8/18-19/07 NOW: OK (TD Erin)

[Rocky Rascovich]

The remnants of Erin are now nearing the Childress area and the spin on radar is still very impressive. Low level shear is evident all across the western half of Oklahoma and for the third time today, a tornado warning has been issued in western Okla., this time for Cotton County as of just moments ago.

Apparently a few hours ago, a tornado was confirmed somewhere in SW Okla. which "blew apart" a barn according to eyewitnesses. I'll have to check the LSR's.

Earlier around 5pm, I walked out of a grocery store in NW OKC and saw a distinct meso with banding and inflow tails in the midlevels about 8000 feet or so AGL. I briefly gave chase, intercepted it around Lake Hefner and experienced near torrential rain and winds to about 15mph... big hoo haa! Still, mid level rotation was surely there albeit slow.

Current radar suggests the humble abode 5 NW of Piedmont may have an action packed night with considerable rain and some lightning with a quick spin up not out of the question... hopefully not AT my place thank you!

 

[Angie Norris]

I intercepted a rather intense shower this afternoon in Moore about 3pm...visiblity went to less than 1/4 mile and traffic came to an almost immediate halt (and no, I wasn't chasing it...I was on the way home from Midwest City). Been watching radar all afternoon...there are currently a couple of imbedded storms moving northeast out of the Lawton area that look to be worth keeping an eye on. If they can hold together, maybe there will be something of interest for Norman in a bit.

 

[Jeff Snyder]

Interesting situation in OK with the large area of very strong winds in southwestern OK. Mesonet is showing a possible mesolow in southwestern OK, but I was surprised to see a couple of stations (Medicine Park and Apache) gusting >45 mph out of the southeast (so it isn't convective outflow). Interestingly, the strongest echoes are northwest of the strongest winds, which only makes me think that the >45mph gusts are associated with intense inflow of some sort. FDR and TLX showing a tight mesoscale circulation down there, and FDR VWP indicating ~55kt flow a couple km off the sfc. Interesting!

 

[Donald Giuliano]

Erin Reintensifying into Tropical Storm in Oklahoma?!?

Apparently Erin has reintensified over land to a tropical storm this evening as per the Oklahoma Mesonet...check out this surface map with sustained winds of 40mph and gusts near 50mph!

http://americium.gcn.ou.edu/ts_erin.gif

Also, the FDR/TLX VWPs are pretty impressive, it's not surprising there have been some embedded supercells with this activity.

 

[Jeff Snyder]

Has a tropical depression EVER been upgraded to a tropical storm while inland? I only ask because there have been a few >60mph wind gusts occurring in Caddo Co (and probably into Blaine Co soon), and a 75 mph wind gust was measured at the Ft. Cobb mesonet site about an hour ago, all associated with the warm-core system that is still Tropical Depression Erin (HPC is maintaining it as TD Erin). >55mph gusts are now being reported as far north as Watonga. The precip looks a little "comma"-like, though sfc obs don't show a whole lot of baroclinity in the different sectors of that comma signature. The temperature is a little lower at locations west of the precip -- low 70s west of the precip, with mid-70s to near 80 in and east of the heaviest precip. The surface obs would not necessarily disagree with a tropical storm classification, though, I suppose, the asymmetry to the wind field and precip pattern may argue against such a label. Very high precipitation efficiencies (2.5"/hr reported recently at the Weatherford mesonet site, with Ft. Cobb reporting almost 7" of rain in the past 3 hrs!) are occurring, not surprising given the tropical nature of the convection. New Flash Flood warning for several counties SW and W of OKC mentioned 5-7" inches of rain possible in the next 3 hours.

Wow, unexpectedly, this is a very interesting event! It's not very often that we get a real Tropical Depression in Oklahoma! As a reminder, this is Tropical Depression Erin (perhaps tropical storm Erin, or subtropical storm Erin?), with advisories being issued by the HPC.

 

[Donald Giuliano]

After that convection really exploded, the surface wind field has really ramped up with this system. There have been a number of wind obs sustained at over 50mph. Amazing stuff!

 

[Danny Neal]

Well with all the flooding you guys have been getting in OK, it still technically is "over water" j/k of course. Itll be interesting to see if this continues to strengthen what other severe weather will occur, namely in the form of tornadoes.

 

[Donald Giuliano]

Decided to plot this in WxScope...wow!

http://americium.gcn.ou.edu/ts_erin.png

 

[Donald Giuliano]

I think a tropical depression was upgraded while inland several years back...IIRC it was in MS/AL, but I could be wrong about that.

 

[David Wagener]

Donald...I believe you are right. I also seem to recall a system over NC back in the 90s that increased in strength over land as well. It was a situation of the remnant low - after being declassified as a TD - sat over an area with heavy rain. The low began to regenerate and they restarted advisories on the tropical system.

 

[Jeff Snyder]

Man, this is just fascinating!

Check out the Watonga OK meteogram below. A few important things to note -- the extreme rainfall (>2"/hr the past couple of hrs), the intensity and duration of severe-level winds, and the extremely impressive pressure falls. The 3 hr pressure fall for Watonga is currently at > 8 mb/3hr. In fact, it looks like the station pressure stopped reporting on that meteogram. It's also interesting to note the periodicity in the wind maxima through the past 2 hours (looks like 3 waves occurred at regular intervals). That's impressive. Lightning is increasing noteably here in Arcadia (NNE of OKC by ~10-15 miles)

 

[David Wagener]

The center of the circulation is easy to pick out now thanks to the donut hole in Blaine County that has developed over the last 20 minutes. Winds around the low is incredible. Looks like sustained winds around it are in the 35-45 mph range with gusts approaching 80 mph.

 

[Jeff Snyder]

The center of the circulation is easy to pick out now thanks to the donut hole in Blaine County that has developed over the last 20 minutes. Winds around the low is incredible. Looks like sustained winds around it are in the 35-45 mph range with gusts approaching 80 mph.

Yup -- the Watonga AWOS site just reported an 82mph wind gust. Below is the weak-reflectivity "eye"-like feature that David is talking about. The SPC just issued a tornado watch for central and southern Oklahoma too. Low-level shear is insane! That Watonga Mesonet ob is now ESE @ 45 G 68, and a new tornado warning just came out for Grady county. OUN VWP showing 50kts <2km above the surface.

 

[David Wagener]

One of the most interesting things going on right now is the banding developing on the western side of the depression. It really is acting like it is trying to reorganize and re-establish the tropical characteristics. The one thing that is keeping that whole idea in check is just the amount of lightning with it right now, which isn't too typical with a tropical system (the amount of lightning that is).

The southern flank of the storm start to show a few more areas of shear now. Going to be a long night.

 

[Rich Thompson]

Jeff beat me to the punch, but I've managed to upload a few images of Erin:

http://www.chasetolive.com/gallery2/v/2007+Chases/18+August+2007/

The first one is of the wall cloud with an early supercell just E of Norman. It's a crappy area to chase, and I was only able to get a few clear views.

I do recall a few systems that reached peak intensity after moving inland over the TX coast. The last one was "Allison" in 1989, which produced a major flood that was overshadowed by the next "Allison" in 2001. The 1989 storm also had the distinction of being a rare cross-over from the ern Pacific.

Rich T.