2005 National Severe Weather Workshop Paul Sirvatka April 20, 2004 Tornado Outbreak Nature Can Still Surprise… Paul L. Sirvatka Professor of Meteorology

2005 National Severe Weather Workshop Paul Sirvatka2005 National Severe Weather Workshop Paul Sirvatka

April 20, 2004April 20, 2004Tornado OutbreakTornado OutbreakApril 20, 2004April 20, 2004

Tornado OutbreakTornado Outbreak

Nature Can Still Surprise…Nature Can Still Surprise…Nature Can Still Surprise…Nature Can Still Surprise…

Paul L. SirvatkaPaul L. SirvatkaProfessor of MeteorologyProfessor of Meteorology

College of DuPageCollege of DuPageGlen Ellyn, ILGlen Ellyn, IL


Event OverviewEvent OverviewEvent OverviewEvent Overview April 20, 2004 in

Iowa, Illinois and Indiana

30 Tornadoes 8 Deaths in Utica

IL Milestone Tavern

Collapsed Sought Safer

Shelter

April 20, 2004 in Iowa, Illinois and Indiana

30 Tornadoes 8 Deaths in Utica

IL Milestone Tavern

Collapsed Sought Safer

Shelter


Northeast IllinoisNortheast IllinoisNortheast IllinoisNortheast Illinois


Photo courtesy of Jim Krancic










Granville, ILGranville, ILGranville, ILGranville, IL

Photos courtesy of Steve Drews


Granville, ILGranville, ILGranville, ILGranville, IL



Utica, ILUtica, ILUtica, ILUtica, IL



F -3 Damage to F -3 Damage to Milestone TavernMilestone TavernF -3 Damage to F -3 Damage to Milestone TavernMilestone Tavern



Video from CBS-Chicago and NWS- LOTJim Allsopp and Al Pietrycha


Synoptic Scale Set-upSynoptic Scale Set-upSynoptic Scale Set-upSynoptic Scale Set-up


Storm Reports 4-20-04Storm Reports 4-20-04Storm Reports 4-20-04Storm Reports 4-20-04

53 tornado reports 53 tornado reports nationwidenationwide

Very few hail reports Very few hail reports in Northern Illinoisin Northern Illinois

Largest hail occurred Largest hail occurred in warm sector but in warm sector but there was tennis ball there was tennis ball hail with the LaSalle hail with the LaSalle County StormCounty Storm

53 tornado reports 53 tornado reports nationwidenationwide

Very few hail reports Very few hail reports in Northern Illinoisin Northern Illinois

Largest hail occurred Largest hail occurred in warm sector but in warm sector but there was tennis ball there was tennis ball hail with the LaSalle hail with the LaSalle County StormCounty Storm


5 Supercells in 5 Supercells in Northeast IllinoisNortheast Illinois5 Supercells in 5 Supercells in

Northeast IllinoisNortheast Illinois


20Z Convective Outlook20Z Convective Outlook


Why the Miss?Why the Miss?Why the Miss?Why the Miss?

Completely missed Completely missed the forecast the forecast instabilityinstability

Pattern recognition Pattern recognition was incorrectwas incorrect

Stratiform rain and Stratiform rain and clouds cleared in a clouds cleared in a narrow band along narrow band along warm frontwarm front

All numerical All numerical guidance was poor guidance was poor (RUC and ETA)(RUC and ETA)

Completely missed Completely missed the forecast the forecast instabilityinstability

Pattern recognition Pattern recognition was incorrectwas incorrect

Stratiform rain and Stratiform rain and clouds cleared in a clouds cleared in a narrow band along narrow band along warm frontwarm front

All numerical All numerical guidance was poor guidance was poor (RUC and ETA)(RUC and ETA)


Favorable for SevereFavorable for SevereFavorable for SevereFavorable for Severe

Incredible low-level Incredible low-level shear 0-1KM north of shear 0-1KM north of warm frontwarm front

Clearing in narrow Clearing in narrow zone north of frontzone north of front

Sufficient moistureSufficient moisture Favorable storm Favorable storm

motion with respect motion with respect to front motionto front motion

Incredible low-level Incredible low-level shear 0-1KM north of shear 0-1KM north of warm frontwarm front

Clearing in narrow Clearing in narrow zone north of frontzone north of front

Sufficient moistureSufficient moisture Favorable storm Favorable storm

motion with respect motion with respect to front motionto front motion


VAD Profile from LOTVAD Profile from LOTVAD Profile from LOTVAD Profile from LOT


Unfavorable for SevereUnfavorable for SevereUnfavorable for SevereUnfavorable for Severe

CAPE was limitedCAPE was limited Rain-cooled air in Rain-cooled air in

spring almost always spring almost always kills the threat of kills the threat of surfaced-based severe surfaced-based severe in NE ILin NE IL

Initiation mechanism Initiation mechanism in warm sector was in warm sector was uncertainuncertain

Despite strong SRH in Despite strong SRH in 0-1km, it won’t be 0-1km, it won’t be realized if storms are realized if storms are elevatedelevated

