October 12-13th "Potential" Severe Outbreak

[andyhb]

Looking at forecast highs on Saturday, the GFS seems about 5-15 degrees too low across many portions of Central and Eastern OK and KS, although obviously previous convection and clouds could change that. It seems to be nudging ever closer to overlaying the better instability with the better moisture (in some areas, it does, and with very significant shear overlapping as well). The GFS also gets a 50+ kt LLJ going along with this.

As Brett mentioned before, this GFS run has more the LL wind profiles I'd tend to expect with this southern oriented vort max as opposed to the runs a few days ago.

[patrick7032]

The HRRR keeps overnight precip to a min.

[chase_stormz]

Looking at forecast highs on Saturday, the GFS seems about 5-15 degrees too low across many portions of Central and Eastern OK and KS, although obviously previous convection and clouds could change that. It seems to be nudging ever closer to overlaying the better instability with the better moisture. The GFS also gets a 50+ kt LLJ going along with this.

Maybe a cold season surprise on Saturday? If the 00z GFS has anything to say about it..

[brettjrob]

Also, based on an initial look, the 00z GFS looks better for Saturday than the NAM.

Not sure I'm seeing that. The LLJ is stronger, but it's also very disjointed from the instability axis throughout the day, as is often seen with these god-forsaken positive-tilt, lifting troughs. I've yet to see a forecast sounding that truly impresses me for Saturday (at least south of I-70), despite the "interesting" model trends over the past 24-36 h. I get the feeling that if morning/early convection weren't a factor, the setup along the DL would be significantly more appealing, though still non-ideal.

All the trends I'm seeing on the hi-res and rapid-cycle modeling for tomorrow have me less and less enthused by the minute. It now seems quite likely that the cold air currently inhabiting SW KS into SE CO will make a good push southward into the mid-morning hours, possibly to I-40 or so. I feel we may well pay a hefty price for the slowing ejection, with slower/weaker cyclogenesis during the day leading to (a) anemic low-level wind profiles, and ( less northward pushback on the boundary. I was quite determined to make a chase of this given the calendar and the happenings of Spring 2012, but desperate as I am, I'm beginning to question the merits.

EDIT: The KAMA 88D depicts the southward-moving boundary in the northern Panhandle quite well right now.

[andyhb]

Not sure I'm seeing that. The LLJ is stronger, but it's also very disjointed from the instability axis throughout the day, as is often seen with these god-forsaken positive-tilt, lifting troughs. I've yet to see a forecast sounding that truly impresses me for Saturday (at least south of I-70), despite the "interesting" model trends over the past 24-36 h. I get the feeling that if morning/early convection weren't a factor, the setup along the DL would be significantly more appealing, though still non-ideal.

Are you sure about that? Looking at the 21z maps seems to look less disjointed, IDK it could be me just seeing things. At least, looking at the GFS, the 500 mb trough doesn't appear to be lifting much at all on Saturday, the base of it hardly gains any latitude between 36 and 48 hours.

[patrick7032]

HRRR simulated reflectivity at 12Z.

[patrick7032]

Are you sure about that? Looking at the 21z maps seems to look less disjointed, IDK it could be me just seeing things. At least, looking at the GFS, the 500 mb trough doesn't appear to be lifting much at all on Saturday, the base of it hardly gains any latitude between 36 and 48 hours.

I agree with you.

[chase_stormz]

Not sure I'm seeing that. The LLJ is stronger, but it's also very disjointed from the instability axis throughout the day, as is often seen with these god-forsaken positive-tilt, lifting troughs. I've yet to see a forecast sounding that truly impresses me for Saturday (at least south of I-70), despite the "interesting" model trends over the past 24-36 h. I get the feeling that if morning/early convection weren't a factor, the setup along the DL would be significantly more appealing, though still non-ideal.

