This is potentially a unique day (Wednesday).

The last HIGH risk to be issued by the SPC was this time last year, and it was the second time ever a HIGH risk was issued on the initial Day 2 outlook. It resulted in 122 tornado reports and 6 people died.

Will be interesting to see if they upgrade tomorrow to make it the third.



This day will most likely have multiple PDS watches issued.

Is there still a lot of uncertainty on where the cold/warm front will end up Wednesday?

Is there still a lot of uncertainty on where the cold/warm front will end up Wednesday?

I'll get into it more after all the models are out for this morning. So just some quick thoughts. Tuesday has a risk of storms, but cap will be strong. If there is any left over convection leading into Wednesday, that can definitely play with the setup and make it more complex. Frontal position is still a little up in the air on just how far into NW OK it will get until it morphs into a cold front and slams south. Looks at the various SPC severe weather indices that have been developed - especially on the 12Z NAM this morning - I'm thinking more and more we are going to see a high risk go out for very large hail and a few intense to violent tornadoes. Obviously chat room will be running that day (Anon and others if you are interested in helping out let me know).

Now let me says this about everything. High risk days are the culmination of perfect conditions coming together. These can have a colossal bust factor though. If one little thing is out of line, it all goes to garbage. They are high risks for a reason, but one little fly in the ointment can be a saving grace.

Like we saw last week, there is going to be a lot of excitement with this. I'm going to do the best I can to control myself as will the other meteo geeks here I'm sure. Just keep in mind when words such as "great", "awesome", "very good", "perfect", and such are used...don't take it the wrong way.

I'll try to make the chat this time. I post here from work and often times it is totally random when I have free time to post.

Venture, is the chat invite by email only or how does one get in? I'll be working that day, but might still be able to get on.

Venture, is the chat invite by email only or how does one get in? I'll be working that day, but might still be able to get on.

Use this link: Live Chat | Weather Spotlight (http://www.weatherspotlight.com/?page_id=40)

You can go there now and put in your email and request a notice once I open it up. It is set to automatically launch tomorrow around Noon.

Side note. Some good details on Day 3 history. Patrick Marsh from SPC put this out: SPC Day 3 Moderates In Context: What Do They Become? - Playing with Data (http://www.pmarshwx.com/2012/04/spc-day-3-moderates-in-context-what-do-they-become/)

I wanted to look at how they actually verified, versus how the Day 3s morphed into the Day 1s, and posted a blog post on it here: Day 3 Moderates ? A Recap | Weather Spotlight (http://www.weatherspotlight.com/?p=144)

The 04/27/2011 super outbreak was nailed by the SPC. It is amazing that over 300 people still died that day.

People MUST heed to weather watches/warnings regardless of bust history.

The 04/27/2011 super outbreak was nailed by the SPC. It is amazing that over 300 people still died that day.

People MUST heed to weather watches/warnings regardless of bust history.

Absolutely agree with what you are saying. I think the major thing with the super outbreak in 2011 was just the shear number of tornadoes combined with them being very fast moving. We also have to recognize that we are very blessed/spoiled here with the quality of coverage we have. No one else can compare.

With that said looking back on the history, I would say only 1 out of the 11 previous Day 3 moderates busted. That is a tremendous amount of accuracy there. While the positioning may have been off 100 miles give or take, that is still tremendous accuracy considering how complex outbreak days are.

Awesome. Taking students to Stillwater for State solo/ensemble contest on Wednesday afternoon. Can't wait.

Better hope Stillwater simply keeps on dodging tornadoes as it has been successfully doing since 1990.

Okay, I know Wednesday is getting all the attention now but need to refocus a bit on today's activity. Slight risk is pretty much SE of I-44 today. HRRR has storm development in that area around 5PM this afternoon. Main risks today hail and wind. Tornado threat is pretty low.

http://rapidrefresh.noaa.gov/HRRR/from_jet/hrrr_jet/2013041513/t5/cref_t5sfc_f10.png

Absolutely agree with what you are saying. I think the major thing with the super outbreak in 2011 was just the shear number of tornadoes combined with them being very fast moving. We also have to recognize that we are very blessed/spoiled here with the quality of coverage we have. No one else can compare.

With that said looking back on the history, I would say only 1 out of the 11 previous Day 3 moderates busted. That is a tremendous amount of accuracy there. While the positioning may have been off 100 miles give or take, that is still tremendous accuracy considering how complex outbreak days are.

Wasn't that April '11 outbreak the one that went through northwestern Birmingham, AL?

Wasn't that April '11 outbreak the one that went through northwestern Birmingham, AL?

Indeed it was.

Some more Wednesday stuff. Forecast soundings. GFS is pink, NAM is blue...both 12Z runs this morning.



http://beta.wxcaster.com/skewts/GFS-test/060/SKT_GFS__koun.png

http://beta.wxcaster.com/skewts/NAM-test/060/SKT_NAM__koun.png

Okay so looking at that I'm sure most are like...huh? Purdy lines! :) So here is a rough crash course on what to look at and the key things to focus on.

The main Skew-T is your 3 lines with wind barbs on both sides. So the lines first off. Solid is air temp and dashed dewpoint. The dotted line is the temp of the parcel of air as it goes up. So follow that up. If the solid line is to the right of that dotted line that is air that is warmer than that parcel and the parcel won't rise. Also known as your cap. When the air parcel gets warmer than air temp that area between the solid line and dotted line, that is your CAPE. This also shows that the parcel of air will continue to rise up until it meets the air temp again. Here is a good video to help explain it...

bOnGFHXkQ8w

Okay so we are looking at that and we can things are going to be unstable with a lot of CAPE. Move of to the wind barbs on the right, that is your wind direction and speed at the various heights. This is also how we detect shear. The two main kinds are going to be speed shear and directional shear. In this exactly we are seeing surface winds out of the SE/SSE, or backed winds as you'll read often, and then they change directions to the SW and WSW as you go up in height. Good example of directional shear. Speed shear is when you have wind speed increase as you go up. We have some of that here as well. All in all this says, good shear. Sometimes you have to be careful of too much shear or speeds being too high in the upper levels because that can just rip updrafts apart.

