nsrobins
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Posts posted by nsrobins
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Looking at latest obs and DL mixing I think a shift west for initiation is in order - Fort Cobb State Park up to El Reno by 20.30Z maybe.
Max shear also adjusted a bit west but LLJ still projected to move in with upper jet entrance flow across N OK later.
Ingredients in pace. -
Thanks for the updates Tom. I repeat my advice, which I'm sure you are completely aware of, that the centre of the metro will be no place to be in a few hours. Sit just east or northeast - the cells will come to you in a more open environment with roads out of trouble.
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Just been following Mike Phelps on www.stormscapelive.tv and the last week he's had the chief forecaster for The Weather Channel chasing with him and on a telephone conversation with him in the last 10 mins he has had word from the SPC in Norman that the risk of tornadoes has increased to 30%. And the overall risk is to be upgraded to high risk in the next update.
Not surprising. A potential PDS on this - looking significant as current obs and high-res models stand.
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I agree OKC as my target. Today is high risk for huge hail IMO. Moderate for Tornadoes..
High risk possible now for tornados too Stu as someone said earlier. Rapidly changing situation with latest guidance briging stroger LLJ over the top by 22Z.
Note: Stout cap fails at 20Z ish. Big loaded gun scenario off the dryline..
Latest SPC:
IT APPEARS THE THREAT OF A FEW STRONG/VIOLENT TORNADOES ARE IN PLACE. HAVE INCREASED SEVERE
PROBABILITIES OVER THIS REGION...AND PORTIONS OF CENTRAL/EASTERN OK
WILL BE CONSIDERED FOR AN UPGRADE TO HIGH RISK AT 20Z IF
SHORTER-TERM MESOSCALE MODELS MAINTAIN THIS SCENARIO.
Watch the skies chaps (and model data, etc, of course!)
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There's contradictory opinions out there. The PWO is warranted and clearly indicates that although the potential is high, the risk of significant tornados is conditional. On the other hand the language on Stormtrack is bullish. The major event of last Monday was actually an isolated severe, long-track event in an otherwise 'standard' spread on the day. The same thing could happen again tonight. An isolated EF4+ out in open countryside won't make headlines. An EF4+ in the 'wrong' place (OKC or Tulsa metro for instance) is a completely different story. That's the principle that underpins the EF rating system, and makes forecasting these situations all the more difficult!
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RAP, whilst increasing deep layer EHI in C OK, has eased off the bulk shear and for this reason I am slightly less confident of significant tornados. The instability however is huge so very large, high-topped supercells are likely nethertheless.
The chase is on - and an active day lasting into the late evening is a given. I am going to go with Shawnee, OK because I wouldn't want to have to get past OKC from West to East at rush hour. That way I'd have room to push east with any cells towards Tulsa.
Storm motions today due east at 18-20mph. -
Structure over tubes again although many of the cells had everything bar touchdowns. The majority of the circulations were broad mesos that fell just below the requirements from tightening sufficient to drop a surface vortex. Just as well considering the proximity of populated areas.
Also note to myself - initial target area significantly too far NW with the DL not the warm frontal feature providing the forcing. Confuddled and confused as per usual but learning all the time LOL.
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What a start to Tour 4. Another potentially dangerous situation for central and east OK, NW AR, SE KS and into IL this afternoon and evening.
Very rich moisture offers CAPE in excess of 5000 from the OKC to NE OK into the AR/OK/KS/IL corners region. The big player is a surface trough expected to extend into S KS providing backing at the surface. There is up to a 70kt wind from the WSW at 500mb. The sounding for Tulsa at 20Z provides the sort of horizontally elongated looped hodo that raises eyebrows. Complex set-up as per usual and caveats apply but once again the potential for strong long-tracked tors exists in the moderate risk area. -
Agreed - Lawton/Rush Springs cell the dominant product just now - mid level rotation and tennis ball hail
Also watch new cells forming to the SW of this.
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Tornado watch about to be issued for OK to add to the areas further east already noted.
It's hot and humid in C OK now - 83F and 74dp in OKC. Watch the lone cell south of Carnegie. It's in an area already below a stout upper wind field. -
You always seem to catch more than the average chaser Paul, though from an overall potential perspective IMO it didn't live up to the projections - and not for the first time this season.
Looking forward to catching images of last night.
Incidentally - there is a risk of cells initiating just west of the I35 around the River area (according to RAP) although it might not be until 22Z for the cap to break.
Might be worth a quick look as you are in range.
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It appears now as though there will be two existing areas of ppn ongoing into the afternoon period - one far SE OK into the Arkalatex and another moving away from far NE OK into MO/IL.
Should the airmass recover - and 3000+ CAPE with 85F surface temps and 72 dps suggests it will - then the area ahead of the DL is primed to fire with the assistance of possibly two OFBs and a straggling warm frontal type boundary already in place.
