June Chase Day 1

[Paul Sherman]

Slight Risk for today and have been chewing over Model Data with Tony Gilbert here at Denver this morning. Looks like a good chance of Supercells today with Possibilities of Tornadoes in North East Colorado. Going to head North East today and try to Intercept some Storms before finishing somewhere in Nebraska in readiness for tomorrow.

TARGET # I-76 Corridoor

INITIATION # 21Z Onwards

RISKS # Supercells with possible Tornadoes & HP Bomb Type Storms

As potty said possible Denver Cyclone Set-Up later today and a BIG Bonus for us which will get us into position for tomorrow.

Regards

Paul Sherman

[Andy Bown]

RISKS # Supercells with possible Tornadoes & HP Bomb Type Storms

Sounds amazing!

What do you mean by 'Bomb Type Stroms'. I know HP stands of High Preciptation as in the supercell categories, but the only 'bomb' noise I recall from storms is when CGs land very close with the immediate thundercrack.

[Paul Sherman]

Sounds amazing!

What do you mean by 'Bomb Type Stroms'. I know HP stands of High Preciptation as in the supercell categories, but the only 'bomb' noise I recall from storms is when CGs land very close with the immediate thundercrack.

Hi Andy

It's just a term we use that means the Storms will transition into HP Supercells very quickly, hardly any chance of Classic Structure shots before they become big hailers and "Bombs" Leaving pretty soon so will report on the way and when we get Wifi again

Paul S

[NL]

Paul and Tony should be well on their journey towards Nebraska/ South Dakota for tomorrows mod risk , currently a meso discussion has been issued for right where the lads are heading...

[Paul Sherman]

Currently leaving Fort Morgan on I76 & Heading towards the Ragged Cumulus field ahead of us, MD & Severe T-Storm watch box issued for above our heads, as NL Says we are heading up towards that area for the big day tomorrow so here goes!!

Paul Sherman

[Nick F]

Storms currently moving East off the Front Range of the Rockies as warm front/moisture plume marches NE across the High Plains:

1800 UTC sfc progs:

Radar, satellite and WV imagery:

Paul and Tony should come across cells intiating ahead of this line over the front range aswell looking at satellite imagery which shows some cumulus fields developing over NE Colorado and into Wern NE.

Tomorrow, although SPC have a MDT risk over Nern NE and the Dakotas, fcst soundings reveal strong cap in place tomorrow evening (Thurs 00z) over the Sern part of the MDT risk - with an elevated mixed layer (EML) putting a lid on convection:

- Thurs 00z fcst soundings for Nebraska and S Dakota.

... this likely to provide an atmosphere of conditional instability where strong convection is only likely to be released if trough arrives in time for maximum potential in the early evening, there are some doubts looking at the SPC outlook discussions that the trough will arrive in time to coincide with best convective potential for the Sern part of the MDT risk area, though where strong forcing does occur to break the cap, be sure of some very severe storms albeit isolated:

ALTHOUGH AN OUTBREAK OF SEVERE STORMS IS POSSIBLE ACROSS PARTS OF

THE MODERATE RISK AREA FROM LATE WEDNESDAY AFTERNOON THROUGH

WEDNESDAY NIGHT...MANY UNCERTAINTIES REMAIN CONCERNING MOISTURE

RETURN AND THE TIMING OF THE UPPER-LEVEL LOW. THE SHORT-TERM MODELS

APPEAR TO BE TOO QUICK WITH RETURNING LOW-LEVEL MOISTURE NWD INTO

THE PLAINS. ALSO...THE MODELS FROM RUN TO RUN HAVE BEEN CONSISTENTLY

TOO FAST AND TOO FAR NORTH WITH THE UPPER-LOW. FOR THESE

REASONS...THUNDERSTORMS THAT DEVELOP ACROSS THE REGION MAY NOT HAVE

ACCESS TO THE GREATEST MOISTURE UNTIL LATER WEDNESDAY NIGHT AND THIS

COULD LIMIT THE OUTBREAK POTENTIAL.