So we got an unstable atmosphere and wind shear. Finally the squiggly line that is the hodograph. Used to find things like shear vectors and storm relative winds. These are good to help determine if you are going to be dealing with splitting storms and such. Typically in class right turning supercells we look for the hodograph to arch from the center to the right. Which we have here...for the most part. I won't get too much more into it right now, but googling should bring up a ton of resources on it. :)

So now we get down to the values. A lot of these are open to interpretation and how they play into storm formation, severe storms, and tornadoes. I'm just going to hit on a few of the variables instead of every one, otherwise this will be a book and probably confuse more than need be. Going left to right since these aren't perfect columns.



LI - Lifted Index. Negative is unstable, usually want lower than -4 for severe.
KI or K Index you usually want mid 20s for storm development and over 35 for strong development.
Equil P - That is where your air parcel meets the air temp again after getting warmer than it.
HAIL - Subjective to this sounding project on estimated hail size.
ConvT - Convective temperature or air temp needed to break cap without much forcing. This is more important in summer usually.
Lapse Rates also need to be looked at, in this care the value is favorable for severe weather.
SRH this is the Storm Relative Helicity in the first kilometer of air from the service...or your low level shear. This is also modified by the direction storms will move. Usually anything over 150 would be pretty significant.
SWEAT Index helps highlight severe storm potential. Usually 300-500 is what we look for, anything higher is significant.
TTI or Total Totals is another index looked at for storm development in general. Mid 40s are usually looked at for storm development, anything higher would indicate a more volatile setup.
Storm Dir/Speed - This is your storm direction in degrees and this is where the storm is coming from. So the example here is ~ 225 degrees which translates into moving NE. Speed is in knots so take the value and multiply by 1.15 to get MPH.
CapI - Strength of cap. Usually you want 2 or lower to help keep somewhat of a lid on things early. Over 4 requires a nuke to get rid of, less would lead to grunge fest.
LCL - Lowest cooling level. This is the atmospheric pressure height (measured in millibars) where the air can condense and form clouds. So a high number here means the level is lower to the ground and better chance for surface based convection. If you see numbers lower than say 850 mb, you are talking mostly high based elevated storms. Tornadoes need high LCL values (or lower cooling levels) since they are tied with surface based storms in most cases.
Sup Potential: Value specific to this product estimating percentage chance if any storm forms that it will be severe.
Precip Water measures the amount of water in the air. Usually you don't want it more than 1.5 or 1.75 for severe storms otherwise you are looking at just heavy rain. Lower than say 0.75 and its going to be too dry for much precip.
CAPE most are familiar with. Anything over 0 is unstable. Depending on the season will determine how much you need. Usually anything over 2000 j/kg is very unstable. However as we get into late spring/summer you'll see values over 5000 but not get anything. Even though its extremely unstable, it doesn't do any good without lift or something to break a cap.
CINH: Convective inhibition. Usually when you start getting lower than -100 you have issues getting anything going.
0-1km Shear - Like earlier this is your shear in the first kilometer of air, but this isn't storm direction dependant. When you start getting over 100 to 150 in this department you need to start being vigilant.
1km EHI or Energy Helicity Index another way to measure energy/shear. Usually more than 2 or 3 is pretty high.


That's pretty much the main ones without going longer...which I already went a bit too long. We can get more specific about the individual values if more clarification is needed. I went pretty general and with a broad brush on a lot of these. This is mainly to give you an idea of what to look for. The main thing to remember is that so much goes into this, and hopefully this is another example of how much there is, that you can't focus on just a few of these and figure big time storms. Think of it as a recipe. You have to have near perfect amounts of each to get a good tasting soup...otherwise you are just left with a pot full of odd smelling/looking/tasting water.

Venture, or maybe Anon, could you offer a ten-cent summary of what those soundings mean?

EDIT: You already did it! THanks

Venture, or maybe Anon, could you offer a ten-cent summary of what those soundings mean?

EDIT: You already did it! THanks

I actually knew you were going to ask. LOL

Okay so looking at that I'm sure most are like...huh? Purdy lines! :) So here is a rough crash course on what to look at and the key things to focus on.

The main Skew-T is your 3 lines with wind barbs on both sides. So the lines first off. Solid is air temp and dashed dewpoint. The dotted line is the temp of the parcel of air as it goes up. So follow that up. If the solid line is to the right of that dotted line that is air that is warmer than that parcel and the parcel won't rise. Also known as your cap. When the air parcel gets warmer than air temp that area between the solid line and dotted line, that is your CAPE. This also shows that the parcel of air will continue to rise up until it meets the air temp again. Here is a good video to help explain it...

bOnGFHXkQ8w

Okay so we are looking at that and we can things are going to be unstable with a lot of CAPE. Move of to the wind barbs on the right, that is your wind direction and speed at the various heights. This is also how we detect shear. The two main kinds are going to be speed shear and directional shear. In this exactly we are seeing surface winds out of the SE/SSE, or backed winds as you'll read often, and then they change directions to the SW and WSW as you go up in height. Good example of directional shear. Speed shear is when you have wind speed increase as you go up. We have some of that here as well. All in all this says, good shear. Sometimes you have to be careful of too much shear or speeds being too high in the upper levels because that can just rip updrafts apart.

So we got an unstable atmosphere and wind shear. Finally the squiggly line that is the hodograph. Used to find things like shear vectors and storm relative winds. These are good to help determine if you are going to be dealing with splitting storms and such. Typically in class right turning supercells we look for the hodograph to arch from the center to the right. Which we have here...for the most part. I won't get too much more into it right now, but googling should bring up a ton of resources on it. :)

So now we get down to the values. A lot of these are open to interpretation and how they play into storm formation, severe storms, and tornadoes. I'm just going to hit on a few of the variables instead of every one, otherwise this will be a book and probably confuse more than need be. Going left to right since these aren't perfect columns.



