Model Watch For Tour 1

[Nick F]

I think the broader picture looks good into the medium range (8-10days range) with both ECM and GFS showing troughing over the Mountain West and ridging across eastern US. Could be worse. trough moving in from west later next week looks to eject NE then replaced by another trough arriving over the Pacific coast next weekend.

[Paul Sherman]

Tour 1 Still Looking Incredible at this range

Thurs - Fri - Sat - Sun - Mon

[Paul Sherman]

Party Time - ECMWF Firmly on Board! :winky:

SPC Also noting that subsequent days will have Severe Threats as well.

Make sure your Cameras are charged and ready to go

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0304 AM CDT SAT APR 24 2010

VALID 271200Z - 021200Z

...DISCUSSION...

00Z ECMWF...GFS AND MEDIUM-RANGE ENSEMBLE GUIDANCE REMAIN IN GOOD

AGREEMENT IN THE DEVELOPMENT OF ANOTHER SIGNIFICANT TROUGH OVER THE

WRN STATES DURING THE FIRST PART OF THE EXTENDED PERIOD...WITH THIS

FEATURE EMERGING INTO THE GREAT PLAINS ON DAY 6 /THU APR 29TH/. A

STRONG SURFACE LOW AND ASSOCIATED FRONTAL SYSTEM WILL ACCOMPANY THE

UPPER TROUGH EWD INTO THE CNTRL PART OF THE NATION WITH THE LATEST

MODEL DATA NOW SUGGESTING THAT A MORE MOIST AND UNSTABLE WARM SECTOR

WILL DEVELOP NWD THROUGH THE SRN INTO CNTRL PLAINS. GIVEN THE

STRENGTH OF THE TROUGH AND THE ATTENDANT WIND FIELD...THE NECESSARY

INGREDIENTS APPEAR SUFFICIENT TO SUPPORT A REGIONAL SEVERE WEATHER

EVENT.

THE THREAT FOR SEVERE WEATHER WILL LIKELY CONTINUE THROUGH THE

REMAINDER OF THE EXTENDED PERIOD. HOWEVER...GIVEN INCREASING

VARIANCE IN MODEL SOLUTIONS AFTER DAY 6...NO ADDITIONAL SEVERE

WEATHER AREAS WILL BE DELINEATED.

[Harry]

Awesome!! I can't wait - the fact that the charts look awesome too is just something else

Am so excited I went out and bought a new lense today, Tamron SP AF10-24mm F/3.5-4.5 Di-II LD Aspherical [iF] (Sorry for the full name, I copied it off the website lol as I don't know it in short). It's ultra wide-angle - tried it out in the garden earlier, and the amount it captures is phenomenal. Also borrowing my partner's Dad's 70-300mm lense, so that gives me three lenses to play with inc the standard 18-55mm that the camera came with

Hoping to get some good shots

Just got to get there now

[Paul Sherman]

Last Look at the Models for our 1st Chase Day - Thursday 29th April!

And also the Landing Temps for the Guests on Tour 1

- This has been consistant for about 10 days now

- Might be an Ok Chase if this verifies

Landing Temps for The Guests on Tuesday at DFW Looks to be around 24c 75f

See you all at DFW Airport

Paul S

[Nick F]

Well, Paul and John should have landed by now and may well have cleared customs on their way to pick up the rental cars, then on to join Tom Lynch.

Weatherwise, a 'text' forecast today for central Texas to the south of the boys in DFW, with a cold front moving SE triggering some storms later as it forces returning warm moist gulf air upwards ... though they won't be chasing! Tomorrow and Wednesday looks pretty quiet, with a ridge of high pressure building in across the mid-west with gulf moisture being pushed back south to the Gulf coast. So clear and sunny for next few days.

However, on Thursday, the next Pacific trough arrives over the Mountain West and heights will start to fall and pressure will drop over the Rockies to allow rich Gulf moisture to return north across the Plains. A strong jet rounding the base of this upper trough moving in from the west will push NE across the Plains, its exit moving across the central Plains and where this area of strong upper divergence in the jet's exit overlaps the warm moist axis pushing norh - with its corridor of high CAPE values, we are likely to see severe potential Thursday PM. I reckon, as it stands with tonight's 12z Model output, that central Kansas maybe down into western Oklahoma will be the optimum area for convective potential, though this may change before then ...