All the trends I'm seeing on the hi-res and rapid-cycle modeling for tomorrow have me less and less enthused by the minute. It now seems quite likely that the cold air currently inhabiting SW KS into SE CO will make a good push southward into the mid-morning hours, possibly to I-40 or so. I feel we may well pay a hefty price for the slowing ejection, with slower/weaker cyclogenesis during the day leading to (a) anemic low-level wind profiles, and ( less northward pushback on the boundary. I was quite determined to make a chase of this given the calendar and the happenings of Spring 2012, but desperate as I am, I'm beginning to question the merits.

EDIT: The KAMA 88D depicts the southward-moving boundary in the northern Panhandle quite well right now.

Wow lol, another negative post. I don't know what you are seeing, but eastern ks down into n ok looks pretty good for saturday off the 00z gfs run. surface winds don't veer, 50kt llj, definitely more turning from looking at those hodos. it's all going to be dependent upon early day convection. and the 250 mb trough definitely looks a lot more neutral on this run than positive tilt.

[JoMo]

Wow lol, another negative post. I don't know what you are seeing, but eastern ks down into n ok looks pretty good for saturday off the 00z gfs run. surface winds don't veer, 50kt llj, definitely more turning from looking at those hodos. it's all going to be dependent upon early day convection. and the 250 mb trough definitely looks a lot more neutral on this run than positive tilt.

And it just doesn't develop a whole lot of CAPE in that area, sure areas farther west near the dryline get decent CAPE but east of there it's pretty marginal until the front moves east and by that time, things may be lining up or prior convection may have stabilized the atmosphere.

[patrick7032]

00Z GFS.

[andyhb]

Wow lol, another negative post. I don't know what you are seeing, but eastern ks down into n ok looks pretty good for saturday off the 00z gfs run. surface winds don't veer, 50kt llj, definitely more turning from looking at those hodos. it's all going to be dependent upon early day convection. and the 250 mb trough definitely looks a lot more neutral on this run than positive tilt.

Not Northern OK, for one...

[tornadotony]

Wow lol, another negative post. I don't know what you are seeing, but eastern ks down into n ok looks pretty good for saturday off the 00z gfs run. surface winds don't veer, 50kt llj, definitely more turning from looking at those hodos. it's all going to be dependent upon early day convection. and the 250 mb trough definitely looks a lot more neutral on this run than positive tilt.

No, it's not as dependent on early morning convection as it is on what happens to the 850mb airmass. The 850mb moisture axis stills progresses east faster than the instability axis, making moisture in the instability axis very shallow. The NAM, which had been looking better than the GFS for the last few runs, also does the same. I'll admit, I bit for awhile this afternoon on the threat rising in OK and KS Saturday, even in IA and nrn MO. But, even though there's still time for changes, but the smart bet is to remain pessimistic about Saturday.

[brettjrob]

To clarify in response to the posts quoting me above: at 21z on the GFS, the LLJ is focused roughly along an ADM-SWO-MCI axis, while the instability axis is a few counties W of there and still rather narrow. There's still low-level shear along the dryline, but I never like to see the LLJ maximum get well out ahead of the storms. Also, I do see significant veering immediately along the dryline, with the closer-to-backed winds again a little too far out ahead.

Basically, IMHO, the most favorable low-level wind profiles are just east of the instability axis from 21z-00z. But I am viewing on TwisterData, so perhaps a zoomed view would clarify a bit better.

[chase_stormz]

Not Northern OK, for one...

lmao, funny how simon brewer agreed with me on n/c ok being in on the action with me.

[chase_stormz]

To clarify in response to the posts quoting me above: at 21z on the GFS, the LLJ is focused roughly along an ADM-SWO-MCI axis, while the instability axis is a few counties W of there and still rather narrow. There's still low-level shear along the dryline, but I never like to see the LLJ maximum get well out ahead of the storms. Also, I do see significant veering immediately along the dryline, with the closer-to-backed winds again a little too far out ahead.

Basically, IMHO, the most favorable low-level wind profiles are just east of the instability axis from 21z-00z. But I am viewing on TwisterData, so perhaps a zoomed view would clarify a bit better.

yea the veering is immediately along the dryline. however i read in i believe it was wichita or topekas afd that storms could fire 100-150 miles off the dryline

[brettjrob]

No, it's not as dependent on early morning convection as it is on what happens to the 850mb airmass. The 850mb moisture axis stills progresses east faster than the instability axis, making moisture in the instability axis very shallow. The NAM, which had been looking better than the GFS for the last few runs, also does the same.