LI - Lifted Index. Negative is unstable, usually want lower than -4 for severe.
KI or K Index you usually want mid 20s for storm development and over 35 for strong development.
Equil P - That is where your air parcel meets the air temp again after getting warmer than it.
HAIL - Subjective to this sounding project on estimated hail size.
ConvT - Convective temperature or air temp needed to break cap without much forcing. This is more important in summer usually.
Lapse Rates also need to be looked at, in this care the value is favorable for severe weather.
SRH this is the Storm Relative Helicity in the first kilometer of air from the service...or your low level shear. This is also modified by the direction storms will move. Usually anything over 150 would be pretty significant.
SWEAT Index helps highlight severe storm potential. Usually 300-500 is what we look for, anything higher is significant.
TTI or Total Totals is another index looked at for storm development in general. Mid 40s are usually looked at for storm development, anything higher would indicate a more volatile setup.
Storm Dir/Speed - This is your storm direction in degrees and this is where the storm is coming from. So the example here is ~ 225 degrees which translates into moving NE. Speed is in knots so take the value and multiply by 1.15 to get MPH.
CapI - Strength of cap. Usually you want 2 or lower to help keep somewhat of a lid on things early. Over 4 requires a nuke to get rid of, less would lead to grunge fest.
LCL - Lowest cooling level. This is the atmospheric pressure height (measured in millibars) where the air can condense and form clouds. So a high number here means the level is lower to the ground and better chance for surface based convection. If you see numbers lower than say 850 mb, you are talking mostly high based elevated storms. Tornadoes need high LCL values (or lower cooling levels) since they are tied with surface based storms in most cases.
Sup Potential: Value specific to this product estimating percentage chance if any storm forms that it will be severe.
Precip Water measures the amount of water in the air. Usually you don't want it more than 1.5 or 1.75 for severe storms otherwise you are looking at just heavy rain. Lower than say 0.75 and its going to be too dry for much precip.
CAPE most are familiar with. Anything over 0 is unstable. Depending on the season will determine how much you need. Usually anything over 2000 j/kg is very unstable. However as we get into late spring/summer you'll see values over 5000 but not get anything. Even though its extremely unstable, it doesn't do any good without lift or something to break a cap.
CINH: Convective inhibition. Usually when you start getting lower than -100 you have issues getting anything going.
0-1km Shear - Like earlier this is your shear in the first kilometer of air, but this isn't storm direction dependant. When you start getting over 100 to 150 in this department you need to start being vigilant.
1km EHI or Energy Helicity Index another way to measure energy/shear. Usually more than 2 or 3 is pretty high.


That's pretty much the main ones without going longer...which I already went a bit too long. We can get more specific about the individual values if more clarification is needed. I went pretty general and with a broad brush on a lot of these. This is mainly to give you an idea of what to look for. The main thing to remember is that so much goes into this, and hopefully this is another example of how much there is, that you can't focus on just a few of these and figure big time storms. Think of it as a recipe. You have to have near perfect amounts of each to get a good tasting soup...otherwise you are just left with a pot full of odd smelling/looking/tasting water.

Thanks for this info. As a scientist in a different field, I enjoy these technical terms and breakdown of the jargon. Keep up the good work!

I actually knew you were going to ask. LOL

Awesome, dude. You rock :) !

Great piece of information. The ingrediants to create events that set off isolated tornado-producing supercells are extremely rare.


One thing to remember if you are new or un rehearsed on severe weather in OK. On a day of forecasted SVR weather I often hear mis informed people question why it is warm and sunny and generally a "great" day the same day that storms are forecasted. The answer is simple, this early day scenario is often two of the important ingrediants to getting sustained severe weather in an area. So next time you wake up and think "gee, it's a beautiful spring day - warm, sunny - weather men wrong again".

For an example - look at how clear the skies are before initiation of multiple supercells that eventually go linear here:

http://www.mesonet.ttu.edu/cases/GrayCountySupercell_051509/vis_sat_loop.GIF

Great piece of information. The ingrediants to create events that set off isolated tornado-producing supercells are extremely rare.


One thing to remember if you are new or un rehearsed on severe weather in OK. On a day of forecasted SVR weather I often hear mis informed people question why it is warm and sunny and generally a "great" day the same day that storms are forecasted. The answer is simple, this early day scenario is often two of the important ingrediants to getting sustained severe weather in an area. So next time you wake up and think "gee, it's a beautiful spring day - warm, sunny - weather men wrong again".



They haven't been introduced to the unofficial weather term "crapvection" either. lol
Here it is used in a sentence:
"Instability will be low this afternoon because of morning crapvection."

They haven't been to introduced unofficial weather term "crapvection" either. lol

Hey now! May 2011 is the first time I used Crapvection here. ;) Yes I really did do a search. haha

http://www.spc.noaa.gov/products/md/mcd0478.gif

MESOSCALE DISCUSSION 0478
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT MON APR 15 2013

AREAS AFFECTED...PARTS OF NORTH CENTRAL TX INTO ERN OK AND NWRN AR

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 151950Z - 152115Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...TSTM DEVELOPMENT IS EXPECTED THIS AFTERNOON ACROSS PART OF
NORTH CENTRAL TX INTO SRN AND ERN OK. SOME OF THESE STORMS WILL BE
CAPABLE OF BECOMING SEVERE WITH ALL SEVERE THREATS POSSIBLE. WHILE
TIMING OF WATCH ISSUANCE REMAINS UNCERTAIN...A WW MAY BE NEEDED
WITHIN THE NEXT COUPLE OF HOURS.

