April 14-17th Severe Weather (Day 3 Mod)

[brettjrob]

I'm assuming the RAP on twisterdata has some sort of dewpoint/CAPE issue that produces these scary looking maps? Yeah that's 5-6, 0-1 KM with storms in NE OK and SE KS at the time displayed.

 

I don't think it's necessarily overdone, because the LLJ is monstrous from the get-go out your way. However, the deep-layer shear profiles are much more unidirectional than farther SW. I'd still be concerned and pay attention, though, obviously. EDIT: actually, I had just clicked on the EHI bullseye, where winds are slightly veered along the front. Farther E into MO the hodos look downright ominous... yikes.

 

The HRRR and RAP are increasing my confidence that a major event will unfold in SW OK tomorrow afternoon and evening. Definitely wouldn't be surprised to see an outlook upgrade so long as the frontal retreat stays on schedule through mid-morning.

[baroclinic_instability]

I'm assuming the RAP on twisterdata has some sort of dewpoint/CAPE issue that produces these scary looking maps? Yeah that's 5-6, 0-1 KM with storms in NE OK and SE KS at the time displayed.

 

 

Actually the RAP has a dry dewpoint bias, if anything. That wicked EHI is largely due to the 50-55 kt core of 850 winds. Some very long hodographs and low LCLs. Verbatim that would be another threat area for strong tornadoes, but convection is going to be messy through that area as most guidance is pegging that area with quite a bit of early morning DMC. That said, if it were to clear, that is another major threat area. Initiation for discrete supercells in the afternoon would be a tougher proposition though. 

[andyhb]

I don't think it's necessarily overdone, because the LLJ is monstrous from the get-go out your way. However, the deep-layer shear profiles are much more unidirectional than farther SW. I'd still be concerned and pay attention, though, obviously.

 

The HRRR and RAP are increasing my confidence that a major event will unfold in SW OK tomorrow afternoon and evening. Definitely wouldn't be surprised to see an outlook upgrade so long as the frontal retreat stays on schedule through mid-morning.

 

You know, despite the obviously different synoptic setup, some of the parameters down there are reminding me of...well older folks in Wichita Falls should know it well. Obviously, it would be foolish to expect an event of that magnitude, but it does look pretty damn stout regardless.

[baroclinic_instability]

Just a curiosity, but the 4 KM SPC WRF initiates nothing across SW OK in the afternoon. Not exactly sure why.

[andyhb]

Just a curiosity, but the 4 KM SPC WRF initiates nothing across SW OK in the afternoon. Not exactly sure why.

 

I did see at least one big one on the NSSL WRF.

 

Current elevated convection north of the front appears to be lifting quickly northward/northeastward per recent radar trends.

[andyhb]

06z NAM has some pretty sick looking backing of the LLJ around the 00z-03z Thursday timeframe.

[JoMo]

Looks like the front is starting to return as the winds have become more easterly between here and the AR border. I've gotta say, I'm somewhat concerned about later today and even tonight along the front for my area. 

[andyhb]

Last obs. I had, it was 74 in Ardmore once the front lifted out of the area, that is some strong WAA.

[JoMo]

Springfield, MO discussion:

 

 

THE RAP AND OTHER SHORT RANGE MODELS REFOCUS A LOW LEVEL JET ACROSS
EASTERN OKLAHOMA AND VEER IT INTO SOUTHWESTERN MISSOURI.
TYPICALLY...A SETUP LIKE THIS WOULD YIELD SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS ACROSS SOUTHEASTERN KANSAS AND WESTERN
MISSOURI. ONE THING THAT WILL BE INTERESTING TO SEE IS OUR 12 UTC
RAOB. INDICATIONS ARE THAT AN ELEVATED MIXED LAYER REMAINS
ENTRENCHED ACROSS THE REGION. EVEN ABOVE THIS LAYER...THERE IS AT
LEAST SOME QUESTION AS TO WHETHER OR NOT PARCELS WILL BE BUOYANT
GIVEN THE IMPINGING LOW LEVEL JET. AT THIS TIME...MY GUT FEELING
SAYS THAT WE WILL SEE ELEVATED CONVECTION DEVELOP ALONG AND WEST
OF THE HIGHWAY 65 CORRIDOR A BIT LATER THIS MORNING.