CAPE was limitedCAPE was limited Rain-cooled air in Rain-cooled air in

spring almost always spring almost always kills the threat of kills the threat of surfaced-based severe surfaced-based severe in NE ILin NE IL

Initiation mechanism Initiation mechanism in warm sector was in warm sector was uncertainuncertain

Despite strong SRH in Despite strong SRH in 0-1km, it won’t be 0-1km, it won’t be realized if storms are realized if storms are elevatedelevated

2005 National Severe Weather Workshop Paul Sirvatka2005 National Severe Weather Workshop Paul Sirvatka 21 Z Surface Map21 Z Surface Map21 Z Surface Map21 Z Surface Map


Visible Satellite ImageryVisible Satellite ImageryVisible Satellite ImageryVisible Satellite Imagery


Radar ReviewRadar ReviewRadar ReviewRadar Review


Watch Number 95 - 5:40 PM Watch Number 95 - 5:40 PM CDTCDT

Watch Number 95 - 5:40 PM Watch Number 95 - 5:40 PM CDTCDT

DISCUSSION...FAVORABLE SHEAR DISCUSSION...FAVORABLE SHEAR PROFILES ON NWD MOVING WARM PROFILES ON NWD MOVING WARM FRONT FOR TORNADIC SUPERCELLS. FRONT FOR TORNADIC SUPERCELLS. STORMS WILL CONTINUE TO STORMS WILL CONTINUE TO DEVELOP AS THE WARM FRONT DEVELOP AS THE WARM FRONT SHIFTS NWD INTO NRN IL/IND.SHIFTS NWD INTO NRN IL/IND.

DISCUSSION...FAVORABLE SHEAR DISCUSSION...FAVORABLE SHEAR PROFILES ON NWD MOVING WARM PROFILES ON NWD MOVING WARM FRONT FOR TORNADIC SUPERCELLS. FRONT FOR TORNADIC SUPERCELLS. STORMS WILL CONTINUE TO STORMS WILL CONTINUE TO DEVELOP AS THE WARM FRONT DEVELOP AS THE WARM FRONT SHIFTS NWD INTO NRN IL/IND.SHIFTS NWD INTO NRN IL/IND.


The result…?The result…?The result…?The result…?


Storms Spun like Tops!Storms Spun like Tops!Storms Spun like Tops!Storms Spun like Tops!


Convergent RotationConvergent RotationConvergent RotationConvergent Rotation


Mini-SupercellsMini-SupercellsMini-SupercellsMini-Supercells

TBSS (Three-body Scatter Spike)


Mini-SupercellsMini-SupercellsMini-SupercellsMini-Supercells

Tornadic cases Tornadic cases have a great deal have a great deal of CAPE below of CAPE below 500mb500mb

Lower total CAPE Lower total CAPE and lower ELand lower EL

Significant shear Significant shear over the depth of over the depth of the storm the storm (30-35k feet)(30-35k feet)

Tornadic cases Tornadic cases have a great deal have a great deal of CAPE below of CAPE below 500mb500mb

Lower total CAPE Lower total CAPE and lower ELand lower EL

Significant shear Significant shear over the depth of over the depth of the storm the storm (30-35k feet)(30-35k feet)


22Z RUC Analysis 22Z RUC Analysis (PIA ua and SPI sfc)(PIA ua and SPI sfc)

22Z RUC Analysis 22Z RUC Analysis (PIA ua and SPI sfc)(PIA ua and SPI sfc)


00Z DVN Sounding00Z DVN Sounding00Z DVN Sounding00Z DVN Sounding


100 mb vs. 50 mb MLCAPE100 mb vs. 50 mb MLCAPE100 mb vs. 50 mb MLCAPE100 mb vs. 50 mb MLCAPE


Summary of April 20th Summary of April 20th EventsEvents


Warm front provided source of lift and Warm front provided source of lift and additional vorticityadditional vorticity

Low LCL’s, high helicity and adequate Low LCL’s, high helicity and adequate moisture and shearmoisture and shear

CAPE appeared to be lacking but was CAPE appeared to be lacking but was more than sufficient with limited sunshinemore than sufficient with limited sunshine

Speed of storms and front matched, Speed of storms and front matched, allowing for storms to stay in “sweet allowing for storms to stay in “sweet zone” for a long period of timezone” for a long period of time

Position of 850mb warm frontPosition of 850mb warm front

Warm front provided source of lift and Warm front provided source of lift and additional vorticityadditional vorticity

Low LCL’s, high helicity and adequate Low LCL’s, high helicity and adequate moisture and shearmoisture and shear

CAPE appeared to be lacking but was CAPE appeared to be lacking but was more than sufficient with limited sunshinemore than sufficient with limited sunshine

Speed of storms and front matched, Speed of storms and front matched, allowing for storms to stay in “sweet allowing for storms to stay in “sweet zone” for a long period of timezone” for a long period of time

Position of 850mb warm frontPosition of 850mb warm front




Forecasters missed the event in Forecasters missed the event in terms of surface-based convectionterms of surface-based convection

The response to what was The response to what was actuallyactually happening was quick, decisive and happening was quick, decisive and showed a good state of readiness - showed a good state of readiness - situational awareness was strongsituational awareness was strong

Forecasters missed the event in Forecasters missed the event in terms of surface-based convectionterms of surface-based convection

The response to what was The response to what was actuallyactually happening was quick, decisive and happening was quick, decisive and showed a good state of readiness - showed a good state of readiness - situational awareness was strongsituational awareness was strong


100% POD!100% POD!100% POD!100% POD!

