy CAPE is related to potential updraft strength in thunderstorms Deep layer (0-6km) wind shear (bulk shear > 35kt) Sufficient shear sustains thunderstorm updrafts and can aid in storm-scale rotation Low level shear (0-1 SRH > 150 m2/s2 or pre-existing boundary) SRH: Storm-Relative Helicity Potential for cyclonic updraft rotation in right-moving supercells High RH values (in BL and aloft) for low cloud bases Low LCL (lifting condensation level) heights Proxy for cloud base heights, lower the better. LCL heights: ~500 m (1600 ) m (4900 ) AGL. ~500 m m is considered favorable for EF2+ tornadoes.

14 Meteorological Summary 6/7/08 Tornadic Supercell Ingredients Instability (varies, usually CAPE > 1000 J/Kg) ~3500 J/kg Deep layer shear (bulk shear > 35kt) ~45kt Low level shear (0-1 SRH > 150 m2/s2 or pre-existing boundary) ~200 m2/s2 (increased to ~300 during event) High RH values (in BL and aloft) Sfc Td depressions ~10 F, LCL ~750 m AGL Where to Find This Information: Full explanation of parameters: Google spc severe weather parameters Operational use: SPC Mesoanalysis. Google spc mesoanalysis (mobile)

15 Meteorological Summary Expectations for that Day: SPC Outlooks 3 pm CDT SPC Day 1 Convective Outlook 3 pm CDT Day 1 Convective Outlook Probability of a Tornado Within 25 mi. of a Point Approximately where tornadic supercell formed

16 Meteorological Summary What changed from expectations in our area? Pontiac, IL: 82/72 Differential Heating Boundary Remnant of MCS Cloudy, cooler Lafayette, IN: 70/68 Weather map at 1pm CDT on June 7, 2008

17 Meteorological Summary Thunderstorm Ingredients Moisture: needed to fuel thunderstorms, often comes from Gulf of Mexico. Farm fields add low level moisture after mid summer, known as evapotranspiration. Instability: warm/humid air (lighter) below cold air (heavier) aloft. The bigger the difference greater instability stronger updraft CAPE is a measurement of instability. Lift: anything to force air upward (fronts/boundaries, thunderstorm outflow, jet streams, etc).

18 What If You Were Spotting that Day? Spotter Positioning Video Courtesy of Andrew Pritchard Andres, IL (SE of Manhattan)

19 Spotter Positioning When spotting a supercell, DO NOT get caught in the heavy rain and hail core! Light Rain Moderate/Heavy Rain & Hail Moderate/Heavy Rain & Hail Storm Motion Forwardflank downdraft Forward-flank downdraft (FFD) Gust Front Gust Front Rear-flank downdraft Rear-flank downdraft (RFD). tornado You should be here

20 What If You Were Spotting that Day? Cyclic Supercells As name suggests, supercell that goes through cycles Rear flank downdraft (RFD) cuts off (occludes) mesocyclone (meso) Once cut off original mesocyclone weakens New mesocyclone forms to the right along RFD Izzi 2009

21 What If You Were Spotting that Day? Cyclic Supercells Given favorable tornadic environment, each mesocyclone can produce tornadoes Mesocyclones tend to develop/intensify more rapidly with time New mesocyclone tends to form right of first Izzi 2009

22 What If You Were Spotting that Day? Cyclic Supercells: Challenges/Dangers Difficult to predict when/where cycles will occur New mesocyclone often apparent aloft first on radar May see burst of inflow at 0.5 prior to tornadogenesis Present unique danger to mobile spotters, new mesocyclone can form overhead without adequate lead time Can result in jump in expected tornado path Izzi 2009

23 L Izzi 2009

24 RFD L Forward Flank Downdraft Inflow Izzi 2009

25 RFD L Forward Flank Downdraft Inflow Izzi 2009

26 L Izzi 2009

27 L Izzi 2009

28 L First Updraft Occludes Izzi 2009

29 Secondary Inflow Max Develops Izzi 2009

30 Old Tornado Becomes Rain-wrapped L Izzi 2009

31 L L Izzi 2009

32 L Izzi 2009

33 L Izzi 2009

34 TMDW Z TMDW SRM KLOT Z Izzi 2009 KLOT SRM

35 Radar Comparison new meso TDWR Left over old hook New hook developing eye tornado cyclone more apparent new meso WSR-88D Izzi 2009

36 Example of Tornado Occluding near Manhattan, IL Izzi 2009

37 What If You Were Spotting that Day? Cyclic Supercells Video Courtesy of Andrew Pritchard Near Monee, IL

38 Preparing for the Next Big Event Weather awareness is key! Goal is to not put yourself in a vulnerable situation Do you have a preparedness plan? What will you be doing during the time of greatest risk? How will you monitor weather information? How will you receive warnings? Can you adjust your plans or your route?

39 Preparing for the Next Big Event Transportation Planning Identify shelters along your route Identify timing of greatest threat Consider altering your schedule Leave work early Work from home if possible Weekend activities Near Blountstown, FL, 11/17/14 NWS Tallahassee

40 Preparing for the Next Big Event Transportation Action! Last Resort Remain calm and assess the situation! Determine the tornado's direction of movement. Can you drive away from it? Too much traffic? Seek shelter in a nearby building. Lie flat in a nearby ditch or depression. Get as low as possible -- that is where the wind speed is the lowest! You don t want to get yourself into this situation!

41 Preparing for the Next Big Event Overpass: Exposure to Winds Image: Google Overpasses are NOT adequate storm shelters!

42 Preparing for the Next Big Event Overpass: Other Issues Blocks traffic Prevents Emergency Personnel from reaching affected areas Potential major traffic disaster in situations of low visibility

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44 Conclusion June 7, 2008 had 8 tornadoes from 1 supercell Location affected was somewhat of a surprise More conditional threat, initial focus was northwest EF2 tornado crossed I-57, extensive impacts to Richton Park, supercell path narrowly missed additional communities Always remember safe spotter positioning Cyclic supercells can be unpredictable, apparently erratic tornado tracks (tornado path jumps ) Important to understand characteristics since new mesocyclone tends to develop closer to well positioned spotter Severe weather planning and safety: Goal is to not put yourself in a vulnerable situation!

45 Acknowledgements & References Izzi, Gino (2009). The June 7th, 2008 Suburban Chicago Cyclic Tornadic Supercell. Presented at 2009 DuPage Seminar. NWS Chicago (2008). June 7, 2008 Severe Weather Event. Friedlein and Bardou (2017). Weather Ready Reminders of the 1967 Outbreak. Presented at 2017 Fermilab Seminar. Thompson, Rich. Explanation of SPC Severe Weather Parameters. Houston CWSU NWS. Mesoscale Analysis Parameters. _parameters/sounding_stuff/mesoscaleparameters.html Thank you to DuPage OHSEM for hosting this event and to the attendees for being a great audience!