ONE SCENARIO WE WILL HAVE TO WATCH VERY CLOSELY TODAY IS THE
POTENTIAL FOR CONVECTION TO BECOME ROOTED IN THE BOUNDARY LAYER.
THERE ARE STILL SOME INDICATIONS BY SHORT RANGE MODELS THAT THIS
COULD OCCUR ACROSS THE MISSOURI OZARKS THIS AFTERNOON. AGAIN...THE
ASSUMED PRESENCE OF THAT ELEVATED MIXED LAYER WILL REALLY PLAY A
ROLE HERE. IF SURFACE BASED CONVECTION CAN DEVELOP...ENOUGH DEEP
LAYER SHEAR EXISTS FOR SUPERCELLS. ADDITIONALLY...THAT WARM FRONT
WILL BE RETURNING NORTH ACROSS THE OZARKS THROUGHOUT THE DAY. THAT
FRONT WILL BEEF UP LOW LEVEL SHEAR PROFILES AND PROMOTE THE
POTENTIAL FOR LOW LEVEL ROTATION. ANY NORTHEASTWARD MOVING LINE
SEGMENTS WOULD ALSO HAVE MESOVORTEX POTENTIAL GIVEN LOW LEVEL
SHEAR PROFILES. WE WILL THEREFORE ADVERTISE A LIMITED RISK FOR ALL
MODES OF SEVERE THIS AFTERNOON.

 

They go on to say that mesovorts will be possible in the squall line later tonight. Gonna be a long day, heh

[Indystorm]

Very rich moisture...dews of 68-72 just south of the Red River moving northward.  Low and mid level helicity extremely high.  Anything that forms is going to spin.  Stay safe, JoMo.

[Indystorm]

RAP sig tor values from 7-10 increasing in geographical areal coverage from sw OK to sw MO as we progress through the day along the I-44 corridor.   Concerning for sure.

[hm8]

Some of the lovely new products at the COD site...

 

 

 

[baroclinic_instability]

Nice plots ^^ I will have to check that out. I like the overlays and crossover data.

 

Interesting day ahead. First off, NAM made a lot of us look pretty stupid (except wxmann). The NAM indeed ended up being correct in developing northerlies across much of western OK, so it doesn't look like the front will advance much farther W...which will end up creating a SW to NE oriented frontal zone. A lot of the dryline looks like it may end up being cutoff from the deep instability to the east. Storms that initiate along the quasistationary/warm front may tend to merge into clusters based on the bulk shear vector/orientation of the front. That said, the area east of I35, especially from 00z on, looks primed for a potential tor outbreak if, as Tony said, the boundary layer remains partially mixed and some sort of semi discrete activity can remain. Toss in some low cloud cover which may hinder daytime activity as well...and my guess is SPC will hold to a mod for the morning issuance.

[Chicago Storm]

Believe it or not, after having a few different opportunities I have decided not to go down and chase today for several reasons.

Oh...And based on surface OBS it's pretty clear the GFS isn't even going to close...with even the 6z run being far off. Ride the NAM.

[baroclinic_instability]

SPC still likes today...increased the 15% hatched into SE Kansas. I trust their judgment any day over my own.

 

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
MUCH OF OK...SOUTHEAST KS...WESTERN NORTH TX...AND FAR WESTERN MO...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS INTO
THE MID MS VALLEY...

...FOCUSED AREA OF SIGNIFICANT SEVERE THUNDERSTORM AND TORNADO
POTENTIAL IS EXPECTED TODAY...