CONCERNING THE SYNOPTIC SETUP...A SFC LOW SHOULD DEVELOP IN THE HIGH

PLAINS WEDNESDAY WITH THE LOW DEEPENING AND MOVING EWD INTO THE NRN

PLAINS BY WEDNESDAY EVENING. WARM MID-LEVEL TEMPS ASSOCIATED WITH AN

ELEVATED MIXED LAYER WILL LIKELY CAP AREAS SOUTH OF THE SFC LOW

ACROSS WCNTRL NEB AND WCNTRL KS WEDNESDAY AFTERNOON. THUNDERSTORMS

SHOULD DEVELOP WEDNESDAY AFTERNOON FROM THE SFC LOW IN WRN SD NWD

ACROSS ERN MT AND WRN ND. INSTABILITY AND VERTICAL SHEAR ON FORECAST

SOUNDINGS IN THIS AREA SUGGEST CONDITIONS WILL BE FAVORABLE FOR

SUPERCELLS. SUPERCELLS SHOULD HAVE ENOUGH INSTABILITY AND VERTICAL

SHEAR TO PRODUCE TORNADOES...LARGE HAIL AND WIND DAMAGE WEDNESDAY

AFTERNOON WITH THE SEVERE WEATHER THREAT SPREADING EWD ACROSS THE

NRN PART OF THE MODERATE RISK AREA LATE WEDNESDAY AFTERNOON INTO THE

EARLY EVENING. CONSIDERING THE STRONG UNIDIRECTIONAL FLOW AND

RELATIVELY DRY BOUNDARY LAYER IN THE WRN DAKOTAS COUPLED WITH THE

VERY STRONG LARGE-SCALE ASCENT COMING OUT WITH THE TROUGH...AN

ENHANCED POTENTIAL FOR WIND DAMAGE MAY ALSO DEVELOP IF A LINEAR MCS

TRACKS EWD ACROSS SRN ND AND NRN SD FROM LATE WEDNESDAY AFTERNOON

INTO THE EVENING. A SIGNIFICANT TORNADO THREAT MAY ALSO DEVELOP

DURING THE LATE EVENING AND OVERNIGHT PERIOD IN ERN ND...ERN SD AND

WRN MN AS THE MCS TRACKS EWD INTO INCREASING LOW-LEVEL MOISTURE AND

NEW SUPERCELLS INITIATE ON THE SOUTH END OF THE MCS.

THUNDERSTORM DEVELOPMENT ACROSS THE SRN PART OF THE MODERATE RISK

APPEARS MORE CONDITIONAL DUE TO A STRONG CAPPING INVERSION THAT WILL

BE IN PLACE. AS THE LARGE-SCALE ASCENT COMES OUT WITH THE

UPPER-LEVEL TROUGH WEDNESDAY EVENING...THUNDERSTORMS MAY FINALLY

INITIATE ACROSS PARTS OF SERN SD...CNTRL NEB SSWWD ACROSS WCNTRL KS

INTO WEST TX. THUNDERSTORMS SHOULD BE MORE ISOLATED SSWWD ALONG THE

DRYLINE. FORECAST SOUNDINGS ALONG AND JUST EAST OF THE DRYLINE

WEDNESDAY EVENING SHOW VERY STEEP LAPSE RATES...HIGH INSTABILITY AND

STRONG LOW-LEVEL FLOW SUGGESTING LARGE HAIL AND A FEW TORNADOES WILL

BE LIKELY. VERY LARGE HAIL WILL ALSO BE POSSIBLE WITH THE MORE

PERSISTENT SUPERCELLS DURING THE LATE EVENING.

[boycie]

Good luck Paul, I'm following the Tempest guys over here from the UK, and wishing I could get back out there !!!!!

[NL]

Yes Nick earlier reports had the cap breaking quite extensively but as usual as it gets closer to the event widespread severe weather gets downgraded, its gonna be really difficult to pin-point exactly where the cap will break case of keep checking the updates and hope ya in the vacinity but like you said where it does it has the potetial to be explosive!!.

[Paul Sherman]

We have booked in Already tonight in readiness for tomorrow's Risk, have settled for North Platte in Nebraska on the Highway 83 & Interstate 80 Junction at the Comfort Inn. Current thinking over here is that "IF" Storms fire they should initiate along and east of Interstate 83 so a nice lazy start for us, blew off the Colorado threat today although we did see the Severe Akron (Co) Storm, no pictures as yet so hopefully tomorrow yields some pictures.

Paul Sherman

[pottyprof]

Tsk.. look at that cell over the panhandles..

