Oklahoma Severe Weather Discussion - May 2011

[venture]

Hi, I have a question and I hope you can answer it.

Lets say there is a broad area of strong cap and a storm successfully bust through an area of weaker cap. Does the surrounding strong cap prevent the storm, or at least slow the movement, from doing much? Like for an example, a ship trying to sail thru thick ice in ocean and sometime getting stuck. Is it that way with the storms? Do they have to struggle moving thru the strong cap or it doesn't matter once they bust an area?

Actually really good question and analogy. So let's take Sunday evening for example. Storms broke the cap and went severe. However around I-35 and to the east the cap was significantly stronger and move convective inhibition was present. As the storm moves into this, the ability to maintain itself becomes harder and it can get choked off. There are occasions where a strong is strong enough that it can start to create its own environment around itself and do what it wants. Those are rare though.

[venture]

Significant Severe Weather risk is increasing for Wednesday.

New Day 3 Outlook from SPC...

Enhanced risk area is roughly along and west of I-35...including most of the OKC metro area.



DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT MON MAY 09 2011

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PORTION OF THE
PLAINS AND UPPER MS VLY/MIDWEST...

...CNTRL/SRN PLAINS...
AN ACTIVE WEATHER WEDNESDAY IS EXPECTED AS PRIMARY PORTION OF THE
WRN STATES UPPER TROUGH BEGINS TO EJECT AS A NEGATIVE-TILT ENTITY
INTO THE CNTRL/SRN PLAINS. ACCOMPANYING LEE LOW WILL DEVELOP FROM
SE CO INTO NCNTRL KS DURING THE AFTN AS THE DRYLINE MIXES EWD INTO
CNTRL KS...WRN OK AND ERN EDWARDS PLATEAU IN TX. 60S SFC DEW POINTS
AND 7-8.5 DEG C/KM MID-LEVEL LAPSE RATES WILL CONTRIBUTE TO VERY
UNSTABLE CONDITIONS FROM CNTRL TX NWD TO THE NCNTRL KS/SCNTRL NEB
BORDER.

THERE ARE SOME MODELS THAT SUGGEST THAT A LEAD SUB-TROPICAL IMPULSE
MAY AID IN THE INITIATION OF TSTMS ACROSS NCNTRL TX INTO SERN OK
DURING THE EARLY-MID AFTN...BUT CONFIDENCE IS LOW AT THIS TIME AS IT
IS UNCLEAR ON EXACTLY WHAT INITIATING BOUNDARY MAY PLAY A ROLE IN
THIS INITIATION. THIS POSSIBILITY WILL HAVE TO BE CONSIDERED AND
WAS INCLUDED IN 15% SVR PROBS SINCE VERTICAL SHEAR/BUOYANCY WILL BE
SUFFICIENT FOR ORGANIZED STORMS.

MEANWHILE...AS MID-LEVEL COOLING AND ASCENT TIED TO THE TROUGH
SPREADS ACROSS THE HIGH PLAINS...COMBINATION OF HEATING AND ERODING
CAP WILL LEAD TO TSTM INITIATION NEAR TRIPLE POINT OVER NWRN/CNTRL
KS SWD ALONG THE DRYLINE INTO CNTRL TX BY MID-LATE AFTN. SUPERCELLS
WILL BE LIKELY WITH VERY LARGE HAIL...TORNADOES AND DMGG WINDS.
STRONGER ASCENT WILL SPREAD ENE ACROSS KS/NEB AND TOWARD IA/NW MO
WEDNESDAY NIGHT AND LIKELY SUPPORT ONE OR MORE CLUSTERS OF
STRONG/SVR STORMS. ADDITIONAL LONGER-LIVED TSTMS WILL LIKELY EXIST
THROUGH MOST OF THE NIGHT ACROSS PARTS OF CNTRL/NRN TX WITH SIMILAR
THREATS FOR HAIL AND HIGH WINDS.

[Thunder]

Thanks.

And its about time when things are set up for the western half. I am sick of all the rain the eastern half kept getting. :-)

[venture]

Sure thing. :-)

Yeah, the west needs some rain...unfortunately the severe weather comes with it this time of year so we just need to prepare.