...OK/WESTERN NORTH TX/SOUTHEAST KS...
THE MORNING SURFACE ANALYSIS SHOWS A WARM FRONT EXTENDING FROM
SOUTHWEST TO NORTHEAST OK. THIS BOUNDARY IS RAPIDLY RETREATING
NORTHWARD AND IS EXPECTED TO LIE ROUGHLY FROM WEST-CENTRAL OK INTO
SOUTHEAST KS BY MID AFTERNOON. RICH LOW LEVEL MOISTURE SOUTH OF THE
BOUNDARY WILL COMBINE WITH AMPLE DAYTIME HEATING TO YIELD AFTERNOON
MLCAPE VALUES OF 3000+ J/KG OVER MOST OF THE SOUTHEAST HALF OF OK
AND SOUTHEAST KS.

VARIOUS MODEL SOLUTIONS CONTINUE TO STRUGGLE WITH SHORT-TERM DETAILS
OF CONVECTIVE POTENTIAL. THIS APPEARS TO BE DUE TO HANDLING OF
SUBTROPICAL SHORTWAVE SEEN IN WATER VAPOR IMAGERY OVER SOUTHERN NM.
LARGE SCALE FORCING FOR ASCENT WILL OVERSPREAD OK THROUGHOUT THE DAY
IN ADVANCE OF THIS SYSTEM...BUT IT APPEARS THAT 700MB TEMPERATURES
APPROACHING 10C WILL SUPPRESS SIGNIFICANT CONVECTION OVER
WESTERN/CENTRAL OK UNTIL THIS AFTERNOON WHEN PERSISTENT LIFT AND
STRONG HEATING WILL WEAKEN THE CAP IN VICINITY OF THE DRYLINE.

PRESENT INDICATIONS ARE THAT ISOLATED THUNDERSTORMS WILL DEVELOP BY
LATE AFTERNOON ALONG THE DRYLINE IN SOUTHWEST OK AND WESTERN NORTH
TX...AND ALONG THE STALLED BOUNDARY EXTENDING ACROSS NORTH CENTRAL
OK INTO SOUTHEAST KS. VERTICAL SHEAR PROFILES WILL BE QUITE STRONG
THROUGHOUT THIS AREA WITH 0-3KM SRH VALUES EXCEEDING 300 M2/S2 AND
STRONG EFFECTIVE SHEAR. DISCRETE SUPERCELL STORMS ARE EXPECTED WITH
A RESULTANT RISK OF VERY LARGE HAIL AND A FEW STRONG TORNADOES.
THESE STORMS ARE EXPECTED TO TRACK NORTHEASTWARD ALONG AND SOUTH OF
THE SURFACE BOUNDARY INTO NORTHEAST OK AND EVENTUALLY WESTERN MO
THIS EVENING.

...MO/IL...
STRENGTHENING SOUTHERLY LOW LEVEL WINDS ARE FORECAST ACROSS MUCH OF
MO/IL TODAY...WITH MODERATE CAPE VALUES ALREADY IN PLACE. OTHER
THAN LOW LEVEL WARM ADVECTION...LARGE SCALE FORCING MECHANISMS ARE
SUBTLE. NEVERTHELESS...STEEP MID LEVEL LAPSE RATES AND SUFFICIENT
EFFECTIVE SHEAR WILL POSE A CONDITIONAL RISK OF HAIL IN THOSE STORMS
THAT CAN DEVELOP TODAY.

...MO/KS/OK/NORTH TX OVERNIGHT...
THE MAIN UPPER TROUGH IS EXPECTED TO SWING EASTWARD INTO THE PLAINS
LATE TONIGHT...RESULTING IN A LARGE SQUALL LINE AFFECTING EASTERN
KS...CENTRAL/EASTERN OK...WESTERN MO...AND NORTH TX. IT APPEARS
LIKELY THAT THESE STORMS WILL POSE A RISK OF RATHER WIDESPREAD
DAMAGING WINDS THROUGH 12Z.