Shear vectors actually look more impressive than yesterday. Both HRRR and RAP continue to initiate cells NW of OKC moving ESE later so Alva, OK it remains for now. -
It's changeover day between tours so you're not likely to be in the field but after the relative dissapointment of last night where the two initiation zones morphed quite quickly into line segments (always seem to lose tornado potential when this happens), more discrete initiation seems likely this evening off a very sharp DL.
Based on a blend of RAP and HRRR composite and dewpoint I would be looking at the area between Alva OK and Medicine Lodge KS from 20Z for a couple of discrete cells to move into rich 72dp moisture and 250+ helicity (increasing towards 00z) in N C OK and S C KS.
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A huge thank you to Arron, Paul and all the Tour 3 members for a memorable experience.
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No news from the tour? Possibly having a easy morning ready for a busy day.
Playing cricket this evening so will check in after 20Z. -
I think the text will likely be adjsuted east in the afternoon update. 13Z RAP confirms that greatest LLJ is now just west of the I35. I hope it doesn't adjust further east as the folks in OKC don't need it.
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PWO from the SPC.
Starting to get jittery about the forecast shear values - the latest RAP, combined with the PWO, has me looking EAST not west from my Elk City position.
Maximised EHI and SRH now in WC OK from 22Z so those storms off the DL will have a shuffle to get into the really strong shear environment. If they do (say 30 miles west of the I35 corridor), then very strong mesocyclonic storms are pretty much a certainty.
As of now I'm completely torn as to where to go, and if I had time I'd be looking for subtle influences in the obs to help. -
This afternoon/evening is all about the helicity IMO. Strongest speed vectors with height for a while in a swathe across N TX into SW KS.
Still too early to call on target but early initiation likely Elk City I agree but the big movers and shakers IMO will be further west towards Canadian, TX to Guymon OK from 21Z.
PS: The Cattle Exchange, Canadian. Any opportunity I have to stop there for lunch I will take it. What a peppered steak! -
What was funny ( and they got richly rewarded) was the number of chasers that stayed at Salina even though cells were erupting to the SW and to the NE - the NE KS cell must have had a very large tornado at one point, but was left in the hope that a cell would develop at Salina which it duly did. I guess they could all see the ground conditions which influenced their decision but at one point I did wonder whether the decision to stay around Salina would backfire.
They were obviously well-advised
The tornado behaved in a way I've rarely seen - practically stationary for over half an hour then a deviant westward shuffle at one point. Upper vectors dictated storm motions of E at 10mph so I can only surmise the cell was snagged on a boundary, possibly a persistant OFB from the earlier system. Whatever it did it was impressive.
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With storm chasing continuing to expand in popularity, the number of vehicles on the roads can get ridiculous at times, especially when the risk area is quite small. Although last night's activity was spread over a large area, a significant number of chasers - including the DOW with Sean Casey, the TIV and many other well-known chasers and spotters decided to focus on NE KS around Salina and they were rewarded with a very long lived large tornado that more or less remained stationary for nearly an hour.
To illustrate the congestion as chasers converge on a slow-moving storm (otherwise known as a chaser CVZ), I took this screen grab from Team Denmark's position at 23.40Z last night from just of the I83 8 miles North of Salina. As you can see they weren't the only ones enjoying the stunning show:
Sorry about the small size.
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HRRR out to 20Z and it's a messy picture TBH. Early convection from 16Z clutters the field but as it moves slowly east towards C OK the slot left behind remains to the east of the DL and potential OFB initiates discrete cells in the central TX Panhandle.
I might be in Elk, OK but I'd be looking towards AMA up to Guymon, OK if HRRR is to be believed. -
A very juicy set-up this evening characterised by significant deep layer shear. Very deeply looped hodos on the Elk City, OK soundings on 06Z RAP are typical for the area. Sharp DL for me as an initial target but this could be a big afternoon for far W OK and the TX panhandle. From SPC: POTENTIALLY WIDESPREAD SURFACE BASED SEVERE TSTM DEVELOPMENT APPEARS PROBABLE ACROSS PARTS OF THE EASTERN TX PANHANDLE/NORTHWEST TX INTO WESTERN AND PERHAPS PARTS OF CENTRAL OK IN ADDITION TO WESTERN KS. SCATTERED SUPERCELLS CAPABLE OF VERY LARGE HAIL AND SOME TORNADOES WILL BE POSSIBLE...WITH A COUPLE POTENTIALLY STRONG TORNADOES WITHIN AN ENVIRONMENT ACCENTUATED BY A DIURNALLY STRONG LOW LEVEL JET.
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Understandable Arron but you have to make the call and think about logistics I suppose.
Still, very well placed for today's events with a big day for the TX and OK Panhandles. -
Wide large rotation with smaller foci - and the cell is almost stationary.
Chase Day 23 Discussion - MODERATE risk OK, KS, AR, MO, IL
in Storm Chase USA
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Sam the 18Z RAP brings deep layer SRH of in excess of 600 into N C OK at 01Z.
You really don't see values like that juxtaposed with such immense instability very often. Hesitant to mention it but it looks very similar to April 2011 Alabama to me.