In my experience, the morning/early afternoon crapvection in these situations makes the low-level veering a lot worse after it moves out, so that's what I meant with that.

[andyhb]

lmao, funny how simon brewer agreed with me on n/c ok being in on the action with me.

Central OK is different than Northern OK. But enough arguing semantics, the wind profiles I was more interested in were further south.

[tornadotony]

In my experience, the morning/early afternoon crapvection in these situations makes the low-level veering a lot worse after it moves out, so that's what I meant with that.

Oh I can agree with that. The cases I mentioned last night (4/10/11 and 4/15/12) all suffered from that up here.

[tornadotony]

The NSSL WRF has an intense discrete cell with extremely strong updraft helicity in the KAMA vicinity at 00z, FWIW.

[Thundersnow12]

To clarify in response to the posts quoting me above: at 21z on the GFS, the LLJ is focused roughly along an ADM-SWO-MCI axis, while the instability axis is a few counties W of there and still rather narrow. There's still low-level shear along the dryline, but I never like to see the LLJ maximum get well out ahead of the storms. Also, I do see significant veering immediately along the dryline, with the closer-to-backed winds again a little too far out ahead.

Basically, IMHO, the most favorable low-level wind profiles are just east of the instability axis from 21z-00z. But I am viewing on TwisterData, so perhaps a zoomed view would clarify a bit better.

use the srn plains view on COD's site

[tornadotony]

Yowza...I-40 special right on the warm front.

[Chicago Storm]

If chasing tomrrow it would likely be a "wait and see situation" in the morning given the already well known concerns, but I'd probably start out in or near HRX and then adjust from there if needed.

In reality though there's no way I'd head down there for one or maybe two iffy chase days. Probably a somewhat easier decision if I lived down there.

[andyhb]

D1:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1235 AM CDT FRI OCT 12 2012

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS WRN KS TO SRN HIGH

PLAINS...

..SYNOPSIS

SPLIT-FLOW PATTERN IN MID-UPPER LEVELS IS EXPECTED TO DEAMPLIFY

SOMEWHAT DURING PERIOD...OVER WRN CONUS. THIS WILL OCCUR AS

WELL-DEFINED CYCLONE -- NOW LOCATED OVER SRN CA -- MOVES ENEWD FROM

SERN SIERRA REGION. THOUGH THIS CYCLONE IS FCST TO FILL

GRADUALLY...IT WILL MAINTAIN HIGH-AMPLITUDE SHORTWAVE TROUGH WITH

POSITIVE TILT AS IT EJECTS FROM ITS MOST EQUATORWARD POSITION...AND

REJOINS PREVAILING WLYS ALOFT. PRIMARY 500-MB VORTICITY LOBE SHOULD

MOVE NEWD ACROSS UT DURING MIDDLE OF PERIOD...EXTENDING FROM WRN NEB

TO S-CENTRAL CO AND WRN NM BY 13/12Z.

AT SFC...COLD FRONT WAS ANALYZED FROM SERN ONT SWWD ACROSS NRN/WRN

IL AND S-CENTRAL KS TO NRN PORTIONS TX PANHANDLE. WRN PORTION OF

THIS FRONT IS PROGGED TO STALL ACROSS PANHANDLE AND NERN NM EARLY IN

PERIOD...THEN RETURN NWD AS WARM FRONT OVER NRN OK...OK/NRN TX

PANHANDLES AND SERN CO. HOWEVER...PRECEDING/MORNING CONVECTION MAY

EFFECTIVELY SHUNT FRONT SWD SOMEWHAT OVER OK...TX PANHANDLE AND NERN

NM...DELAYING ITS NWD MOVEMENT THROUGH DAYLIGHT HOURS. DRYLINE

SHOULD SET UP OVER ERN NM DURING MID-LATE AFTERNOON...AND DEVELOP

NWD ACROSS SERN CO/SWRN KS AREA OVERNIGHT AS MORNING CONVECTIVE AIR

MASS DISSIPATES AND FRONT PROCEEDS NWD OVER WRN/SRN/CENTRAL KS.

