General Weather Discussion - April 2014

[OkieHornet]

duly noted. will have my phone with me and be keeping an eye on the sky.

[bchris02]

I added some emphasis and it appears SPC is starting to hint at what some of us starting to pick up on. It doesn't happen often, but we might be looking at a nighttime event. Not locked in at all. A lot of things still have to come together. Moisture needs to be rich and get in place. Initiation has to be well underway before the dryline retreats and storms established. Among other things. Depending on which model solution works out, storm coverage - as mentioned earlier - could increase as the night goes on which means the risk will remain. This possibly won't be a situation where the threat ends shortly after the sun goes down. Get the coffee ready...

How much of a punch do you see these storms having when they move into the metro overnight Saturday? From what I've seen there won't be much of a tornado risk but very large hail and damaging winds appear to be a threat.

[LocoAko]

How much of a punch do you see these storms having when they move into the metro overnight Saturday? From what I've seen there won't be much of a tornado risk but very large hail and damaging winds appear to be a threat.

I'd say that's probably true, particularly with regard to hail.

[Anonymous.]

60 and 70s dewpoints coming up in south TX today, should be streaming into OK tomorrow morning and afternoon.

Still a question of whether the dryline fires or not, but I think it will. I think we could have several supercells ongoing in W/SW OK as the sun sets. These cells could be carried in towards C OK as the night progresss and this is where we could have a time window of enhanced tornado potential (definite hail if they stay together). Then late in the night/early AM, the cold front should blast through with a line of storms regardless of what happened earlier, and sweep through most of OK. I think all this could be out of here by sunrise on Sunday. Tomorrow night will be nowcast situation if storms pop, if not - it will likely just be a heavy thunderstorm in a linear fashion (small hail, wind).

If craziness goes down tomorrow night, don't claim you weren't warned. This is what I posted 3 days ago:

04-22-2014, 09:41 AM
Saturday into Sunday looks interesting; however, I have a feeling we could see a nocturnal event in the timing of the low. Again this can change, but nocturnal supercells are crazy.

There is no reason to try and pinpoint bullseyes and population impacts 4 days out, we won't have a good idea until morning of the event. By Friday, we should at least have a weak idea on setup. Right now it is looking like classic dryline supercell machine, still curious on the timing of intiation etc, though.

[venture]

I'm waiting on the Euro to come out this afternoon before getting in-depth into things anymore than what we are. Anon's nocturnal solution is definitely appearing to be a more likely scenario now. NWS Norman has update their graphics and seem to side with the thinking that the tornado window will run from 7PM to Midnight. 12Z GFS and NAM seem to back this up. I watched the morning weather shows to see what their thinking is and many defaulted to the "storms weaken after dark" line of thinking that is typical - but probably won't apply to this. If this unfolds like the models are hinting, this isn't going to be a typical Oklahoma severe weather day. Conditions will improve near or after sunset for a few tornadoes. Most Oklahoma nocturnal events are either hail events or the big derecho events early in the Summer (though we haven't had a classic one in awhile). With nocturnal storms capable of tornadoes not being normal around here, I expect a bias to get exposed in the local TV mets way of thinking.

Just keep in mind. Nothing is set in stone yet. We have been fairly consistent that this is going to be a more nowcasting scenario and following it in real time. Through today and early tomorrow we need to watch the green area on this map and see how far north it actually gets...

[bchris02]

Out of curiosity, when was the last time there was a nocturnal tornado warning in central Oklahoma?

[venture]

Out of curiosity, when was the last time there was a nocturnal tornado warning in central Oklahoma?

This one in 2012 is probably the best candidate.

04/13/2012

2352-2355

2

75

EF1

0

0

Canadian

SW OKC (1 N - 3 NNW Mustang; just SW of SW 54th/Mustang - near SW 29th/Tucson)

[FritterGirl]

I seem to remember nighttime sirens waking us up a few years ago, so I don't think it's been that long.

Looks like per these most recent models, I'll be napping during the day so I can stay up and be on weather watch while Mr. Fritter gets his sleep for Sunday's marathon. Going to be an interesting start.


Sent from my iPhone using Tapatalk

[venture]

New Day 2...

