Chase 2011 - Day 1 Discussion

[Paul Sherman]

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1241 AM CDT FRI APR 29 2011

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF AR...NERN

TX...SERN OK...SERN MO...

...SYNOPSIS...

A LARGE UPPER TROUGH WILL SINK SWD ACROSS THE ROCKIES...WITH AN

UPPER LOW CENTER SHIFTING INTO THE NRN PLAINS/UPPER MS VALLEY BY

00Z. THIS WILL ALLOW FOR AN EXPANSIVE AREA OF MODERATE FLOW ALOFT TO

OVERSPREAD THE PLAINS STATES. AT THE SURFACE...ONE LOW WILL BE OVER

NRN MN BY 00Z...WITH A LOW PRESSURE TROUGH EXTENDING SWD ALONG THE

MS RIVER AND THEN SWWD INTO SRN OK/NWRN TX. SLY FLOW OFF THE GULF OF

MEXICO WILL ALLOW FOR A RAPID RETURN NWD OF MID TO UPPER 60S F

DEWPOINTS ACROSS TX...LA...AR AND ERN OK.

...NERN TX/SERN OK INTO AR AND SRN MO...

THE WARM SECTOR WILL REMAIN CAPPED FOR MUCH OF THE DAY WITH A WARM

NOSE NEAR 700 MB...BUT STRONG INSTABILITY WILL EXIST S OF THE FRONT

AS THE MOISTURE RETURNS AND HEATING OCCURS. WEAK CONVERGENCE AND

PERSISTENT LIFTING NEAR THE PRE FRONTAL TROUGH IS EXPECTED TO

EVENTUALLY RESULT IN AREAS OF THUNDERSTORMS FROM FAR NERN TX/SERN OK

INTO AR AND SRN MO...MOST LIKELY LATE AFTERNOON/EVENING. DEEP LAYER

SHEAR AROUND 50 KT WILL BE NEARLY PARALLEL TO THE SURFACE

BOUNDARY...SUGGESTING THAT STORM STRUCTURE COULD BECOME SOMEWHAT

LINEAR...OR AT LEAST WITH MERGED STORMS LEADING TO TRAINING ECHOS.

THIS IN TURN SHOULD YIELD MAINLY A DAMAGING WIND THREAT...WITH SOME

HAIL THREAT AS WELL WITH STEEP LAPSE RATES ALOFT.

A TORNADO THREAT WILL EXIST...ESPECIALLY IF STORMS CAN ACQUIRE

ROTATION BEFORE MERGING. BUT...POOR LOW LEVEL LAPSE RATES IN THE

LOWEST 3KM...ESPECIALLY AFTER DARK...WILL HELP MITIGATE THE TORNADO

THREAT.

[nsrobins]

The biggest problem as I see it is inhibition - and over the I35 corridor I don't see it breaking in time.

I favour further east - say Paris/Mt Pleasant to the AR line where I think daytime heating will break the cap around 22Z releasing sufficient energy for some reasonable convection.

Mesoscale boundaries may provide some shear for rotation but hailers look more likely.

Have a good first day proper. Personally I am still in shock at the events of Weds evening and am finding it difficult getting into the groove of virtiual chasing again.

[Dorsetbred]

See told yah SPC had upgraded

Smells like chase weather to me....

THE GREATEST SEVERE THREAT SHOULD BE LOCATED IN NE TX AND SW AR

WHERE MID-LEVEL LAPSE RATES ARE FORECAST TO BE STEEP AND DEEP LAYER

SHEAR SHOULD BECOME ENHANCED DUE TO THE STRENGTHENING LOW-LEVEL JET

SATURDAY EVENING. THE THERMODYNAMIC AND SHEAR ENVIRONMENT SUGGESTS

SUPERCELL DEVELOPMENT WITH LARGE HAIL WILL BE PROBABLE ONCE STORMS

INITIATE. A TORNADO THREAT MAY ALSO DEVELOP EARLY SATURDAY EVENING

AS THE LOW-LEVEL JET STRENGTHENS. DEPENDING ON THE STRENGTH OF THE

CAPPING INVERSION...THE SEVERE WEATHER EVENT COULD BE CONCENTRATED

AFTER DARK AS A LARGE CONVECTIVE CLUSTER OR BROKEN LINE OF STORMS

ORGANIZES FROM AROUND DALLAS IN NE TX NEWD INTO CNTRL AR. THE MAIN

UNCERTAINTY IS THE CAPPING INVERSION WHICH COULD RESULT IN MORE

ISOLATED INITIATION ACROSS THE RED RIVER VALLEY AND ARKLATEX

SATURDAY EVENING. CONSIDERED ADDING A 30 PERCENT SIGNIFICANT SEVERE

AREA FOR PARTS OF NE TX...FAR SE OK AND SW AR FOR THE POSSIBILITY OF

WELL-ORGANIZED SUPERCELLS. :D

Edited April 29, 2011 by Dorsetbred

[Paul Sherman]

A few Pictures from Travel Day

- The Chase Beasts

- The Chasers

- Tornado Alley Film at DFW Imax

[duckeyh]

and from the rear....