..WRN KS TO SRN HIGH PLAINS

TSTMS ARE FCST TO DEVELOP DIURNALLY ACROSS PORTIONS ERN NM ALONG AND

E OF DRYLINE AND OVER HIGHER TERRAIN. REGIONAL TSTM INITIATION MAY

COMMENCE AS EARLY AS 18Z-20Z TIME FRAME GIVEN FCST OF RELATIVELY

WEAK MLCINH...AND TIME SERIES OF FCST SOUNDINGS SUGGESTING REMOVAL

OF CINH FOR SFC TEMPS MID-70S F IN SOME AREAS AWAY FROM MOUNTAINS.

COMPLICATING FACTOR WILL BE PRESENCE OF MID-UPPER LEVEL

CLOUDS...BASED ON CURRENT/UPSTREAM SATELLITE TRENDS AND PROGS OF

HIGH RH ALOFT. THIS FACTOR ALSO MAY DELAY OR GRADATE TSTM

INITIATION PROCESSES...DEPENDING ON MESOSCALE CHARACTER OF CLOUD

COVER.

BY LATE AFTERNOON...CONVECTIVE COVERAGE/INTENSITY SHOULD BE

INCREASING ACROSS TX/NM BORDER REGION. LOW-LEVEL MOISTURE AND

STRENGTHENING DEEP SHEAR ALONG/AHEAD OF DRYLINE WILL SUPPORT MORE

ORGANIZED SVR POTENTIAL..INCLUDING RISK OF SUPERCELLS WITH LARGE

HAIL AND DAMAGING GUSTS...AS WELL AS POTENTIAL FOR SVR CLUSTERED OR

BOWING STORM MODES. FOR THOSE CELLS THAT STILL ARE RELATIVELY

DISCRETE DURING 00Z-03Z TIME FRAME...TORNADO POTENTIAL MAY INCREASE.

THIS WOULD BE DURING TEMPORAL OVERLAP OF TWO PROCESSES...

1. STRENGTHENING LLJ THAT FAVORABLY ENLARGES LOW-LEVEL

HODOGRAPH...BOOSTING EFFECTIVE SRH VALUES PAST 200 J/KG...AND

2. PRECONVECTIVE/EFFECTIVE LIFTED PARCELS S OF WARM FRONT AND E OF

DRYLINE REMAINING SFC-BASED...EVEN WITH VERY SHALLOW LAYER OF

EARLY-STAGE DIABATIC COOLING.

UPSCALE GROWTH OF NNE-SSW ALIGNED CONVECTIVE BAND SHOULD OCCUR

DURING EVENING AND OVERNIGHT HOURS -- 03Z-09Z TIME FRAME -- WITH

CONVECTION SHIFTING EWD AND PERHAPS GROWING NEWD INTO ENLARGING KS

WARM SECTOR. SPORADIC LARGE HAIL AND DAMAGING GUSTS WILL BE MAIN

CONCERNS AFTER ABOUT 06Z...WITH SVR THREAT DIMINISHING TOWARD

NOCTURNAL INSTABILITY MIN NEAR END OF PERIOD.

..S-CENTRAL ROCKIES

POTENTIAL FOR ISOLATED HAIL/GUSTS NEAR SVR LIMITS MAY EXTEND NWWD

FROM MAIN SVR RISK AREA ACROSS MOUNTAINS AND ADJOINING BASINS OF NRN

NM AND SRN CO. MOISTURE/BUOYANCY WILL BE SUBSTANTIALLY MORE LIMITED

IN THIS REGION THAN FARTHER E. HOWEVER...STRENGTHENING DEEP-LAYER

ASCENT/SHEAR WITH TIME WILL SUPPORT MRGL/CONDITIONAL SVR THREAT

PRIMARILY WITH MID-LATE AFTERNOON CONVECTION OVER THIS REGION.