- gfs jetstream and slp Friday 00z (Thursday 18z USA CDT)

- GFS CAPE and LI Friday 00z (Thursday 18z USA CDT)

- WRF SBCAPE and preciptn. friday 00z (18z CDT)

- WRF 3km Helicity Friday 00z (18z CDT)

[Nick F]

Looking good for Thursday, a corridor of slight risk from N-central TX way up to Sern MN, though best potential looks to be central Kansas. Doesn't ATM look like a big tornado day though:

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0229 AM CDT TUE APR 27 2010

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY REGION

SSWWD INTO PARTS OF OK/N TX...

...SYNOPSIS...

LARGE UPPER LOW/TROUGH INITIALLY CENTERED OVER THE INTERMOUNTAIN

WEST WILL MAKE SLOW EWD PROGRESS THIS PERIOD...INCREASINGLY

AFFECTING THE CENTRAL CONUS.

AT THE SURFACE...AN OCCLUDED SYSTEM WILL PROGRESS ACROSS THE NRN AND

CENTRAL PLAINS. BY THE END OF THE PERIOD...THE OCCLUDED FRONT IS

EXPECTED TO ARC SEWD FROM A LOW OVER THE ND/NRN MN VICINITY ACROSS

THE UPPER MS VALLEY...AND THEN ON SWWD AS A COLD FRONT ACROSS

IA...ERN KS/WRN MO...ERN OK...AND INTO CENTRAL TX.

...MID MO VALLEY REGION SSWWD INTO PARTS OF OK/N TX...

BOUNDARY-LAYER MOISTURE WILL CONTINUE SPREADING NWD INTO THE CENTRAL

U.S. AS STRONG SLY FLOW CONTINUES...WITH DEWPOINTS AROUND 60 F

SPREADING INTO OK/KS AND INTO THE MID MO VALLEY REGION. DAYTIME

HEATING OF THE MOISTENING -- BUT CAPPED -- BOUNDARY LAYER WILL

CONTRIBUTE TO AFTERNOON DESTABILIZATION...WITH 1000 TO 1500 J/KG

MIXED-LAYER CAPE EXPECTED TO EVOLVE.

WHILE SURFACE EVOLUTION ACROSS THE CENTRAL PLAINS DIFFERS WITHIN THE

NAM AND GFS SOLUTIONS...ATTM EXPECT CAP EROSION ALONG SOME

COMBINATION OF A FRONT AND/OR DRYLINE FROM THE MID MO VALLEY INTO

CENTRAL KS/WRN OK TO EVENTUALLY RESULT IN ISOLATED STORM

DEVELOPMENT.

WHILE THE CAP SHOULD LIMIT STORM COVERAGE DURING THE

AFTERNOON...VERY STRONG/VEERING FLOW WITH HEIGHT SPREADING ACROSS

THE CENTRAL U.S. WILL YIELD SHEAR VERY FAVORABLE FOR

STRONGLY-ROTATING SUPERCELL STORMS. THUS...ANY STORM WHICH DEVELOPS

SHOULD QUICKLY BECOME SEVERE...WITH VERY LARGE HAIL EXPECTED ALONG

WITH THE POTENTIAL FOR LOCALLY-DAMAGING WINDS. WHILE DEGREE OF

LOW-LEVEL SHEAR WILL BE VERY SUPPORTIVE OF TORNADO

POTENTIAL...SOMEWHAT LIMITED LOW-LEVEL MOISTURE - AND THE FAIRLY

DEEP BOUNDARY LAYER WHICH SHOULD RESULT -- SHOULD LIMIT THE OVERALL

TORNADO THREAT.

OVERNIGHT...STORMS SHOULD BECOME MORE LINEARLY-ORGANIZED ALONG THE

ADVANCING COLD FRONT. WHILE DECREASING INSTABILITY AND CHANGE IN

STORM MODE SHOULD YIELD A SLOW DECREASE IN HAIL/TORNADO

POTENTIAL...MARGINAL HAIL/DAMAGING WIND POTENTIAL WILL LIKELY

PERSIST WELL INTO THE OVERNIGHT HOURS.

..GOSS.. 04/27/2010

[Gorky]

This morning's GFS is really nice for the week afterwards though the entire period and into Tour 2's timeframe. Some of the earlier models had been showing this massive low to be scouring a lot of the moisture out of the way, but the 6z shows moisture remaining healthy up through TX for most of Tour 1 with quite few interesting chase opportunities. The jet doesn't really budge much for the entire tour...

[Paul Sherman]

One crumb of Comfort in the SPC Update is that they are starting to trend towards the ECMWF With regards to the speed and placement of the Trough so hopefully the Dryline comes into play and the cells remain discrete longer before the CF Overtakes it. They also state that Supercells should strongly rotate so I am not too woried and Tour 1 Guests should be looking forward to this. Looks like the Storms will rumble well into the night into an MCS Or Line Segment so a Hotel well to the East and maybe our First Lightning shots. Whatever happens it looks like at least a few days of Severe weather in the offing.

