Oklahoma’s Secret Tropical Storm

Good morning. Oklahoma had a tropical storm overnight.

At least that’s a legitimate claim that can be made, since Erin still was being classified as a tropical depression last evening before strengthening to produce sustained tropical storm force winds. Isolated surface gusts even exceeded hurricane force. [Watonga’s airport station gusted to 82 mph in a thunderstorm at 745Z — 2:45 a.m. CDT.] Pending research and postmortem study by NHC and Oklahoma-based meteorologists, I’ll just call it a warm-core low for now.

What follows are excerpts from a series of messages I sent privately to others overnight. They give one atmospheric scientist’s running, real-time perspective on a bizarre event that isn’t going to be forgotten in meteorological circles, even if it doesn’t get a lot of public airplay.

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It has been impressive to watch how well this system has held together a circulation after moving inland — indeed, looking better inland than it ever did over the Gulf in many respects.

Admittedly I had checked out for a few hours after going home tonight, then “woke up” to find all this going on. It reminds me of one of those Australian “landphoons,” which are fairly rare even there, and nearly unprecedented here. Alicia is the last tropical system that was so well defined by the time it got into these parts, and it was in a steadily weakened state from being a hurricane. By contrast, Erin is stronger in many ways than it ever was over the Gulf, stronger than Alicia was at this point too, now that this LLJ (low level jet) has strengthened and mixed down to the surface.

Yesterday, Elke and I watched a small, tilted updraft with scary looking but nonrotating lowerings while we were eating lunch, and after getting to work and going through the usual routine of setting up numerous workstation loops and performing analyses, it became apparent from the large hodographs, diurnally aided buoyancy, discrete cells with some shear, and weak CINH, that an mesoscale discussion obviously was needed. About the time I started typing it, a storm over Kiowa County spun up, did some damage, and prompted a tornado warning from WFO Norman, for the next county to its N. After a few hours of this, the storm modes got less discrete and the convection started to consolidate under some cooling cloud tops with aid from this deepening/strengthening LLJ, prompting a flurry of heavy rain related products (flash flood warnings from Norman, heavy rain mesoscale discussion from me, etc.).

What went wrong was my thinking that the LLJ would weaken by now. Not so! The heavy rain threat is there, as expected, but the severe potential came back. Thanks to ridiculously high sfc theta-e, no stable layers atop the BL, and the virtual temperature correction, SBCINH<25 J/kg even at this wee hour. As for what to call this, how about simply a low? No use categorizing this inland iteration of Erin until the inevitable round of conference then formal paper(s) are done (as so often happens with bizarre events in Oklahoma, where mesonet data allows a more precise sampling than usual). ITMT, I can say with confidence that it is warm core aloft, per 00Z 500 mb analysis but may have had some weak baroclinic tendencies down low.

Still a lot left to learn about this crazy atmosphere of ours…

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None-the-less… 🙂

A thought occurred to me as I was posting about this in a private forum:

As of 4 a.m. CDT, Erin still is being called a tropical depression by HPC, but has been producing tropical storm force sustained winds right here in Oklahoma. That discussion is incorrect, in that those are sustained TS force winds (as shown in this OK mesonet plot and others overnight) — not just gusts, and not just in thunderstorms either. There also have been TS force, southeasterly inflow (not outflow) winds.

NHC cannot have the luxury to wait for conference papers or articles in the formal meteorology journals (even one with a relatively fast turnaround time like EJSSM). They’ll have to classify this burst of intensification as something over Oklahoma.

How is this going to be handled in the NHC best tracks? How should it be handled?

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If you catch this post in the next hour or two, check out this loop showing the “eye” from OKC’s terminal Doppler weather radar (TDWR):

If not, I’ve saved a still image from TDWR.

BTW, for those nor familiar with OK Mesonet plots like that above, those winds are not in kt, but in MPH. Still, thanks to a low-level jet that has mixed substantially down to the surface, we’ve had sustained, tropical storm strength gradient winds in the area from what still is a warm core low, and was a named tropical storm at one point. Call it what you will.

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There were a few tornado reports in the east semicircle of Erin yesterday in NW TX and W OK…nothing significant, just small/brief touchdowns…but that was more than anyone believed would occur before the event began to unfold. Check out the tornado and wind reports received so far.

Although it was east of the strongest low level wind fields, and nontornadic, a small supercell also moved just E of Norman and was photographed by Rich Thompson. Note the pronounced wall cloud in this picture.

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Now it’s approaching 6 a.m., and I still can’t go to sleep, but probably will try soon. The main spiral band is moving past me now. Surface sustained winds still are legit TS strength farther NW near the eye. Yes, eye. [See reflectivity image at top.]

Check out the base Doppler velocity image at the next scan. Classical…

Yes, you’re reading it right: There are a few pixels of 60-70 kt inbound velocities just off the deck, on the south side of the eye. There were hurricane-force winds above the surface, over Calumet, Oklahoma. It’s hard to believe I’m typing this.

Those who are up will be able to follow this amazing event for the rest of the morning on the Twin Lakes (Oklahoma City) radar:
OKC radar from COD
…and linked loops.

Maybe it will spin down from here on…maybe not. I’ve lost all confidence in my ability to predict this system and have decided to just enjoy it!

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655 a.m.: Geez, I need to go to bed. Bad.

Now, why am I calling this a “secret storm”? It certainly isn’t going to be a secret for meteorologists…far from it! But while Elke and I were standing outside a few minutes ago marveling at this beautiful, windy, rainy weather, I realized how different media treatment would be with the very same conditions and radar imagery superimposed on South Florida and called a tropical storm. TV stations there would be going wall to wall, all night. The Weather Channel would have crews in dripping blue ponchos reporting from every nook and cranny of the area. Matt Drudge would have red-colored headlines about a tropical storm in Florida. CNN would be showing pictures of harried crowds filling shopping carts with bottled water at Publix. Panic and mayhem everywhere…live at 11!

But here in Oklahoma, it’s a scientific curiosity for the semantic dickering and curious investigation of weather scientists and enthusiasts — but for the public, merely a nuisance.

Displayed radar imagery courtesy College of DuPage


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