Couple of side notes...

The chat room is up and running at www.chatokc.com and will be moderated during active weather or when conditions warrant.

The new sister site for the chat room, www.storm-scope.com is back up and running with a new format. I'm in the process of adding more content to it. Any requests will tried to be honored. Want to have a fast and easy to navigate one stop site to find critical weather info.

[Charlie40]

Venture, Does Wednesdays storms look like a mod to high end even for us here in central Oklahoma or just a few scattered storms popping up here and there? Whats the timeline for the Metro to see storms roll through on Wednesday? Thanks for all you do !!

[ou48A]

Venture,,,,,What are the chances of long tracked large and damaging Tornados on Wednesday?

Thanks

[Thunder]

The chances are there. All of that. There is the potential. I think this is the greatest potential of the season so far and that the coverage is now including the western half. Slight risk that I see now and possibly upgrade to Mod risk (just my opinion) tomorrow maybe. I dunno, Venture knows it all, tho. :-)

His best advice will be just to be prepared. That is all we can do. Just be prepared and expect to change plans, etc. Keep watch on the weather, etc, there are multiple text and email alerts you can subscribe to for current on-goings. There are a whole lot of factors in play.

Its like next to impossible to predict if there will be long-track tornadoes, etc. Each storm/super cell has a mind of their own and it just depend. But the chances is there for severe storms with the potential. That is the best I can say. Venture can provide more.

[ou48A]

The chances are there. All of that. There is the potential. I think this is the greatest potential of the season so far and that the coverage is now including the western half. Slight risk that I see now and possibly upgrade to Mod risk (just my opinion) tomorrow maybe. I dunno, Venture knows it all, tho. :-)

His best advice will be just to be prepared. That is all we can do. Just be prepared and expect to change plans, etc. Keep watch on the weather, etc, there are multiple text and email alerts you can subscribe to for current on-goings. There are a whole lot of factors in play.

Its like next to impossible to predict if there will be long-track tornadoes, etc. Each storm/super cell has a mind of their own and it just depend. But the chances is there for severe storms with the potential. That is the best I can say. Venture can provide more.

Thanks
It’s those high end EF5 armageddon tornadoes that really scare me.

[Thunder]

Thanks
It’s those high end EF5 armageddon tornadoes that really scare me.

I get excited watching them out in open fields, but quickly become scared when they get closer.

[Thunder]

This is the current risk for Wednesday.



Venture has the basics all on the First Post, so look there often to see the updates.

Day 1 is today. Day 2 is tomorrow. Day 3 is next day, and so on.

Today's Day 3 is Wednesday. Tomorrow's Day 2 is Wednesday.

Sometime the weather guys (usually KFOR is first to do it) post Moderate/High/Exceptional risk way ahead of SPC/NWS based on their own experience. As Venture would say... Take those TV guys' statement with a grain of salt. :-P

[venture]

Venture, Does Wednesdays storms look like a mod to high end even for us here in central Oklahoma or just a few scattered storms popping up here and there? Whats the timeline for the Metro to see storms roll through on Wednesday? Thanks for all you do !!

If we go by the favored models of HPC this morning, Canadian and European, it would place the higher risk in most of Central and a bit of Eastern OK. It appears far western OK will have the dryline pass early but most areas east of US 183 would be in the higher risk (not "High Risk"). Time line is too early to narrow down right now until we get into either later tomorrow or early Wednesday.

Venture,,,,,What are the chances of long tracked large and damaging Tornados on Wednesday?

Thanks

Way too early to say now. The models that we have the most access to, GFS and NAM, have pulled instability figures way down this morning but I'm not buying into those runs. Will there be tornadoes? Yes. They typically cause damage when on the ground...but whether or not they will be long track or strong, it is too early to say right now since the models aren't all lined up.

[Jesseda]

is there any activity forming for today yet? it is clear at the airport not really a cloud yet

[venture]

is there any activity forming for today yet? it is clear at the airport not really a cloud yet

Short term model guidance does suggest we could see additional storms form much like yesterday. Generally south of I-40 in Southwest or South Central OK. The risk though is much lower today. On radar, it does appear we have some light precip trying to form just across the Red River in Western North Texas.