..CENTRAL PLAINS N OF I-70 TO PORTIONS SRN MN/IA

LOW-LEVEL WAA AND MOISTURE ADVECTION/TRANSPORT REGIME WILL SPREAD

NEWD RAPIDLY ACROSS CENTRAL PLAINS INTO MID MO VALLEY REGION

OVERNIGHT...SUPPORTING LIKEWISE SHIFT IN ELEVATED THETAE LAYER

SUPPORTING MUCAPE 1000-1500 J/KG. FCST SOUNDINGS SUGGEST EFFECTIVE

SHEAR MAGNITUDES IN 35-45 KT RANGE ARE POSSIBLE...SUPPORTING A FEW

SPORADICALLY WELL-ORGANIZED TSTMS WITH HAIL NEAR SVR LEVELS.

..EDWARDS/DEAN.. 10/12/2012

[MnWeatherman]

lmao, funny how simon brewer agreed with me on n/c ok being in on the action with me.

simon brewer?

[andyhb]

simon brewer?

Chaser for "Storm Riders" on TWC.

[MnWeatherman]

Chaser for "Storm Riders" on TWC.

I know that, but who here is simon brewer?

[andyhb]

D2:

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1253 AM CDT FRI OCT 12 2012

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN AND CNTRL

PLAINS...NRN OZARKS...MID MO VALLEY AND MID TO UPPER MS VALLEY...

..MID MO VALLEY/UPPER MS VALLEY/ERN KS/MO

A RATHER POTENT UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD FROM THE

CNTRL ROCKIES INTO THE SRN AND CNTRL PLAINS SATURDAY. AHEAD OF THIS

SYSTEM...A WELL-DEVELOPED LOW-LEVEL JET WILL TRANSPORT MOISTURE NWD

ACROSS THE SRN AND CNTRL PLAINS DURING THE DAY WITH A WELL-DEFINED

MOIST AXIS SETTING UP FROM NWRN OK EXTENDING NNEWD ACROSS ECNTRL KS

INTO NW MO AND SRN IA WHERE SFC DEWPOINTS ARE FORECAST TO BE IN THE

LOWER TO MID 60S F BY AFTERNOON. SOME THUNDERSTORM ACTIVITY MAY BE

ONGOING SATURDAY MORNING BUT SFC HEATING AND STRONG LARGE-SCALE

ASCENT AHEAD OF THE UPPER-LEVEL TR0UGH SHOULD RESULT IN A RAPID

INCREASE IN CONVECTIVE COVERAGE SATURDAY AFTERNOON. MODEL FORECASTS

SUGGEST A NEARLY CONTINUOUS LINE OF THUNDERSTORMS SHOULD ORGANIZE

AND MOVE EWD ACROSS SCNTRL IA...NRN AND WRN MO AND ERN KS DURING THE

LATE AFTERNOON AND EVENING.

FORECAST SOUNDINGS ALONG THE MOIST AXIS AT 00Z/SUNDAY FROM DES

MOINES SSWWD ACROSS THE KANSAS CITY METRO AND INTO ERN KS SHOW

MUCAPE OF 1000 TO 1500 J/KG WITH SFC DEWPOINTS IN THE MID 60S F.

THIS COMBINED WITH 0-6 KM SHEAR IN THE 50 TO 60 KT RANGE ALONG WITH

850 TO 500 MB LAPSE RATES OF 7.0 TO 7.5 C/KM SHOULD BE FAVORABLE FOR

SUPERCELLS WITH LARGE HAIL AND POSSIBLY SOME TORNADOES. THE

POTENTIAL FOR LARGE HAIL AND TORNADOES MAY BE THE GREATEST EARLY IN

THE EVENT WHEN SUPERCELLS SHOULD TEND TO BE DISCRETE. AS A LINEAR

MCS ORGANIZES IN THE EARLY EVENING...A TRANSITION TO WIND DAMAGE AS

THE PRIMARY THREAT COULD OCCUR. AN ENHANCED THREAT FOR WIND DAMAGE

APPEARS POSSIBLE ACROSS A LARGE AREA FROM NEAR DES MOINES SWD INTO

SE KS AND SW MO. THE WIND DAMAGE THREAT COULD PERSIST THROUGH MUCH

OF THE NIGHT AS THE LINEAR MCS PROGRESSES STEADILY EWD ACROSS THE

SLIGHT RISK AREA.

