Shane Adams
Not sure what you're seeing...Mon is a capbust and Tuesday's in the trees as of now. FWIW, IMO, Fri looks better at this point.
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4/2/10 FCST: TX/OK
- Thread starter Skip Talbot
- Start date
Not sure what you're seeing...Mon is a capbust and Tuesday's in the trees as of now. FWIW, IMO, Fri looks better at this point.
Mikey Gribble
EF5
What makes you think the models are over forecasting dewpoints by 5-15 degrees. The NAM picked up on Friday last night and it is pretty much in line with the GFS showing >55 already over the warm sector at 12Z with >60 over the southern half of Texas. Both the GFS and NAM also show a very strong LLJ in place. As long as that LLJ isn't veering badly, it won't take long at all to advect dewpoints in the upper 50's all the way up past the Red River.
5-15 degrees is a lot. I usually drop dewpoints a couple degrees from what the models are showing on early spring setups, but I think upper 50's along the Red River and low 60's across southern Texas are reasonable with this setup. If the models are off 5-15 degrees that would mean dewpoints are actually going to be 39-54 degrees across the target area. I don't see that happening.
Justin Teague
EF3
Mikey,
Greg was referencing the 03/29 12z model forecast for 03/30 0z vs the observed readings. It isn't my intent to speak for Greg, but I believe that he is making the assumption that the erroneus 0z Td forecast (Tds of 5-15 degrees above observed readings) is playing into subsequent model output for surface dewpoints.
I haven't formulated my own opinion on the potential for substantial moisture return. I will say that with 3-4 days of strong southerly flow, it certainly isn't out of the question. With that said, we've endured a long winter and a slow storm season (to date), so it's understandable that we are all a little excited to see the models forecasting some decent moisture underneath a potent system.
Greg was referencing the 03/29 12z model forecast for 03/30 0z vs the observed readings. It isn't my intent to speak for Greg, but I believe that he is making the assumption that the erroneus 0z Td forecast (Tds of 5-15 degrees above observed readings) is playing into subsequent model output for surface dewpoints.
I haven't formulated my own opinion on the potential for substantial moisture return. I will say that with 3-4 days of strong southerly flow, it certainly isn't out of the question. With that said, we've endured a long winter and a slow storm season (to date), so it's understandable that we are all a little excited to see the models forecasting some decent moisture underneath a potent system.
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Andrew Ryan
EF3
Don't have a lot of time, so I'll quickly type some thoughts...
The 12z GFS and NAM have me worried but I haven't given up yet. Both models are still showing meriodinal flow in the Upper Levels which makes it likely for a squall line mess. Also, the LLJ is displaced to the east of the best thermodynamics, although the GFS is not as far off as the NAM. CAPE is nonexistant on the NAM but it's marginal on the GFS with values >1000 in the warm sector.
The good news in all of this, the models *seem* to be handling the moisture a little bit better. Although we still have mid-40s to low-50 dews in GOM. But the winds have switched to the S/SW. Not great, but better than it was before.
The 12z GFS and NAM have me worried but I haven't given up yet. Both models are still showing meriodinal flow in the Upper Levels which makes it likely for a squall line mess. Also, the LLJ is displaced to the east of the best thermodynamics, although the GFS is not as far off as the NAM. CAPE is nonexistant on the NAM but it's marginal on the GFS with values >1000 in the warm sector.
The good news in all of this, the models *seem* to be handling the moisture a little bit better. Although we still have mid-40s to low-50 dews in GOM. But the winds have switched to the S/SW. Not great, but better than it was before.
Skip Talbot
EF5
The 12z NAM and 12z GFS are in fairly good agreement with the position and orientation of the upper level trough and low level jet. The GFS is still a little faster, however. i was really hoping we'd see more veering between the 850 mb and 500 mb winds as this setup approached, but they are almost completely unidirectional on both models. The GFS is even veering the surface winds. This really does not bode well for storm mode, and its looking like a messy squall line will form in central OK down through TX. The 12z NAM has much better backed surface winds, but then it seriously drops the moisture and instability. Both models are not suggesting good chase opportunities at this point. The GFS is indicating enough bulk shear and instability for supercells, but with the forcing, lack of cap, and undirectional wind profile, the best we could hope for are embedded supercells in a training line. The NAM is indicating a similar scenario with less instability. It looks like a tough chase at this point, one that will involve being on the storms at imitation, and trying to find a break in the line.