[jn1780]

Here's a conversion chart of how the NWS classifies risk areas for anyone curious.

[venture]

Conditional severe risk extended North through SW and Central OK for today.

...SRN PLAINS...
CONDITIONAL/MRGL SVR POTENTIAL...FOR WIND/HAIL...IS EXTENDED NWD
ALONG AND JUST AHEAD OF DRYLINE AS FAR N AS PORTIONS SWRN/CENTRAL
OK. NARROW SPATIAL/TEMPORAL OPPORTUNITY EXISTS LATE THIS AFTERNOON
FOR INTENSE SFC HEATING TO OVERCOME INITIALLY STG CINH ASSOCIATED
WITH LONGSTANDING/ANTECEDENT EML FROM NW TX NWD. SOME OF THIS
ACTIVITY...WHICH WOULD BE HIGH-BASED...MAY BECOME ORGANIZED BRIEFLY
WITH POTENTIAL FOR HAIL AND STG-SVR GUSTS...GIVEN AMBIENT 35-45 KT
EFFECTIVE SHEAR AND WELL-MIXED SUBCLOUD LAYER.

[venture]

MESOSCALE DISCUSSION 0704
NWS STORM PREDICTION CENTER NORMAN OK
0423 PM CDT MON MAY 09 2011

AREAS AFFECTED...PORTIONS OF CNTRL TX INTO SWRN OK

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 092123Z - 092330Z

AN ISOLATED SVR STORM OR TWO COULD DEVELOP ACROSS PORTIONS OF CNTRL
TX INTO SWRN OK LATER THIS AFTERNOON. GIVEN THE ANTICIPATED SPARSE
COVERAGE OF ANY SVR STORMS...THE ISSUANCE OF A WW IS UNLIKELY.

MID-AFTERNOON SFC ANALYSIS DEPICTS A DRYLINE EXTENDING FROM 20 NNE
CSM TO THE RED RIVER 20 SSW LTS TO 45 NNW ABI AND FARTHER SSW TO 55
WSW SJT. STRONG INSOLATION OVER THE ERN PERIPHERY OF A THERMAL AXIS
/LOCATED WEST OF THE DRYLINE/ HAS RESULTED IN TEMPERATURES WARMING
INTO THE UPPER 90S TO 103 DEGREES. MODIFIED 12Z OBSERVED SOUNDINGS
AND RAPID REFRESH FORECAST SOUNDINGS SUGGEST THAT THE STRONG
DIABATIC HEATING HAS SUBSTANTIALLY REDUCED SURFACE-BASED CINH WITHIN
A NARROW CORRIDOR ALONG AND JUST EAST OF THE DRYLINE. THE REDUCTION
IN CINH...ALONG WITH LOW-LEVEL CONVERGENCE ASSOCIATED WITH THE
DRYLINE...HAS LED TO THE INITIATION OF A FEW HIGHER-BASED CU WEST OF
THE DRYLINE. THIS INITIAL ATTEMPT AT CONVECTION MAY ALSO BE
SUPPORTED BY A SUBTLE MID-LEVEL WAVE EMERGING FROM THE HIGHER
TERRAIN OF NRN MEXICO INTO TX...ALSO RESPONSIBLE FOR HIGH-LEVEL
CLOUDINESS OVER THE MOIST SECTOR.