..SRN PLAINS/OZARKS

A WELL-ORGANIZED UPPER-LEVEL TROUGH IS FORECAST TO MOVE FROM THE SRN

AND CNTRL ROCKIES EWD INTO THE SRN HIGH PLAINS DURING THE DAY ON

SATURDAY. AHEAD OF THE SYSTEM...A LOW-LEVEL JET WILL TRANSPORT

MOISTURE QUICKLY NWD ACROSS THE SRN AND CNTRL PLAINS WITH A NARROW

AXIS OF MODERATE INSTABILITY DEVELOPING SATURDAY AFTERNOON. SOME

ELEVATED THUNDERSTORM ACTIVITY MAY BE ONGOING ALONG THE WRN EDGE OF

THE INSTABILITY AXIS EARLY IN THE DAY BUT SFC-BASED THUNDERSTORMS

APPEAR LIKELY TO DEVELOP ALONG THE INSTABILITY AXIS BY MID

AFTERNOON. THE MODELS SUGGEST A NEARLY CONTINUOUS LINE OF STORMS

WILL ORGANIZE ACROSS OK BUT THAT CONVECTION SHOULD BE MORE SCATTERED

IN NATURE FROM FAR SRN OK SWD ACROSS NORTH TX NEAR THE SRN EDGE OF

THE LOW-LEVEL JET. THE LINE OF STORMS IN CNTRL OK SHOULD PROGRESS

EWD ACROSS ERN OK DURING THE EVENING AND EARLY OVERNIGHT PERIOD.

FORECAST SOUNDINGS EARLY SATURDAY EVENING NEAR OKLAHOMA CITY AND

WICHITA FALLS SHOW MLCAPE AROUND 1500 J/KG AND SFC DEWPOINTS IN THE

MID 60S F. THIS COMBINED WITH 0-6 KM SHEAR OF 50 TO 60 KT SHOULD BE

FAVORABLE FOR SUPERCELLS WITH LARGE HAIL. LOW-LEVEL SHEAR IS

FORECAST TO BE STRONG WITH 0-1 KM SHEAR AROUND 30 KT SUGGESTING A

TORNADO THREAT MAY ALSO OCCUR WITH THE BETTER ORGANIZED SUPERCELLS.

A WIND DAMAGE THREAT MAY ALSO EXIST WITH SUPERCELLS IN THE RED RIVER

VALLEY DURING THE LATE AFTERNOON AND EARLY EVENING. THE WIND DAMAGE

THREAT SHOULD BE THE GREATEST FROM THE OKLAHOMA CITY METRO EWD TO

THE AR STATE-LINE WHERE A LINEAR MCS IS FORECAST TO DEVELOP. THE

WIND DAMAGE THREAT COULD BECOME ENHANCED ACROSS ECNTRL OK WHERE A 30

PERCENT SEVERE PROBABILITY HAS BEEN INTRODUCED BASED ON THE LATEST

MODEL GUIDANCE WHICH IS MORE AGGRESSIVE ON THE SRN END OF THE LINE.

..BROYLES.. 10/12/2012

[andyhb]

I know that, but who here is simon brewer?

No one, he probably got that off of his Twitter or something.

[LocoAko]

Wow, that's a surprisingly enticing outlook for OKC (though I haven't looked at anything from 00Z) for Day 2.

[Minnesota Meso]

I'm just a amateur weather enthusiast, so I have question for the pro's here, ( I think the Minnesota area belongs in this sub forum). I'm really not seeing a reason for the SPC to have the 15% risk area as far north as they have it, very near MSP, am I missing something? or are they doing that out of precaution? I'm thinking it could cover the MN portion of the ARX cwa from RST to ARX and not much else.