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT FRI APR 25 2014

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
PLAINS AND MIDDLE MO RIVER VALLEY...

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS ARE ANTICIPATED ACROSS THE SOUTHERN
AND CENTRAL GREAT PLAINS TO MID-MISSOURI VALLEY SATURDAY LATE
AFTERNOON AND NIGHT. LARGE HAIL IS EXPECTED TO BE THE PRIMARY
HAZARD...BUT DAMAGING WINDS AND A TORNADO RISK WILL ALSO EXIST.

...SYNOPSIS...
A RELATIVELY AMPLIFIED/PROGRESSIVE LONGWAVE PATTERN WILL EXIST ON
SATURDAY...WITH THE PRIMARY SEVERE POTENTIAL INFLUENCED BY AN
EASTWARD-SHIFTING SOUTHERN STREAM SHORTWAVE TROUGH/JET STREAK OVER
THE SOUTHWEST/SOUTHERN ROCKIES AND EVENTUALLY SOUTHERN HIGH PLAINS
EARLY SUNDAY. AT THE SURFACE...LEE CYCLOGENESIS WILL OCCUR ACROSS
THE CENTRAL HIGH PLAINS WITH A SHARPENING WARM FRONT EXTENDING
EASTWARD TO THE MO RIVER VALLEY. THE DRYLINE SHOULD MIX EASTWARD
INTO CNTRL KS AND ACROSS WEST TX...BEFORE RETREATING WESTWARD DURING
THE EVENING. A PACIFIC COLD FRONT WILL SWEEP EASTWARD AND EVENTUALLY
OVERTAKE THE DRYLINE ACROSS THE SOUTHERN HIGH PLAINS EARLY SUNDAY.

...CENTRAL/SOUTHERN PLAINS...
MODIFIED GULF MOISTURE WILL GENERALLY BE CONFINED TO CENTRAL/COASTAL
TX SATURDAY MORNING...BUT STEADY LOW-LEVEL MOISTURE ADVECTION WILL
OCCUR THROUGH THE DAY AS SOUTHERLY FLOW STRENGTHENS BENEATH A STOUT
ELEVATED MIXED LAYER. THIS WILL RESULT IN A BROADENING PLUME OF
UPPER 50S/LOWER 60S F SURFACE DEW POINTS TO THE EAST OF THE DRYLINE
FROM SOUTHWEST/WEST-CENTRAL TX INTO WESTERN OK/CENTRAL KS BY
SATURDAY LATE AFTERNOON/EVENING. REGARDING THE QUALITY OF THE
MOISTURE...AFTER MOISTENING THE BOUNDARY LAYER THROUGH THE FIRST
PART OF THE DAY...GUIDANCE SUCH AS THE 12Z NAM/00Z ECMWF REFLECT
DIURNAL MIXING /REDUCTION OF SURFACE DEWPOINTS/ ESPECIALLY ACROSS
WEST-CENTRAL OK INTO KS...WHICH IS LIKELY TIED TO SOME MARGINALITY
OF THE MOISTURE PROFILE PROGGED IN THOSE AREAS PRIOR TO SUNSET /25+F
TEMP-DEW POINT SPREADS AT PEAK HEATING/.

AS HEIGHT FALLS GRADUALLY INCREASE AND MIXING/DESTABILIZATION
PEAKS...ISOLATED/WIDELY SCATTERED SURFACE-BASED TSTMS ARE LIKELY TO
DEVELOP BY SATURDAY LATE AFTERNOON/EARLY EVENING...INITIALLY WITHIN
A NEAR-DRYLINE CORRIDOR FROM WEST-CENTRAL TX/TX SOUTH PLAINS TO FAR
WESTERN OK AND WEST-CENTRAL KS. WHILE LOW-LEVEL/DEEP-LAYER WIND
PROFILES WILL BE MODEST MUCH OF THE AFTERNOON...A CONSIDERABLE
STRENGTHENING IS EXPECTED IN BOTH REGARDS INTO THE EVENING
/EFFECTIVE SHEAR INCREASING TO 40-50 KT/. SCENARIO WILL SUPPORT
RELATIVELY HIGH-BASED SUPERCELLS WITH LARGE HAIL /SOME VERY LARGE/
AS THE PRIMARY SCENARIO. AS THESE STORMS SHIFT EASTWARD...LOCALLY
DAMAGING WINDS AND/OR SOME INCREASE IN TORNADO RISK MAY OCCUR
TOWARD/JUST AFTER SUNSET PENDING A PERSISTENT SUPERCELL MODE AS
MOISTURE/LOW-LEVEL SRH EACH NOCTURNALLY INCREASE. ALTHOUGH...WARM
SECTOR INHIBITION SHOULD NONETHELESS TEND TO INCREASE BY LATE
EVENING IN MOST AREAS WITH UNCERTAINTIES RELATED TO SURFACE-BASED
STORM/TORNADO LIKELIHOOD DEEPER INTO THE EVENING/OVERNIGHT HOURS.

