Severe Weather Thread November 7-8

[JoMo]

The medium range modeling indicates there will be multiple disturbances that will ride the jet stream in the coming weeks. This is probably one of the more active patterns we've seen in awhile. While it is impossible to point out which, if any, of these disturbances will produce a severe weather event at this juncture, I think the potential is higher than what we've seen in recent Novembers.

If there are breaks between the rains, then maybe. If it rains all the time, there isn't going to be much instability.

[thewxmann]

If there are breaks between the rains, then maybe. If it rains all the time, there isn't going to be much instability.

Definitely. In fact, in fall it might be bigger issue due to the weaker lapse rates this time of year. Another concern might be if our current system over the South winds up cutting off over the central ATL. Depending on how that ends up, the moisture trajectories may not be quite ideal... but yeah, still too early for specific details.

[Ed Lizard]

Still hope for next week...

THIS TROUGH WILL MINOR OUT ACROSS THE UPPER MS VALLEY/GREAT LAKES

REGION ON SUN/D5...WITH A BROAD SWLY FLOW REGIME IN PLACE OVER THE

CNTRL AND WRN STATES. LOW LEVEL MOISTURE WILL BEGIN TO RETURN NWD

WITH NEAR 60 F SURFACE DEWPOINTS INTO OK BY SUN AFTERNOON. WITH

SUBSTANTIAL SWLY FLOW ALOFT...A FEW SEVERE STORMS COULD OCCUR BUT

SUBTLE NATURE OF FORCING SUGGESTS WIDESPREAD SEVERE WILL NOT OCCUR.

MOISTURE RETURN WILL PERSIST OVERNIGHT AHEAD OF THE NEXT TROUGH AXIS

WHICH WILL BE OVER THE CO RIVER VALLEY 12Z MON/D6.

BY D6...THERE APPEARS TO BE MORE SPREAD IN MODEL SOLUTIONS...BUT THE

ECMWF...THE TYPICALLY PREFERRED MODEL...INDICATES A DEEPER UPPER LOW

AND TROUGH...SUGGESTING SOME SEVERE WEATHER WILL BE POSSIBLE AS IT

EMERGES INTO THE PLAINS ON MON/D6. IF THIS IS THE CASE...THEN A TWO

DAY PERIOD OF SEVERE WEATHER MAY OCCUR MON AND TUE. LOW LEVEL

MOISTURE WOULD BE EVEN GREATER ON TUE/D7 OVER THE SRN PLAINS AND

LOWER MS VALLEY...WITH MID TO UPPER 60S F BOUNDARY LAYER DEWPOINTS

POSSIBLE. HOWEVER...IT ALL DEPENDS ON THE PATTERN EVOLUTION AND

PREDICTABILITY IS CURRENTLY TOO LOW FOR ANY SEVERE AREAS.

..JEWELL.. 11/02/2011

[on_wx]

D5/6 outlined

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0355 AM CDT THU NOV 03 2011

VALID 061200Z - 111200Z

..DISCUSSION

ON SUN/D4...AN UPPER TROUGH WILL BE DEAMPLIFYING ACROSS THE UPPER MS

VALLEY/GREAT LAKES REGION...WITH A BROAD BELT OF SWLY FLOW ALOFT

EXTENDING SWWD INTO THE SWRN STATES INTO THE BASE OF THE NEXT

TROUGH. WITH SLIGHTLY RISING HEIGHTS ALOFT...SWLY FLOW WILL INCREASE

OVER THE PLAINS HELPING TO BRING GULF MOISTURE NWD OVERNIGHT.

BY MON/D5...MODELS ARE IN GOOD AGREEMENT BRINGING THE UPPER TROUGH

AND LEADING EDGE OF HEIGHT FALLS ACROSS THE FOUR CORNERS STATES AND

INTO THE SRN HIGH PLAINS BY MON AFTERNOON. LOW PRESSURE IS FORECAST

TO DEEPEN OVER THE TX PANHANDLE AREA...WITH SLY FLOW INTENSIFYING

THROUGH THE DAY AND OVERNIGHT WITH A 50+ KT LLJ AND AT LEAST LOWER

60S F DEWPOINTS INTO OK. THE GFS SHOWS A WARM FRONT ALONG THE KS/OK

BORDER...BUT THE ECMWF SUGGESTS THIS FEATURE WILL BE MUCH FARTHER N

INTO NRN KS/SRN NEB. WHILE THE NRN EXTENT OF ANY SEVERE THREAT MAY

BE IN QUESTION...IT APPEARS LIKELY THAT SEVERE STORMS WILL OCCUR

OVER PORTIONS OF WRN OK AND NWRN TX NEAR THE DRYLINE. HERE...STEEP

LAPSE RATE PROFILES SHOULD EXIST. WHILE INSTABILITY WILL NOT BE

PARTICULARLY LARGE WITH ONLY NEAR 60 DEWPOINTS...SHEAR PROFILES WILL

BE QUITE FAVORABLE FOR SUPERCELLS DURING THE AFTERNOON AND EVENING.