RECENT RUNS OF THE EXPERIMENTAL HRRR SUGGEST SOME POTENTIAL FOR ONE
OR TWO DEEPER CONVECTIVE PLUMES TO EMANATE FROM THE CU FIELD AS
HEATING CONTINUES AND THE BOUNDARY LAYER DEEPENS. ANY INCIPIENT
CONVECTION WILL BE HIGH BASED...WITH THE POTENTIAL FOR SUPERCELLULAR
STRUCTURES TO EVOLVE GIVEN EFFECTIVE BULK SHEAR MAGNITUDES OF 35-45
KT. THE THREAT FOR LARGE HAIL WILL EXIST PROVIDED VERY STEEP
MID-LEVEL LAPSE RATES /IN EXCESS OF 8.5 C PER KM/ ASSOCIATED WITH A
STRONG ELEVATED MIXED LAYER. STEEP LOW-LEVEL LAPSE RATES...IN PART
YIELDING DCAPE VALUES AOA 1300 J PER KG...SUGGESTS A POTENTIAL FOR
DMGG WINDS...AS WELL. THE THREAT FOR VERY LARGE HAIL /ALBEIT A LOW
THREAT/ MAY OCCUR IF CONVECTION CAN SUSTAIN ITSELF EAST OF THE
DRYLINE AND TRAVERSE RICHER LOW-LEVEL MOISTURE AND A VERY UNSTABLE
AIR MASS -- I.E. SFC DEWPOINTS AOA THE MIDDLE 60S SUPPORTING MLCAPE
VALUES OVER 3500 J/KG. HIGH LCL HEIGHTS AND RELATIVELY WEAK
LOW-LEVEL FLOW WILL MITIGATE THE THREAT FOR ANY TORNADOES. WITH THE
ONLY SUBSTANTIAL FORCING FOR CONVECTION EXPECTED TO BE MAINLY TIED
TO THE DRYLINE...AND GIVEN THE STRONG CINH AWAY FROM THE
DRYLINE...ANY SEVERE CONVECTIVE COVERAGE IS EXPECTED TO BE SPARSE.

..COHEN.. 05/09/2011

[tornado74]

Way too early to say now. The models that we have the most access to, GFS and NAM, have pulled instability figures way down this morning but I'm not buying into those runs. Will there be tornadoes? Yes. They typically cause damage when on the ground...but whether or not they will be long track or strong, it is too early to say right now since the models aren't all lined up.

Thanks for posting such great information on this site. It is very helpful. I have looked at the GFS and NAM CAPE values for Day 3 and I am puzzled why the instability is so low. My meteorology skills are very basic, so forgive me if there is an obvious answer to this. The instability is already in place today, and it doesn't seem like there is anything moving through that would "strip" the atmosphere of this instability before Wednesday. So why do the models show the instability as marginal on Wednesday? Thanks in advance.

[venture]

Norman NWS has upped the strong wording for Wednesday calling for a "Potentially Significant Severe Weather Event."

Live chat is rolling at ChatOKC.com and new blogging and resources are going at Storm-Scope.com.

[Thunder]

Just caught a story on KOCO. They are attempting to induce mass panic when they displayed 3 images of recent outbreaks happening on all 3 different dates and implying that is what we will be getting on Wednesday.

[venture]

Just caught a story on KOCO. They are attempting to induce mass panic when they displayed 3 images of recent outbreaks happening on all 3 different dates and implying that is what we will be getting on Wednesday.

I wouldn't say that, but the one thing that I did take issue with is the promoting of their Radar Predictor as a way to find out "where storms will be 2 days in advance."

[redrunner]

Just caught a story on KOCO. They are attempting to induce mass panic when they displayed 3 images of recent outbreaks happening on all 3 different dates and implying that is what we will be getting on Wednesday.

*cough, cough*
http://www.okctalk.com/showthread.ph...689#post427689
http://www.okctalk.com/showthread.ph...715#post427715

[venture]

So evening model runs look like they don't have a clue on what is going to happen Wednesday. Some quick looks appear to show several initialization errors with the data, so we'll just have to wait and see. GFS decided to hit the gas on Wednesday and move a lot of precip east, with scattered storms along the dryline. HPC guidance is recommending a blend of the UKMET/ECMWF for Wednesday. NAM is a bit too far north for their liking.

The setup looks very classic to a Great Plains Spring severe day, but instabilities all over the place. SPC outlooks are out now, and they are going Moderate for Central OK. Will post those in a second. The best line sums things up best in the evening Forecast Discussion from NWSFO Norman...

WEDNESDAY LOOKS LIKE TROUBLE. `NUFF SAID.

[venture]

VERY strong wording here from SPC for Central OK for Wednesday...



DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 AM CDT TUE MAY 10 2011

VALID 111200Z - 121200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER A PART OF CNTRL KS AND CNTRL OK...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPR MS VLY SWD INTO CNTRL TX...

