Virtual Storm Chase 3

[kold weather]

Yep looks like a fairly active week is going to happen. As you say Paul the raw progs from the models probably suggestive of a mod risk but for now they are probably holding back simply because there are probably still some slight differences present in the models plus obviously there could yet still be downgrades so its a case of wait and see!

I will have a better look at the models for next week tomorrow a little too tired from staying up all night last night to make a decent rational conclusion!

[Cookie]

I look forward to it then

[Nick F]

Think I will target SW OK tomorrow - where the dryline is forecast to arrive in the evening. Thinking either Weatherford or Clinton to target. Was looking at going a little further NW to Arnett to target the fcst area of the triple point of the dryline and warm front, but I did this last time a similar triple point occured over NW OK and busted in Woodward while storms fired on the dryline down at Clinton.

Anyway, t+36 ADDS forecast prog for the surface shows the positions of the dryline and triple point at 00z Tues:

NAM shows some deccent warm moist air advecting north over west and central OK out of GoM head of the dryline - with some good CAPE values as a result:

Seems to be a fair bit of talk of SPC maybe downplaying the risk tomorrow - with the potential of quite a big event with maybe a major tornado forming from supercells firing along the dryline - given the warm moist air with Td's in the low 60F across SW OK and some strongly backed winds possible ahead of the dryline - looking at the windfields from NAM. Some uncertainties it seems though with mositure returns for this area still - getting that moisture north across TX tomorrow will be critical then.

[Paul Sherman]

Latest Text for tomorrow is very Interesting!!

SHOULD AIR MASS DESTABILIZE AS IS CURRENTLY FORECAST AND

DISCRETE...DIURNAL TSTM DEVELOPMENT OCCUR IN SYSTEM WARM

SECTOR...THE POTENTIAL WILL EXIST FOR A CLUSTER TORNADO EVENT ACROSS

OK MONDAY AFTERNOON INTO EVENING. AS SUCH...AN UPGRADE TO MODERATE

RISK MAY BECOME NECESSARY IN SUBSEQUENT DAY ONE OUTLOOKS ONCE

FINER-SCALE DETAILS BECOME MORE CLEAR.

Would absolutely love to Chase this if we were out there, looks like the best set-up of the year so far.

Paul S

[Nick F]

Well, the overnight NAM-WRF model is less keen on the moisture return north from the Gulf today, but we still see some warm moist air arrive across SW Oklahoma at 00z tonight (18z their time) south of the front (which looks further south now) and east of the dryline. Looking at the charts for 00z-06z Tues, I think I'll choose Clinton, OK as today's target:

NAM-WRF ppn 00z-06z Tues:

NAM-WRF theta-e 00-06z Tues:

NAM-WRF MLCAPE 00z Tues:

Sfc chart for 06z Tues:

...SRN KS/OK AND VICINITY...

WARM FRONT IS FORECAST TO MOVE SLOWLY NWD ACROSS THE RED RIVER INTO

OK DURING THE FIRST HALF OF THE PERIOD...AS LEE LOW DEVELOPS OVER

THE SRN HIGH PLAINS. BY AFTERNOON...THE FRONT SHOULD LIE W-E ACROSS

OK...WITH A DRYLINE EXTENDING SWD FROM SWRN OK ACROSS CENTRAL TX

TOWARD DEL RIO.

S OF THE FRONT/E OF THE DRYLINE...SLOW MOISTENING OF THE BOUNDARY

LAYER IS FORECAST...AS SELY FLOW ADVECTS GULF MOISTURE NWD. BY LATE

AFTERNOON...DEWPOINTS NEAR 60 COMBINED WITH BOUNDARY-LAYER HEATING

BENEATH STEEP LAPSE RATES ALOFT ADVECTING EWD ACROSS THE REGION WILL

RESULT IN MODERATE INSTABILITY /1000 TO 1500 J/KG MIXED-LAYER CAPE/.

AS A WEAK SHORT-WAVE TROUGH EMERGES INTO KS/OK WITHIN LARGER-SCALE

CYCLONIC FLOW ALOFT...FOCUSED UVV INVOF BOTH THE FRONT AND THE

DRYLINE SHOULD RESULT IN ISOLATED TO SCATTERED STORM DEVELOPMENT

OVER WRN OK.

DEEP-LAYER WIND FIELD WILL BE FAVORABLE FOR SUPERCELLS...WITH SELY

LOW-LEVEL FLOW VEERING AND INCREASING WITH HEIGHT TO WLY AT 40 TO 50

KT AT MID LEVELS. THUS -- DEVELOPING UPDRAFTS SHOULD RAPIDLY

ACQUIRE ROTATION AND SPREAD EWD TOWARD CENTRAL OK WITH TIME. THOUGH

LACK OF RICHER BOUNDARY-LAYER MOISTURE SHOULD LIMIT THE OVERALL

TORNADO POTENTIAL SOMEWHAT...ISOLATED TORNADOES ARE EXPECTED --

PARTICULARLY WITH ANY STORM MOVING EWD ALONG W-E SURFACE FRONT.