A FEW TORNADOES ALONG WITH HAIL AND WIND WILL BE POSSIBLE.

OVERNIGHT...A COLD FRONT WILL EVENTUALLY MOVE INTO CNTRL OK AND TX.

IT IS POSSIBLE MORE CONVECTION WILL OCCUR ALONG THIS FRONT...BUT THE

PRIMARY THREAT WILL LIKELY BE WITH DIURNAL SUPERCELLS.

BY TUE/D6...MODELS START TO DIVERGE WITH THE ECMWF LIFTING THE UPPER

LOW/JET MAX NEWD MUCH QUICKER THAN MANY OF THE MREF MEMBERS. EVEN

WITH THESE DIFFERENCES...STRONG SWLY FLOW ALOFT WILL EXIST ATOP MID

TO UPPER 60S F DEWPOINTS AND FORCING ALONG THE COLD FRONT AND

DRYLINE. THUS...SOME RESIDUAL SEVERE THREAT IS LIKELY FROM E TX INTO

AR AND LA WITH THE MAIN THREAT DAMAGING WINDS AND A FEW TORNADOES.

SOME THREAT MAY LINGER INTO WED/D7 MAINLY ACROSS LA AND MS...BUT THE

MOIST AXIS WILL BEGIN TO NARROW WITH STORMS DRIVEN MAINLY BY THE

COLD FRONT AS PERHAPS THE LOW DEPARTS TOWARD THE N.

..JEWELL.. 11/03/2011

[andyhb]

Long time since a longer than day 5 outlook has been outlined...

[brettjrob]

The Monday setup looks amazingly solid for NOV on paper. Broad but high-amplitude trough digging into the Four Corners area... that pretty much spells great chasing in the Southern Plains when you see it in April or May. Kinematically, there's not a lot to complain about, and moisture return appears as good as any robust system we've seen in years this late in the fall. However, I'm skeptical on that front, because low-level trajectories don't look particularly great (going strictly by the GFS)... mainly thanks to that damn cutoff low E of Bermuda that Jim pointed out yesterday. Widespread rain before peak heating could also play spoiler, but even if so, there could still be a window of opportunity well S of the forcing -- say, ABI-SJT.

[BeauDodson]

The analog's are ticking upward with each run - for severe

Here is one of the recent runs

See what today's run shows

[JoMo]

12z GFS does show a lack of instability, but the shear profiles are really impressive.

[Ed Lizard]

12z GFS does show a lack of instability, but the shear profiles are really impressive.

Skinny CAPE, but with winds like that above just above the surface, easy to picture at least damaging wind gusts. With a sounding like that, a little more Sun than expected would really go a long way...

[brettjrob]

Skinny CAPE, but with winds like that above just above the surface, easy to picture at least damaging wind gusts. With a sounding like that, a little more Sun than expected would really go a long way...

No doubt... the model sounding there is completely saturated from top to bottom due to ongoing crapvection that develops early in the day. The severe threat will hinge mainly on whether at least part of the dryline can remain rain-free and see partial insolation during the afternoon.

[Ed Lizard]

Looking at the two 12Z display times of the freely available Euro, and sort of interpolating between, especially closer to the 12Z Tuesday morning, 850 mb winds look quite strong and 500 mb pattern looks favorable. My AccuWx PPV Euro graphics haven't updated yet, I'd like to look at Monday afternoon, and look at forecast skew-Ts.

But so far, if the instability can get there, looks like everything else is set.

[Ed Lizard]

Monday late afternoon/early evening, thin axis of CAPE >1000 J/Kg along 100ºW from midway Texas midway into Oklahoma, coincident with precip per AccuWx PPV. Skew-T generator not working, but looking at free Euro products, I don't think shear would be an issue.

[BeauDodson]

The afternoon analog

http://www.eas.slu.edu/CIPS/ANALOG/COLD/analog.php

[andyhb]

The afternoon analog

http://www.eas.slu.e...COLD/analog.php

That's pretty interesting, looks like some pretty prolific svr wx events with similar orientation/strength to this upcoming system.