Here are some notes I took w.r.t the morning runs...
- the GFS needs Pepto-Bismol cause its way too progressive in the frontal position and timing of things. As a result it busts out a squall line from MKC to ADM @ 18Z while the NAM has nothing over the eastern Plains, keeping all the QPF back over WRN KS down into the TX Panhandle. However...
- the GFS is bullish with the moisture return bringing 62 dews in the DFW metroplex at 18Z while the NAM only has 60dews barely making it to I-20 corridor. As a result...
- the GFS is more bullish with CAPE along I-35 corridor in N TX painting ~1500 SBCAPE over said area
- the GFS 850 winds are slightly more backed and also stronger
David Goines
I'm assuming the SPC is going with the GFS for Friday as they have a wide slight risk already out.
"VERTICAL SHEAR WILL BE STG ENOUGH TO SUPPORT TORNADO POTENTIAL...WHICH WILL DEPEND LARGELY ON FACTORS SUCH AS PREDOMINANCE OF DISCRETE OR SEMI-DISCRETE STORM MODES THAT ARE TOO SMALL IN SCALE TO FCST THIS FAR IN ADVANCE."
I'm assuming their "slight risk" is more for the hail/wind threat of the squall line but with the NAM only showing CAPE barely above 500 J/kg in north central Texas, I would think they have to be basing their outlook on the GFS as it still shows CAPE 1500+.
"VERTICAL SHEAR WILL BE STG ENOUGH TO SUPPORT TORNADO POTENTIAL...WHICH WILL DEPEND LARGELY ON FACTORS SUCH AS PREDOMINANCE OF DISCRETE OR SEMI-DISCRETE STORM MODES THAT ARE TOO SMALL IN SCALE TO FCST THIS FAR IN ADVANCE."
I'm assuming their "slight risk" is more for the hail/wind threat of the squall line but with the NAM only showing CAPE barely above 500 J/kg in north central Texas, I would think they have to be basing their outlook on the GFS as it still shows CAPE 1500+.
Jeff House
Supporter
WRF/NAM had major changes at 12Z Wed. Will assume it's a rouge run and focus on the Euro 12Z and GFS 6/12Z. Euro/GFS have better pattern agreement, than outlier WRF/NAM, but still have differences including all-important timing of s/w ejection.
Moving to moisture: Still quite comfortable in H-Town so we have lots of moisture homework to do. Gulf is still hurting but rich moisture is down in the Bay of Campeche. It will not be pulled north through tonight. However trajectories tug on that Thursday. We also have evapo-transpiration; however, that can mix out pretty quick when afternoon breezes start. Combining above thoughts I'm thinking Td=60 in the target zone Friday afternoon even if morning dews somehow reach as high as 68 in Texas. Some will mix out, but I'm not a Td 50s bear either. Afternoon dews along Red River about 60 IMO.
The 850 winds are a challenge right now. They appear to veer off in OK; might not be so bad in North Texas up to mid-afternoon Fri before veering off. TX 850s look to start out SSW up through about 18-21Z Fri.
The 500mb flow has been covered well; better veering in TX. Could be linear action in OK before 18Z Fri. As always, that does not slam the door shut. Could lay out good boundaries. However my target is North Texas up to far southern OK. Hoping to keep DFW out of it, partly out of concern for the population but mainly my selfish desire to avoid traffic. At least I admit it.
Bottom line: Will seek out the triple point. If CF is too fast will seek DL/CF intersection south. I'm not particularly excited about this chase, but with a Holiday Weekend it's game on. Happy chasing!
Moving to moisture: Still quite comfortable in H-Town so we have lots of moisture homework to do. Gulf is still hurting but rich moisture is down in the Bay of Campeche. It will not be pulled north through tonight. However trajectories tug on that Thursday. We also have evapo-transpiration; however, that can mix out pretty quick when afternoon breezes start. Combining above thoughts I'm thinking Td=60 in the target zone Friday afternoon even if morning dews somehow reach as high as 68 in Texas. Some will mix out, but I'm not a Td 50s bear either. Afternoon dews along Red River about 60 IMO.