...TN VALLEY TO CENTRAL/SOUTHERN APPALACHIANS...
AT LEAST ISOLATED TO WIDELY SCATTERED TSTMS ARE EXPECTED TO
DIURNALLY INCREASE THIS AFTERNOON ACROSS THE REGION. WHILE FORCING
ON THE LARGE SCALE WILL BE MODEST AND MID-LEVEL LAPSE RATES/
VERTICAL SHEAR WILL BE WEAK...STEEPENING LOW LEVEL LAPSE RATES
DURING THE AFTERNOON MAY CONTRIBUTE TO SOME POTENTIAL FOR EPISODIC
BOUTS OF LOCALLY DAMAGING WINDS/HAIL.

..HART/GARNER.. 04/17/2013

[brettjrob]

Nice plots ^^ I will have to check that out. I like the overlays and crossover data.

 

Interesting day ahead. First off, NAM made a lot of us look pretty stupid (except wxmann). The NAM indeed ended up being correct in developing northerlies across much of western OK, so it doesn't look like the front will advance much farther W...which will end up creating a SW to NE oriented frontal zone. A lot of the dryline looks like it may end up being cutoff from the deep instability to the east. Storms that initiate along the quasistationary/warm front may tend to merge into clusters based on the bulk shear vector/orientation of the front. That said, the area east of I35, especially from 00z on, looks primed for a potential tor outbreak if, as Tony said, the boundary layer remains partially mixed and some sort of semi discrete activity can remain. Toss in some low cloud cover which may hinder daytime activity as well...and my guess is SPC will hold to a mod for the morning issuance.

 

Good summary. While the NAM will likely end up having been too stubborn on lifting the front overall, its frontal orientation looks likely to verify. Unfortunately for chasers, this puts a kibosh on the "dream scenario" of opening up all of SW OK for play, instead favoring mainly along and SE of I-44 (well, if you mentally "extend" I-44 WSW past LAW, that is). More concerning are storm motions nearly parallel to the WF, if not across it in some cases. The degree of cold air behind it makes me skeptical on the idea of a supercell just riding the front and going ape for hours on end, as I'd typically want to see a more diffuse buoyancy gradient. I'd much prefer to chase a dryline storm as it traverses the open warm sector, but that may have to be S of the Red River in an area of slightly less impressive low-level shear.

 

Otherwise, RAP/HRRR soundings remain insistent on a pronounced kink/weakness centered around H7 for the SW OK/NW TX area, which improves rather dramatically nearing sunset. Overall, I definitely agree with staying at MDT, likely through the day now at this point. Between the hodograph kink and H5 flow that appears slightly more backed than I would've hoped based on the global/regional models over the past few days, there are *still* some major question marks. I do think we end up with at least several tornado reports across the MDT area by early morning.

[LocoAko]

Well that was a rapid warm frontal passage. Fogged up the windows, lol.

 

[David Reimer]

The 4 KM NAM lights up several discrete supercells late this afternoon and keeps them going for several hours. Should its solution verify, a major tornado event will likely occur this evening. 

[David Reimer]

OUN will be launching a special sounding at 10:30 AM. 

[SmokeEater]

[IsentropicLift]

First activity is starting to fire west of I-44

[Jim Marusak]

looking at the 12z upper air analyses this morning as well as the latest surface, it confirms what everyone is saying that areas near and east of that boundary near i-44 is just looking at the potential for an ugly day, with a plume of >+15c at 850 going from BRO to SGF and TOP as well as a plume of dd's greater than 15 from SGF thru DFW and DRT. once the main jet streak comes in from Arizona towards the Tx Panhandle and western KS, it's game on.

[wxmeddler]

First activity is starting to fire west of I-44

 

Morning convection.. the main course is near or after sunset.

[baroclinic_instability]

I love meteorology. It is awesome looping vis and visualizing air parcels ascending across the WCB/sloping warm front before reaching the LFC across eastern KS. Anyways... 12z operational NAM (not the hi res) seems to be having all sorts of convective feedback issues, and has a load of convection across eastern OK by 18z forming into a cluster and sinking south into N Texas. That obviously won't happen, so it does seem like the warm sector will remain relatively pristine heading into the afternoon. Best of luck to chasers who go out. I for one am highly interested in seeing how this event plays out. This has been one of the more interesting severe events to track in a while. Unfortunately I won't be watching this one unfold as I just finished a midnight shift. 