Looking at the sat pic, you should be in just the right place for tomorrow's fireworks.. Don't quote me if you get a damp squib.. just change your trousers..

It's starting to look very mucky chaps.. and coming in fast..

I'd head further north tonight and look at a clear sky.. Just my thoughts.. I'm in New Witten SD ready for tomorrow.. (virtually speaking)

[Paul Sherman]

Tsk.. look at that cell over the panhandles..

Looking at the sat pic, you should be in just the right place for tomorrow's fireworks.. Don't quote me if you get a damp squib.. just change your trousers..

It's starting to look very mucky chaps.. and coming in fast..

I'd head further north tonight and look at a clear sky.. Just my thoughts.. I'm in New Witten SD ready for tomorrow.. (virtually speaking)

Tsk Indeed

Unfortunately we do not have the luxury of your Virtual Helicopter over here Pots!! If we had chased the Panhandle and ended up at your favourite place tonight then we would have missed today 6/6 :lol: Big chances of Bustola's tomorrow but also big risks of Big Tornadoes as well. Add in the fact my Canon has decided to kill itself, literally snapped the prongs in my card reader today and you can see all is going well That is pretty much written off until the mender get hold of it, my face was a picture this morning, and some language not allowed on here was heard in Denver!

Things can only get better as Dream said in that Political song

Paul S

[Roger J Smith]

Have just seen the latest 00z run, things become mega-severe very quickly after 18z Wednesday, the overnight should be very active and Thursday will be a case of fast-moving fronts with huge severe potential.

The low now deepens to 972 mbs in west central SD on Thursday morning. This suggests to me that the cold front spilling over the Wyoming ranges mid-afternoon will have explosive severe development for Wednesday evening in west-central NE and western KS. I think your positioning is very good for tomorrow (Wed).

As to the overnight, huge severe storm potential all night through eastern NE, southeast SD and east-central KS, winds behind this system now look capable of large-scale gusts to 80 mph, so F4-5 potential seems almost guaranteed to me. With this deep a low and such a strong gradient, there is virtually no chance of any kind of misfire or non-event here. The chance of an extreme event is high, from about 19z Wednesday on, through the overnight and all day Thursday.

The Thursday storm situation is likely to be very fast-moving and volatile, reaching Wisconsin by late afternoon and evening, so a very flexible schedule is probably a key here, given that you are likely to get almost zero sleep Wednesday night if located near the front, both from excitement factor and constant thunder and lightning.

This system has all the makings of a historic severe weather event and could be very dangerous for chasers, be ultra careful as the gradient behind the second front could whip up a vicious crosswind of 50-80 mph from the NNW behind the SW winds of the front, and produce a blinding dust storm in parts of western and central SD, north and west Nebraska, into western KS. Sometimes these systems produce hours of near-zero visibility in blowing dust. You'll likely be staying ahead of that zone but it would not be too difficult to be blocked by storms and plunged into this windstorm blowing regionally rather than locally.

Personally, I think the most severe weather will come overnight in eastern NE and southeast SD, possibly north central KS as well, and then repeat in Wisconsin and eastern Iowa on Thursday afternoon and evening. If there is to be a massive severe tornado like Greensburg, this could occur anywhere in this zone but most likely close to Concordia KS to Lincoln NE, then draw a severe tornadic watch box e.n.e. through n.w. IA and southern MN into north central WI, ending at Green Bay to Marquette MI around midnight Thursday.

[Paul Sherman]

Great Post Roger and you are pretty much on the money with all of your thoughts, Am VERY Excited about tomorrow and it is going to be one of the most Dangerous Chases I have ever had in my 4 year Career over here. All the parametres are looking like somewhere is going to kop a Bigun, lets just hope it stays over open farmland and not near populated areas this time.

Paul Sherman

[MAF]

Good post there Roger. hope your call for severe weather gives Paul something worth chasing.

[pottyprof]

Unfortunately we do not have the luxury of your Virtual Helicopter over here Pots!!

Paul S

You couldn't afford my virtual helicopter!! :lol: And anyway high tech gadgets don't seem to be your thing..

Great post Roger and it looks like the models are agreeing with you for today.

Looking good for the afternoon with things falling into place for the GFS model at least. The cap looks to break nicely

Some very high temps for when it does go...

