Severe Weather - Apr 25 (Sat)

[venture]

Just doing the weekend in this post. Monday will have another risk, but will leave it to then...as well as the rest of next week.

Initial Discussion

A strong cold front will be dipping into NW Oklahoma throughout the day, as well as a dryline from NW OK through the NW Texas Panhandle into NM. Deep moisture has returned from the Gulf with dewpoints well into the mid 60s in a lot of locations. Some heating is also taking place out west this morning with partly cloudy skies. Current short term model guidance points to development during the mid to late afternoon today in NW Oklahoma. Most of the activity looks like it will be from I-40 North until it potentially consolidates until a compacted area of thunderstorms that will move east later tonight across Central Oklahoma. For SW Oklahoma, there will be less forcing in this area for most of the day due to the dryline being pretty far west. It looks like it may make a run for the state line this evening which should spark a few storms along it. Either way, the majority of the area today will be very unstable with CAPE values from 2000-4000 j/kg and LI numbers in the -4 to -9 range. Helicity values also appears to be reasonably high across western OK today, which will lead to a isolated tornado threat.

Primary Threats
Tornado: Moderate - 15% chance with in 25 miles of any given point in Western OK.
Hail: Very High - 45% chance with in 25 miles of any given point in Western OK of hail greater than 1", with a 10% or higher prop that hail will get over 2".
Wind: Moderate - 15% chance with in 25 miles of any given point in the Western half of OK of winds over 57 mph.

Will post more through out the day and add a discussion for tomorrow as well.

Day 1 Severe Weather Outlook: Storm Prediction Center Apr 25, 2009 1300 UTC Day 1 Convective Outlook

Day 2 Severe Weather Outlook: Storm Prediction Center Apr 25, 2009 0600 UTC Day 2 Convective Outlook

Real Time Weather Information

Satellite Image (1KM)


NEXRAD Mosaic Radar


Oklahoma Mesonet Current Conditions (red air temp, green dewpoint)

[Thunder]

I love reading Venture's posts on weather.

I just hate it when clouds want to stick around before all the action.

[Charlie40]

Latest data is now pointing to the front pushing further into oklahoma than earlier expected. The triple point should now be focused just west of OKC so the higher severe threat will most likely be farther south than earlier predicted and include the okc metro and surrounding areas.

[PennyQuilts]

I also love these reports.

[Thunder]

Wow! Now, we look at the threat being pushed further south than earlier predicted, then all of the metro area should definately be on alert, because the storms can still hold together as they travel E/NE.

[Jon27]

You know what's funny. I was talking to my wife last night about what the weather will do this weekend. I said to her "I bet venture will have a forecast up in the morning that I can check." I think venture should be the official OKCTalk weatherman.

Thanks for what you do venture.

[westsidesooner]

You know what's funny. I was talking to my wife last night about what the weather will do this weekend. I said to her "I bet venture will have a forecast up in the morning that I can check." I tenture should be the official OKCTalk weatherman.

Thanks for what you do venture.

I'll second the nomination for Venture. And Charlie is right the cold front is moving further south than expected so far. Its now from about AMA to Woodward and still moving south. It should stall soon however. The clearing line is moving into western Oklahoma ATTM so it should start to warm up quickly. It cold be a very dangerous day for parts of the state. The storms should start mid to late afternoon and quickly become tornadic. Strong Tornadoes are very possible especially after dark this evening, so everyone keep your heads up. And stay safe.

For anyone interested there will be a storm chasing frenzy in western Oklahoma today. These sites have been posted here before but here they are again in case anyone missed them.

http://www.tornadovideos.net/full-sc...aser-video.php

TwisterChasersLive

Live Storm Chase Video Network | SevereStudios.com

[Charlie40]

Moderate Risk already posted for Sunday This includes central Oklahoma also. This could be upgraded to possibly a High Risk tomorrow if things come together right we could be looking at a tornado outbreak for tomorrow and also large hail is a pretty good bet as well baseball or larger. Stay weather aware today and tomorrow for sure.

[venture]

MESOSCALE DISCUSSION 0562
NWS STORM PREDICTION CENTER NORMAN OK
0127 PM CDT SAT APR 25 2009

AREAS AFFECTED...SOUTHEAST TX PANHANDLE...WESTERN OK...SOUTH CENTRAL
KS

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 251827Z - 252100Z

CORRECTED FOR INTERSTATE NUMBER

A TORNADO WATCH WILL BE REQUIRED BEFORE 22Z.

