01/16/2006 FCST: North Texas

[C Brian Batey]

Anyone care to comment on the severe storm potential for Monday in N. Texas?

I'm really new to this forecasting stuff, but the ETA model seems to suggest that Monday could be interesting.

Thanks in advance.

brianb
N5ACN

 

[Jeff Snyder]

The 0z NAM doesn't show much in the way of severe potential north of a Dallas to Paris line, with the cold front progged to be along a Dallas to Joplin MO line by 1pm. With Tds in the 58-62F range, instability isn't forecast to be much better than marginal, even in SE TX and adjacent areas. Convection does seem like a good bet in eastern TX (primarily southeastern TX) and into southern AR and LA as a strong, high-amplitude longwave trough approaches from the west, resulting in strong DPVA and associated upward vertical motion.

As a disclaimer, the models differ in how the trough will develop. The 0z NAM cuts it off and puts a cut-off low along the Mexican / NM border, while the GFS keeps the trough open and slowly pushes it eastward across the central US. Regardless, it does appear that much of TX could see substantial precipitation in the Mon-Tues timeframe. Hopefully, the cold front won't progress as far south as models currently prog, as OK could certainly use some of that precip!

 

[C Brian Batey]

Thanks to both of you.

As an 'extreme novice', seeing your thinking on comparing the models and how you as individuals analyze the data is very beneficial.

I'd love to see a nice 'rare event' first of the week, but will certainly be happy with some much needed precip.

brianb
N54ACN

 

[Robert Dewey]

You should also look at the Euro and Canadian models too... They have been performing better than the US models, at least in the +72HR frame. ECMWF and UKMET keep more of a closed system, while the GFS is a bit more open. The NAM is the only model showing the system cutting off and retrograding. As of now, I would completely throw it out.

This looks very similar to this past storm, except we have a tighter baroclinic zone... The GFS wants an open wave while the Euro's want more of a closed system. If this current system is any indication, I would say a closed wave/stronger solution is the way to go.

 

[nickgrillo]

The NAM continues to show stronger instability with each run. The current 12z NAM run shows slightly more robust boundary layer moisture advecting into the warm sector (with low 60's sfc Tds across eastern TX), which is supporting the stronger surface-based instability (a swath of 1000 j/kg SBCAPE develops by 0z). Deep-layer shear values will could support a few supercells -- with weak low-level shear (<75m2/s2 0-1km SRH) in the same timeframe possibley supporting an isolated tornado with any sustained surface-based storms. The biggest benefit will obviously be the heavy rainfall, with the latest NAM bringing in 1.5-2.0 inches of precip by early TUE across eastern TX.

 

[Evan Stubbart]

Chasing

Based on models- Anyone planning on chasing in NE Texas? Just moved here and I'm itching to get out and check out some storms. Looking at everything I really don't know if this line of storms will come together like we are hoping for. It looks to be a bit more of a solid rain event with no real action in the way of super cells, etc.

 

[Robert Dewey]

Looks like the NAM has done just what I said... It has completely lost the retrograding closed low. Now the focus is on where development of the sfc low will take place with every model having a significantly different solution. Yet another tough forecast with a high bust potential.

 

[C Brian Batey]

Re: Chasing

Originally posted by Evan Stubbart
Based on models- Anyone planning on chasing in NE Texas? Just moved here and I'm itching to get out and check out some storms.

I'll be watching the skies and the numbers as things progress. If something pops, I'll be here to chase it.

I probably won't chase into east Texas. It's definitely not 'prime chasing terrain' from Canton east.

Personally, I'm enjoying the mental exercies of trying to put all the info together in my head and coming up with my own forecast.

I've been hitting the books here lately. Trying to make a coherant picture from all I've learned is quite challenging.

brianb

 

[Bill Tabor]

Monday doesn't look too good for a Tx chase to me. Best chance is se TX near the coast and eastern Tx - mostly along the LA border. However good precip probably won't break out until nearly dark due primarily to the approaching mid level wave. SFC to 850 winds are somewhat parallel and front moving fairly quick so expect a bit of a squall to form. I am not impressed with the winds at lower levels for supercells.

So for TX mostly a waste of time during the day. Looks like the wave will break out some good after dark precipitation and hopefully we'll get some rain.

 

[Carrie Halliday]

Originally posted by Bill Tabor
Monday doesn't look too good for a Tx chase to me. Best chance is se TX near the coast and eastern Tx - mostly along the LA border. However good precip probably won't break out until nearly dark due primarily to the approaching mid level wave. SFC to 850 winds are somewhat parallel and front moving fairly quick so expect a bit of a squall to form. I am not impressed with the winds at lower levels for supercells.

So for TX mostly a waste of time during the day. Looks like the wave will break out some good after dark precipitation and hopefully we'll get some rain.

I was debating taking the Taurus out for a run, but will not chase E of Houston. I prefer between Bill's home and mine. I also agree this will be a squall line event, later in the day and if anything does manifest...it will most likely be rainwrapped. Might as well watch everything from home and save $2.25/gal.

 

[Bill Tabor]

Forecast has changed based on latest model run (in particular NAM) which indicates northern sfc low will move further north and east elongating the sfc trough extending NE/SW through SPS and north Central Tx / west Tx by 12z. Additionally the new model supports the development and intensification of a secondary sfc low in northern Mexico near south Tx border during the day. Due primarily to southern surface low better moisture will be advected during the day providing much of the se 1/3 of Tx with 60 dewpoints. Already 55 dewpoints can be seen along the Tx coast. Winds at the sfc and 850 will be backed slightly more than previous run indicated providing better low level directional shear. Orientation of the sfc trough and lower level winds may be sufficient to provide some non-linear structures and convergence to assist in inititation before 0Z. There is expected to be a zone of -2 to perhaps as high as -6 LI and sometime after 18z some of the area of interest in the se tx 1/3 should become uncapped. This will be amplified by the approach of a 500mb wave which should start affecting parts of the same area near the sfc boundary after 18z and along with upper jets / reasonable lapse rates due to temperature of approaching wave to support some supercell storms.