Look at that temperature gradient on the dew points!!!!!!

The jet also comes to play...

The CAPE doesn't look as crazy as it has been on previous runs but still plenty available. Its just a case of wait and see what happens in reality.

Today's outlook from the SPC...

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1256 AM CDT WED JUN 06 2007

VALID 061200Z - 071200Z

...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT

ACROSS THE NORTHERN PLAINS...INCLUDING A LARGE PORTION OF THE

DAKOTAS/CNTRL AND ERN NEBRASKA...PARTS OF NW IA....AND WRN MN....

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK

AREA ACROSS MUCH OF THE REMAINDER OF THE NORTHERN AND CENTRAL

PLAINS....

...SYNOPSIS...

A SIGNIFICANT CLOSED LOW/UPPER TROUGH CONTINUES TO SHIFT

SOUTHEASTWARD ACROSS THE PACIFIC NORTHWEST COAST STATES INTO THE

INTERMOUNTAIN WEST...AS AN ASSOCIATED VERY STRONG MID/UPPER JET

STREAK BEGINS TO NOSE EASTWARD THROUGH THE GREAT BASIN. AS THIS

OCCURS...DOWNSTREAM RIDGE CONTINUES TO SHIFT EAST OF THE ROCKIES.

LATTER FEATURE IS PROGGED TO BUILD THROUGH MUCH OF THE REMAINDER OF

THE EASTERN STATES LATER TODAY THROUGH EARLY THURSDAY...WHILE

DOWNSTREAM TROUGH LIFTS OUT OF THE ATLANTIC SEABOARD INTO THE

WESTERN ATLANTIC.

MODELS REMAIN CONSISTENT IN INDICATING THAT A VIGOROUS LEAD SHORT

WAVE IMPULSE EMBEDDED WITHIN WESTERN TROUGH WILL RAPIDLY LIFT OUT OF

THE EASTERN GREAT BASIN THROUGH THE NORTHERN PLAINS DURING THIS

PERIOD. THIS IS EXPECTED TO OCCUR JUST AHEAD OF ANOTHER SIGNIFICANT

IMPULSE DIGGING THROUGH THE CENTRAL CANADIAN PROVINCES ...AROUND THE

SOUTHWESTERN PERIPHERY OF A RETROGRADING UPPER LOW.

IN RESPONSE TO THE EVOLVING UPPER PATTERN...STRONG SURFACE

CYCLOGENESIS IS PROGGED TO THE LEE OF THE NORTHERN ROCKIES THROUGH

THE DAKOTAS. MODELS ARE SUGGESTIVE THAT THE PERIOD OF MOST RAPID

DEEPENING WILL OCCUR BETWEEN 12-18Z...WITH A MORE GRADUAL DEEPENING

CONTINUING INTO LATE AFTERNOON...WHEN LOW SEEMS LIKELY TO BECOME

CENTERED OVER SOUTHEAST MONTANA. DEEP TRAILING SURFACE TROUGH AXIS

IS EXPECTED TO ARC SOUTHEASTWARD THROUGH WEST CENTRAL SOUTH

DAKOTA...THEN SOUTHWARD ACROSS CENTRAL NEBRASKA/WEST CENTRAL KANSAS

INTO WEST TEXAS...AND BECOME THE FOCUS FOR RAPID NORTHWARD MOISTURE

RETURN/DESTABILIZATION BENEATH STEEP MID-LEVEL LAPSE RATES.

...PLAINS...

A STRONG CAPPING ELEVATED MIXED LAYER ACROSS MUCH OF THE PLAINS BY

THE BEGINNING OF THE FORECAST PERIOD IS EXPECTED TO ALLOW UNIMPEDED

MOISTURE RETURN THROUGH AT LEAST MUCH OF THE NORTH CENTRAL PLAINS BY

LATE AFTERNOON...ALONG WITH CONSIDERABLE SURFACE HEATING. THIS IS

EXPECTED TO CONTRIBUTE TO MODERATE TO STRONG DESTABILIZATION...WITH

MODEL GUIDANCE INDICATING MIXED LAYER CAPE IN EXCESS OF 2000 J/KG

ACROSS A LARGE PORTION OF THE NORTHERN PLAINS...AND PROBABLY IN

EXCESS OF 3000 J/KG IN A NARROW TONGUE FROM THERMAL LOW IN SURFACE

TROUGH ACROSS SOUTH CENTRAL SOUTH DAKOTA...SOUTHWARD THROUGH NORTH

CENTRAL KANSAS.