MORE SIGNIFICANT THREAT WILL BE LARGE HAIL WITH PERSISTENT SUPERCELL

STORMS.

OVERNIGHT...WARM ADVECTION ASSOCIATED WITH LOW-LEVEL JET INCREASING

TO 50-PLUS KT WILL ALLOW ONGOING STORMS TO CONTINUE MOVING EWD

ACROSS OK...WITH AN EXPANSION IN STORM COVERAGE NEAR AND N OF THE

SURFACE BOUNDARY INTO ERN KS/WRN MO. POTENTIAL FOR ISOLATED

TORNADOES SHOULD PERSIST THROUGH THE EVENING NEAR AND S OF THE FRONT

ACROSS OK...WHILE A MORE EXPANSIVE HAIL THREAT IS EXPECTED THROUGH

THE END OF THE PERIOD.

[Paul Sherman]

Going to join Nick in Clinton today, as good a target as any!

Paul S

[Gorky]

I can't disagree with Clinton at all, but I'll position myself in Lawton I think. Hope it's not too far east!

[kold weather]

From having a quick look at the models they still don't agree with where and when the storms will break out so seems like a broad risk area will be the way to go.

I have to admit low level jet winds don't look all that impressive, they may be enough for weak tornadoes but at 30kts around the time of convection at 850hpa its not all that impressive. Still despite that helicity is pretty extreme esp at 0-3km and this expands down to 0-1km level by 6z which is very suggestive of supercells so no trouble in that department. Plenty of cape as well, GFS progs 1600 whilst the WRF (upgraded NAM) goes evn higher and upto a very impressive 2600. So no problem with that either. Moisture returns wmay be a problem for the more northern area in the risk zone but for most of Texas and the southern half of OK it looks good enough.

Models do show a cap present in place with most of the models eroding it between 21-00z which seems reasonable. After that convection should develop fairly readily, if convection can get going earlier in the day there will be slightly better shear to tap into which may increase the risk of tornadoes a touch but even then I wouldn't have thought there'd be more then a few weak ones about. Still looks like a good day for strong supercells to be about and I suspect maybe a few tornadoes as well...certainly worth chasing.

I'll go for Atlus as a starting point.

[Nick F]

I have to admit low level jet winds don't look all that impressive, they may be enough for weak tornadoes but at 30kts around the time of convection at 850hpa its not all that impressive. Still despite that helicity is pretty extreme esp at 0-3km and this expands down to 0-1km level by 6z which is very suggestive of supercells so no trouble in that department. Plenty of cape as well, GFS progs 1600 whilst the WRF (upgraded NAM) goes evn higher and upto a very impressive 2600. So no problem with that either. Moisture returns wmay be a problem for the more northern area in the risk zone but for most of Texas and the southern half of OK it looks good enough.

The low-level jet tends not to come into play and crank-up until after dark anyway - as its a night-time phenomenum - caused by the temperature gradient increasing between the high plains which cool down considerably at night and the warm gulf air further east. The LL jet tends to be responsible for MCS/MCC storms at night and also night-time tornadoes over the Sern Plains in spring.

As long as the S to SErly low-level winds advect warm moist air up to SW OK, its game on for our targets when the dryline and shortwave arrives from the west tonight.

[Nick F]

60F+ dew points begining to advect north into the far SW of Oklahoma now - which is a good sign. Was bit worried that the sfc Tds would remain too dry - but with a good 2-3 hrs or so of northwards advection of warm moist air until the dryline arrives to the west - things looking good for storms to fire over SW OK around 21z.

OK Mesonet obs and SPC hourly Mesoscale data at 1800:

[kold weather]

Fair enough Nick i'm still learning about these aspects of convective weather out in the plains, a little out of my range of what I'm used to...also it'll be good to expand my knowleadge of the states, esp given my geographical knowleadge extends only along the US coasts...for obvious reasons I think!

Anyway as you say Nick the higher dew points now being advected into Sw OK which I'm very happy about looks like moisture shouldn't be a problem them with the arrival of the higher dew-points now just got to wait for the dry line to come eastwards a little and for the cap to decay and then things should get going hopefully.

This week does look very interesting doesn't it, hopefully you get these sorts of weeks whilst you are out there, Thursday still looks very juicy IMO.