DISCUSSION...EARLY-MID AFTERNOON SURFACE ANALYSES SHOWED A NEARLY
STATIONARY FRONT EXTENDING SWWD FROM NERN OK TO NEAR KMKO...AND 25
NNW KADM WHERE IT INTERSECTED A DRY LINE. THE DRY LINE THEN EXTENDED
SWWD INTO NRN TX TO THE TX BIG COUNTRY WHERE THERE WAS A SECOND
INFLECTION WITH THE DRY LINE EXTENDING MORE SWD ACROSS THE EDWARDS
PLATEAU. LOW LEVEL MOISTENING ACROSS THE WARM SECTOR AND STRONG
SURFACE HEATING FROM THE TX BIG COUNTRY INTO SOUTH CENTRAL OK IS
AIDING IN A MODERATELY UNSTABLE AIR MASS /MLCAPE 1500-2000 J PER
KG/.

VISIBLE SATELLITE IMAGERY SHOWED CU INCREASING IN COVERAGE AND DEPTH
INVOF THE FRONT/DRY LINE INTERSECTION IN SRN OK AND SWWD/SWD ALONG
THE DRY LINE INTO THE TX BIG COUNTRY. FORCING ALOFT MAY INCREASE
SOME AS AN APPARENT MIDLEVEL WIND MAX/JET MOVES FROM FAR W TX INTO
NRN TX LATE THIS AFTERNOON. THIS COMBINED WITH FURTHER SURFACE
HEATING AND INCREASING LOW LEVEL CONVERGENCE ALONG AFOREMENTIONED
BOUNDARIES SUGGESTS SCATTERED TSTM DEVELOPMENT IS PROBABLE.
EFFECTIVE BULK SHEAR OF 35-45 KT IS SUFFICIENT FOR STORM
ORGANIZATION WITH STEEP LAPSE RATES SUPPORTING HAIL AND STRONG
DAMAGING WINDS. LOW LEVEL VERTICALLY VEERING WINDS IN NRN TX WITH
0-3 KM SRH AROUND 200 M2/S2 SUGGESTS A TORNADO THREAT CANNOT BE
RULED OUT.

..PETERS/KERR.. 04/15/2013

Tornado Watch...THIS INCLUDES Southern and Eastern Metro.

WW 108 TORNADO AR OK TX 152040Z - 160400Z
AXIS..70 STATUTE MILES EAST AND WEST OF LINE..
45NW FYV/FAYETTEVILLE AR/ - 20S MWL/MINERAL WELLS TX/ ..AVIATION COORDS.. 60NM E/W /33WNW RZC - 57WSW TTT/ HAIL SURFACE AND ALOFT..2.5 INCHES. WIND GUSTS..60 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 25030.

BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH OUTLINE UPDATE FOR WT 108
NWS STORM PREDICTION CENTER NORMAN OK
340 PM CDT MON APR 15 2013

TORNADO WATCH 108 IS IN EFFECT UNTIL 1100 PM CDT FOR THE
FOLLOWING LOCATIONS

ARC007-015-033-047-087-131-143-160400-
/O.NEW.KWNS.TO.A.0108.130415T2040Z-130416T0400Z/

AR
. ARKANSAS COUNTIES INCLUDED ARE

BENTON CARROLL CRAWFORD
FRANKLIN MADISON SEBASTIAN
WASHINGTON


OKC001-005-013-019-021-023-027-029-041-049-061-063-067-069-077-
079-085-087-091-095-097-099-101-107-111-121-123-125-127-133-135-
137-145-160400-
/O.NEW.KWNS.TO.A.0108.130415T2040Z-130416T0400Z/

OK
. OKLAHOMA COUNTIES INCLUDED ARE

ADAIR ATOKA BRYAN
CARTER CHEROKEE CHOCTAW
CLEVELAND COAL DELAWARE
GARVIN HASKELL HUGHES
JEFFERSON JOHNSTON LATIMER
LE FLORE LOVE MARSHALL
MAYES MCCLAIN MCINTOSH
MURRAY MUSKOGEE OKFUSKEE
OKMULGEE PITTSBURG PONTOTOC
POTTAWATOMIE PUSHMATAHA SEMINOLE
SEQUOYAH STEPHENS WAGONER

http://www.spc.noaa.gov/products/watch/ww0108_radar.gif

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 108
NWS STORM PREDICTION CENTER NORMAN OK
340 PM CDT MON APR 15 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

PART OF NORTHWEST ARKANSAS
PARTS OF SOUTHERN AND EASTERN OKLAHOMA
PART OF NORTH CENTRAL TEXAS TEXAS

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 340 PM UNTIL
1100 PM CDT.

SEVERAL TORNADOES
SCATTERED LARGE HAIL
ISOLATED HAIL TO 2.5 INCHES IN DIAMETER POSSIBLE
WIDELY SCATTERED DAMAGING WINDS TO 70 MPH

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 45 MILES NORTHWEST OF
FAYETTEVILLE ARKANSAS TO 20 MILES SOUTH OF MINERAL WELLS TEXAS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU8).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...SCATTERED INTENSE THUNDERSTORM DEVELOPMENT IS EXPECTED
WITHIN THE NEXT COUPLE OF HOURS...NEAR A SURFACE FRONT AND DRYLINE
ACROSS EASTERN OKLAHOMA INTO NORTH CENTRAL TEXAS...BEFORE SLOWLY
DEVELOPING NORTHEASTWARD THIS EVENING. LARGE HAIL AND LOCALLY
DAMAGING WIND GUSTS MAY BE THE PRIMARY SEVERE WEATHER THREATS
INITIALLY...BUT...BY EARLY EVENING...THE RISK FOR TORNADOES PROBABLY
WILL INCREASE WITH STRONGEST STORMS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 25030.

Initial cell is active now in North Central TX. We'll see how this goes. If the risk gets close to Central OK, I'll bring the chat room up early.

Watch Probability Table...

Tornadoes
Probability of 2 or more tornadoes
Mod (40%)

Probability of 1 or more strong (F2-F5) tornadoes
Low (20%)

Wind
Probability of 10 or more severe wind events
Low (20%)

Probability of 1 or more wind events > 65 knots
Low (20%)

Hail
Probability of 10 or more severe hail events
Mod (40%)

Probability of 1 or more hailstones > 2 inches
Mod (30%)

Combined Severe Hail/Wind
Probability of 6 or more combined severe hail/wind events
High (70%)

Is that just for the cell that popped up or the overall watch for today?