...PLAINS...
ONLY MINOR DIFFERENCES EXIST IN MODEL GUIDANCE ON THE ARRIVAL OF THE PRIMARY UPPER TROUGH INTO THE CNTRL/SRN HIGH PLAINS BY WEDNESDAY AFTN. A SUBTROPICAL IMPULSE WILL EJECT ENE AHEAD OF THE MAIN FEATURE...MIGRATING ACROSS CNTRL/NRN TX EARLY IN THE DAY. IN THE LOWER LEVELS...A LEE LOW WILL INTENSIFY OVER SWRN KS AND TRAVEL ENE INTO CNTRL KS BY WEDNESDAY NIGHT. A DRYLINE WILL MIX EWD INTO SCNTRL KS...CNTRL OK AND NCNTRL TX BY EVENING WHILE A FRONT EXISTS ENE FROM THE LOW ACROSS SRN NEB AND INTO NWRN WI.

SLY LLVL FLOW WILL MAINTAIN A MOIST BOUNDARY LAYER AIR MASS AHEAD OF THE DRYLINE WITH MLCAPE OF 2000+ EXISTING THROUGHOUT THE CNTRL/SRN PLAINS. ARRIVAL OF THE LEAD SUBTROPICAL IMPULSE WILL BE SOMEWHAT PROBLEMATIC AS STRONG PCPN SIGNAL HAS EXISTED FOR A COUPLE DAYS FROM CNTRL/NRN TX INTO ERN OK...SERN KS AND THE MO OZARKS. WHILE COVERAGE OF THIS ACTIVITY IS SOMEWHAT IN QUESTION...MODEST MID-LEVEL SWLY FLOW WILL ACCOMPANY THE SYSTEM AND BOOST VERTICAL SHEAR TO SUPPORT SUPERCELLS AND ORGANIZED LINES/CLUSTERS. LARGE HAIL APPEARS TO BE THE PRIMARY THREAT WITH THIS ACTIVITY...ALTHOUGH ISOLD TORNADOES AND DMGG WINDS WILL ALSO BE POSSIBLE.

MEANWHILE...NARROW CORRIDOR ALONG/E OF THE DRYLINE WILL PERCOLATE NW OF THE E TX/OK CLOUD SHIELD AND RESULT IN MLCAPES 2000-3000 J/KG FROM THE TX BIG COUNTRY NWD INTO CNTRL KS. AS LARGE-SCALE HEIGHT FALLS AND COOLING ASSOCD WITH THE APPROACHING TROUGH SPREAD NE...TSTMS WILL INITIATE. FIRST STORMS WILL FORM NE OF THE TRIPLE POINT/FRONT ACROSS SCNTRL NEB AND NCNTRL/NWRN KS AND THEN FARTHER SWD INTO WRN/CNTRL OK AND TX BIG COUNTRY AREA BY LATE AFTN.
INCREASING MERIDIONAL FLOW WILL RESULT IN DEEP SOUTHERLIES IN NEB/NRN KS RESULTING IN MESSY STORM MODES. STILL...BACKED NEAR SFC FLOW VCNTY THE LEE LOW WILL BE FAVORABLE FOR SUPERCELLS WITH A FEW TORNADOES AND LARGE HAIL. FARTHER S...MORE CROSS-COMPONENT DEEP LAYER SHEAR VECTORS WILL RESULT IN LONGER-LIVED DISCRETE SUPERCELLS ACROSS CNTRL/SCNTRL KS AND CNTRL OK WHERE VERY LARGE HAIL AND TORNADOES WILL BE LIKELY.

STRONGER SUPPORT FOR SUSTAINED ORGANIZED STORMS WILL CONTINUE ENE INTO ERN NEB AND IA OVERNIGHT AS SLY LLJ INTENSIFIES. STORMS WILL CONTINUE TO PRODUCE HIGH WINDS/LARGE HAIL. FARTHER S...ACTIVITY MAY NOT BE AS LONG-LIVED AS PRIMARY FORCING FOR ASCENT PASSES TO THE N AND CAP INCREASES IN THE INFLOW LAYER.

..RACY.. 05/10/2011

[redrunner]

Fack!

[jn1780]

Poor western OK, everyday everything is pushed a little bit further east. Not that they want to deal with severe weather, but the rain would be nice.