[warreng88]

What are the predicted conditions for the Memorial Marathon Sunday morning?

[venture]

What are the predicted conditions for the Memorial Marathon Sunday morning?

Probably still have some storms around - severity should be low by that time though. Hopefully. LOL

[venture]

Here is the afternoon model review...

Severe weather is likely going into Saturday for parts of the state. Duh statement I know.

Key things to watch tomorrow: 1) Moisture return from the Gulf, 2) Dryline timing, and 3) Exact time initiation takes place.

Right now we still have a cold front draped across Southern Texas that is effectively shutting off moisture return from the Gulf. High pressure is off to the east and approaching Low from the west will give us a good SE flow off the Gulf. How fast this gets established and how deep the moisture is will directly impact what happens tomorrow. Short Term HRRR guidance suggests moisture return from the Gulf could start later this evening, around 7-8pm and bring dews in the 60s north to near Dallas by 3AM. If we look at the other models, Euro has the 60 degree line further south down by Waco, 12Z NAM is in agreement with Euro, and GFS is just a tad further south. The 3 models get the 60 degree dews in place by 1PM tomorrow (GFS is actually a bit earlier). This cutting it pretty close in my opinion, but with a late show it may not be a big deal. The 4km NAM has dews in the mid to upper 60s in SW OK by 10PM tomorrow which should help feed the storms.

Dryline time now...looks like it will hang out west most of the day and wait until after midnight to start marching east. To I-35 by Noon-ish on Sunday. It will likely advance slightly tomorrow and then retreat a bit before pushing back east. If storms can survive and push off of the dryline and survive - we'll need to watch them.

Instability ahead of the dryline looks good. Euro has widespread CAPE values 2000-2800 along the dryline, NAM has 2500-3000, and GFS around 3000 j/kg. More on the environment in a bit.

Initiation of convection is mixed, but all say yes it will happen. Euro fires by 7PM on the dryline over W OK (it might be in a column of counties or two). NAM fires off SW OK by 10PM. GFS initiates by 10PM along the dryline. Keep in mind when I say "by 10PM" that these precip forecasts are 3 hour precip totals so they will start well before 10 in most cases.

So as previous advertised, main threat will be very large hail early. If storms are on going and survive past dark the LLJ and overall conditions will mean a more favorable environment for tornadoes. We'll keep an eye on things, nothing is set in stone, but nighttime tornadoes are never fun.

The new NAM is running now so will post any updates from the 4km NAM product. The 12Z run hinted as rotating supercells moving up from the SW.

[venture]

Here is part of the OUN afternoon discussion in respect to tornado chances...

WITH RESPECT TO TORNADOES... THERE GENERATION
WILL HINGE ON A MULTITUDE OF FACTORS... ONE OF WHICH IS TIMING.
CURRENTLY... THERE MAY BE A NARROW WINDOW WHERE SFC WINDS REMAIN
BACKED ON THE SURGE OF THE DRYLINE INTO SRN OK... NEAR THE I-44
CORRIDOR... LIKELY BETWEEN 27/00Z AND 27/04 OR 05Z. THIS WILL COUPLE
WITH BETTER SFC/BL MOISTURE AND LCLS IN THE 1200 TO 1500 M RANGE. IF
THESE INGREDIENTS ARE ABLE TO COME TOGETHER... CONVECTIVE INITATION
TIME REMAINS THE BIG QUESTION.

