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andyhb

May 7th-9th Severe Weather Episodes

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Considering heading south to Ardmore-Durant to see if any storms can fire up and ride the heating boundary (as Andy mentioned above). Otherwise I'll just stay in OUN and watch the show from afar. 

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I don't want to beat a dead horse or regress, but in no way was Brett implying that hi-res NWP will/should replace forecasters. Not sure where you got that from. He was acknowledging how well CAMs seem to be performing this season, and that ignoring their consensus should be done at one's own peril (e.g., dewpoints in the 60s yesterday, characteristics of UH swaths from the past few threats, etc). 

 

Of course epic fails will still occur given the extremely nonlinear nature of convective initiation and the occasional failure of parameterization schemes to capture things like surface fluxes during droughts, etc. Observations are still crucial and nothing can really be substituted for forecaster intuition and experience, but IMO we are beginning to enter a time where hi-res stuff offers insight that you can't get otherwise. Once a model is spun-up and the physics adjust and balance, it's totally reasonable to expect these models to have represent extremely small scale features that models with lower grid spacings and especially our current network of observations can't capture. Of course if all models are showing a certain UH swath that comes to verify it can be a bit of a black box problem to determine what exactly they all honed in on to cause that. But given the relatively low density of our observing networks, and assuming proper analysis and quality control of the data fed in, I think one has to at least strongly consider the immense value that a model data assimilation system (that is, the optimal combination of both the observation networks and the model's physical constraints, carrying information from past assimilation cycles forward, and having a complete suite of physics (i.e. a soil model for surface fluxes, etc)) can offer as a forecasting tool.

 

Completely agree with all this.

 

With regard to my post last night about "old fashioned meteorology," that was just sarcasm with a tinge of truth to it. I should probably be less sarcastic here in general lol.

 

There's probably more common ground between the two warring sides on NWP than the past few days would lead one to believe. We all agree that human forecasters are an integral part of the warning process, and will continue to be so for the foreseeable future. We all also (hopefully) agree that NWP has monumentally improved the accuracy of our convective forecasts over the past 20 years. Quibbling over the details within the middle ground is perhaps needless in some ways, yet not in others. Speaking strictly for myself (not representative of the school or any institution here), I sense there may be some psychological bias that comes into play wherein some forecasters "try too hard" to beat the models in some cases. This isn't really addressed at NWS/SPC, but moreso among the rest of us who forecast for our own purposes. At the risk of copping out, it's such a fine line with so many caveats, though. CAMs have failed spectacularly plenty of times, and will do so again in the future. Increasingly, though, we will become well calibrated to these biases and failure modes, making stunning forecast failures less likely. Ensemble approaches like the one currently operated by NCAR, along with the upcoming HRRR ensemble, will also help to smooth out the rough edges of CAM-based forecasting.

 

Looking at yesterday as an example, I don't want to speak for NWS/SPC, but my hunch is that even they would admit the CAM guidance altered their SWODY1 outlooks in a notable way from what they would've been 10-20 years ago. Large scale models like the GFS, NAM, and RGEM generally lacked any QPF signal to the south of N OK during the daylight hours. Point soundings from these models, along with the 08/00z AMA sounding, certainly lent credence to serious capping concerns. But then the CAMs came in, especially yesterday morning, and generally supported convection in SW OK with high confidence. And then there's the moisture return issue, which has already been beaten to death. But suffice it to say, NWP and particularly CAM guidance was an indispensable tool yesterday. And at the risk of being slightly controversial, "good old fashioned hand analysis" approaches to assessing moisture return and CI on the dryline did not hold up particularly well in this case.

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Watch the differential heating boundary near the Red River later on for enhanced tornado potential, RAP forecasts seem to not have this boundary indicated and thus low level shear/SRH may be underdone significantly. Would think any storm that tracks in this vicinity could keep going into AR for a distance too.