[Roger J Smith]

00z guidance suggesting rapid development 00z-03z Saturday evening around FTW west to north (Mineral Wells to Sherman) and likely to become strong MCS moving south overnight. Sunday chase likely to be San Antonio south and east.

My analysis -- dry line will stall, drift back west to about Midland southeast to Del Rio line by 21z, temps near 42C west of dry line, 34 C with high dew points southeast of dry line, stationary (warm) front SPS to ADM to LIT will produce supercells 23z-02z, these will drift south then accelerate about sunset through DFW metroplex.

Dangerous storm chase conditions likely with tornadic storms accelerating south. Would recommend scouting safe shelter such as open-walled car wash or stronger in case storms accelerate at critical phase. Most likely intercept for severe, MWL to Brownwood.

[dogs32]

A few Pictures from Travel Day

- The Chase Beasts

- The Chasers

- Tornado Alley Film at DFW Imax

awesome pics...

have a GREAT TIME

[nsrobins]

09 RUC

Still think capping will be an issue in far NE TX and SW AR until 21-22Z, but there is a rapid disolution of inibition in a hole Paris/Sherman.

EHI (due mainly to enhanced directional shear) has increased in this run in the TX/OK/AR corner so pre-trough discrete organisation has an increased tornadic potential IMO.

In conclusion, better tor chances this morning for your chase target and definately worth a serious go and not too far to move so enjoy your breakfast! Of course terrain becomes a big issue as you head into the region Fort Worth/Texakarna but as Roger says maybe you won't have to go that far east.

[Paul Sherman]

Yep there is a risk the Cap will not break out further west.......but I am bouyed by the latest RUC Model which is showing a weakening of the CINH & A few storms breaking out just south of the Red River in North Central Texas around the 4pm mark, GFS & NAM Show nothing and have a mass of convection over Arkansas, we will take out chances with the Sherman to Paris to Texarkana line for today, if anything else there will be elevated storms moving eastwards from North West Texas and SW Oklahoma later for some Hailers and Lightning Ops at the overnight Hotel. As Neil says there is a brief chance at a few Tornadoes across our target zone before darkness so will be keeping an eye on obs through out the day. Really happy with the 70f Dp's along the Texas coast and the 61f currently just south of DFW, It feels very juicy out there already at 7am

Barons is up and running along with GRLevel3 and Streaming will be live later.

Paul S & Team

[Arron]

Yeehaa! Let the games begin Good luck guys'n'gals!

[TornadoJo]

yay. jo n claire happy dance x

[Supercell]

First chase day ever for me today !

We'll be on our way shortly.

[Gorky]

The RUC is promising showing a fair few cells popping in TX from north of DFW down into Central Texas. This would be a late show with initiation possibly not until after 6pm. The latest HRRR shows the cap winning however at least in Texas. If things do pop, the Texas play will be a good chase. Slow storm speeds, possible isolated cells and late initiation would mean for some nice photo ops. Outside chance of a tornado though I suspect it would be a structure, lightning and possibly severe hail chase if you fancy risking the nice new cars already

[ian cameron]

heading east on the I30 going to stop and have lunch at mount pleasant

Ian

[Nick F]

Good call by the team to head east, looking at surface obs, the cold front lies from the Red River area of N-central TX down to DFW area and SW from there, with rich moisture to the east with DPs hiting 70F:

cu fields developing over far NE TX too in this hot moist air:

Hourly mesoscale analysis shows strongest 0-1km and 0-3km storm-relative helicity towards Arkansas currently:

RUC shows precip breaking out along cold front east of DFW by 00z UTC (18Z CDT):

[Roger J Smith]

I think the most severe storm development zone is likely to be north-south through Dallas as the fronts have stalled and the wave in New Mexico will tend to pull moisture back north and west, turning winds in that region around to provide a frontal upslope boundary and storm development may be rapid after 22z. Also this area has been sunny while there is 70-90 per cent cloud cover further east in the debris of the old front.

I would expect some chase situations to develop possibly between Dallas and Sherman although with cells not likely to move very fast perhaps view rather than chase would be the right word here.

Watch for this complex to become a meso-scale complex moving south by sunset to midnight CDT and Sunday's storm potential will be greatest south of Waco to San Antonio.

[nsrobins]

Just got in from a wedding reception. I see from surface obs that the CF has stalled further west than any model predicted earlier, with an initiation now underway in the just pre-frontal zone around Tyler. I think this is where the most active convection will be, in the rich airmass ahead of teh CF, rather than the front itself.

Some potential in the pre-sunset period of a tornado in this region.

Edit: Paul that cell around Canton looks likely but I guess you've aleady spotted it!

Are you driving?

Edited April 30, 2011 by nsrobins

[Gorky]

Stream is working great. Looks like a nice storm you guys are on!

[Gorky]

Frozen now.. just as the base comes into view... D'oh!