Warnings were issued Warnings were issued prior to all tornadoes prior to all tornadoes

FAR = .58 CSI = .42FAR = .58 CSI = .42 Average lead time is Average lead time is

15.6 minutes15.6 minutes Utica tornado had a Utica tornado had a

lead time of 26 lead time of 26 minutesminutes

Excellent spotter Excellent spotter reports from chasers, reports from chasers, spotters and law spotters and law enforcement officersenforcement officers

Warnings were issued Warnings were issued prior to all tornadoes prior to all tornadoes

FAR = .58 CSI = .42FAR = .58 CSI = .42 Average lead time is Average lead time is

15.6 minutes15.6 minutes Utica tornado had a Utica tornado had a

lead time of 26 lead time of 26 minutesminutes

Excellent spotter Excellent spotter reports from chasers, reports from chasers, spotters and law spotters and law enforcement officersenforcement officers


So What Can We Learn?So What Can We Learn?So What Can We Learn?So What Can We Learn? We need more skill in weather We need more skill in weather

forecasting - models are not 100% forecasting - models are not 100% reliablereliable

Spring warm fronts can produce very Spring warm fronts can produce very dangerous weather eventsdangerous weather events

Lift, moisture, instability, wind shear: Lift, moisture, instability, wind shear: what is missing? Watch for the last what is missing? Watch for the last ingredient to show up!ingredient to show up!

High CAPE is overrated!High CAPE is overrated!

We need more skill in weather We need more skill in weather forecasting - models are not 100% forecasting - models are not 100% reliablereliable

Spring warm fronts can produce very Spring warm fronts can produce very dangerous weather eventsdangerous weather events

Lift, moisture, instability, wind shear: Lift, moisture, instability, wind shear: what is missing? Watch for the last what is missing? Watch for the last ingredient to show up!ingredient to show up!

High CAPE is overrated!High CAPE is overrated!


Questions to AnswerQuestions to AnswerQuestions to AnswerQuestions to Answer

Why did the models miss the CAPE Why did the models miss the CAPE so badly? Should forecasters have so badly? Should forecasters have anticipated the miss?anticipated the miss?

Why did the air clear north of the Why did the air clear north of the early spring warm front?early spring warm front?

Would we anticipate this event in Would we anticipate this event in the future?the future?

Why did the models miss the CAPE Why did the models miss the CAPE so badly? Should forecasters have so badly? Should forecasters have anticipated the miss?anticipated the miss?

Why did the air clear north of the Why did the air clear north of the early spring warm front?early spring warm front?

Would we anticipate this event in Would we anticipate this event in the future?the future?


The “No-duh” info that we The “No-duh” info that we need to hear over and need to hear over and

over…over…

The “No-duh” info that we The “No-duh” info that we need to hear over and need to hear over and

over…over… Supercells come in many shapes Supercells come in many shapes

and sizes but they are all and sizes but they are all dangerousdangerous

Be prepared in all circumstancesBe prepared in all circumstances Meteorology can always find ways Meteorology can always find ways

to surprise us and teach usto surprise us and teach us Tornadoes are cool!!!!Tornadoes are cool!!!!

Supercells come in many shapes Supercells come in many shapes and sizes but they are all and sizes but they are all dangerousdangerous

Be prepared in all circumstancesBe prepared in all circumstances Meteorology can always find ways Meteorology can always find ways

to surprise us and teach usto surprise us and teach us Tornadoes are cool!!!!Tornadoes are cool!!!!


AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements

Al Pietrycha and Al Pietrycha and Jim Allsopp of theJim Allsopp of theChicago National Chicago National Weather ServiceWeather Service

Jon DaviesJon DaviesSteve DrewsSteve DrewsJim KrancicJim Krancic

College of DuPage College of DuPage Meteorology StaffMeteorology Staff

Al Pietrycha and Al Pietrycha and Jim Allsopp of theJim Allsopp of theChicago National Chicago National Weather ServiceWeather Service

Jon DaviesJon DaviesSteve DrewsSteve DrewsJim KrancicJim Krancic

College of DuPage College of DuPage Meteorology StaffMeteorology Staff


Close-up of Joliet Close-up of Joliet Tornadic StormTornadic Storm

Close-up of Joliet Close-up of Joliet Tornadic StormTornadic Storm


Amazing RFDAmazing RFDAmazing RFDAmazing RFD


LaSalle County FlyoverLaSalle County FlyoverLaSalle County FlyoverLaSalle County Flyover


Kankakee TornadoKankakee TornadoKankakee TornadoKankakee Tornado

Documents

2005 National Severe Weather Workshop Paul Sirvatka April 20, 2004 Tornado Outbreak Nature Can Still Surprise… Paul L. Sirvatka Professor of Meteorology