I was thinking about that yesterday. There may be something of an extra moist warm sector with 70 dew points, advancing into a a mostly-warm warm sector, possibly with a little extra wind backing (SE winds) near Texarkana. Now that there is an outflow boundary in this area, this would be called an outflow boundary edge, (or differential heating boundary, as you put it,) perhaps moreso than it would be called a warm front.

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I don't want to beat a dead horse or regress, but in no way was Brett implying that hi-res NWP will/should replace forecasters. Not sure where you got that from. He was acknowledging how well CAMs seem to be performing this season, and that ignoring their consensus should be done at one's own peril (e.g., dewpoints in the 60s yesterday, characteristics of UH swaths from the past few threats, etc).

Of course epic fails will still occur given the extremely nonlinear nature of convective initiation and the occasional failure of parameterization schemes to capture things like surface fluxes during droughts, etc. Observations are still crucial and nothing can really be substituted for forecaster intuition and experience, but IMO we are beginning to enter a time where hi-res stuff offers insight that you can't get otherwise. Once a model is spun-up and the physics adjust and balance, it's totally reasonable to expect these models to have represent extremely small scale features that models with lower grid spacings and especially our current network of observations can't capture. Of course if all models are showing a certain UH swath that comes to verify it can be a bit of a black box problem to determine what exactly they all honed in on to cause that. But given the relatively low density of our observing networks, and assuming proper analysis and quality control of the data fed in, I think one has to at least strongly consider the immense value that a model data assimilation system (that is, the optimal combination of both the observation networks and the model's physical constraints, carrying information from past assimilation cycles forward, and having a complete suite of physics (i.e. a soil model for surface fluxes, etc)) can offer as a forecasting tool.

Of course.

I think I was unclear in my comments. But given it was beaten to death already.. I will leave it at that.

Btw - are you enrolled or have you been a sit in? ;)

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Wikipedia lists the tornado outbreaks of the year, and this web page shows there have been no EF-3s since February. I don't personally remember seeing any storm surveys of EF-3 or better damage since February.

 

Last EF-3 I think was the Appomatox VA tornado which was in late February

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Sfc temps across much of SE OK are pretty brutal right now in the wake of the morning MCS. It will take rapid airmass modification for sustained supercells in that environment. If we manage to get CI at all on the dryline in OK, the latest HRRR scenario of maximized intensity near I-35 and then weakening to the E of there is plausible. Down in TX is a different story, but I haven't looked at that portion of the setup in enough detail to comment yet.

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Wikipedia lists the tornado outbreaks of the year, and this web page shows there have been no EF-3s since February. I don't personally remember seeing any storm surveys of EF-3 or better damage since February.

 

you are correct. last EF3 was 2/24 in VA

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Last EF-3 I think was the Appomatox VA tornado which was in late February

Actually the most recent one was the Tappahannock, VA tornado later that night.

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Actually the most recent one was the Tappahannock, VA tornado later that night.

 

Evergreen, VA, EF3 2027 to 2044

Middle Peninsula, VA EF3 2334 to 0005

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Looks like pretty decent initiation near Medicine Lodge KS... hail already up to ping pong ball sized indicated by radar

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Cu field looks to be deepening closer to the Red River N/NNW of the metroplex.

 

Also looks like some towers going up around Duncan, OK. 

 

GOES19252016130Xp5iA8.jpg

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Things seem to be progressing as expected.  It is curious that the now svr warned southern OK cell initiated near where the Lawton/Frederick cell from yesterday expired.  Points in se OK seem to be prime with a stronger low level inflow than yesterday. Could make for an interesting evening.

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There is some rotation near Pauls Valley OK. It has a supercell shape too. (thankfully, not left-moving like yesterday!) It seems to be in a fairly good environment for tornadoes.

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Developing severe-warned supercell north of Ardmore is looking interesting, already has a hook-like appendage... Directional shear on TLX, while not exactly strong, is certainly enough for low-level mesocyclone production. Looks as though that storm should remain isolated as well... Interested to see if it can root itself and become well established. 

 

EDIT:TOG

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Big cone, getting stronger.

Has some pretty sweet motion on it too. Finally a legit supercell tornado!

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