I am surprised the watch was issued so far north, per visible satellite, the boundry is considerably much further south.

Storm trying to go up over southern Seminole County right now. Really nice look towering CU from East Norman. There is an area of convergence that runs through that area up into Cleveland County. Might be why they want further north with the watch.

And the line of cumulus I saw towering as I left work was clearly east and slightly south of the metro

Looking out my office window in DT, I can see the towers off to the east.

Nothing is really able to get going out there. Looking at meso analysis it appears that CIN is still pretty high right in this area, but once you get to Holdenville down to Ada and Ardmore it is all gone.

Seeing some more cloud development over head now here in East Norman. Here are the interesting boundary features on radar.

http://www.weatherspotlight.com/screencap/41513-535.png

Another large batch of CU trying to go up just SE of Norman...probably in the intersection of the boundaries above.

EDIT: The main cell I'm watching appeared to top off for a bit and then the top just blew on it. It is continuing to go up pretty rapidly right now.

Looks like we are starting to get some upper level precip returns on radar now in Pott County. Looking at mesonet and the radar, the boundaries are the stationary front and dryline intersecting. So that is definitely a focal point to watch. Dryline is lift back to the Northwest slightly and the front is moving southwest slightly in that area.

This is going it seems. I can't see the tower that well...stupid tree. :)

http://www.weatherspotlight.com/screencap/ktlx_20130415_2252.png

Storm is intensifying pretty quickly now. Hail up to a half inch nwo possible with it. Don't be shocked to see a warning for Northern Pott and Seminole Counties if trends continue.

More towers going up rapidly now downstream of the initial cell. They are looking very impressive out the window. These are on the dryline, the other cell is ahead of the warm front.

http://www.weatherspotlight.com/screencap/ktlx_20130415_2304.png

First cell is dead, next one up over Tribbey to south of Brooksville. Some small hail possible.

Question for venture or others. How come boundaries can be so clearly defined on radar, but you can't see anything outside or on visible satellite?

Radar is going to pick up on dust, bugs, and other things that will cause some level of reflectivity.

http://www.spc.noaa.gov/products/md/mcd0479.gif
MESOSCALE DISCUSSION 0479
NWS STORM PREDICTION CENTER NORMAN OK
0650 PM CDT MON APR 15 2013

AREAS AFFECTED...NWRN AR...SRN/ERN OK...N-CNTRL TX

CONCERNING...SEVERE THUNDERSTORM WATCH 108...

VALID 152350Z - 160045Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 108
CONTINUES.

SUMMARY...SVR TSTMS CURRENTLY ONGOING ACROSS PORTIONS OF N-CNTRL TX
ARE EXPECTED TO PERSIST FOR THE NEXT FEW HOURS BEFORE THE LOSS OF
HEATING AND INCREASING CINH SLOWLY DIMINISHES THEIR STRENGTH. SOME
ADDITIONAL DEVELOPMENT IS POSSIBLE ACROSS THE WATCH AREA BUT OVERALL
COVERAGE SHOULD REMAIN ISOLATED.

DISCUSSION...TSTMS INITIATED NEAR THE TRIPLE POINT /CURRENTLY OVER
SRN YOUNG COUNTY PER KDYX RADAR IMAGERY/ AND PROGRESSED EWD INTO AN
UNSTABLE AIRMASS. SUPERCELL WITH A HISTORY OF PRODUCING SVR HAIL HAS
DISSIPATED...LIKELY A RESULT OF INCREASING CINH ACROSS THE ERN
PORTIONS OF THE WATCH /WHERE THE BOUNDARY LAYER IS NOT AS DEEPLY
MIXED/. ADDITIONAL DEVELOPMENT ALONG THE OUTFLOW BOUNDARY OF THIS
SUPERCELL CONTINUES TO SUPPORT STRONG TO SVR STORMS ACROSS
JACK...CLAY...MONTAGUE...AND COOKE COUNTIES. THESE STORMS WILL
LIKELY FOLLOW A SIMILAR DIMINISHING TREND TO THE EARLIER SUPERCELL
AS THEY MOVE EWD.

MULTIPLE BOUNDARIES ARE VISIBLE ON KTLX RADAR WITH SOME ATTEMPTS AT
CONVECTIVE INITIATION. EARLIER UPDRAFT ACROSS POTTAWATOMIE COUNTY
HAS DISSIPATED WITH INDICATION THERE IS STILL TOO MUCH CINH. ANOTHER
UPDRAFT IS INCREASING ACROSS THE SRN PORTION OF THE COUNTY WHERE
RADAR IMAGERY CONFIRMS CONTINUED BOUNDARY INTERSECTION.

ADDITIONAL DEVELOPMENT REMAINS POSSIBLE...PARTICULARLY ALONG
BOUNDARY INTERSECTIONS...BUT MESOANALYSIS REVEALS MLCINH ACROSS MUCH
OF THE WATCH AREA AND OVERALL TSTM COVERAGE WILL BE LIMITED.

..MOSIER.. 04/15/2013

Another futile attempt at storm development. New cell just east of Purcell trying.

Storm to the east of Slaughterville south of Etowah has has up to 1.11" with it now. This is the best any storm has done so far.

Seeing several more cells pop up now behind this main cell that is increasing.

http://www.weatherspotlight.com/screencap/ktlx_20130416_0041.png

Oh, dear, just realized I think my daughter is going to that this week. But I don't think she said Stillwater... * sigh *

*Hate* springtime storm season. Hate it. Lived here 47.9 of my 48 years, love Oklahoma to pieces, but *hate* severe storm season.

Vocal or instrumental? Vocal is in Shawnee, instrumental (both strings and winds/percussion) are in Stilly. Either way, congrats to her! We'll just hope that it will hold off to the evening, as these storms so often do around here. My kids don't play until 3-5pm, so we're going to be home way later than usual, which makes me nervous. SO glad I'm going to be in a rental van ::sarcasm:: Good thing for that extra insurance I'll now be purchasing. And good thing (no sarcasm) for having smartphones with GPS and radar capabilities.