The 850 winds are a challenge right now. They appear to veer off in OK; might not be so bad in North Texas up to mid-afternoon Fri before veering off. TX 850s look to start out SSW up through about 18-21Z Fri.
The 500mb flow has been covered well; better veering in TX. Could be linear action in OK before 18Z Fri. As always, that does not slam the door shut. Could lay out good boundaries. However my target is North Texas up to far southern OK. Hoping to keep DFW out of it, partly out of concern for the population but mainly my selfish desire to avoid traffic. At least I admit it.
Bottom line: Will seek out the triple point. If CF is too fast will seek DL/CF intersection south. I'm not particularly excited about this chase, but with a Holiday Weekend it's game on. Happy chasing!
Chris Lott
EF4
I'm sticking further south between the Waco-DFW area on Friday. GFS does show better moisture return than the NAM, and the 850 and 500mb winds look better to me in this area. If that 1500 j/kg CAPE that the GFS is forecasting would verify, I think we might have a few discrete cells before it blows up into a massive MCS. I think the northern target has MCS written all over it.I'm sure it will change before Friday, but I'm off and hopefully won't have to burn a whole lot of gas on this one. It's April, so I'll take what I can get. Come on GFS, please be right.
Well guess Ill sum everything up now by stating whats very obvious...
...N TX...
Storms should be ongoing in the morning across the WRN half of OK/KS in squall-line type fashion. As the morning hours progress, the line of storms should build southward into WRN portions of N TX and this is where there is the only slightest hope of chasing. The problem here is that the dryline will already be on the move in the morning hours across N TX and extensive stratus will retard daytime heating. Moisture will not be a problem as all SREF ensemble members show 60 dews north to the Red River. The best we can hope for is a QLCS in that its not a complete solid squall line like we saw last Wednesday (3/24) across N TX. If we can just get a broken line of storms and strong enough capping to offset the incredible amount of forcing then we may at least have a chance but I have strong doubts. I do know that CINH will be stronger the further south you go, say towards Waco, and like Chris Lott has pointed out above, that may be your best chance of getting more discrete storms but not shear that the shear will be better further south.
Think I may sit this one out as a result, even though Im sitting right in the DFW metroplex. Think the biggest severe threat will occur across ERN and NERN parts of TX as the line wont arrive there until peak heating and enough mixing should occur to allow for some breaks in the stratus there.
...N TX...
Storms should be ongoing in the morning across the WRN half of OK/KS in squall-line type fashion. As the morning hours progress, the line of storms should build southward into WRN portions of N TX and this is where there is the only slightest hope of chasing. The problem here is that the dryline will already be on the move in the morning hours across N TX and extensive stratus will retard daytime heating. Moisture will not be a problem as all SREF ensemble members show 60 dews north to the Red River. The best we can hope for is a QLCS in that its not a complete solid squall line like we saw last Wednesday (3/24) across N TX. If we can just get a broken line of storms and strong enough capping to offset the incredible amount of forcing then we may at least have a chance but I have strong doubts. I do know that CINH will be stronger the further south you go, say towards Waco, and like Chris Lott has pointed out above, that may be your best chance of getting more discrete storms but not shear that the shear will be better further south.
Think I may sit this one out as a result, even though Im sitting right in the DFW metroplex. Think the biggest severe threat will occur across ERN and NERN parts of TX as the line wont arrive there until peak heating and enough mixing should occur to allow for some breaks in the stratus there.
Tim Marshall
EF2
TARGET: CANTON, TX TIME OF DEPARTURE: 12:30 PM - Squall line has weakened significantly this morning and will redevelop later this afternoon. PROS - Strong upper dynamics with cold pool will move slowly eastward today so I can at least keep ahead of the line, CONS - Linear forcing, veered surface winds progged, low clouds/low CAPE east of the line. I'm primarily going out for some hail video and to begin the new year with my first chase.
