Chase Case #15

[Paul Austin]

Urgent Notice

<3 short crackly tones, 1 long clear tone>

"From the National Weather Service in..."

At 0020z multiple vortex tornado was reported 8 miles south of Haskell, TX.

At 0040z law enforcement reported a tornado 2 miles southwest of Shadehill, SD.

At 0052z an off duty sheriff deputy reported a tornado on the ground 2 miles south of Flora, MS.

 

[Paul Townsend]

Presuming it was not my vehicle that was hit by debris.......I am filming at least my second tornado of this storm.

 

[Jared Farrer]

Finally getting this southern storm to produce. Yeah!

 

[Paul Austin]

1z Update

1Z Observations:


Surface Observations:
Eastern CONUS

Radar Imagery:
Northern Plains
Central Plains
Southern Plains
Upper Mississippi Valley
Middle Mississippi Valley
Lower Mississippi Valley

Infrared Satellite Imagery:
National


Mesoscale Discussions and Weather Watches:

MD 16 Graphic

MESOSCALE DISCUSSION 16[FONT=&quot]
[/FONT]NWS STORM PREDICTION CENTER NORMAN OK[FONT=&quot]
[/FONT]0729 PM CDT[FONT=&quot]
[/FONT]AREAS AFFECTED...PORTIONS OF ND[FONT=&quot]
[/FONT]CONCERNING...SEVERE THUNDERSTORM POTENTIAL [FONT=&quot]

[/FONT]VALID 0029Z - 0130Z[FONT=&quot]
[/FONT]ISOLATED STORMS WITH LARGE HAIL WILL BE LIKELY FOR THE NEXT COUPLE[FONT=&quot]
[/FONT]OF HOURS. WW NOT ANTICIPATED.[FONT=&quot]

[/FONT]REGIONAL RADARS SHOW CONVECTION OVER CENTRAL ND WITHIN AN[FONT=&quot]
[/FONT]INSTABILITY AXIS WHICH EXTENDS NWD INTO THIS REGION FROM WRN SD. [FONT=&quot]
[/FONT]00Z BIS SOUNDING SHOWS MARGINAL INSTABILITY WITH DEEP LAYER SHEAR[FONT=&quot]
[/FONT]AROUND 35 KT TO SUPPORT MULTICELLS WITH ISOLATED SUPERCELLS. LOW[FONT=&quot]
[/FONT]WET-BULB ZERO HEIGHTS WITH STEEP LAPSE RATES AND 500 MB TEMPERATURES[FONT=&quot]
[/FONT]NEAR -20C WILL SUPPORT HAIL WITH THE STRONGEST STORMS. HOWEVER...[FONT=&quot]
[/FONT]THE MARGINAL INSTABILITY IS EXPECTED TO LIMIT THE SEVERE COVERAGE[FONT=&quot]
[/FONT]AND NOT WARRANT THE ISSUANCE OF A WW.[FONT=&quot]


MD 17 Graphic

[/FONT]MESOSCALE DISCUSSION 17[FONT=&quot]
[/FONT]NWS STORM PREDICTION CENTER NORMAN OK[FONT=&quot]
[/FONT]0833 PM CDT[FONT=&quot]
[/FONT]AREAS AFFECTED...FAR NERN CO/WRN NEB[FONT=&quot]
[/FONT]CONCERNING...TORNADO WATCH...[FONT=&quot]

[/FONT]VALID 0133Z - 0230Z[FONT=&quot]
[/FONT]PARAMETERS REMAIN FAVORABLE FOR TORNADOES OVER WRN NEB AS STORMS[FONT=&quot]
[/FONT]CONTINUE TO DEVELOP AND MOVE EWD.[FONT=&quot]

[/FONT]01Z SURFACE ANALYSIS SHOWS A SURFACE LOW OVER NERN CO WITH A FRONTAL[FONT=&quot]
[/FONT]BOUNDARY EXTENDING NEWD INTO THE NEB PANHANDLE FROM BANNER COUNTY TO[FONT=&quot]
[/FONT]NRN GARDEN COUNTY. REGIONAL RADARS INDICATE TORNADIC SUPERCELLS[FONT=&quot]
[/FONT]OVER NRN GARDEN AND MORRILL COUNTIES...WITH VIS IMAGERY SHOWING[FONT=&quot]
[/FONT]ANOTHER CB TO THE WEST AND ALONG THE FRONTAL BOUNDARY OVER BANNER[FONT=&quot]
[/FONT]COUNTY. PERSISTENT PRESSURE FALLS OVER ERN CO INTO THE SRN HALF OF[FONT=&quot]
[/FONT]THE NEB PANHANDLE IS SUPPORTING SELY LOW-LEVEL TO THE E AND S OF THE[FONT=&quot]
[/FONT]CURRENT STORMS OVER WRN NEB...AND SUBSEQUENTLY TRANSPORTING MOISTURE[FONT=&quot]
[/FONT]NWWD INTO THIS REGION. ENHANCED LOW-LEVEL SHEAR IN THE VICINITY OF[FONT=&quot]
[/FONT]THE E-W BOUNDARY OVER WRN NEB WILL CONTINUE TO FAVOR THE THREAT OF[FONT=&quot]
[/FONT]TORNADOES. [FONT=&quot]