IN WAKE OF A LEAD DISTURBANCE MOVING ACROSS THE CENTRAL
PLAINS...SATELLITE SUGGESTS WEAK RIDGING RAPIDLY TRANSLATING OUT OF
NM. BACK EDGE OF THE LARGE SCALE RIDGING IS EXTRAPOLATED TO CLEAR
THE SOUTHERN HIGH PLAINS 21-22Z WITH INCREASING LARGE SCALE ASCENT
THEREAFTER.

COLD FRONT HAS ESSENTIALLY STALLED FROM NORTHWEST OF
WICHITA-WOODWARD-AMARILLO WITH THE DRYLINE BEGINNING TO MIX EAST
ALONG THE I-27 CORRIDOR. CLEARING NORTH OF THE FRONT MAY SIGNAL
THAT THE BOUNDARY WILL MOVE SLIGHTLY NORTHWEST THROUGH LATE
AFTERNOON AS THE DRYLINE MIXES INTO THE SOUTHEAST TX PANHANDLE.

THUNDERSTORM INITIATION SHOULD TAKE PLACE AROUND 22Z ALONG THE
DRYLINE/FRONT OVER THE SOUTHEAST TX PANHANDLE INTO SOUTH-CENTRAL
KS...THEN BUILD SOUTHWARD ALONG THE DRYLINE TOWARD CHILDRESS 22-00Z.
MLCAPES WILL RANGE 2000-2500 J/KG.

SOMEWHAT ANEMIC VERTICAL SHEAR PROFILES NOTED CURRENTLY SHOULD
IMPROVE BY INITIATION TIME AS STRONGER SOUTHWESTERLY MID-LEVEL WINDS
OVER THE SOUTHERN ROCKIES EDGE SOUTHEASTWARD. WIND PROFILES WILL
BECOME VERY CONDUCIVE FOR SUPERCELLS WITH GIANT HAIL GREATER THAN 2
INCHES IN DIAMETER. IN FACT...AS THE GREAT BASIN UPPER TROUGH
CONTINUES TOWARD THE SOUTHERN ROCKIES...SOUTHERLY BOUNDARY LAYER
FLOW IS EXPECTED TO INCREASE TO OVER 55 KTS DURING THE EVENING.
THIS WILL NOT ONLY MAINTAIN DISCRETE SUPERCELL STRUCTURES AS RICH
MOISTURE INFLOW CONTINUES...BUT ALSO BOOST 0-1KM STORM RELATIVE
HELICITY TO AT OR ABOVE 400 M2/S2. THIS WILL LIKELY YIELD
LONG-LIVED SUPERCELLS WITH POSSIBLE STRONG TORNADOES WHICH MAY LAST
WELL BEYOND SUNSET ACROSS WEST-CENTRAL/ NORTH-CENTRAL OK INTO
SOUTH-CENTRAL KS.

..RACY.. 04/25/2009


ATTN...WFO...ICT...OUN...DDC...LUB...AMA...

[venture]

Strongly worded MCD from the SPC. This is definitely going to be a serious situation out west. Short term models are showing development to occur anytime between now and 5PM. Moisture convergence is pretty strong right now in NW OK, but is showing signs of increase farther south. There is still some inhibition left in the atmosphere, but again this will fade as instabilities increase.

Eastward extent is questionable right now, but wouldn't be shocked to see OKC included in the risk area before too long.

[Thunder]

Venture, can you tell us the estimate speed movement of the storms that do develop? I also wonder if the high south wind will play a factor in shoving these storms into a squall line again.

[Thunder]

Quote from KOCO's Andy

We’ve focused so much on the tornadoes that I feel the need to re-emphasize hail. Any of these storms will have the potential to produce damaging hail. Clean the garage out so you can put the car in. Even in central Oklahoma, clean it out today in case you have to put it in there tomorrow.

Today will be the day if anyone have their garage cluttered. Start cleaning them out, put them inside or out back in the shed/barn. Make room for that xtra car to put in the garage.

Also, if a neighbor have a carport, discuss with them if it is okay to borrow the space for the car, if they are not using it (car in garage) or if they do not plan to be home during specific time.

[Thunder]

Venture, the radar is showing spotty development in the metro, but light. Are these only echos of the moisture in the air or an actual early development stage?

[Karried]

I don't see any watches or warnings..

What's happening Venture?!!!