[Srain]

This has the makings of a pinned worthy thread...SPC Update will be worth the read, IMO...

[Thundersnow12]

I'm curious to see what the 12z NAM tomorrow will show as all of monday will be within its range.

[David Reimer]

The words "synoptically evident" come to mind when looking at this graphic. This is off the 0Z NAM and for 6 AM Monday, or the morning of the potential event.

[andyhb]

Definitely some solid backing of the winds at the surface and with those wind fields aloft, that can only mean trouble.

00z GFS shows a substantial reservoir of 1000+ J/kg SBCAPE across Texas by 18z Monday.

[andyhb]

New Day 4-8

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0321 AM CDT FRI NOV 04 2011

VALID 071200Z - 121200Z

MON/D4...WHILE SEVERE WEATHER STILL APPEARS POSSIBLE...ESPECIALLY

ACROSS PORTIONS OF WRN TX/OK...HIGHER END THREAT APPEARS LOWER THAN

WITH PREVIOUS MODEL RUNS. MODELS ARE IN GOOD AGREEMENT THAT NEUTRAL

TO SLIGHTLY POSITIVELY TILTED SHORTWAVE TROUGH WILL SHIFT ENEWD FROM

SRN NM INTO THE TX PANHANDLE REGION BY THE END OF THE PERIOD...

RESULTING IN ONLY WEAK SURFACE CYCLOGENESIS. ALSO...ALTHOUGH

DEWPOINTS ARE LIKELY TO BE IN THE 60S ACROSS THE OK/TX REGION...

STRONG DIFFLUENCE BETWEEN THE POLAR AND SUBTROPICAL JETS SHOULD

RESULT IN WIDESPREAD CLOUDS/PCPN...AND CONSEQUENT WEAK SURFACE BASED

INSTABILITY. WHILE SEVERE STORMS MAY DEVELOP IN THE TX PANHANDLE

MONDAY AFTERNOON...WHERE BEST FORCING WILL BE LOCATED AND MORE

HEATING IS POSSIBLE...TOO MUCH UNCERTAINTY EXISTS FOR A 30% SEVERE

WEATHER THREAT AREA.

TUE/D5...SEVERE WEATHER APPEARS MORE LIKELY AS THE UPPER WAVE BEGINS

TO LIFT NEWD...BECOMES NEGATIVELY TITLED...AND AIDS IN DEEPENING OF

SURFACE LOW. THE SPEED AND INTENSITY OF THE UPPER WAVE VARIES ON THE

MREF RUNS AND DETERMINISTIC ECMWF AND GFS. USED A COMPROMISE AMONGST

THE VARIOUS MODELS FOR INCLUDING A 30% SEVERE WEATHER THREAT AREA.

THE MAGNITUDE AND INTENSITY OF THE EVENT IS DEPENDENT ON HOW THE

WAVE EVENTUALLY LIFTS OUT AND SHOULD BE BETTER RESOLVED IN FUTURE

OUTLOOKS.

WED/D6...UPPER WAVE AND SURFACE LOW PRESSURE ARE FORECAST TO LIFT

NEWD INTO THE OH/WRN TN VALLEYS. THOUGH INSTABILITY WILL BE WEAK...

SHEAR/WIND FIELDS MAY CONTINUE TO SUPPORT A SEVERE THREAT.

HOWEVER...TOO MUCH VARIANCE IN THE MODELS TO CONSIDER A SEVERE AREA

ATTM.

THU/D7 AND FRI/D8...

SHORTWAVE TROUGH IS FORECAST TO AMPLIFY INTO A DEEP TROUGH OVER THE

ERN CONUS. WHILE SOME CONVECTION WILL BE POSSIBLE AS SYSTEM SHIFTS

EWD...WEAK INSTABILITY SHOULD LIMIT SEVERE THREAT.

[Ed Lizard]

The afternoon analog

http://www.eas.slu.e...COLD/analog.php

I wasn't in Houston in 1992 (was in Austin, and just discovering the internets) but that almost looks like the analog caught some 1992.

Day4/TX dropping below 30%, on concerns of too much clouds/precip squelching instability, it still looks (to me) like a situation where any clearing at all could really change things. Between 0Z Tuesday (Monday late afternoon/evening) and 6Z, the Euro >500 J/Kg CAPE marches as far East as almost I-35, and reaches almost to OKC. Euro Day 5 CAPES don't look any better in Day 5 outlooked area, really. Only clear advantage, as seen on ECMWF web site, is a larger area of strong 850 mb flow, with peak in excess of about 50 knots as compared to in excess of 40 knots Hour 120 over Hour 96.