#OUN (https://twitter.com/search?q=%23OUN&src=hash) issues Severe Thunderstorm Warning for Pottawatomie [OK] till 8:30 PM CDT

Developing cell behind the severe garbage between Dibble and Purcell moving NE and might skirt far eastern Norman (Lake T-Bird area). The main severe garbage appears to have some stronger winds near St. Louis moving towards Maud.

New Warning...

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A


* SEVERE THUNDERSTORM WARNING FOR...
SOUTHEASTERN POTTAWATOMIE COUNTY IN CENTRAL OKLAHOMA...
SEMINOLE COUNTY IN EAST CENTRAL OKLAHOMA...


* UNTIL 900 PM CDT


* AT 820 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM LOCATED NEAR MAUD...MOVING EAST AT 30 MPH.

HAZARDS IN THE WARNING INCLUDE...
HALF DOLLAR SIZE HAIL...
DAMAGING WINDS IN EXCESS OF 60 MPH...

* LOCATIONS IMPACTED INCLUDE...
SEMINOLE...WEWOKA...MAUD...EARLSBORO...BOWLEGS...S T. LOUIS...
BROOKSVILLE...LITTLE...LIMA AND HARJO.

Okay the storm approach Seminole is getting more interesting. It definitely has an inflow notch area/hook on the south side. There is also a gust front extending from the southern tip of the storm and arcing back to the South and Southwest. Max hail now up to 1.62". Strong winds appear to be increasing. Nice, what could be an overshooting top, appearing on the 3D radar imagery.

http://www.weatherspotlight.com/screencap/ktlx_20130416_0125.png

I'm no expert, but I'm seeing a hook and it's turning more easterly...

If the 00z NAM has anything to do with it there will be no mdt or high risk in OKC on Wednesday -- but it seems to be the outlier at this point in terms of location of the CF.

If the 00z NAM has anything to do with it there will be no mdt or high risk in OKC on Wednesday -- but it seems to be the outlier at this point in terms of location of the CF.

Ehhh. It has the front right on the NW side of OKC, so it'll be a tight gradient in the risk area. The front also don't move much at all so that could make it a focal point for continued regeneration until it blasts through as a cold front. At this point I'm more concerned about on going convection or early initiation to make it extremely complicated.

I'll wait to see what the 06Z and 12Z runs look like as well before adjusting my thinking on this. GFS and ECMWF have been the preferred solutions for Wednesday.

If the 00z NAM has anything to do with it there will be no mdt or high risk in OKC on Wednesday -- but it seems to be the outlier at this point in terms of location of the CF.

I sure hope the NAM is right!

I sure hope the NAM is right!

If we want to nit pick every new model run that comes out its probably ever so slightly more north and west than the last run. lol

00Z GFS stays the course with front placements.

New Day 2 Outlook continues Moderate Risk

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1215 AM CDT TUE APR 16 2013

VALID 171200Z - 181200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS OK INTO EXTREME SERN KS...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM WCNTRL TX TO IL...

...SRN PLAINS TO MID MS VALLEY...

SIGNIFICANT LARGE SCALE DIFFLUENCE IS EXPECTED TO OVERSPREAD THE SRN PLAINS WEDNESDAY AS UPPER TROUGH SHIFTS INTO THE ROCKIES. MODELS CONTINUE TO SUGGEST A CORRIDOR OF 500MB FLOW IN EXCESS OF 50KT WILL SPREAD ACROSS A MOISTENING WARM SECTOR THAT SHOULD BECOME QUITE UNSTABLE BY MID DAY. INCREASING LARGE SCALE ASCENT AND FAVORABLE BUOYANCY SUGGEST A CONSIDERABLE AMOUNT OF CONVECTION WILL ULTIMATELY EVOLVE ACROSS THE BODY OF OK...NEWD INTO THE MID MS VALLEY...MUCH OF IT POTENTIALLY SEVERE.

AS UPPER TROUGH APPROACHES THE SRN PLAINS THERE IS REASON TO BELIEVE EARLY FRONTAL SURGE WILL STALL NEAR THE RED RIVER THEN ADVANCE NWD AS A WARM FRONT DURING THE DAY2 PERIOD. THERE IS SOME UNCERTAINTY HOW FAR NORTH THIS BOUNDARY WILL RETREAT WITH THE GFS THE MOST AGGRESSIVE ALLOWING WARM FRONT TO ULTIMATELY REACH THE I-70 CORRIDOR ACROSS KS. WHILE THIS MODEL HAS CONSISTENTLY FORECAST THIS SCENARIO CURRENT AIRMASS ACROSS THE CNTRL PLAINS IS DISTURBINGLY COLD AND ANY WARM ADVECTION PRECIPITATION ACROSS KS DURING THE DAY1 PERIOD MAY PREVENT THE WARM SECTOR FROM ADVANCING NORTH OF THE OK BORDER. BOTH THE NAM AND ECMWF MAINTAIN A MORE SLY POSITION AND FOR THIS REASON HAVE OPTED TO PERPETUATE ENHANCED SEVERE RISK PRIMARILY ACROSS OK WITH PERHAPS A NEED TO EXTEND HIGHER PROBS INTO PORTIONS OF NWRN TX.