[Ed Lizard]

First activity is starting to fire west of I-44

 

AXS looks to be in the cool air...

[jcwxguy]

BULLETIN - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH OUTLINE UPDATE FOR WT 114

NWS STORM PREDICTION CENTER NORMAN OK

1110 AM CDT WED APR 17 2013

TORNADO WATCH 114 IS IN EFFECT UNTIL 1000 PM CDT FOR THE

FOLLOWING LOCATIONS

ILC001-009-013-061-083-117-149-180300-

/O.NEW.KWNS.TO.A.0114.130417T1610Z-130418T0300Z/

IL

. ILLINOIS COUNTIES INCLUDED ARE

ADAMS BROWN CALHOUN

GREENE JERSEY MACOUPIN

PIKE

KSC011-021-037-091-103-107-121-209-180300-

/O.NEW.KWNS.TO.A.0114.130417T1610Z-130418T0300Z/

KS

. KANSAS COUNTIES INCLUDED ARE

BOURBON CHEROKEE CRAWFORD

JOHNSON LEAVENWORTH LINN

MIAMI WYANDOTTE

MOC007-009-011-013-015-019-021-025-027-029-033-037-039-041-043-

047-049-051-053-055-057-059-067-071-073-077-083-085-089-095-097-

099-101-105-107-109-113-115-117-119-121-125-127-131-135-137-139-

141-145-151-159-161-163-165-167-169-173-175-177-183-185-189-195-

205-209-213-217-219-221-225-229-510-180300-

/O.NEW.KWNS.TO.A.0114.130417T1610Z-130418T0300Z/

MO

. MISSOURI COUNTIES INCLUDED ARE

AUDRAIN BARRY BARTON

BATES BENTON BOONE

BUCHANAN CALDWELL CALLAWAY

CAMDEN CARROLL CASS

CEDAR CHARITON CHRISTIAN

CLAY CLINTON COLE

COOPER CRAWFORD DADE

DALLAS DOUGLAS FRANKLIN

GASCONADE GREENE HENRY

HICKORY HOWARD JACKSON

JASPER JEFFERSON JOHNSON

LACLEDE LAFAYETTE LAWRENCE

LINCOLN LINN LIVINGSTON

MACON MARIES MARION

MCDONALD MILLER MONITEAU

MONROE MONTGOMERY MORGAN

NEWTON OSAGE PETTIS

PHELPS PIKE PLATTE

POLK PULASKI RALLS

RANDOLPH RAY SALINE

SHELBY ST. CHARLES ST. CLAIR

ST. LOUIS STONE TANEY

VERNON WARREN WASHINGTON

WEBSTER WRIGHT

MISSOURI INDEPENDENT CITIES INCLUDED ARE

ST. LOUIS CITY

ATTN...WFO...LSX...SGF...EAX...

[JoMo]

Long tornado watch... Until 10 PM... 

[jcwxguy]

Probability of 2 or more tornadoes 

Mod (60%)

Probability of 1 or more strong (F2-F5) tornadoes

Mod (40%)

Wind

Probability of 10 or more severe wind events

Mod (40%)

Probability of 1 or more wind events > 65 knots

Low (10%)

[IsentropicLift]

AXS looks to be in the cool air...

Yeah I've noticed that the main axis of cape seems to be south and west of OKC right now.

[JoMo]

 

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE NORMAN OK

1116 AM CDT WED APR 17 2013

.UPDATE...