[/FONT] URGENT - IMMEDIATE BROADCAST REQUESTED[FONT=&quot]
[/FONT]TORNADO WATCH NUMBER 9
NWS STORM PREDICTION CENTER NORMAN OK [FONT=&quot]
[/FONT]805 PM CDT[FONT=&quot]
[/FONT]THE NWS STORM PREDICTION CENTER HAS ISSUED A[FONT=&quot]
[/FONT]TORNADO WATCH FOR PORTIONS OF [FONT=&quot]

[/FONT]WESTERN OKLAHOMA[FONT=&quot]
[/FONT]EASTERN TEXAS PANHANDLE AND NORTHWEST TEXAS[FONT=&quot]

[/FONT]EFFECTIVE THIS NIGHT AND MORNING FROM[FONT=&quot]
[/FONT]805 PM UNTIL 200 AM CDT.[FONT=&quot]

[/FONT]TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS[FONT=&quot]
[/FONT]TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.[FONT=&quot]

[/FONT]THE TORNADO WATCH AREA IS ALONG AND 95 STATUTE MILES EAST AND WEST[FONT=&quot]
[/FONT]OF A LINE FROM 20 MILES EAST OF GAGE OKLAHOMA TO 15 MILES SOUTH[FONT=&quot]
[/FONT]SOUTHEAST OF ABILENE TEXAS.[FONT=&quot]

[/FONT]REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR[FONT=&quot]
[/FONT]TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.[FONT=&quot]
[/FONT]PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING[FONT=&quot]
[/FONT]WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE[FONT=&quot]
[/FONT]WARNINGS.[FONT=&quot]

[/FONT]OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO[FONT=&quot]
[/FONT]WATCH NUMBER 4. WATCH NUMBER 4 WILL NOT BE IN EFFECT AFTER 805[FONT=&quot]
[/FONT]PM CDT. CONTINUE...WW 5...WW 6...WW 7...WW 8...[FONT=&quot]

[/FONT]DISCUSSION...LEFT AND RIGHT MOVING SUPERCELLS WILL PERSIST FOR[FONT=&quot]
[/FONT]ANOTHER COUPLE OF HOURS ACROSS NW TX AND SW OK. THE ENVIRONMENT[FONT=&quot]
[/FONT]OVER WRN OK IS BECOMING MORE FAVORABLE FOR RIGHT MOVING SUPERCELLS[FONT=&quot]
[/FONT]WITH INCREASING LOW-LEVEL SHEAR...ALONG THE AXIS OF 2000-3000 J/KG[FONT=&quot]
[/FONT]MLCAPE CAPE AND 65-70 DEW POINTS. THERE IS SOME CONCERN THAT THE[FONT=&quot]
[/FONT]CAP WILL INHIBIT ADDITIONAL DEVELOPMENT GIVEN THE LOSS OF DAYTIME[FONT=&quot]
[/FONT]HEATING...BUT CONVERGENCE ALONG THE DRYLINE REMAINS PRONOUNCED AND A[FONT=&quot]
[/FONT]MID-UPPER SPEED MAX WILL APPROACH THE NW TX PANHANDLE IN THE NEXT[FONT=&quot]
[/FONT]3-6 HOURS. VERY LARGE HAIL AND A COUPLE OF TORNADOES WILL BE[FONT=&quot]
[/FONT]POSSIBLE... ESPECIALLY IF ADDITIONAL STORMS CAN FORM ACROSS WRN OK[FONT=&quot]
[/FONT]THIS EVENING.[FONT=&quot]

[/FONT]AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL[FONT=&quot]
[/FONT]SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND[FONT=&quot]
[/FONT]GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600.[FONT=&quot]
[/FONT]MEAN STORM MOTION VECTOR 29020.[FONT=&quot]
[/FONT]
[FONT=&quot]
Chaser Positioning Map


[/FONT]

 

[Paul Austin]

<3 short crackly tones, 1 long clear tone>

"From the National Weather Service in..."