LATEST THINKING IS LOW LEVEL WARM ADVECTION WILL LIKELY AID EARLY MORNING ELEVATED TSTMS...POSSIBLY SEVERE...ACROSS KS INTO NRN MO. DIURNAL HEATING ACROSS THE WARM SECTOR WILL CONTRIBUTE TO DESTABILIZATION AS FAIRLY MOIST LOW LEVELS...DEW POINTS WELL INTO THE 60S...CONTRIBUTE TO SBCAPE IN EXCESS OF 2000 J/KG. STRONGEST HEATING IS EXPECTED ALONG DRYLINE WHICH SHOULD ESTABLISH ITSELF OVER WRN OK/NWRN TX AND INSTABILITY JUST EAST OF THIS BOUNDARY SHOULD APPROACH 3000 J/KG. GFS FORECAST SOUNDINGS ARE QUITE IMPRESSIVE NEAR THE DRYLINE WITH STRONG VEERING WIND PROFILES WITH HEIGHT AND LOW LCLS. IF WARM FRONT INDEED RETREATS TOWARD THE KS BORDER DISCRETE SUPERCELLS SHOULD EVOLVE ALONG THE DRYLINE WHICH SHOULD TRACK ENEWD INTO THE BODY OF OK. REGARDLESS...INCREASING DIFFLUENCE ALOFT WILL CONTRIBUTE TO NUMEROUS TSTMS INTO THE OVERNIGHT HOURS AIDED BY 50-60KT SLY LLJ.

AN EXTENSIVE CORRIDOR OF FRONTAL CONVECTION IS EXPECTED TO EXTEND NEWD ACROSS SERN KS/MO INTO PORTIONS OF WCNTRL IL. THIS ACTIVITY SHOULD BE WELL ORGANIZED ALONG THE WIND SHIFT BY LATE EVENING BEFORE ADVANCING DOWNSTREAM WITH PROGRESSIVE BOUNDARY.

LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES ARE POSSIBLE ACROSS THE SEVERE RISK REGION...ESPECIALLY OK INTO PORTIONS OF NWRN TX.

..DARROW.. 04/16/2013

http://www.spc.noaa.gov/products/outlook/day2probotlk_0600_any.gif

Model Preference Discussion from HPC...now WPC.

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1221 AM EDT TUE APR 16 2013

VALID APR 16/0000 UTC THRU APR 19/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES...

ANY NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR
SHORT RANGE FORECASTS.

DEEP CYCLONE DEVELOPING IN THE MIDWEST/PLAINS THU INTO FRI...
WEAK FRONTAL WAVE RIPPLING THROUGH MICHIGAN THURSDAY...
PREFERENCE: 00Z GFS WITH A DASH OF 12Z CANADIAN LATE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GUIDANCE SHOWS ISSUES WITH THE FIRST WAVE MOVING THROUGH
MICHIGAN THURSDAY, WITH THE 12Z UKMET AND 00Z NAM TRACKING THE
SYSTEM MORE EASTWARD DUE TO THEIR STRONGER NORTHERN STREAM
SHORTWAVE IN CANADA WHICH FLATTENS THE TOP OF THE BROAD/STRONG
MID-LEVEL RIDGE -- A MODEL BIAS OCCASIONALLY SEEN IN ALL THE
GUIDANCE. WITH THIS FIRST SYSTEM, A COMPROMISE OF THE 00Z GFS/21Z
SREF MEAN LOOKS IDEAL AND HAS THE GREATEST 12Z GLOBAL ENSEMBLE
SUPPORT.

WITH THE MAIN EVENT -- THE DEEP CYCLONE FORMING IN THE MIDWEST
THURSDAY INTO FRIDAY -- THE 12Z UKMET REMAINS ON THE
SLOW/AMPLIFIED END OF THE GUIDANCE. WHEREAS SUNDAY IT HAD NO 12Z
GLOBAL ENSEMBLE SUPPORT, IT HAS PICKED UP THE SUPPORT OF ONE-TENTH
OF THE GLOBAL ENSEMBLE GUIDANCE ON THE MONDAY 12Z RUN, WHICH IS
NOT ENOUGH TO BELIEVE QUITE YET. DUE TO THE DISTANCE BETWEEN THE
NORTHERN STREAM SHORTWAVE IN SOUTHERN CANADA AND THE ENERGY IN THE
PLAINS/MIDWEST, A CLOSED CYCLONE MAKES SENSE, THOUGH THERE REMAINS
A BIT OF SPREAD WITH THE 00Z NAM THE FARTHEST SOUTH (THOUGH IT
DOES LIE WITHIN THE 12Z GLOBAL ENSEMBLE SPREAD USING THE 5400
METER 500 HPA HEIGHT LINE AS A GUIDE). THE 12Z ECMWF AND ITS
ENSEMBLE MEAN, ALONG WITH THE 21Z SREF MEAN APPEAR TO PLACE TOO
MUCH DISTANCE BETWEEN THE MID-LEVEL CYCLONE AND THE SURFACE
REFLECTION OF THE FEATURE, SO WILL NOT CONSIDER THEM CONTENDERS.
A SOLUTION ON THE SOUTHWEST CORNER OF THE BEST GLOBAL ENSEMBLE
CLUSTERING APPEARS BEST HERE, IN CASE THE GUIDANCE CLOSES OFF THE
SYSTEM SOONER ON LATER RUNS. THIS LEADS TO A 00Z GFS/12Z CANADIAN
COMPROMISE, WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE CONSIDERING THE
GOOD DAY-TO-DAY CONTINUITY IN THIS IDEA AND PREFERENCE AND THE
SYSTEM'S AMPLIFIED NATURE.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE APR 16 2013

VALID 161200Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
PLAINS TO THE OH/TN VALLEYS...

...SYNOPSIS...
GRADUAL LARGE SCALE PATTERN AMPLIFICATION WILL CONTINUE TO OCCUR
THROUGH THE PERIOD...HIGHLIGHTED BY AN INCREASINGLY PROMINENT
WESTERN STATES LONGWAVE TROUGH AND PHASING POLAR/SUBTROPICAL JETS
OVER THE SOUTHWEST DESERTS/FAR NORTHERN MEXICO INTO TONIGHT. TSTM
POTENTIAL /INCLUDING SOME SEVERE/ WILL GENERALLY BE FOCUSED ALONG AN
EAST-SOUTHEASTWARD MOVING COLD FRONT ACROSS THE OH VALLEY...WITH A
SLOW-MOVING/STALLED PORTION OF THE FRONT EXTENDING SOUTHWESTWARD
ACROSS THE OZARKS INTO THE SOUTHERN HIGH PLAINS INCLUDING NORTHWEST
TX.