GIVEN THE MAGNITUDE OF THE INSTABILITY...THE STRENGTH OF THE SHEAR

IN THE EXIT REGION OF A 70-90 KT 500 MB JET...AND STRONG MID/UPPER

FORCING...AN OUTBREAK OF SEVERE STORMS SEEMS ALMOST CERTAIN LATE

THIS AFTERNOON AND EVENING. EXTENT OF TORNADO POTENTIAL IS THE

PRIMARY UNCERTAINTY...MOSTLY DUE TO ANTICIPATED SIZABLE

TEMPERATURE/DEW POINT SPREADS IN LOWER/MID-LEVELS OF FORECAST

SOUNDINGS.

THE BEST TORNADO POTENTIAL MAY EXIST IN TWO CORRIDORS...ONE IN A

FAVORABLE UPSLOPE FLOW REGIME ACROSS EASTERN MONTANA...WHERE

MAGNITUDE OF DESTABILIZATION IS STILL IN SOME QUESTION...AND

LOW-LEVEL HODOGRAPHS...WHILE SUFFICIENT...WILL NOT BE EXTREMELY

LARGE. THE OTHER...ALONG SURFACE TROUGH FROM SOUTH CENTRAL SOUTH

DAKOTA THROUGH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS. SURFACE DEW

POINTS SEEM MOST LIKELY TO INCREASE THROUGH THE MID/UPPER 60S ACROSS

THIS REGION...AND LOW-LEVEL HODOGRAPHS WILL BE QUITE LARGE ALONG

40-50 KT SOUTHERLY LOW-LEVEL JET...BENEATH UPPER JET AXIS. CAPPING

WILL BE A BIT STRONGER ACROSS THIS REGION THAN FARTHER NORTH...BUT A

MORE DISCRETE CONVECTIVE DEVELOPMENT MAY FAVOR SUPERCELLS WITH

POTENTIAL FOR ISOLATED STRONG TORNADOES.

BY EARLY THIS EVENING...STRONG MID/UPPER FORCING IN THE EXIT REGION

OF THE UPPER JET STREAK IS EXPECTED TO SUPPORT RAPID...WIDESPREAD

CONVECTIVE DEVELOPMENT ACROSS MUCH OF THE DAKOTAS. ALTHOUGH INITIAL

ACTIVITY MAY BE SUPERCELLULAR...STRONG EVAPORATIVE COOLING LIKELY

WILL CONTRIBUTE TO STRONG DOWNBURSTS AND SURFACE COLD POOL

DEVELOPMENT. UPSCALE GROWTH INTO A LARGE CONVECTIVE CLUSTER IS

EXPECTED...AND DOWNWARD TRANSFER OF MOMENTUM ASSOCIATED WITH

INTENSIFYING LOW-LEVEL JET...IN CONJUNCTION WITH THERMODYNAMIC

ENVIRONMENT...SUPPORTS POTENTIAL FOR A FEW INTENSE DOWNBURSTS WITH

VERY DAMAGING WIND GUSTS...ALONG WITH A BROADER SCALE DAMAGING WIND

THREAT ACROSS THE EASTERN DAKOTAS. ACTIVITY MAY CONTINUE WELL INTO

THE NIGHT BEFORE WEAKENING.

...SOUTHEAST...

A BAND OF CONFLUENT LOW-LEVEL FLOW IN THE WAKE OF UPPER TROUGH

LIFTING OUT OF THE ATLANTIC SEABOARD MAY PROVIDE THE FOCUS FOR

DESTABILIZATION AND CONVECTIVE DEVELOPMENT THIS AFTERNOON...FROM

PARTS OF SOUTHEAST ALABAMA INTO NORTHERN FLORIDA. FLOW/SHEAR WILL

BE WEAK...BUT MIXED LAYER CAPE AROUND 2000 J/KG MAY SUPPORT A FEW

VIGOROUS STORMS WITH LOCALIZED HAIL/GUSTY WIND POTENTIAL.

..KERR/TAYLOR.. 06/06/2007