Except for CAPE below 500 J/Kg, I really like what I see for, say, Dallas, on the 0Z GFS. Helicity is over 400 J/Kg. LCL below 900 mb. All they need is a couple of hours of unexpected Sun and just a touch more CAPE. I'll trade in a little LCL for an extra few hundred J/Kg of CAPE. (0Z sounding data not from NIU page, but from PPV AccuWx page. NIU GFS soundings from 6Z run at 12 hour intervals...)

[baroclinic_instability]

Not just a severe threat but another potential decent rain maker for many drought stricken areas.

I modified the thread title as well.

[JoMo]

12z 84 hour NAM (lol) is getting impressive for SW OK. Long looping hodos, decent instability as well.

[David Reimer]

Our first run of the SREF for Monday. This graphic shows the significant tornado ingredients parameter.

[brettjrob]

12z 84 hour NAM (lol) is getting impressive for SW OK. Long looping hodos, decent instability as well.

Agreed. I thought the original D5 outlook from yesterday was probably overdone in scope, but I also am slightly surprised to see the whole thing taken out today (at least if Tuesday still merits one). The NAM says clouds and rain are a non-factor south of the Red River, with very good lapse rates and 1500-2500 J/kg SBCAPE developing by mid-afternoon. I'm still thinking supercells with at least large hail, and possibly a tornado threat, for NW TX.

[Ed Lizard]

Looking at the model surface features map and then the skew-Ts, I think the Red River could be potentially an exciting place Monday afternoon near what appears to be an effective warm front. Between Ardmore and Duncan, based on soundings.

Ardmore, just a little more Sun than the GFS expects and that is big time...

[David Reimer]

Agreed. I thought the original D5 outlook from yesterday was probably overdone in scope, but I also am slightly surprised to see the whole thing taken out today (at least if Tuesday still merits one). The NAM says clouds and rain are a non-factor south of the Red River, with very good lapse rates and 1500-2500 J/kg SBCAPE developing by mid-afternoon. I'm still thinking supercells with at least large hail, and possibly a tornado threat, for NW TX.

It just makes me all tingly inside... You gonna be out chasing on Monday?

[Thundersnow12]

Agreed. I thought the original D5 outlook from yesterday was probably overdone in scope, but I also am slightly surprised to see the whole thing taken out today (at least if Tuesday still merits one). The NAM says clouds and rain are a non-factor south of the Red River, with very good lapse rates and 1500-2500 J/kg SBCAPE developing by mid-afternoon. I'm still thinking supercells with at least large hail, and possibly a tornado threat, for NW TX.

dont forget 0-1km SRH >200 along and south of the red river at 0z

a great looking sounding and hodograph for Breckenridge, TX.....15kt southeasterly flow at the sfc to 40kts at 850mb to 60kts WSW flow in the mid-levels.

[RUAHusker]

Our first run of the SREF for Monday. This graphic shows the significant tornado ingredients parameter.

Not too shabby. If things stay at least moderately favorable for tornadoes on Monday, Team Weather Weenies will be making the trip from Nebraska. It's funny how a setup like this wouldn't interest me in the least in May (at least for a 1500 mile + chase) , but since it is November, lets Rock it! haha

[brettjrob]

It just makes me all tingly inside... You gonna be out chasing on Monday?

I'm game for anything near or north of I-20, pretty much... my class gets out at 10am. Really hoping the NAM wins this battle, though, cause the GFS suggests the "real" juice would be confined to the Permian Basin and Big Bend area. Also, I got my windshield absolutely pulverized on October 22 (C OK supercell swarm) and haven't replaced it yet cause I've been sick all week... gonna have to hope the TX cops aren't bored enough to harass me, unless I can find a buddy willing to take their car.

[David Reimer]

I'm game for anything near or north of I-20, pretty much... my class gets out at 10am. Really hoping the NAM wins this battle, though, cause the GFS suggests the "real" juice would be confined to the Permian Basin and Big Bend area. Also, I got my windshield absolutely pulverized on October 22 (C OK supercell swarm) and haven't replaced it yet cause I've been sick all week... gonna have to hope the TX cops aren't bored enough to harass me, unless I can find a buddy willing to take their car.

Yeah, we'll see what happens. I'm pretty confident the NAM will go through at least one cycle where it throws the setup to crap. The good news is that both of us should receive some decent rainfall from this event. We'll see what happens. It's interesting to note that Dr. Forbes over at TWC already has some decent numbers on his TORCON index.