God what am I doing up at 6am!

Paul S

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0325 AM CDT TUE APR 27 2010

VALID 301200Z - 051200Z

...DISCUSSION...

DRASTIC DIFFERENCES BETWEEN THE GFS AND ECMWF ARE AGAIN APPARENT

THIS FORECAST...AS EARLY AS DAY 4 /FRI. APR. 30/. SUBSTANTIAL

DISAGREEMENT BETWEEN THE MODELS IN THE EVOLUTION OF THE COMPLEX

UPPER SYSTEM AFFECTING THE WRN AND CENTRAL U.S. RESULTS IN A GFS

FORECAST OF THE DAY 4 AFTERNOON SURFACE FRONTAL POSITION FROM STL

SWWD INTO SERN TX. MEANWHILE...THE ECMWF DEPICTS THE FRONT AT THE

SAME TIME ACROSS CENTRAL KS/CENTRAL OK/CENTRAL TX. WHILE SEVERE

POTENTIAL WILL LIKELY EXIST INVOF THE SURFACE FRONT REGARDLESS OF

ITS ACTUAL LOCATION -- AS AMPLY MOIST/UNSTABLE WARM SECTOR WOULD

LIKELY EXIST ALONG WITH FAVORABLE SHEAR...THE LOCATION OF THIS

THREAT WOULD OBVIOUSLY DIFFER BY SEVERAL HUNDRED MILES BASED ON A

PERFECT PROG OF THE TWO RUNS.

ATTM...IT WOULD APPEAR THAT THE ECMWF SOLUTION IS MORE LIKELY --

WITH MAIN SEVERE POTENTIAL EXTENDING FROM PARTS OF IA ACROSS MO/ERN

KS AND INTO OK AND PERHAPS N TX. HOWEVER...ATTM CONFIDENCE IS NOT

HIGH ENOUGH TO HIGHLIGHT A SPECIFIC THREAT AREA.

SUBSTANTIAL MODEL DIFFERENCES CONTINUE THROUGH THE MEDIUM

RANGE...AND THEREFORE CONFIDENCE IS LIKEWISE INSUFFICIENT TO WARRANT

ANY THREAT AREAS THROUGH THE END OF THE PERIOD.

[Nick F]

God what am I doing up at 6am!

Paul S

Obviously buzzing with enthusiasm for the start of tour 1!

So are you planning to head to North up the I-35 tomorrow to get in position for Thursday's risk? Dave Ewoldt's house up through east central Kansas looks a good bet atm, though will have a better look this evening.

Thing I like about the charts is that the trough arriving from the west for Thursday doesn't move very far over the following days, so should have some reloading severe potential for Tour 1.

[kold weather]

Yep Nick that upper trough/low doesn't really move very far form the western parts of the US and at the same time an upper high develops over the SE of the States which allows both a good feed from the Gulf as well as blocking the upper low from moving very far out of the way, therefore allowing the possiblity of several reloads, its the type of pattern that could very easily lead to several big outbreaks for tour 1.

[Roger J Smith]

For Thursday, would suggest that development is likely to be late but explosive around the TX panhandle, with daylight storms most likely near Amarillo and Borger. This line of storms would race east through OK and s KS and could be quite severe all night, but for daylight viewing opportunity, I suspect the action will start with a late-breaking cap just west of AMA-LBB. Note the rapid eastward motion of the thickness countours but most of TX-OK under a cap until near 00z Fri (which is 7 pm Thurs CDT). Very strong winds at 500 mb do not phase with frontal zone or dry line until around that time, which is why I am thinking it will be late-breaking and explosive.

[Nick F]

Might be an opportunity on Thursday PM for some storms across north/northeast Kansas. An upper trough moves east out of the Montana/Wyoming/Colorado across the central/northern plains on Thursday and just ahead of the upper trough, a 'lee' cyclone develops across W/SW Kansas by the afternoon/evening and this will draw warmth and moisture in from the E and SE overlaid by a strong jet streak:

CAPE 00z Friday:

However, there looks to be a strong cap in place, thanks to layers of warmth/moisture aloft (technically known as an Elevated Mixed Layer or EML), shown by the 850mb theta-e chats, which will tend to inhibit parcels of warmed moist air rising to form cbs, at least from the surface:

So, storm initiation most likely after dark when the Low-Level Jet cranks up and the forcing from the upper trough moves in. Perhaps some lightning opportunities at least.

WRF and GFS break out ppn across northern KS and eastern NE by 06z Friday (midnight Thurs night CDT)