Edited April 7, 2008 by kold weather

[Nick F]

Fair enough Nick i'm still learning about these aspects of convective weather out in the plains, a little out of my range of what I'm used to...also it'll be good to expand my knowleadge of the states, esp given my geographical knowleadge extends only along the US coasts...for obvious reasons I think!

Equally, there's alot I don't know about hurricanes :lol:

I think a strong low-level jet can also be enhanced by pressure gradient created by low pressure systems moving east across the States - though these pressure gradients tend to be less frequent in spring and summer . So the main factor for low-level jet development is the west to east temp gradient across the plains at night - the LL jet usually is a strong Serly wind at 850mb and transports large volumes of moisture from the Gulf of Mexico north across the mid-west and hence night time MCS thunderstorms are often the result of the LL jet.

[Nick F]

Got a feeling I might have to head down the Hwy 183 towards Snyder, further south of Clinton to catch the intiation - but will hold tight for the mo. Sitting in some hotel car park somewhere in Clinton having a subway and checking the latest on wi-fi.

[Paul Sherman]

As i thought a few days ago, SPC Have now Upgraded to a Moderate this is due to Moisture return being realised with low to Mid 60's Dews, This looks like it could be a Good Un Today, Set your Weather Radios to SW Oklahoma and listen for the warning come flooding through.

Paul S

[Nick F]

Looks like some Cu or TCu bubbling up just south of Vernon in northwest TX, things about to kick off I think towards the Red River area of NW Texas and SW Oklahoma:

Dryline must be close to this area now, this was the 18z plot:

DPs as high as 66F though generally 61F advecting into far southwest/southcentral OK now too, sfc winds nicely backed to the SE:

EDIT: Good news Paul, only wish I was there right now, looks like we chose a good target area too:

....CNTRL/SRN PLAINS...

19Z SFC ANALYSIS PLACES A WEAK SFC LOW OVER THE ERN TX PNHDL WITH A

WARM FRONT DEVELOPING NWD INTO CNTRL OK. A DRYLINE EXTENDS S FROM

THE LOW INTO WRN NORTH TX AND THE ERN LOW ROLLING PLAINS. AHEAD OF

THE DRYLINE...NEAR 60F DEW POINTS HAD ADVECTED NWD INTO CNTRL/SRN OK

BENEATH AROUND 8 DEG C/KM MID-LVL LAPSE RATES. GIVEN RAPIDLY

WARMING TEMPERATURES...MLCAPES WERE APPROACHING 2000 J/KG WITH

WEAKENING INHIBITION.

CONTINUED WARMING INTO THE UPR 70S/NEAR 80F AND APPROACH OF A LARGER

SCALE MID-LVL WAVE OVER THE SRN HIGH PLAINS WILL LIKELY RESULT IN

SUSTAINED TSTM INITIATION ALONG/E OF THE DRYLINE FROM SWRN OK SWD

INTO WRN N TX/BIG COUNTRY BY 21Z. EFFECTIVE BULK SHEAR AROUND 50

KTS AND MAGNITUDE OF LAPSE RATES/INSTABILITY SUGGEST THAT SUPERCELLS

WILL BE POSSIBLE WITH VERY LARGE HAIL. MOREOVER...TORNADO

PROBABILITIES WILL BECOME MAXIMIZED EARLY THIS EVENING OVER

SWRN...CNTRL...SCNTRL OK AND WRN NORTH TX WHERE BOUNDARY LAYER WINDS

REMAIN BACKED /SRH 250+ M2/S2/ IN A REGION WITH A RELATIVELY MOIST

BOUNDARY LAYER. LATEST TORNADO PROBABILITIES HAVE INCLUDED A

SIGNIFICANT TORNADO RISK OVER THE MDT RISK AREA ALONG WITH AN

UPGRADE TO VERY LARGE HAIL PROBABILITIES. GIVEN A MERE 5 DEG F

INCREASE IN THE SFC DEW POINTS WOULD BOOST THE CONFIDENCE LEVEL FOR

MORE ROBUST TORNADO PROBABILITIES...BUT THIS LEVEL OF CONFIDENCE IS

LACKING ATTM. ACTIVITY WILL MOVE ENEWD INTO PORTION OF ERN OK

OVERNIGHT WITH A CONTINUED RISK FOR LARGE HAIL...DMGG WIND GUSTS AND

ISOLD TORNADOES.

[kold weather]

Radar shows those clouds have developed into a cell Nick, cloud tops about 35k, currently near electra and so I'd guess this is the start of the event and more cells should break out soon, I think at this time in real life I'd be heading a little further to the east. I suspect this cell marks the eastern extent of the dryline?

Anyway Steve Miller is chasing this one today, seems to have a few feedback issues and from the looks of things David Drummond is going to as well so will be good to watch.