...MIDDLE MS AND OH/TN RIVER VALLEYS...
SCATTERED CONVECTION WILL BE ONGOING THIS MORNING ALONG/IMMEDIATELY
NORTH OF A COLD FRONT ACROSS THE MIDDLE MS VALLEY/MIDWEST.
RELATIVELY LITTLE IF ANY SEVERE POTENTIAL IS EXPECTED DURING THE
MORNING HOURS...BUT TSTMS SHOULD DIURNALLY INTENSIFY ALONG THE COLD
FRONT AS IT CONTINUES A SLOW BUT STEADY EAST-SOUTHEASTWARD
PROGRESSION THIS AFTERNOON ACROSS THE OH VALLEY. AROUND 60/LOWER 60S
F SURFACE DEWPOINTS WILL BECOME INCREASINGLY PREVALENT WITHIN THE
WARM SECTOR...WITH MODERATE INSTABILITY/WEAK INHIBITION EXPECTED BY
EARLY/MID AFTERNOON. IN SPITE OF MID-LEVEL HEIGHT RISES...MODERATE
SHEAR WILL COINCIDE WITH THE FRONTAL ZONE...SUCH THAT
SEMI-ORGANIZED/SUSTAINED TSTMS ARE EXPECTED. CONVECTIVE
LIKELIHOOD/CONFIDENCE IS NOT PARTICULARLY HIGH FARTHER SOUTH ACROSS
THE TN VALLEY...BUT AT LEAST ISOLATED SEVERE TSTMS MAY BE
POSSIBLE...PERHAPS AIDED BY A MID/HIGH LEVEL JET STREAK AND/OR WEAK
LOW LEVEL CONFLUENCE. IN ALL...ISOLATED BOUTS OF DAMAGING WIND MAY
BE THE PRIMARY RISK ACROSS THE REGION...WITH MARGINALLY SEVERE HAIL
POSSIBLE AS WELL.

...SOUTHERN HIGH PLAINS LATE AFTERNOON/EARLY EVENING...
BACKGROUND FORCING FOR ASCENT WILL BE WEAK AT BEST WITH NEAR-NEUTRAL
HEIGHT TENDENCIES THROUGH PEAK HEATING. EVEN SO...AMPLE HEATING
SHOULD OCCUR ACROSS THE SOUTHERN HIGH PLAINS INCLUDING PORTIONS OF
WEST/NORTHWEST TX...WITH AT LEAST MODEST MASS CONVERGENCE NEAR AT
LEAST A LOOSE ARCING FRONTAL BOUNDARY/WEAK SURFACE LOW/DRYLINE
INDUCED TRIPLE POINT. ALONG WITH A RELATIVELY MOIST AIRMASS /LOWER
60S F SURFACE DEWPOINTS/...THESE FACTORS SHOULD BE SUFFICIENT FOR
ISOLATED/WIDELY SCATTERED TSTM DEVELOPMENT LATE THIS AFTERNOON/EARLY
EVENING...MOST PROBABLE ACROSS THE LOW ROLLING PLAINS OF TX.

IF/WHERE STORMS DO DEVELOP THROUGH LATE AFTERNOON/EARLY
EVENING...VEERING WIND PROFILES/40+ MID-LEVEL SOUTHWESTERLIES WILL
BE MORE THAN ADEQUATE FOR A FEW SUSTAINED SUPERCELLS GIVEN THE
DEGREE OF INSTABILITY /2000+ J PER KG MLCAPE/. LARGE HAIL WILL BE
THE PRIMARY HAZARD...BUT SOME TORNADO THREAT MIGHT EXIST AS WELL
IMMEDIATELY NEAR THE TRIPLE POINT/ARCING SYNOPTIC FRONTAL BOUNDARY.

...SOUTH-CENTRAL PLAINS TO LOWER MO VALLEY/MIDWEST TONIGHT...
ALTHOUGH SPATIAL VARIABILITY IS CONSIDERABLE WITH RESPECT TO
SHORT-TERM NUMERICAL GUIDANCE DETAILS...IT DOES SEEM LIKELY THAT
STORMS WILL NOCTURNALLY INCREASE AND EXPAND EAST-NORTHEASTWARD
ACROSS THE SOUTH-CENTRAL PLAINS TO OZARKS/LOWER MO VALLEY TONIGHT.
THIS WOULD BE WILL BE AS SOUTH-SOUTHWESTERLY LOW LEVEL JET
STRENGTHENS/VEERS...WITH ASSOCIATED WARM/MOIST ADVECTION ABOVE A
SHALLOW COOL/STABLE LAYER. COMBINATION OF MODERATE ELEVATED
INSTABILITY/STRONG EFFECTIVE SHEAR WILL BE FAVORABLE FOR BOUTS OF
LARGE HAIL INTO THE OVERNIGHT HOURS. WHILE GUIDANCE VARIABILITY
/UNCERTAIN SPATIAL DETAILS/ PRECLUDES SUCH AT THIS TIME...HIGHER
PROBABILITIES /SUCH AS A 30 PERCENT HAIL AND-OR SIG HAIL/ MAY
ULTIMATELY BE WARRANTED.

http://www.spc.noaa.gov/products/outlook/day1otlk_1200.gif

Well 12Z runs covering tomorrow are in, will do a full write up a bit later. Just wanted to get out there that there is plenty of consistency in the GFS still. So we'll see if it verifies. NAM is still the outlier keeping the front around the I-44 corridor throughout the event, versus GFS and others pulling it much further north. Forecast discussion will focus on GFS.

hmm weather.com is giving us a TOR CON value of 5. It should be interesting to see what happens tomorrow and when the cold front arrives

Guess I better put the top back up on the Jeep.

SPC has trimmed the slight risk for today pretty substantially. OK is no longer included.

This is due to the thick, low hanging clouds we have around at this time that are aiding in the cooler temperatures.