COMPLEX SEVERE WEATHER SITUATION CONTINUES TO UNFOLD. WARM FRONT

HAS LIFTED NORTH IN THE METRO AREA CURRENTLY LYING ACROSS THE

OKLAHOMA CITY METRO /73 OVER 68 AT WILL ROGERS AIRPORT AND 56 OVER

52 AT WILEY POST AIRPORT./ THIS FRONT HAS SLOWED OR STALLED THIS

MORNING. DEVELOPMENT OF ELEVATED PRECIPITATION ABOVE THE FRONTAL

SURFACE AND PERSIST NORTH WINDS ACROSS NORTHWEST OKLAHOMA AND

KANSAS LIKELY ARE SIGNALS THAT THE FRONT WILL LIKELY NOT MOVE

NORTH MUCH FARTHER. MESOSCALE MODELS ALSO INDICATE THAT THE FRONT

MAY START MOVING SOUTH AGAIN LATER THIS AFTERNOON. ANOTHER ISSUE

IS THAT CONVECTIVE INHIBITION LOOKS TO REMAIN SMALL SO STORM

DEVELOPMENT APPEARS LIKELY... MAY BE RELATIVELY WIDESPREAD AND

DEVELOP EARLY /DEPENDING ON HOW SOON STRATUS THINS./ T 16Z

SOUNDING FROM OUN MAY SHED MORE LIGHT ON THIS. THERE IS ALSO A

PERSISTENT SIGNAL OF THE DEVELOPMENT OF A SURFACE LOW THIS

AFTERNOON... MOST LIKELY ACROSS SOUTHWEST OKLAHOMA.

RESULTANT ISSUES ARE... /1/ TEMPERATURE GRADIENT WILL LIKELY

REMAIN STRONG ACROSS THE WARM FRONT. THIS MEANS THAT THE WARM

FRONT AS A SOURCE OF ENHANCED VORTICITY WITH STORMS ALONG THE

BOUNDARY WILL NOT BE IDEAL AS ANY STORM WOULD QUICKLY BECOME

ELEVATED ABOVE THE FRONTAL BOUNDARY IF IT GETS EVEN A SHORT

DISTANCE NORTH OF THE FRONT. IF WINDS STAY NORTHERLY IN THE COOL

SECTOR... THAT WILL NOT BE AN IDEAL WIND PROFILE EITHER. /2/ THE

BEST LOW-LEVEL WIND SHEAR WILL BE IN THE VICINITY OF THE SURFACE

LOW/TRIPLE POINT LIKELY TO DEVELOP ACROSS SOUTHWEST OKLAHOMA THIS

AFTERNOON AND MOVE TOWARD CENTRAL OKLAHOMA THIS EVENING. THIS WILL

BE THE AREA OF MOST CONCERN FOR TORNADO DEVELOPMENT... ALTHOUGH

TORNADOES WILL BE POSSIBLE THROUGHOUT THE WARM SECTOR. /3/ IT

REMAINS UNCERTAIN WHAT WILL RESULT FROM THE BALANCE OF DELAYED

WARMING DUE TO STRATUS AND THE APPARENT LOW CIN WHICH WOULD

OTHERWISE FAVOR EARLY AND/OR WIDESPREAD DEVELOPMENT. /4/ EVEN

NORTH OF THE SURFACE FRONT... ELEVATED STORMS WITH A RISK OF LARGE

HAIL WILL PERSIST.

CURRENT THOUGHTS ARE THAT SCATTERED STORMS WILL LIKELY DEVELOP

EARLY TO MID AFTERNOON WITH THE POTENTIAL OF SUPERCELL

DEVELOPMENT IN THE WARM SECTOR. ELEVATED SEVERE STORMS WILL ALSO

BE LIKELY NORTH OF THE WARM FRONT. DURING THE EVENING... STORMS

WILL BECOME MORE WIDESPREAD AS THE FRONT MOVES THROUGH AND DEVELOP

INTO A SQUALL LINE.

THERE IS STILL SOME UNCERTAINTIES /MORE THAN USUAL/ ON HOW THINGS

WILL EVOLVE... ESPECIALLY WITH RESPECT TO THE COUNTERACTING

INFLUENCES OF CIN VS. DELAYED WARMING. BUT THE RISK OF SIGNIFICANT

SEVERE WEATHER STILL EXISTS... ESPECIALLY FROM SOUTHWEST TO

CENTRAL PORTIONS OF THE FORECAST AREA.