At 0020z multiple vortex tornado was reported 8 miles south of Haskell, TX.

At 0040z law enforcement reported a tornado 2 miles southwest of Shadehill, SD.

At 0052z an off duty sheriff deputy reported a tornado on the ground 2 miles south of Flora, MS.

Decent chaser convergence in TX and a "sheriff-nado" to boot,

 

[Bob Hartig]

Whew...at last. I'm on the cell in Morrill County. It's dark, but I've come too far not to take the storms now that I've got 'em. The one I'm on looks just fine, but I may drop south to the developing storm in Banner County. Road options east of Angora look virtually non-existent.

 

[Wes Carter]

Wow, I'm watching my second tornado, a multiple vortex tube! I wish all of these cars weren't around me, I need to take a whiz! All of that coffee and the excitement is just too much for my bladder.

 

[Danny Neal]

Blasting south out of Woodward to hope meet up with that supercell in time coming out of SW OK.

 

[Michael O'Keeffe]

We are also just saw our second tube all alone on a dirt road near Haskell, TX. Tornado was only a 1/2 mile from us! Storms still cranking with rapidly rotating wall cloud!

 

[Bob Gould]

At this point, from Crowell I can either head south into a dangerous core punch or north to try and catch the cell in SW Ok. I think I will head north.

 

[Paul Austin]

Urgent Notice

<3 short crackly tones, 1 long clear tone>

"From the National Weather Service in..."

At 0110z spotters reported a large tornado 10 miles southeast of Haskell, TX.

At 0112z spotters reported the development of a tornado with the new mesocyclone to the southeast of the old one associated with the large tornado over Lake Stamford. New tornado was located 15 miles southeast of Haskell, TX.

 

[Charles Kuster]

After frantically driving south all afternoon out of Kansas, I am finally at least seeing a storm. I missed the show down in Texas, but at least I will see some something (mostly lightning)! I was in Cheyenne, OK at 0Z, so I would have easily been able to position on the storm now in southeast Beckham County. I will be chasing this storm into the night. Approximate position as of 1Z, Retrop, OK.

 

[Wes Carter]

OMG! I can't wait to put this video on YouTube!

 

[Paul Austin]

2z and Results

It's been a long chase day, very long for some of us, rewarding for some. Final details are below:

2Z Observations:


Radar Imagery:
Northern Plains
Central Plains
Southern Plains
Upper Mississippi Valley
Middle Mississippi Valley
Lower Mississippi Valley

Infrared Satellite Imagery:
National


Mesoscale Discussions and Weather Watches:

MD 18 Graphic

MESOSCALE DISCUSSION 18[FONT=&quot]
[/FONT]NWS STORM PREDICTION CENTER NORMAN OK[FONT=&quot]
[/FONT]0925 PM CDT[FONT=&quot]
[/FONT]AREAS AFFECTED...CENTRAL SD[FONT=&quot]
[/FONT]CONCERNING...SEVERE THUNDERSTORM WATCH...[FONT=&quot]

[/FONT]VALID 0225Z - 0330Z[FONT=&quot]
[/FONT]SEVERE THREAT WILL CONTINUE TO DIMINISH OVER CENTRAL SD DURING THE[FONT=&quot]
[/FONT]NEXT FEW HOURS...WITH LOCALIZED HEAVY RAIN BEING THE PRIMARY CONCERN[FONT=&quot]
[/FONT]FROM CENTRAL INTO NERN SD.[FONT=&quot]

[/FONT]02Z SURFACE ANALYSIS SHOWS A FRONTAL BOUNDARY EXTENDING FROM SWRN SD[FONT=&quot]
[/FONT]IN THE VICINITY OF SHANNON COUNTY NEWD TO SULLY COUNTY AND THEN[FONT=&quot]
[/FONT]ENEWD TO ROBERTS/GRANT COUNTIES. ALTHOUGH CONVECTION IS EXPECTED TO[FONT=&quot]
[/FONT]CONTINUE FOR THE NEXT SEVERAL HOURS AS THE NOSE OF A STRENGTHENING[FONT=&quot]
[/FONT]LLJ FROM THE SRN PLAINS INTO THE SD INTERSECTS THE SURFACE BOUNDARY[FONT=&quot]
[/FONT]OVER CENTRAL SD...DECREASING INSTABILITY WILL DECREASE THE OVERALL[FONT=&quot]
[/FONT]SEVERE THREAT. MODEST DEEP LAYER SHEAR AND STEEP LAPSE RATES[FONT=&quot]
[/FONT]WILL...HOWEVER...SUPPORT AN ISOLATED HAIL THREAT.[FONT=&quot]