For chasing I see the entire southeastern 1/3 of Tx as chase potential primarily during the afternoon (after dark I don't really care and it heads toward LA too probably). My particular area of interest and higher instabilities would be the corridor bounded by (east of AUS/SAT but west of HOU,to Beeville, to just north of Williamson county, to Corsicana, Conroe, Huntsville. Supercells in this area should be cabable of producing an occasional tornado.

My target is College Station / Bryan at perhaps 21z and waiting for convection and tornadic maximum which may be closer to 0z. Unfortunately at this time of the year getting dark early is always a problem. I'd probably go slight over se 1/3 of Tx and 5% chance of tornadoes in the smaller area I mentioned and 2% for other areas.

 

[Bill Schintler]

Chase target for Monday, January 16

Chase Target:
Lufkin, TX.

Timing:
This will be a late morning event. Rain and embedded storms should initiate near the Nacogdoches and Henderson, TX areas around 10 AM CDT. Within a few hours, a large expanse of storms and rain should fill into the region in an area in TX bounded to the N by I-20 and to the W by I-35.

Storm type and intensity:
Given the overall lack of instability coupled with fairly strong dynamical forcing, storms will quickly evolve into a number of fast-moving lines. The largest threat for any marginal severe WX will be wind gusts to 50 mph.

Discussion:
00Z UA analysis indicates a highly amplified, full latitude, and positively-tilted trough in the WRN CONUS. A 150kt H3 streak extends from NWRN Mexico into CNTRL OK, while another piece of energy is diving S through NRN CA. At the surface, meager SFC moisture was lifting NWRD into SERN TX, with Td’s AOA 50F S and E of a GRK/CRS/TYR line. A moderate SWRLY LLJ has developed in this area, and this feature will only back slightly by mid-day tomorrow; which should serve to keep any Gulf moisture return confined to a very shallow layer in all but the very SERN part of TX. Better moisture return is underway further to the E, as indicated by a nearly 150mb-deep moist layer on both the 00Z SHV and LCH soundings.

Tomorrow, a highly divergent right-entrance region of a 170kt H3 streak will be positioned over ERN TX, while a number of mesoscale disturbances will approach the area. Buy mid-day, a “Leadâ€￾ vorticity ribbon is advertised to be aligned along a LBR to GRK line, while a more significant disturbance will be oriented along an SPS to SJT line. Throughout this period, UVV’s will rapidly increase and precipitation should initiate in ECNTRL TX where the CAP will erode first, well S and E of significant SFC boundaries. Despite SFC Td’s into the low 60’s, the shallow nature of the nature of the moisture along with widespread cloud cover will contribute to very low mixed-parcel CAPE’s. This alone should minimize severe potential, despite impressive shear parameters (SFC-6 km shear to 70 kts).

- bill

 

[Bill Tabor]

Ok, well latest NAM results in and it isn't what we wanted if chasing is desirable. Basically looks to me that the whole thing looks similar to my previous forecast but the southern low may move a bit further se and not intensify as much. This will mean less return flow and good storm food in Tx and elimination of much of our lower level tornadic wind fields. Correspondingly storms probably won't be as severe either. Another variable is the light rain we are experiencing across the target area tonight. While that may help in evapotranspiration it may inhibit insolation due to cloud cover.

Right now I'm reducing those torn probabilities to 2% and based on this model run that may still be too high. Target area is still generally the same - but I might move it a bit south and perhaps east a bit.

Additionally latest run seems to show crappy sfc wind component except near coast and closer to 0Z. 850mb winds at 0Z are even more messed up with some from the nw. EHI's have dropped very low, and LI's are now forecast to max just below -2.

Guess we'll see how the next run is tomorrow along with RUC input and mesoscaleanalysis as the day wears on. I'm not that far away so can jump if something worth while. Otherwise my current expectation level is somewhat low. At the moment I doubt it is something for any of you to make a fairly long drive over unless the situation improves.

Perhaps the rest of you have an angle or opinion?

Edit: Just noticed my post timestamp is showing as almost an hour later than actually post. It isn't even 12:52 as I type this it is 12:10. Is the server on eastern time? I may post a note to Tim and others about this.

 

[Bill Tabor]

Update: After looking at RUC, NAM, and mesoscale analysis products it looks pretty poor for chasing. Instabilities are staying low, 500mb vort show negative pva and subsidence expected over area, low level winds aren't great. Oh well it is January. At least it appears to be raining a bit, and that seems to be helping the allergy based asthma I've had the last week.

 

[C Brian Batey]

Originally posted by Bill Tabor
Update: After looking at RUC, NAM, and mesoscale analysis products it looks pretty poor for chasing. Instabilities are staying low, 500mb vort show negative pva and subsidence expected over area, low level winds aren't great. Oh well it is January. At least it appears to be raining a bit, and that seems to be helping the allergy based asthma I've had the last week.

We only got a few, disappointing sprinkles here in Ft. Worth. The lack of rain is a far greater issue than the missed chase potential.

I watched the numbers till noon, then took the wife and kids to the zoo. Not a wasted day.

Can't wait for the 'real' season to arrive!

brianb
N5ACN