So this is pretty much what we've been talking about. If storms get going and established, there will be a window from roughly 7PM to Midnight where a tornado threat will develop. Most ideal location is, naturally, along/near I-44.

[NikonNurse]

I just saw Mike Morgan's 430 forecast.....If he did it in one word, it would have been "meh".

[venture]

I just saw Mike Morgan's 430 forecast.....If he did it in one word, it would have been "meh".

Yeah watching Payne and Morgan to see how they are handling. Morgan's risk area is just weird. Payne's is closer to the SPC's outlook. Both are staying pretty low key, from what I can tell, with this so at least it isn't a super hype storm.

[zookeeper]

Yeah watching Payne and Morgan to see how they are handling. Morgan's risk area is just weird. Payne's is closer to the SPC's outlook. Both are staying pretty low key, from what I can tell, with this so at least it isn't a super hype storm.

I'm sure that a certain incident isn't ever far from Mike Morgan's thoughts every time he goes on the air this season for severe weather coverage.

[venture]

18Z 4km NAM Discussion

Right off the bat...nothing has significantly changed. I just know these images are floating around out there now, and they are bound to make it to Twitter, Faceplace, other forums and people will start going a little crazy. This look is for informational purposes and should be used in conjunction with everything else we have gone over.

Storm initiation around 6PM in Hardeman County, TX and maybe far south Harmon and Jackson counties. Looking at an area with CAPE values near 3000 j/kg in this area and dews in the low 60s. Deeper moisture is sititng just off to the east. Moisture will continue to increase through the evening getting into the mid 60s from SW back into Central OK.

By 7PM looking at storms developing from Hobart-Altus back to the SW into TX. Additional development would continue and growing in coverage. Looks like storms start to move into the fart west Metro area between 9 and 10PM. Storms continue through probably 3AM when it seems the tail end charlie storm moves through. Keep in mind simulated radar is a guess and not to be taken literally.

This 10PM...


This is at Midnight


The image is simulated reflectivity on the left and the right is 2-5km Max Updraft Helicity.

This has been showing up with some variations for a bit now, so please just stay weather aware for tomorrow night.

[Plutonic Panda]

Yeah watching Payne and Morgan to see how they are handling. Morgan's risk area is just weird. Payne's is closer to the SPC's outlook. Both are staying pretty low key, from what I can tell, with this so at least it isn't a super hype storm.

I wonder if the network told them to

[venture]

Well...the last time we had a watch he didn't clean it out. Granted I guess it is time, but just saying.

Rick Smith ‏@ounwcm 35m
Storm shelter is clean and ready for human occupancy. Sorry spiders! #okwx pic.twitter.com/AMgOLLjOVH

[PennyQuilts]

Will take that as a hint. If it gets hinky, tomorrow, I'll toss my overnight bag, the dogs' water dish and a couple of cans of dogfood into the shelter. Other than that, we're already good to go.

[Dessert Fox]

Will take that as a hint. If it gets hinky, tomorrow, I'll toss my overnight bag, the dogs' water dish and a couple of cans of dogfood into the shelter. Other than that, we're already good to go.

I wish I could do the same with my hallway hah

[Uncle Slayton]

AccuJackWeather.com is still going with "Dallas to Kansas City: Worst Tornado Outbreak Yet" as of 8:18PM tonight. So the national hype continues.

[Mel]

This afternoon going North on Mustang road to hook up with I-40 East at the intersection at Reno I saw one of those twister suv's, the ones that look like a Cival War Ironclad and a New, to me at least, Channel 9 WX vehicle that I think was some thing like a PT Cruiser with a mini radome on top. Somebody is freaking.

[PennyQuilts]

This afternoon going North on Mustang road to hook up with I-40 East at the intersection at Reno I saw one of those twister suv's, the ones that look like a Cival War Ironclad and a New, to me at least, Channel 9 WX vehicle that I think was some thing like a PT Cruiser with a mini radome on top. Somebody is freaking.

Just hearing that description of the tornado fleet freaks me out.

[venture]

The iranclad sounds like one of the Dominators with KFOR has one of - driven by Reed Timmer. I think there are 4 total or something.

As far as News 9, Payne tweeted out a photo of their fleet today...