[venture]

Looks like from the morning profiler, we would have storm motion from 250 degrees or ENE at around 25 mph. If the storms don't root down, they'll move a lot faster than that and more NE.

Anything around us is from the high moisture content in the air. Don't worry. We are going to have two areas of development. 1) Along the front to the NW and 2) in SW OK along the TX line.

Karrie - can you edit the topic for this thread to just have today's date. I'm going to do a second one for tomorrow due to the serious nature of having a tornado outbreak impacting the metro tomorrow.

[Thunder]

I don't see any watches or warnings..

What's happening Venture?!!!

I am wondering about that myself.

I've seen watches posted way early with a lot less chance to be severe. Now, look at today, they are taking forever to post watches. The chances is there, it's all real, they must be posting watches in advance before people start making plans and going out.

[venture]

On set of activity is planned for around 5PM, they'll probably put the tornado watch up anytime from now until 4PM.

[Karried]

Well, my youngest is going (without us) to see the Lion King with neighbors tonight... should I be worried?

I hate when we're not together when storms are approaching.

[Charlie40]

Tornado Watch should be posted for western/NW Oklahoma by or before 5 pm, it is possible that this may be issued as a PDS Watch stay tuned.

[venture]

Update on SPC's new outlook...

...LATEST THINKING FOR SRN KS/OK...
ALTHOUGH SOME QUESTION REMAINS CONCERNING THE EXACT TIMING OF INITIATION...THUNDERSTORMS MAY INITIATE IN THE 22 TO 23Z TIMEFRAME ACROSS THE ERN TX PANHANDLE WITH SUPERCELLS MOVING INTO FAR WRN OK ALONG A FRONTAL BOUNDARY LOCATED FROM NEAR ALVA OK SWWD TO THE SERN TX PANHANDLE. THIS IS SUPPORTED BY THE LATEST 12Z HIGH RES NMM MODEL WHICH THEN INITIATES STORMS WITH LARGE HAIL AND WIND DAMAGE POTENTIAL ACROSS SRN AND ERN KS. THE THINKING CONTINUES THAT SUPERCELLS WITH VERY LARGE HAIL ARE LIKELY WITH AN ISOLATED STRONG TORNADO POSSIBLE IN WRN OK ESPECIALLY AS THE LOW-LEVEL JET CRANKS UP JUST AFTER DARK.

...CHANGES TO THE OUTLOOK...
THE GREATEST CHANGE TO THE OUTLOOK IS TO EXTEND THE 5 PERCENT TORNADO PROBABILITY INTO NERN KS AND 10 PERCENT TORNADO PROBABILITY NEWD ACROSS THE SRN KS WHERE MODERATE INSTABILITY AND LOW-LEVEL SHEAR WILL BE FAVORABLE FOR A FEW TORNADOES WITH SUPERCELLS THAT INITIATE LATE THIS AFTERNOON OR EARLY THIS EVENING. OTHER MINOR CHANGES INCLUDE BETTER ALIGNING THE MODERATE AND SLIGHT RISK TO THE LATEST SFC ANALYSIS...SHORT-TERM THUNDER GUIDANCE AND INITIALIZED RUC FIELDS. THIS CUTS SOME OF NRN LOWER MI OUT OF THE SLIGHT...ADDED PART OF NRN KS INTO THE SLIGHT AND MOVED THE 5 PERCENT HAIL AND WIND PROBABILITIES WWD INTO AREAS SOUTH OF MIDLAND TX. ANOTHER CHANGE IS TO NARROW THE 5 PERCENT PROBABILITY ACROSS NE TX AND THE ARKLATEX TO FAVOR THE MOST LIKELY STORM INITIATION AND GREATEST COMBINATION OF INSTABILITY AND VERTICAL SHEAR. ALSO EXTENDED THE 5 PERCENT HAIL AND WIND PROBABILITIES NEWD ACROSS SRN MD WHERE THE COMBINATION OF SHEAR AND INSTABILITY APPEARS FAVORABLE FOR A MARGINAL SEVERE THREAT IF STORMS CAN INITIATE.

[venture]

Well, my youngest is going (without us) to see the Lion King with neighbors tonight... should I be worried?

I hate when we're not together when storms are approaching.

If they have a cell phone on them, have them keep it handy. Guidance is suggesting these will move north of the Metro, but things can change. Considering the dynamics available today, we'll have a few discrete supercells that usually have a tendency to hang a right and move more east than the current flow of storms.

[venture]

Tornado Watch until 11PM coming out now.