Edited April 7, 2008 by kold weather

[Paul Sherman]

Nick

Absolutely Gutted this has happened now, this would be Chasing Nirvana today, great Chase Country and all the signs of some Significant Tornadoes with everything in place, The Cu field is quite extensive now and there is also an apparant Dryline Bulge near the Red River.

Lets hope for more of these events in 3-4 weeks time

Paul S

[Gorky]

Hmm, I se a PDS tornado watch has been issued! I can't complain with my starting location either as it should be perfect to catch supercells as they track over the Red River.

90% chance of 2 or more tornadoes with 50% chance of a strong tornado in this watch.

[kold weather]

Yep I suppose it makes sense to issue one given all the factors in place Gorky.

Also first warning with the cell near electra:

BULLETIN - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE NORMAN OK

328 PM CDT MON APR 7 2008

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

NORTHWESTERN WICHITA COUNTY IN NORTHERN TEXAS...

SOUTHEASTERN WILBARGER COUNTY IN NORTHERN TEXAS...

* UNTIL 400 PM CDT

* AT 328 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM 5 MILES SOUTHWEST OF ELECTRA...MOVING NORTHEAST

AT 20 MPH. THIS STORM IS QUICKLY BECOMING SEVERE. HAIL TO THE SIZE

OF GOLFBALLS AND WINDS OF 65 MPH WILL BE POSSIBLE.

* LOCATIONS IN THE WARNING INCLUDE ELECTRA...HARROLD AND HAYNESVILLE.

Cell has really strengthened in the past 15 mins now tops of 40k and some decent radar returns. Also another cell is rapidly forming to its west along the dryline bulge which also will probably need a warning pretty soon I think given conditions are going to broadly the same. Still it looks a little linear right now but we will have to wait and see what happens.

Edited April 7, 2008 by kold weather

[Paul Sherman]

Keep watching the link below today and you will see Tornadoes Real time, with David Drimmond and Rogers Live Stream above each other you can see it all on one screen, they are travelling towards some Impressive Towers at the Moment.

Keep glued to the live streams Tonight!!

http://www.severestudios.com/livechase

Weather radio warning of Softball Hail Impacts!

Paul S

[Nick F]

2140 satellite vis satellite shows the cells over Electra towards Wichita Falls nicely :

Currently I would be moving south from Clinton towards Snyder - reckon something will develop in the next hr and cross the Hwy between the two towns.

[kold weather]

Yep I'm watching the stream as well Nick, the best we've got to see these storms (I wonder would it be possible to do a similar thing for when you guys are out there Nick?) Also Steve Miller (infact there appears to be two of them!) is also chasing these storms heading towards the target zone.

Cells are still developing to the west of the orginal cell, very linear at the moment, looks like a decent line of cells at the moment, wouldn't mind driving into them!

I think I'd drive a little further east probably towards Frederick and wait there, that should be far enough east to get the cells as they come up from the SE, just hope it doesn't get too messy with regards to cloud cover due to the close nature of the cells in a line.

Edited April 7, 2008 by kold weather

[Paul Sherman]

Roger is about 10 miles North of those Cells along the Red River heading East on 62, He will probably get ahead and then go South down the Eastern Side of the Storm, good position to be in.

Paul S

[Nick F]

Visible satellite shows signs of CU development along highway 183 between Hobart and highway 62. This should be the next area to put off a storm and this is where I would chase. I would move East out of Hobart about 15 miles and wait. Whichever storm comes off this area with a clear opening to its South, that's my storm. Any storms forming in this area should have good tornado potential over the next four hours.

Sounding good for the 183 road between Clinton and Snyder, may hang around Hobart area then half way between.

Those storms now crossing the Red River into SW Ok are rather slow moving - so easy enough to follow if you are lucky to be in the vicinity

TVS on the south side of the storm between Vernon and Electra - a split cell on the NW side needs watching too as it maybe close to a dry line bulge:

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE NORMAN OK

433 PM CDT MON APR 7 2008

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A

* TORNADO WARNING FOR...

NORTHWESTERN WICHITA COUNTY IN NORTHERN TEXAS...

EASTERN WILBARGER COUNTY IN NORTHERN TEXAS...

* UNTIL 500 PM CDT

* AT 433 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED

A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO ANYTIME 5

MILES WEST OF HARROLD...MOVING NORTHEAST AT 20 MPH. TAKE YOUR

TORNADO PRECAUTIONS NOW!

* LOCATIONS IN THE WARNING INCLUDE ELECTRA...HARROLD...HAYNESVILLE

AND OKLAUNION.

[Gorky]

Steve Miller (Tx) cam is amazing at the moment!

http://texastailchaser.com/livechase/

Edited April 7, 2008 by Gorky