[/FONT]MD 19 Graphic

MESOSCALE DISCUSSION 19[FONT=&quot]
[/FONT]NWS STORM PREDICTION CENTER NORMAN OK[FONT=&quot]
[/FONT]0942 PM CDT[FONT=&quot]
[/FONT]AREAS AFFECTED...WRN AND CENTRAL NEB[FONT=&quot]
[/FONT]CONCERNING...TORNADO WATCH...[FONT=&quot]

[/FONT]VALID 0242Z - 0315Z[FONT=&quot]
[/FONT]NEW WW WILL BE ISSUED BY 03Z FOR PORTIONS OF WRN INTO CENTRAL NEB.[FONT=&quot]
[/FONT]AS A SLY LLJ CONTINUES TO STRENGTHEN THIS EVENING OVER THE SRN/[FONT=&quot]
[/FONT]CENTRAL PLAINS...RICH MOISTURE WILL ADVECT NWD RESULTING IN STRONG[FONT=&quot]
[/FONT]DESTABILIZATION ABOVE THE SURFACE. STRONG DEEP LAYER SHEAR SUPPORTS[FONT=&quot]
[/FONT]SUPERCELLS WITH STEEP LAPSE RATES SUGGESTING LARGE HAIL WILL BE THE[FONT=&quot]
[/FONT]PRIMARY THREAT INTO THE OVERNIGHT HOURS AS THE CONVECTION BECOMES[FONT=&quot]
[/FONT]MORE ELEVATED AND DEVELOPS EWD ACROSS NEB.[FONT=&quot]


[/FONT]MESOSCALE DISCUSSION 20[FONT=&quot]
[/FONT]NWS STORM PREDICTION CENTER NORMAN OK[FONT=&quot]
[/FONT]1000 PM CDT[FONT=&quot]
[/FONT]AREAS AFFECTED...WRN OK...NW TX...ERN TX PANHANDLE[FONT=&quot]
[/FONT]CONCERNING...TORNADO WATCH 227...[FONT=&quot]


[/FONT]
FINAL RESULTS for May 3, 2003:

SPC Reports for May 3, 2003

Yes, that's right - just one day prior to the May 4 outbreak simulated in an earlier Chase Case scenario. Interestingly, the two days bypassed western/central KS completely.

Compare to the 12z Convective Outlook[FONT=&quot] and 12z Tornado Probability

(Neither of which I originally provided to keep the date less recognizable for those who might have chased this setup) and the 3 day outlook provide on page 1 of the thread, and one can see why it's not a good idea to just chase SPC bullseyes. If you busted on this virtual chase, don't feel bad; it was indeed a challenging forecast even for the experts at the Storm Prediction Center. And you didn't waste any real gas, but perhaps some real time. If you scored, congratulations on a chase well done. Go get your steak (perhaps well done as well ).

It was interesting to watch everyone struggle with the cloud cover and the slow moisture return in making a decision to either sit tight or make a major reposition in a hurry. I could literally feel your agony; been there, done that. Change of plans don't always pan out, but those who pulled the trigger early enough on this day were rewarded. I didn't chase this day in rl, but I could easily see myself enjoying a big ol' blue sky (or perhaps cirrus-y sky is more appropriate) bust.

A few of you guessed the date, and I know a couple of you actually chased this event. So how did you do in real life? With a different set of data available to you, did you play it differently? How many of you would have set up further south if a synoptic map had originally been provided with the warm front draped south of the Red River? I'm interested to hear how those of you who picked up on the upslope setup arrived at your conclusion. This is a great learning op for some of us (including me). Anyone with pics or video of this event or links to such?


Chaser Positioning Map


[/FONT]

 

[Bob Hartig]

Ah, well...skunked. Verne and Andrea, you guys made a great call to head north when you did. I was just too smart for my own breeches, and passed up storms that were in progress for storms that I expected to form. By the time I got to where I needed to be, it was too late.

Paul, this was a fabulous chase scenario. Bravissimo! A real chess game of moisture return, and interesting to see the Nebraska supercells crank out so many tornadoes with such low dewpoints. Thanks for picking this frustrating but fascinating setup, and for managing it so nicely.