Edit 339PM:
WW 183 TORNADO KS OK TX 252040Z - 260400Z
AXIS..75 STATUTE MILES NORTH AND SOUTH OF LINE..
60NNW CDS/CHILDRESS TX/ - 40SE TOP/TOPEKA KS/ ..AVIATION COORDS.. 65NM N/S /47E AMA - 37NW BUM/ HAIL SURFACE AND ALOFT..3 INCHES. WIND GUSTS..70 KNOTS.

Edit 341PM:
TORNADO WATCH PROBABILITIES FOR WT 0183
NWS STORM PREDICTION CENTER NORMAN OK
0339 PM CDT SAT APR 25 2009

WT 0183
PROBABILITY TABLE:
PROB OF 2 OR MORE TORNADOES : 70%
PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 30%
PROB OF 10 OR MORE SEVERE WIND EVENTS : 50%
PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 40%
PROB OF 10 OR MORE SEVERE HAIL EVENTS : 90%
PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : 70%
PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : >95%

&&
ATTRIBUTE TABLE:
MAX HAIL /INCHES/ : 3.0
MAX WIND GUSTS SURFACE /KNOTS/ : 70
MAX TOPS /X 100 FEET/ : 550
MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 24030
PARTICULARLY DANGEROUS SITUATION : NO

EDIT 341PM:
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 183
NWS STORM PREDICTION CENTER NORMAN OK
340 PM CDT SAT APR 25 2009

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

PARTS OF SOUTHERN AND EASTERN KANSAS
PARTS OF NORTHERN AND WESTERN OKLAHOMA
PARTS OF EASTERN TEXAS PAN HANDLE

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

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 60 MILES NORTH NORTHWEST OF CHILDRESS TEXAS TO 40 MILES SOUTHEAST OF TOPEKA KANSAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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.

OTHER WATCH INFORMATION...CONTINUE...WW 182...

DISCUSSION...SEVERE THUNDERSTORMS EXPECTED TO DEVELOP RAPIDLY ALONG NEARLY STALLED FRONTAL ZONE FROM NEAR EMP SWWD TO S OF AMA. WITH MLCAPES ABOVE 2500 J/KG AND VEERING SHEAR PROFILES IN PLACE...SUPERCELLS SHOULD BE THE PRIMARY MODE INTO THE EVENING. VERY LARGE HAIL GIVEN THE STEEP LAPSE RATES AND INSTABILITY IS EXPECTED WITH TORNADOES BECOMING AN INCREASED THREAT WITH ANY SUPERCELL THRU THE EVENING AS LOW LEVEL JET INCREASES AND BACKS AHEAD OF STRONG TROUGH APPROACHING FROM THE SRN ROCKIES.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 24030.

[venture]

Couple areas I am watching right now. Strong tower cumulus (TCU) developing in Wa****a/Caddo counties right now. As I'm typing this a weak radar echo as appeared. Another batch of TCU is in Major and Alfalfa counties. Decent CU field is spread out through the rest of W and SW Oklahoma, but there is little right now back along the dryline. This would tend to signal moisture isn't as deep there so the dryline should continue to mix east pretty well.

[venture]

Mesoscale discussion 0565
nws storm prediction center norman ok
0349 pm cdt sat apr 25 2009

areas affected...eastern tx panhandle...western ok and south-central ks

concerning...severe potential...tornado watch likely

valid 252049z - 252245z

update to earlier discussion.

Radar/satellite indicate the stalled front has begun a very slow retreat nwd through the tx panhandle and northwest ok while the dryline was mixing ewd to armstrong to crosby counties in tx.
Towering cu was bubbling at the intersection of the two over southwest gray county tx...in the free warm sector over wcentral ok and northeast along the front.

Larger scale ascent will improve after 22z in wake of the earlier disturbance moving into eastern ks per water vapor imagery. This will act to deepen the dryline/frontal circulation and initiation still looks to be across the eastern tx panhandle...northeast along the front into west-central/northwest ok in an hour or two /aside from activity developing in cntrl/ern ks/. Modifying the 20z norman sounding for a 88/58 air parcel suggests very little cap and mlcapes of over 2000 j/kg. Corridor from jericho-turkey tx northeast across erick...elk city...clinton...watonga and enid north to just nw of the front will have the highest severe probabilities through early evening.

[Luke]

Thanks so much for doing this for us. I feel like we get a behind the scenes look at the weather. Very interesting. Keep it up!