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Severe Weather Thread November 7-8


David Reimer

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Really one of the only times I've seen it even close to spot-on was the April 27th outbreak, which a lot of people could see the potential far before the runs ever came out for that afternoon (And it was kind of hard to overestimate the dynamics for that one).

I've seen the HRRR nail plenty of setups....but also blow some too.

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I haven't looked at the current run of the NAM, but a few prior runs did hint at some convective-related stabilization across ctrl TX. I just mentioned it as a reason not to completely discount the HRRR just yet, so no I am not trolling.

I'm not accusing you of trolling. It's just that I looked back through the past 8 runs of the NAM and they have been remarkably consistent w/r/t instability. The main difference is that each run has slowly increased instability and expanded the good instability northward.

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I haven't looked at the current run of the NAM, but a few prior runs did hint at some convective-related stabilization across ctrl TX. I just mentioned it as a reason not to completely discount the HRRR just yet, so no I am not trolling.

Here. Note that I am NOT taking these verbatim as is, just wanted to provide some evidence for what I was talking about:

QPF

eta24hrsfcprcp.gif

Sfc T

eta24hrsfctemp.gif

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I'm not accusing you of trolling. It's just that I looked back through the past 8 runs of the NAM and they have been remarkably consistent w/r/t instability. The main difference is that each run has slowly increased instability and expanded the good instability northward.

I know you aren't accusing me. I was responding to both you and Andy, and some parts of it were directed more towards Andy than you.

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I haven't looked at the current run of the NAM, but a few prior runs did hint at some convective-related stabilization across ctrl TX. I just mentioned it as a reason not to completely discount the HRRR just yet, so no I am not trolling.

Was just joking man.

But yeah, the new day 1 is intriguing, if earlier convection fails to influence the threat significantly, I could potentially see a mod at some point within the next outlooks.

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Was just joking man.

But yeah, the new day 1 is intriguing, if earlier convection fails to influence the threat significantly, I could potentially see a mod at some point within the next outlooks.

Sorry about that then, haha. I agree that if the morning convection ends up not doing much, a MDT ought to be in the works.

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I'm not accusing you of trolling. It's just that I looked back through the past 8 runs of the NAM and they have been remarkably consistent w/r/t instability. The main difference is that each run has slowly increased instability and expanded the good instability northward.

Got to give the new NAM some credit for being remarkably consistent. Even the EC and other globals trending towards it regarding a much slower ejection of the western wave and a break in the early DMC. This is how any model is supposed to operate...make very slow trends so it is actually usable in an operational environment. I still have hope for the NAM even though it has not been stellar since it first came out a few weeks ago...this is something the previous NAM never would have been capable of--steady and consistent trends/changes without erratic run by run differences.

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I've seen the HRRR nail plenty of setups....but also blow some too.

The HRRR is a tough one since it runs hourly. Hard to analyze something that may whiff one hour then nail it the next. That said, the HRRR seems to be more effective where there is clear linear forcing for initiation when significant capping is not a concern. As tornadotony said, it otherwise seems to be overly sensitive to diffuse and/or non-existent forcing mechanisms at times, and this can make it challenging to use operationally. SPC rarely mentions it for this reason I believe.

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New Day 1 keeps the same probs, makes the 10% hatched tornado contour a little bigger.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0646 AM CST MON NOV 07 2011

VALID 071300Z - 081200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE SOUTHERN

PLAINS...

A BROAD UPPER TROUGH IS NOW IN PLACE ACROSS THE WESTERN

STATES...WITH THE MAIN MID/UPPER LEVEL JET AXIS EXTENDING FROM

NORTHERN MEXICO INTO WEST TX. A WELL-DEFINED SHORTWAVE TROUGH NOW

OVER SOUTHERN AZ WILL TRACK EASTWARD AND HELP TO PRODUCE THE RISK OF

SEVERE STORMS LATER TODAY ACROSS PARTS OF THE SOUTHERN PLAINS.

SCATTERED THUNDERSTORMS ARE ONGOING THIS MORNING ACROSS OK IN A

REGION OF BROAD WARM ADVECTION. THESE STORMS WILL LIFT NORTHWARD

THROUGH THE DAY WITH A RISK OF MARGINALLY SEVERE HAIL. IN THE WAKE

OF THIS ACTIVITY...STRENGTHENING SOUTHERLY LOW LEVEL WINDS WILL HELP

TO MOISTEN/DESTABILIZE THE AIR MASS ACROSS PORTIONS OF WESTERN NORTH

TX AND WESTERN OK. A FEW BREAKS IN THE CLOUDS ARE EXPECTED IN THIS

REGION LEADING TO TEMPERATURES IN THE 70S AND AFTERNOON MLCAPE

VALUES OF 1500+ J/KG. FORECAST SOUNDINGS BY MID-LATE AFTERNOON

INDICATE SUBSTANTIAL LOW LEVEL AND DEEP LAYER VERTICAL SHEAR

FAVORABLE FOR SUPERCELL STORMS. MOST MESOSCALE MODEL SOLUTIONS

AGREE ON THE DEVELOPMENT OF ISOLATED THUNDERSTORMS DURING THE MAX

HEATING PERIOD ACROSS WESTERN OK AND PORTIONS OF WESTERN NORTH TX.

THESE STORMS WILL POSE A RISK OF VERY LARGE HAIL AND A FEW

TORNADOES. AN ISOLATED STRONG TORNADO IS POSSIBLE. THE ACTIVITY

WILL SPREAD NORTHEASTWARD INTO NORTH-CENTRAL OK DURING THE EARLY

EVENING AND SLOWLY WEAKEN.

AFTER DARK...A SECOND ROUND OF INTENSE STORMS IS EXPECTED TO FORM

ALONG THE SURFACE DRYLINE/PACIFIC COLD FRONT ACROSS WEST TX AND

WESTERN OK. THESE STORMS ARE LIKELY TO GROW RATHER QUICKLY INTO A

BROKEN SQUALL LINE AND TRACK EASTWARD ACROSS THE SLIGHT RISK AREA.

WHILE THE INTENSITY OF SEVERE WEATHER IS EXPECTED TO BE LESS WITH

THESE STORMS THAN EARLIER IN THE DAY...ALL MODES OF SEVERE WEATHER

ARE POSSIBLE ESPECIALLY PRIOR TO MIDNIGHT.

..HART/COHEN.. 11/07/2011

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The 12Z NAM makes Childress, TX look like the sweet spot around 6 PM this evening. Overall, it's looking like this is going to be a long-duration event with the tornado threat lasting well into the evening. Eventually, a very impressive squall line should fire off the dry line/cold front which will then chase me back home to Dallas.

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Looking at the 12z suite, I see the RUC and the HRRR not backing surface flow as much as the NAM. I mean it's not a huge difference, due south at the surface versus SSE, but it might be the difference between a couple tornadoes and a mini-outbreak.

I'd say that's something to watch later in the day, if the surface winds back as much as we hope they will.

Edit: closer to 0z the HRRR finally remedies the situation, although up through at least 22z the winds are still due S until you get north of the axis of instability

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